WCMC Biodiversity Series No. 8

Freshwater Biodiversity:
a preliminary global
assessment

WORLD CONSERVATION
MONITORING CENTRE

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in 2010 with funding from
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gents

WCMC Biodiversity Series No. 8

Freshwater Biodiversity: a
preliminary global assessment

World Conservation Monitoring Centre

Brian Groombridge and Martin Jenkins

WORLD CONSERVATION
MONITORING CENTRE UNEP

WCMC - World Conservation Press

1998

The World Conservation Monitoring Centre, based in Cambridge, UK, is a joint venture between three
partners in the World Conservation Strategy and its successor Caring for the Earth: [UCN — The World
Conservation Union, UNEP — United Nations Environment Programme, and WWF — World Wide
Fund for Nature. The Centre provides information services on the conservation and sustainable use of
species and ecosystems and supports others in the development of their own information systems.

UNEP — The United Nations Environment Programme is a secretariat within the United Nations which
has been charged with the responsibility of working with governments to promote environmentally
sound forms of development, and to coordinate global action for development without destruction of
the environment.

UNEP has as its mission “to promote leadership and encourage partnerships in caring for the
environment by inspiring, informing and enabling nations and people to improve their qualify of life
without compromising that of future generations”.

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WORLD CONSERVATION eS
MONITORING CENTRE UNEP
Published by: WCMC -— World Conservation Press, Cambridge, UK.
ISBN: 1 899628 126
Copyright: 1998. World Conservation Monitoring Centre, Cambridge

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The views expressed in this book do not necessarily reflect those of
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The designations of geographical entities in this publication and the
presentation of the material do not imply the expression of any
opinion whatsoever on the part of WCMC, UNEP or other
participating organisations concerning the legal status of any country,
territory, or area, or of its authorities, or concerning the delimitation of
its frontiers or boundaries.

Citation: World Conservation Monitoring Centre. 1998. Freshwater
Biodiversity: a preliminary global assessment. By Brian
Groombridge and Martin Jenkins. WCMC — World Conservation
Press, Cambridge, UK. vii + 104 pp + 14 Maps.

Cover design by: Michael Edwards
Printed by: Unwin Brothers, Martins Printing Group, Old Woking, Surrey
Available from: World Conservation Monitoring Centre

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CONTENTS

PREFACE ill
1. FRESHWATER SYSTEMS 1
2. BIODIVERSITY IN FRESHWATERS 17
3. STATUS, TRENDS AND THREATS 25
4. IMPORTANT AREAS FOR FRESHWATER DIVERSITY 39
5. DIVERSITY, RISK AND PRIORITIES: A FRAMEWORK FOR ANALYSIS
OF RIVER BASINS 61
REFERENCES 75

ANNEX | Larger rivers of the world, including a list of basins analysed in this

report and a preliminary revised list of international basins 83
ANNEX 2 River basin analysis: select data from WCMC freshwater biodiversity

database 93
ANNEX 3 Technical notes 103
LIST OF TABLES
Table 1. The world water resource 2
Table 2. Distribution by continent of freshwater resources j 3
Table 3. Mayor water quality issues in different systems 4
Table 4. Animal groups exploited in inland waters 7
Table 5. Inland water fish: select data on catch and consumption 10
Table 6. Summary of key aspects of continental freshwater fisheries 13
Table 7. The major groups of organisms in freshwater 18
Table 8. Aquatic plants: a selection of species-rich or economically important groups 21
Table 9. Numbers of threatened freshwater fishes in select countries Di,
Table 10. Freshwater fish extinctions: number of known species extinctions

by decade 29
Table 11. Scale and source of factors impacting freshwater biodiversity 31
Table 12. Fish introductions: inland species by continent and decade 35
Table 13. Summary of sources of stressors affecting threatened aquatic species

in USA 36
Table 14. Change in lake condition: a preliminary assessment 37
Table 15. Physical and biodiversity features of major long-lived lakes 40
Table 16. Partial list of global hotspots of freshwater biodiversity 42
Table 17. Important areas for freshwater biodiversity 43

Table 18. Thirty high priority river basins 73

LIST O

Figure 1.
Figure 2.
Figure 3.
Figure 4.

Figure 5.

Figure 6.
Figure 7.
Figure 8.
Figure 9.

F FIGURES

Population trends in sample of inland water species

Inland water biodiversity index

Freshwater fish species: percent threatened in selected countries
Freshwater fish extinctions: graph to show known species extinctions
by decade

Fish introductions: graph to show known inland species introductions
by decade

Changes in condition in a sample of lakes worldwide

Relationship between species number and basin area

Relationship between species number and basin discharge volume
Species richness against basin latitude

Figure 10. Relationship between number of fish species and fish families in catchment

basins

Figure 11. Scatter diagram of fish family richness per basin against

‘vulnerability’
LIST OF MAPS
Map |. Location of basins included in study
Map 2. Global hotspots of freshwater biodiversity: a preliminary selection
Map 3. Areas of special importance for freshwater fish diversity
Map 4. Areas of special importance for inland water crustacean diversity
Map 5. Areas of special importance for freshwater mollusc diversity
Map 6. Number of fish species in major river basins
Map 7. Fish species: relative richness
Map 8. Freshwater fish families: the global pattern
Map 9. Number of fish families in major river basins
Map 10. Fish families: relative richness
Map 11. Relative wilderness value of major river basins
Map 12. Pressure on water resources
Map 13. Overall vulnerability
Map 14. River basins: possible global priorities for action

26
26
28

30
35
37
62
62
63
66

72

PREFACE

PURPOSE

This document has been prepared on behalf of the United Nations Environment
Programme (UNEP) by the World Conservation Monitoring Centre (WCMC). Its
purpose is to provide useful information on inland waters and their biodiversity to
a wide audience, ranging from those interested in the state of the world
environment generally, to those needing an overview of the global and regional
context in order to improve planning, management and investment decisions.

This report is explicitly preliminary in approach, largely because of the enormous
scope of the issues involved, but by striving to be geographically comprehensive
and to use existing data and expertise to best advantage, we aim to provide a firm
foundation for subsequent more detailed assessment of freshwater biodiversity.

Within this general context, the project has three principal objectives:

« to present a global overview of freshwater biodiversity, covering notable
aspects of distribution, use, status and trends: see chapters I, 2 and 3;

+ to produce a preliminary global assessment of areas of special importance
(hotspots) for freshwater biodiversity: see chapter 4;

« to develop a framework for comparative analysis of major river basins, using
indicators of biodiversity, the condition of catchment basins and pressures on
water resources, in order to generate indices of importance and risk: see
chapter 5.

The ‘hotspots’ assessment is based on a compilation of expert knowledge. A
number of leading specialists on the systematics and biology of four better-known
animal groups kindly agreed to provide documented information on areas of
special importance within each continent, ‘importance’ here being defined in terms
of high species number or high endemism, or both, relative to other parts of the
continent. The areas are mapped in this report and the supporting data summarised
in table format. Information on these four groups was synthesised to arrive at a
preliminary global list of key areas for freshwater biodiversity. This list is far from
definitive, but will be of great value for many immediate purposes, while more
detailed and quantified analysis will perforce await more prolonged research.

Similarly, a main aim of the comparative catchment basin analysis was to explore
the extent to which sets of global data (either readily available or possible to
generate within a reasonable period) could be analysed in order to derive
meaningful indices of the status of drainage basins. The results appear promising
enough to consider extending the analysis using fine-scale data, and make it
possible to suggest a potential scheme for prioritising river basins with a view to
biodiversity maintenance.

No attempt has been made to address directly the issue of water availability and
quality for human use; this complex area has been comprehensively analysed in an
overview document (UN [CSD], 1997) and a series of supplementary reports
published by the Stockholm Environment Institute.

Whilst this document addresses various aspects of the biodiversity of inland waters
in general, emphasis is given to large rivers and lakes as opposed to the variety of
shallow, often well-vegetated systems (bogs, marshes, mires, swamps and coastal
lagoons) traditionally referred to as wetlands.

WCMC TEAM

Text, analysis: Brian Groombridge, Martin Jenkins. GIS analysis: Jonathan Rhind.
Research: Neil Cox, Janina Jakubowska. Final document production: Julie Reay.
Other assistance: Igor Lysenko (GIS services), Mary Cordiner (information
services).

CONTRIBUTORS TO ‘HOTSPOTS’ COMPILATION

Gerald R Allen (Western Australian Museum); Philippe Bouchet (Laboratoire de
Biologie des invertébrés marins et malacologie, Muséum National d’Histoire
Naturelle, Paris); Keith Crandall (Dept. of Zoology, Brigham Young University);
Neil Cumberlidge (Department of Biology, Northern Michigan University);
Olivier Gargominy (Laboratoire de Biologie des invertébrés marins et
malacologie, Muséum National d’Histoire Naturelle, Paris); Maurice Kottelat
(Cornol, Switzerland); Sven O Kullander (Dept. of Vertebrate Zoology, Swedish
Museum of Natural History, Stockholm); Robert Lesslie (Dept. of Geography,
Australian National University, Canberra); Christian Lévéque (ORSTOM, Paris);
R von Sternberg (Centre for Intelligent Systems, State University of New York at
Binghamton); Guy Teugels (Lab. Ichthyologie, Musée Royal de V Afrique
Centrale, Tervuren).

OTHER CONTRIBUTORS

Angelo Antonio Agostinho; Tadeusz Backiel; Nixon Bahamon, Fernando Gertum
Becker; Jonathan Benstead; Arthur Bogan, Jianbo Chang; Brian Coad; Salvador
Contreras-Balderas; Adele Crispoldi (FAO); Mike Dadswell; Volodymyr
Domashlinets; Benigno Elvira; Jens Floeter; Raghavendra Gadakar; Lance
Grande; Tong Haowen; Charles Hocutt; Erling Holm; Bernard Hugueny; K. C.
Jayaram; Erkki Jokikokko; Pulsri Kanjanamyoon; Chen Kelin; Kip Keller; Stefan
Kuhardt; Sakari Kuikka; Guo-Qing Li; Paul Loiselle; Ricardo Moran Lopez;
Massimo Lorenzoni; John Lundberg; G. Maiorana; Mearelli Mario; Petr Mashkin;
Jascha Minnow; Rolando Mufioz; Daniel Paz; Tadeusz Penczak; Winston Ponder,
Didier Pont; King Yue Poon; Asad Rahmani; T. V. Ramachandra; Patrick de
Rham; Jon Paul Rodriguez; Richard Ruggiero; Tyson Roberts; Vladimir Sal'nikov;
Scott Schaefer; Guiseppe Notarbartolo di Sciara; Melanie Stiassny; Glenn
Switkes; Henne Ticheler; Cor de Van; Richard Vari; Lorenzo Vilizzi; Mauricio
Zarate Villareal; Asbjgrn Vgllestad; Lee White; Rick Winterbottom; Christian
Wolter; Ted Zimmerman

ACKNOWLEDGEMENTS

WCMC is particularly grateful to numerous colleagues (see above) who have
kindly provided information used in this report. Not all have had the opportunity to
review our use of information provided; any errors, omissions or inconsistencies
are the responsibility of WCMC. Special thanks are due to Rob Lesslie (ANU), for
providing data resulting from his global wilderness analysis, and to a number of
field and museum colleagues working on freshwater biodiversity.

Many thanks also to Pat Foster-Turley (formerly coordinator, TUCN-SSC
Freshwater Biodiversity Initiative) for facilitating involvement of the SSC
Specialist Groups on Molluscs and Inland Water Crustaceans.

Part of the data compilation on fish diversity at catchment level was first carried
out for the World Resources Institute (WRI), who kindly allowed further use of the
data here. We also are indebted to the many people who made time to provide data
on fish diversity in major rivers, or advice on data sources. We are especially
grateful to Dr Hamdallah Zedan (UNEP, Nairobi) for his interest in this study and
for providing support. Thanks also to Paul Akiwumi (Water Branch, UNEP) for
providing pertinent review comments. Part of this document is based on material
first collated in a discussion paper on freshwater biodiversity prepared by WCMC
for the CBD Secretariat in 1996.

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1. FRESHWATER SYSTEMS

THE IMPORTANCE OF WATER

Water has the central role in mediating global-scale ecosystem processes, linking
atmosphere, lithosphere and biosphere by moving substances between them and
enabling chemical reactions to occur. Natural waters are never pure H,O but a
complex and ever-changing mixture of dissolved inorganic and organic molecules
and suspended particles.

Water is by far the most abundant single substance in the biosphere. It is unique or
extreme in most of its physical properties and these are the basis of its biological
importance. Living cells are around 75% water; liquid water is essential for life
processes and organisms must obtain water, in amounts broadly proportional to
size, from their environment. Spatial and temporal differences in the availability of
water and its solutes are important determinants of ecosystem richness

At the Earth's surface, freshwater forms the habitat of large numbers of species.
These aquatic organisms and the ecosystems in which they participate represent a
substantial sector of the Earth's biological diversity.

Water as a resource has two key features:
e itis absolutely essential for human survival,

¢ the amount of water in the world is constant, so that although it is used, the stock
is not globally diminished but nor can it be increased.

At below global level, water is often not available where and when needed, nor in
the appropriate amounts, nor with the necessary quality. The two last are
particularly important to the maintenance of freshwater biodiversity.

The finite supply of freshwater on the Earth is now being used by a human
population that has grown exponentially in the past few hundred years, and
continues to grow, and which demands increasing volumes of water to service
agricultural and industrial processes on which economic development depends.
Freshwater systems are under growing pressure, as flow patterns are disrupted and
the load of waste substances increases. Inevitably per capita shares of water for
human use are decreasing and water stress is becoming more widespread (UN,
1997).

Freshwater Biodiversity: a preliminary global assessment

Agriculture consumes around 70% of all water withdrawn from the world's rivers,
lakes and groundwater (FAO, 1996b). In places, more than half the water diverted
or pumped for irrigation does not actually reach the crop, and problems of
waterlogging and salinisation (deposition in soil of salts left by evaporation of
pumped groundwater) are increasing. However, irrigated agriculture produces
nearly 40% of world food and other agricultural commodities on only 17% of the
total agricultural land area, and is thus disproportionately important to global food
security (FAO, 1996b).

THE WORLD WATER RESOURCE

The total volume of water on Earth has been estimated at around 1,500,000,000
km’. Salt water in the world's oceans and seas accounts for almost all, perhaps
97%, of the total volume. Freshwaters make up most of the remaining 3%; this
component consists largely of water in the form of polar ice (mostly Antarctica)
and groundwater. See Table 1.

Table 1. The world water resource

Area % total area Volume % total % fresh
million km’ million km’ water. water
Earth surface 510
land 149 29
world ocean 361 71 1338 96.5
fresh water: - - 35 2.5
ice 16 - 24 1.75 69
ground water z . 10.5 1) 30
weds 2.6 : 0.1 0.0008 0.03
lakes **
; ie) - 0.09 0.007 0.26
nvers
- - 0.02 0.0002 0.006

Notes: 1) all estimates are approximations and vary according to the methods used to derive them; for
consistency we have taken data from a single source. * in the traditional sense, ie. marshes, swamps, mires,
lagoons, floodplains etc; ** excluding saline lakes.

Source: Anon. (USSR Committee for the International Hydrological Decade) 1978.

The world water cycle is the overall process by which water is redistributed
between sources and sinks, with more or less transient residence in rivers, lakes
and living organisms. Water is moved over the Earth by rivers, by ocean currents
and (manifest in weather patterns) by circulation of the atmosphere.

Over the oceans, evaporation exceeds input from rivers and rainfall, and over land,
precipitation exceeds evaporation, but at global level a broad balance exists

1. Freshwater systems

between the volume of water entering the atmosphere as water vapour and the
volume leaving it as precipitation. Sub-globally there is considerable variation in
the distribution of water, eg. there is about twice as much atmospheric water in
equatorial than in temperate latitudes

Groundwater, ie. water below the Earth’s surface held within rocks or between
rock strata constitutes perhaps 30% of global freshwater resources. The more
superficial deposits are linked to the global water cycle, and are used for human
consumption or agricultural purposes, whereas the deeper layers tend to be
somewhat saline and do not (except over geological time scales) participate in
exchanges with other parts of the system.

Water in lakes and rivers constitutes less than one-hundredth of one percent
(<0.01) of the world’s total water volume; lake water is the largest component in
this vanishingly small subtotal.

Water passing through an area of land is available either in the form of soil
moisture (‘green water’) where it is used in production of natural or agricultural
plant biomass, or in aquifers or surface systems (‘blue water’) where it is a
component of aquatic ecosystems and is used for human social and economic
production.

Table 2. Distribution by continent of freshwater resources

Africa Europe Asia Australia* N. Am. S. Am.
large lakes 30,000 2,027 27,782 154 25,623 913
rivers 195 80 565 25 250 1,000
reservoirs 1,240 422 1,350 38 950 286
ground water 5,500,000 1,600,000 7,800,000 1,200,000 4,300,000 3,000,000
wetlands ** 341,000 ‘Eurasia’ 925,000 4,000 180,000 1,232,000

Notes: 1) data refer to volume in km’, except for wetlands which refer to area in km’. 2) all estimates are
approximations and vary according to the methods used to derive them; for consistency we have taken figures
from a single source. * The ‘Australia’ column variously includes New Zealand or Oceania as well as
Australia; ** in the traditional sense, ie. marshes, swamps, mires, lagoons, floodplains etc.

Source: Anon. (USSR Committee for the International Hydrological Decade) 1978.

There are very large regional differences in the distribution of freshwater in all its
forms, depending on the volume of precipitation and the area and geomorphology
of continental land surfaces, and deep geology, in the case of groundwater reserves
(see Table 2). For example, South America has few lakes - only about one
twentieth of the lake volume average for other continents, but around four times as
much water flowing in rivers, and a very large total wetland area (this high
discharge volume may underlie the extreme diversity shown by Amazon fishes).

Freshwater Biodiversity: a preliminary global assessment

WATER QUALITY

In contrast to the World Ocean, which is relatively uniform in composition over
very large distances, waters on the Earth’s surface vary widely over short
distances, according to catchment geology, land cover and climate, and the
materials of anthropogenic origin introduced to them.

Important variables affecting water composition include: solubility and weather
resistance of basin rocks, distance from the marine environment (aerosol source),
aridity, nutrient flow through basin vegetation, temperature, and uplift rates. Some
watercourses are naturally unfit or poorly suited for some human uses, including
drinking (Meybeck and Helmer, 1989).

Anthropogenic changes in water quality are superimposed on the natural
background variations. A similar sequence of water quality issues became
apparent in both Europe and North America during rapid socio-economic
development over the past 150 years. Problems of faecal and other organic
pollution were evident in the mid-19" century, followed by salinisation, metal
pollution, and eutrophication in the first half of the 20" century, with radioactive
waste, nitrates and other organic micropollutants, and acid rain most prominent in
recent decades (Meybeck and Helmer, 1989). At the same time, the scale of water
quality problems tends to increase from local to regional and global. Newly-
industrialising countries are likely to face these problems over a much more
compressed period, and typically without the capacity to monitor and analyse
water quality, or manage water use appropriately.

Table 3. Major water quality issues in different systems

rivers lakes reservoirs groundwater
organic micropollutants eco ooo coe coe
trace elements eco coe eve coe
organic matter ee eve
(exogenous)
eutrophication ee eve
acidification ee ooo
pathogens ooo
dams, diversions etc eve
suspended solids eco
nitrate eve
salinisation eve

Note: s** indicates severe or global or significant regional deterioration, absence of symbol indicates not
globally important, but may be of local significance.
Source: modified after Chapman (1992).

1. Freshwater systems

Levels of organic micropollutants (organochlorine pesticides, polychlorinated
biphenyls, inductrial solvents) and of trace elements (mercury, arsenic, cadmium,
copper, etc) give rise to water quality problems worldwide in the four main classes
of water system (Table 3) (Chapman, 1992; UNEP, 1991, 1995). With regard to
quality for human use, contamination by pathogens of faecal origin is the major
problem in river systems, and eutrophication probably the most widespread
problem affecting lake and reservoir waters.

RIVERS AND CATCHMENT BASINS

A river system is a complex but essentially linear body of water draining under the
influence of gravity from elevated areas of land toward sea level. The typical
drainage system consists of a large number of smaller channels at higher elevation
merging as altitude falls into progressively fewer but larger channels, which in
simplest form discharge by a single large watercourse. Most such systems
discharge into the coastal marine environment; some discharge into lakes within
enclosed inland basins; a few watercourses in arid regions enter inland basins
where no permanent lake exists.

The source area of all the water passing through any given point in the drainage
system is the catchment area for that part of the system. In parallel with the
hierarchical aggregation of tributaries of the major river system, sub-catchments
aggregate into a single major catchment basin; this is the entire area from which all
water at the final discharge point of the system - ie. usually the sea - is derived.
Strictly, the watershed is the line of higher elevation dividing one catchment basin
from another, but this term is increasingly used as a synonym of catchment.

The speed and internal motion of river water depends largely on water volume and
the shape of its channel. These factors typically differ greatly through the river
system, from narrow, steep and fast upland feeder streams, to broad level and slow
downstream reaches. Combined with differences in depth, riparian vegetation,
seasonal variation in flow, and other factors, there is a great variety of potential
habitats. Different organisms within the system tend to be adapted to different
sectors of it, with consequent differences in form and function.

Two features are of primary importance with respect to the habitat quality of a
river:

e materials, such as nutrients, pollutants or sediment particles are capable of
entering the drainage system from any point within the watershed boundary of
that system, and

Freshwater Biodiversity: a preliminary global assessment

- dissolved substances or particles are transported in a downstream direction and
so can have an effect far distant from the point of entry (eg. sediment particles
derived from watershed slopes can be carried into the coastal and marine
environment where they frequently have an adverse effect on local habitats).

A large river and its drainage basin make up a large-scale ecosystem, with both
terrestrial and aquatic components, which must be addressed in an integrated
manner for management interventions to have a chance of success; ie. the
catchment is the basic unit of management at the landscape scale.

THE AGE OF FRESHWATER SYSTEMS

Freshwater habitats are widely considered to be transient in time and space in
comparison with both terrestrial and marine habitats. This is broadly true, certainly
for very small or very shallow freshwater habitats. However, although individual
water bodies vary in extent and persistence, the main types of freshwater habitat
have probably existed since precipitation first fell on the Earth, and large rivers are
probably much longer-lived as a class of systems than lakes (Gray, 1988).

River systems can change course radically as a result of deposition and erosion of
their channel, and the uplift and erosion of watershed uplands. Despite the
dynamic physical state of these systems, large rivers rarely disappear, and
although direct evidence is scarce, indications are that some have been in
continuous existence for tens of millions of years. This is consistent with the fact
that running waters include representatives of almost all taxonomic groups found
in freshwaters, and that several invertebrate taxa occur only in running waters or
attain greatest diversity there.

The great majority of existing lakes, of which around 10,000 exceed 1 km’ in
extent, are geologically very young, and occupy basins formed by ice masses or
glacial erosion during recent ice ages (Gorthner, 1994). These lakes date from the
retreat of continental ice-sheets some 10,000 years before present. All such lakes
are expected to fill slowly with sediment and plant biomass, and to disappear
within perhaps the next 100,000 years along with any isolated biota.

Only about 10 existing lakes are known to be much older (Gorthner, 1994: and see
Table 15), and most of these occupy basins formed by large scale subsidence of
the Earth's crust, dating back to at most 20 million (Lake Tanganyika) or 30
million (Lake Baikal) years before present.

1. Freshwater systems

There is good evidence that some extinct lake systems in the geologic past were
very large and very long-lived under different climatic and tectonic conditions. In
general, the long-lived lakes are of particular interest in terms of biodiversity
because these systems tend to be rich in species of several major groups of animals
and many of these species are restricted to a single lake basin.

USES OF FRESHWATER SYSTEMS AND SPECIES

Humans rely heavily on biological resources in freshwaters, and use freshwater
systems for a wide range of purposes. A large river provides a moving and
apparently endlessly renewable stream of water, for transport, water supply, waste
disposal, and from which food and hydroelectric energy can be extracted.

In addition to utilitarian benefits derived from freshwaters and freshwater
biodiversity, humans also derive many benefits from freshwater systems as
elements in the landscape, particularly so in wildlands, but also in highly modified
agricultural or urban settings. The aesthetic and cultural benefits are derived in
part from the visual appearance of the system in the landscape setting, and may not
depend directly on the health of freshwaters, or the levels of biodiversity therein.

The principal use of freshwater species, not considering properties of aquatic
systems themselves, is as food. Subsidiary uses include the aquarium trade,
materials for medicinal or ornamental use, and as fertilizer. For many human
communities, particularly in countries less-developed industrially, capture
fisheries provide a major portion of the diet. Finfishes aside (see below), other
exploited animal groups in inland waters are far less important globally but may still
be highly significant (see Table 4).

Table 4. Animal groups exploited in inland waters

group use

crustaceans crayfishes, shrimps food

molluscs mussels, clams food, pearls

frogs mainly Ranidae food

crocodilians food, leather, ranch stock

chelonians turtles, especially softshells food, medicinal products (esp. E Asia)
(Trionychidae)

waterfowl ducks, geese, and others food, sport hunting

fur-bearing mammals beavers Castor, otters (subfamily skins

Lutrinae) and muskrats (Ondatra
zibethicus, Neofiber alleni),
sirenians manatees (Trichechidae) food, also used on a small scale for
biological control of weeds

Freshwater Biodiversity: a preliminary global assessment

Relatively few plants associated with inland waters are heavily exploited in the
wild state; most are marginal or wetland species. Some (eg. Aponogeton spp. in
Madagascar) are collected for use as ornamentals; reeds are used as building
materials (eg. thatch); and some are collected for food or as medicines (eg.
Spirulina algae). Rhizomes, tubers and seeds (rarely leaves) of aquatic and
wetland plants are used as a food source, mainly in less developed regions where
they can be important to food security in times of shortage, but globally they make
a relatively minor contribution to human nutrition. Most important are some forms
of edible aroid (Araceae), notably some cultivars of Colocasia (taro) and the giant
swamp taro Cyrtosperma chamissonis which grow in flooded conditions and are
important food crops in the Caribbean, West Africa and the Pacific islands.
Conservation and collection of wild forms of these is considered a high priority.
Sago Palms Metroxylon spp. in southeast Asia and the Pacific and Watercress
Rorippa nasturtium-aquaticum in Europe are other examples of cultivated aquatic
plants whose wild relatives merit conservation.

Rice is the major cultivated wetland plant, and provides the staple food of around
half the world’s people. Most current strains are based on Asian Rice Oryza sativa
and African Rice O. glaberrima. Worldwide, more than 500 million metric tonnes
of rice are produced each year, from around 150 million hectares; most production
is based on rice paddies, which form an important artificial wetland ecosystem in
the tropics, especially in Asia. There are about nineteen species in the genus
Oryza; wild populations of some are in decline but varieties of O. sativa are well
represented in germplasm collections, notably at the International Rice Research
Centre in the Philippines.

Aquatic plants have been widely used for medicinal purposes, documented for at
least two millennia, but such use appears at present to be minor and probably of
real significance in few areas. However, interest in ornamental or aquarium water
plants is very widespread and of some economic importance.

The true value to humans of different inland water ecosystems can only be
estimated by seeking more comprehensive means of evaluating these systems in
economic, social and cultural terms, so as to take account of the less tangible
values of ecosystem goods and services, including those provided by biological
diversity. A recent attempt to ascribe a global value to ecosystems (Costanza et al.,
1997) estimated mean values per hectare of major ecosystem types, taking as
many of these less tangible factors as possible into account. Of non-marine
ecosystems, wetlands (average value US$ 14,785 per hectare) and lakes and rivers
($8,498 per ha) were several times more valuable per unit area than terrestrial
ecosystems such as forests ($969) and grasslands or rangelands ($232). Taken

1. Freshwater systems

together, inland water ecosystems were estimated to contribute more to total global
flow value (US$ 6579 x 10° per year) than all other non-marine ecosystems
combined (US$ 5740 x 10” per year) despite their far lesser extent. This provides a
strong case for effective conservation management of extant inland water
ecosystems.

FRESHWATER FISHES AS FOOD

Where countries have access to both marine and inland aquatic resources, reported
yield from inland waters is a small fraction of marine yield, a pattern reflecting the
higher productivity of marine shelf waters and reinforced by weak marketing and
distribution infrastructure for freshwater catch. Even in land-locked countries, the
recorded inland harvest is often, but not always, low both in absolute size and in
relation to consumption of meat and other agricultural produce.

The total inland water fishery production has two components: capture fisheries
and aquaculture. National statistics do not adequately reflect the actual magnitude
or location of inland fisheries. The reported inland capture production is certainly
an under-estimate because much of the catch is made far from recognised landing
places where catches are monitored, and is consumed directly by fishers or
marketed locally without ever being reported. The evidence suggests that actual
capture fisheries catch may be twice the reported total, ie. around 12 million mt
per year (Coates, 1995), and inland waters are suspected by some to provide food
(as opposed to oils and meals) in amounts not much less than the recorded marine
catch (Borgstrém, 1994).

Inland water capture fisheries, particularly in countries less-developed industrially,
do provide a staple part of the diet for many human communities. This is the case
in West Africa generally, locally in East Africa, and in parts of Asia and
Amazonia. In some land-locked countries inland fisheries are of crucial
importance, providing more than 50% of animal protein consumed by humans in
Zambia (Scudder and Conelly, 1985), and nearly 75% in Malawi (Munthali,
1997). Fish protein may be critical in times of food stress. It is impossible at
present to develop a global view of the rdle of inland fisheries because these
operate mainly at artisanal and local level in rural areas, in general far outside the
scope of available statistical data.

Table 5 shows reported inland fishery data for a selection of countries. It should be
noted that two-thirds of the 30 countries showing the highest apparent per capita
consumption of inland fish are classed as LIFDs (low income food-deficit
countries), and around half of those with the highest catch. Bangladesh is foremost

Freshwater Biodiversity: a preliminary global assessment

Table 5. Inland water fish: select data on catch and consumption

annual catch LIFD mt apparent LIFD mt/cap.
consumption es

1 China + 13,752,283 Finland 10.79
2 India + 3,151,988 Tanzania + 9.99
3 Indonesia - 1,172,772 Uganda 9.89
4 Bangladesh + 969,224 Hong Kong 9.66
5} Peru 581,170 Macau 9.49
6 USA 567,608 Zambia + 8.66
7 Viet Nam 423,516 Turkestan + 8.21
8 Romania 406,330 Congo + 7.44
9 Philippines + 350,202 Bangladesh + 6.82
10 Tajikistan + 306,467 Malawi + 6.70
11 Tanzania + 295,333 Cambodia + 6.69
12 Japan 271,762 Norway 6.34
13 Egypt + 255,915 Laos + 6.25
14 Myanmar 243,682 China + 6.07
15 Brazil 238,438 Japan 5.89
16 Uganda 232,090 Mali + 5.87
17 Syria + 200,141 Chad + 5.70
18 Taiwan 198,322 Kenya + 5.46
19 Mexico 192,781 Korea D PR + 5.06
20 Kenya + 185,386 Azerbaijan + 4.77
21 Zaire + 168,668 Philippines + 4.69
22 Ukraine 139,700 Thailand 4.58
23 Thailand 134,643 Iceland 4.45
24 Korea DPR + 124,883 Cent Af Rep + 4.12
25 Nigeria + 124,148 Sierra Leone + 4.06
26 Iran 117,791 Benin + 3.82
27 Russia. 116,108 Burundi + 3.63
28 France 111,388 Viet Nam 3.56
29 Italy 102,649 Indonesia + 3.53
30 Germany 91,910 Senegal + 3.52

Notes: data are annual means for 1990-1995; ‘catch’ includes aquaculture plus capture fisheries, only the 30
countnes with the highest reported catch and calculated apparent consumption are shown; + = LIFD = low
income food-deficit country.

Sources: calculated from data kindly supplied by Adele Crispoldi (Fishery Statistician, FAO).

among countries appearing in both lists; others include China, Indonesia, Viet
Nam.

Overall inland capture production has risen moderately during the decade from
1984, around 1.7% annually, but there are significant regional differences. Inland
production has declined in Europe and the former USSR, mainly because of
deteriorating habitat quality and excess exploitation. In Asia, excluding new states
of the former USSR, and in Africa, production has risen. However, this cannot be
attributed to any improvement in the health of inland waters. Increase in Asia is
attributed mainly to fisheries based on stocking of large artificial reservoirs created

10

1. Freshwater systems

during recent rapid economic development, and increase in Africa is mainly due to
capture fisheries in the Rift Lakes, where the introduced Nile Perch is the basis of
a significant export trade system.

It is difficult rigorously to assess the condition of inland fish stocks because they
appear able to respond rapidly to changing environmental conditions. However,
there is a consensus that, regionally, most stocks are fully exploited and in some
cases over-exploited.

Exploitation has become more efficient because of new technologies, and
developing infrastructure has allowed easier access to freshwater resources. Some
stocks, especially in river fisheries, appear to be in decline, but this is seemingly a
result mainly of anthropogenic changes to the freshwater environment.

Inland fisheries, and freshwater biodiversity generally, do not receive sufficient
attention in local, catchment-wide or national planning decisions. These sectors are
often strongly impacted by decisions made in eg. the hydroelectric, navigational,
flood control or agricultural development sectors, without reference to the need to
maintain biodiversity or fishery production.

Salient features of inland water fisheries are summarised in Table 6.

THE IMPORTANCE OF INLAND CAPTURE FISHERIES FOR FOOD
SECURITY

In recent years reported inland production has made up around 7% of the world
total capture production. Despite this relatively low figure, and without taking
account of under-reporting of inland capture, inland production has special
significance because (Coates, 1995):

* many more people have access to inland waters than to coastal marine waters;
gears for subsistence fishing’ do not have to be technologically advanced
(although such equipment is increasingly available) and costly to purchase, and
often many sectors of the community are involved in inland capture fisheries;

* a greater proportion of the inland catch appears to be used for direct human
consumption, close to point of origin;

* some countries are land-locked and have no internal source of fish other than
freshwaters;

Freshwater Biodiversity: a preliminary global assessment

e most of the marine catch is landed by highly industrialised fleets from a small
number of countries but inland production exceeds marine landings in about
25% of reporting countries, including a large number of Low Income Food
Deficit Countries;

e waste through discarded bycatch is large in marine fisheries but negligible
inland.

INTERNATIONAL INLAND WATERS

Inland waters typically intersect several subnational administration units (counties,
provinces, etc) and are subject to management and use decisions made within
several different sectors (forestry, navigation, fishery, waste disposal, recreation,
etc). Although it has been recognised for some time that the catchment basin is the
fundamental unit within which management must be formulated, reconciling the
many different interests concerned and coordinating actions have proved difficult.

Waters that delineate or cross international boundaries present a special class of
management issues. Such waters and the living resources they contain are shared
by one or more countries, and require positive international collaboration for
effective use and management.

Available water in any given country within an international basin (or other
administrative unit within a basin more generally) can be divided into endogenous,
ie. locally generated runoff available in national aquifers and surface water
systems, and exogenous, ie. remotely generated runoff imported in flow from
upstream. Some countries (eg. Canada, Norway) have an abundance of water from
endogenous sources, others (eg. Egypt, Iraq) have a small endogenous supply but
large exogenous volumes (others have small supplies from both sources). Use of
exogenous water carries an increasing risk because of dependence on sufficient
supply from upstream countries.

The United Nations Register of International Rivers (Anon., 1978) recognised 214
major international river basins in 1978. Since that time, fragmentation of some
previous country units, eg. the USSR, has compounded problems of international
cooperation by increasing the number of countries having a share of international
inland waters. A preliminary revised listing of countries within basins included in
the present assessment is incorporated in Annex 1.

12

1. Freshwater systems

Table 6. Summary of key aspects of continental freshwater fisheries

Features

AFRICA

Africa below the Sahara has a large variety of
inland water bodies, including upland crater lakes,
rift lakes, and major floodplain rivers. Fisheries
make an important contribution to food security in
sub-Saharan Africa, and almost all production is
consumed within the region. Nigeria, Zaire, and
East Africa (Kenya, Uganda, Tanzania) contribute
most to overall reported catch. Inland fisheries in
North Africa very small; most production in Egypt,
based on the Nile and L. Nasser. Continent catch
has increased up to 1990 and then levelled.

Floodplain fisheries, especially around L. Chad and
the inland delta of the Niger, dominate production
in West and Central Africa and the Sahelian region.
Floodplain systems tend to allow rapid stock
recovery after heavy exploitation and there is no
overall evidence of excess harvest.

Production in Eastern Africa is based mainly on
natural lakes, the larger of which are shared
between countries. The largest fishery by far
(around 25% of total inland production in Africa) is
for Nile Perch in L. Victoria, and this generates
significant export earnings. Easy access, good
transport and market proximity mean that most
waters are exploited at or above maximum
sustainable levels, eg. in Rwanda and the Malawi
sector of L. Malawi.

Inland fisheries mostly remain at small-scale
artisanal level, which is advantageous in that it
tends to maintain social patterns in waterside
communities while avoiding the drive to over-
exploitation characteristic of many commercial
fisheries.

NORTH AMERICA
The recreational catch appears to greatly exceed
commercial catch, and considerable resources are

devoted to environmental restoration and the
maintenance of sport fish stocks.

Non-recreational fisheries are based mainly on the
Great Lakes region and on migratory salmon
stocks. The latter are particularly important for
indigenous people in the northeast Pacific and
northwest Atlantic.

13

Issues

Catch in many areas is: subject to great annual
fluctuation depending on extent of drought or
flood. Exploitation of natural stocks is high (but
below estimated total potential catch at continent
level). Fishing pressure is increasing and most
fisheries show signs of intensive exploitation.

The number of fishers using the inland Niger delta
in Mali has risen over the two decades to 1990 and
there are signs of local over-fishing. The artificial
L. Volta in Ghana, with a steady total annual yield
but greatly reduced individual catch by an
increasing number of fishers.

There is an increasing need for management of
inland fisheries. Remote regions and lake stocks of
small pelagics may provide for increased
production from natural sources.

Large lakes are increasingly subject to pollution,
including waste discharge and siltation. Many lakes
have very clear water and high fish production
based on a deep zone of primary production, but
land conversion to agriculture in catchment areas,
leading to increased turbidity, is an increasing
concer.

Floodplains and other wetlands are continually at
risk from agricultural expansion. Damming on the
Senegal River has restricted fish movement and
low flow in drought conditions reduces production.

Damming, drainage, pollution and sedimentation
have led to a widespread and locally severe decline
in the health of fish stocks in North America during
the 20" century. This has been marked in western
USA, where several species extinctions have
occurred. Intensive management directed in part at
sport fisheries has locally reversed this trend.

Freshwater Biodiversity: a preliminary global assessment

Features

SOUTH AMERICA, CENTRAL AMERICA

Because of strong traditional preference for meat,
fish consumption in the continent as a whole is
relatively low. Total reported catch relatively low
although region includes two of the world’s largest
drainage basins (Amazon, Parana-Paraguay).
Small-scale river and lake fisheries are locally
important to food security,

Fisheries in the tropics largely based on rivers; but
in cooler and cold temperate southern areas, and
mountains, lakes and reservoirs more important.

‘Black water’ systems, draining lowland forests
tend to have low productivity; higher in ‘white
water’ systems draining uplands.

Fisheries often artisanal, but heavily commercial on
the Amazon with some features of marine fisheries
(over-capitalisation, local over-exploitation).

Inland catch near zero in Caribbean region due to
lack of suitable waters. Cuba has a nutritionally
important, stable and well managed fishery based
on stocked reservoirs (largely reported as
aquaculture). Lake eutrophication may be cause of
increased catch in El Salvador, and in Mexico
systematic stocking of alien fishes has increased
catch.

ASIA

Reported catch highest of all continent regions,
showing a steady increase to peak around 1990, but
catch statistics are relatively poor.

Inland fisheries are especially important in several
countries in the region, notably Bangladesh and
Cambodia, where inland harvests exceed marine
catch.

China alone produces around half the world total
reported yield from inland capture fisheries, and
around 80% of aquaculture yield; but stocking of
Tivers contributes greatly to capture catch (and
begins to erase the distinction between capture and
aquaculture). Recent upward trends in reported
inland catch in China appears to be due to stock
enhancement of lakes and reservoirs (often with
attempts to eradicate natural predators).

14

Issues

Overall catch rose up to late 1980s then declined
somewhat. Fisheries dominated by characins and
catfishes, but introduced species (tilapia, black
bass, carp) becoming important. Over-fishing is
evident locally.

Catch from Amazon system appears well below
potential, but reported catch is mostly from the
river mouth and around urban centres. A significant
part of total catch in Brazil is from hydro
impoundments, eg. on the Upper Parana. Reported
catch in Bolivia is relatively low, based mainly on
the Amazon system, the Pilcomayo, and a small
fishery on Lake Titicaca (shared with Peru). Recent
decline in Colombia has been attributed to excess
catch and local pollution.

Mineral extraction has major impact on rivers and
lakes. Waste copper, zinc, cadmium apparently
responsible for fishery decline in Lake Poopo
(Bolivia). Mercury, used in gold extraction, is
accumulating in river fishes and being widely
dispersed, eg. in the Araguaia basin (Brazil).

Agriculture is seen as major pollution source (silt,
pesticides, fertilizer). Farming communities in
floodplain areas turning increasingly to fishing
because of land competition with ranchers and
falling commodity prices.

Up to one half of the inland catch in Bangladesh is
based on Hilsa (a clupeid fish that migrates
upstream to spawn) but stocks have declined
upstream because of barrages on the lower Ganges.

Natural fisheries in India are in some decline but in
South Asia generally stocking of reservoirs and
controlled fishing have supplied an increasing
proportion of total inland catch.

In Cambodia, the major part of the inland catch is
derived from Tonle Sap lake and surrounding
floodplains, but the yield has declined since the
1960s, apparently because of excess exploitation
and environmental degradation, including silting up
of drainage systems following forest clearance and
agricultural conversion.

River fisheries have in general been severely
degraded by development pressures and water
quality is widely too poor to sustain fisheries.

Features

EUROPE

Catches have risen in western Europe although
inland resources are not of great economic
importance to most countries. The volume of fish
production is low to moderate, contributing around
16% of the world production. The species diversity
of the catch is low.

Eastern Europe is a major producer due in part to
the extensive resources of the Danube delta, also to
traditional use of fishponds

Recreational fishing is, or is becoming, the major
component and consumption is typically on a
modest scale, largely for local use. It appears that
there has been a decline in production from these
fisheries, however, recreational fishing remains
largely undocumented.

Aquaculture production has fallen somewhat. A
rise is expected within the transitional countries of
Eastern Europe. The development of these may be
constrained by size availability

1. Freshwater systems

Issues

There has been a rise in recreational fishing and
this has caused a conflict with those still utilising
the resources at a commercial level.

European rivers have faced a decline in stocks due
to pollution from industrial effluent, domestic
sewage and agricultural run off. Many basins have
been affected by damming, creating problems for
migratory species .

Most lakes have undergone severe environmental
degradation over the last decade. Many have
become eutrophic due to pollution and the fish
populations reflect this, although many (such as
Lake Geneva) now have management programmes
which aim to combat the pollution.

The demand for fish remains higher than
production and the import of fish from other
continents will continue to be necessary.

Notes: this table outlines key features of inland water fisheries and is a highly selective and simplified overview

of a complex subject with a vast technical literature.

Sources: information derived mainly from FAO (1996) and Coates (1995).

15

2. BIODIVERSITY IN FRESHWATERS

SPECIES NUMBERS IN FRESHWATERS

At high taxonomic levels the diversity of freshwater organisms is much narrower
than on land or in the sea: no extant phyla or classes, and few orders, are restricted
to freshwater habitats. The number of species overall (species richness) is low
compared with marine and terrestrial groups. However, species richness in relation
to habitat extent is extremely high in many freshwater groups.

For example, about 10,000 (40%) of the 25,000 known fish species are freshwater
forms. Given the distribution of water on the Earth's surface this is equivalent to
one fish species for every 100,000 km’ of sea water, compared with one species
for every 15 km’ in freshwaters. This high diversity of freshwater fishes relative to
habitat extent is probably promoted by the extent of isolation between freshwater
systems. Many lineages of fishes and invertebrates have evolved high diversity in
certain water systems, and in some cases, species richness and endemism tend to
be positively correlated between different taxonomic groups (eg. Watters, 1992).

At global level, species richness increases strongly toward the equator; ie. in most
groups of organisms, there are many more species in the tropics than in temperate
regions. The same applies to freshwater fishes in general and to other groups in
freshwaters, although certain groups, eg. freshwater crayfish, are much less diverse
in the tropics than temperate regions. The number of fish species present in rivers
is highly correlated with the area and annual discharge of the drainage basin
(especially the latter).

Table 7 provides an outline of the major groups of plants and animals present in
freshwaters. There are more than 600 species of freshwater fungi known, currently
more from temperate regions than from the tropics, although probably only a small
fraction of existing species have been described, and the tropics have been little
sampled (Goh and Hyde, 1996). There is no group of plants as diverse and species-
rich in freshwater habitats as fishes, bivalve molluscs, dragonflies and other
animal groups. Although important along water margins, and sometimes on the
water surface, plants other than microscopic forms are in general nowhere as
prominent in freshwater ecosystems as animals.

17

Freshwater Biodiversity: a preliminary global assessment

Table 7. The major groups of organisms in freshwater

General features

Viruses

Microscopic; can reproduce only within the
cells of other organisms, but can disperse and
persist without host.

Bacteria

Microscopic; can be numerically very
abundant, eg. 1,000,000 per cm’, but less so
than in soils. Recycle organic and inorganic
substances. Most derive energy from inorganic
chemical sources, or from organic materials.
Fungi

Microscopic. Recycle organic substances;
responsible for decay of dead material; tend to
follow bacteria in decomposition processes.

Able to break down cellulose plant cell walls
and chitinous insect exoskeletons.

Algae

Microscopic and macroscopic; include variety
of unicellular and colonial photosynthetic
organisms. All lack leaves and vascular tissues
of higher plants. Green Algae (Chlorophyta)
and Red Algae (Rhodophyta) include
freshwater species; Stoneworts (Charophyta)
mostly freshwater.

Plants

Photosynthetic organisms; mostly higher
plants that possess leaves and vascular tissues.
Mosses, quillworts, ferns important in some
habitats. Some free-floating surface species
(eg. Water Fern Salvinia, Duckweed Lemna);
most are rooted forms restricted to water
margins.

Invertebrates: protozoans

Microscopic mobile single-celled organisms.
Tend to be widely distributed through passive

dispersal of resting stages. Attached and free-
living forms; many are filter-feeders.

Invertebrates: rotifers

Near-microscopic organisms; widely
distributed; mostly attached filter-feeders,
some predatory forms.

Invertebrates: myxozoans

Microscopic organisms with complex life
cycles, some with macroscopic cysts. Formerly
classified with protozoa but are metazoa.

pirat

Significance in freshwaters

Cause disease in many aquatic organisms, and
associated with water-borne disease in humans (eg.
hepatitis).

Responsible for decay of dead material. Present on all
submerged detritus where a food source for aquatic
invertebrates. Many cause disease in aquatic organisms
and humans.

Present on all submerged detritus where a food source
for aquatic invertebrates. Some cause disease in aquatic
organisms and humans.

Responsible for most primary production (growth in
biomass) in most aquatic ecosystems. Free-floating
phytoplankton main producers in lakes and slow
reaches of rivers; attached forms important in shallow
parts of lakes and streams.

Provide a substrate for other organisms and food for
many. Trees are ecologically important in providing
shade and organic debris (leaves, fruit), structural
elements (fallen trunks and branches) that enhance
vertebrate diversity, in promoting bank stabilisation,
and in restricting or modulating flood waters.

Found in virtually all freshwater habitats. Most
abundant in waters rich in organic matter, bacteria or
algae. Feed on detritus, or consume other microscopic
organisms; many are parasitic on algae, invertebrates or
vertebrates.

Important in plankton communities in lakes and may
dominate animal plankton in rivers.

Important parasites in or on fishes.

2. Biodiversity in freshwaters

General features Significance in freshwaters

sane eS Pent TNA 78 ms om sa rane

Invertebrates: flatworms

A large group of worm- or ribbon like Turbellaria include mobile bottom-living predatory
flatworms, includes free-living benthic flatworms. The Trematodes includes various flukes,
(Turbellaria), and parasitic forms (Trematoda, such as the tropical schistosome that causes bilharzia;
Cestoda). Cestodes are tapeworms: both these groups are

important parasites of fishes and other vertebrates
including humans. Molluscs often intermediate hosts.

Invertebrates: nematodes

Generally microscopic or near-microscopic May be parasitic, herbivorous or predatory. Typically
roundworms. inhabit bottom sediments. Some parasitic forms can
reach considerable size. Poorly known; may be more

diverse than recognised.

Invertebrates: annelid worms

Two main groups in freshwaters; oligochaetes Oligochaetes are bottom-living worms that graze on

and leeches. sediments; leeches are mainly parasitic on vertebrate
animals, some are predatory.

Invertebrates: molluscs

Two main groups in freshwaters; Bivalvia Snails are mobile grazers or predators; bivalves are
(mussels etc) and Gastropoda (snails, etc). attached bottom-living filter-feeders. Both groups have
Very rich in species; tend to form local speciated profusely in certain freshwater systems. The
endemic species. larvae of many bivalves are parasitic on fishes. Because

of the feeding mode, bivalves can help maintain water
quality but tend to be susceptible to pollution.

Invertebrates: crustaceans

A very large Class of animals with a jointed Include larger bottom-living species such as shrimps,
exoskeleton often hardened with calcium crayfish and crabs of lake margins, streams, alluvial
carbonate. forests and estuaries. Also larger plankton: filter-

feeding Cladocera and filter-feeding or predatory
Copepoda. Many isopods and copepods are important
fish parasites.

Invertebrates: insects

By far the largest Class of organisms known. In rivers and streams, grazing and predatory aquatic
Jointed exoskeleton. The great majority of insects (especially larval stages of flying adults)
insects are terrestrial, because they are air- dominate intermediate levels in food webs (between the
breathing. microscopic producers, mainly algae, and fishes). Also

important in lake communities. Fly larvae are
numerically dominant in some situations (eg. in Arctic
streams or low-oxygen lake beds), and are vectors of
human diseases (eg. malaria, river blindness).

Vertebrates: fishes

More than half of all vertebrate species are Fishes are the dominant organisms in terms of biomass,
fishes. These are comprised of four main feeding ecology and significance to humans, in virtually
groups: hagfishes (marine), lampreys all aquatic habitats including freshwaters. Certain water
(freshwater or ascend rivers to spawn), sharks systems, particularly in the tropics, are extremely rich

and rays (almost entirely marine), and ray- in species. Many species are restricted to single lakes or
finned 'typical' fishes (>8,500 species in river basins. They are the basis of important fisheries in

freshwaters, or 40% of all fishes).

inland waters in tropical and temperate zones.

Freshwater Biodiversity: a preliminary global assessment

General features Significance in freshwaters

Vertebrates: amphibians

Frogs, toads, newts, salamanders, caecilians. Larvae of most species need water for development.

Require freshwater habitats. Some frogs, salamanders and caecilians are entirely
aquatic; generally in streams, small rivers and pools.

Larvae are typically herbivorous grazers, adults are

predatory.
Vertebrates: reptiles
Turtles, crocodiles, lizards, snakes. All Because of their large size, crocodiles can play an
crocodilians and many turtles inhabit important role in aquatic systems, by nutrient
freshwaters but nest on land. Many lizards and enrichment and shaping habitat structure. They, as well
snakes occur along water margins; a few as freshwater turtles and snakes are all predators or
snakes are highly aquatic. scavengers.
Vertebrates: birds
Many birds, including waders and herons, are Top predators. Wetlands are often key feeding and
closely associated with wetlands and water staging areas for migratory species. Likely to assist
margins. Relatively few, including divers, passive dispersal of small aquatic organisms.
grebes and ducks, are restricted to river and
lake systems.
Vertebrates: mammals
Relatively few groups are strictly aquatic (eg. Top predators, and grazers. Large species widely
River Dolphins, platypus), several species are impacted by habitat modification and hunting. Through
largely aquatic but emerge onto water margins damming activities, beavers play an important role in
(eg. otters, desmans, otter shrews, water voles, shaping and creating aquatic habitats.

water oppossum, hippopotamus).

Among the ‘lower’ (non-vascular) plants, the mosses and liverworts are virtually
all terrestrial, although flourishing only in moist environments; but the larger algae
are primarily aquatic. The larger algae comprise some 5,000 species in three major
groups (the green, brown and red algae), the great majority of which are marine or
brackish water forms (‘seaweeds’). The green algae Chlorophyta include one order
of around 80 species (Ulotrichales) that is mainly freshwater. However, one major
group sometimes associated with the green algae - the stoneworts (Charophyta) - is
almost entirely freshwater. The stoneworts include some 440 species, most of
which are endemic at continent level or below; they tend to be very sensitive to
nutrient enrichment and have declined in many areas (Tittley, 1992).

The higher (vascular) plants include ferns and allies (pteridophytes), conifers and
allies (gymnosperms) and flowering plants (angiosperms). It has been estimated
that at most 2 percent of pteridophytes and 1 percent of angiosperms, ie. up to 250
and 2,500 species respectively, are aquatic forms (Sculthorpe, 1967). These groups
together comprise around 400 families; only some 33 of these include aquatic
species, and most of these are not rich in species. Most of these aquatic species
occur in freshwaters but some 50 species of seagrass grow in shallow coastal

20

2. Biodiversity in freshwaters

marine habitats. Table 8 includes basic information on a small selection of the
approximately 33 plant families that include freshwater species.

Table 8. Aquatic plants: a selection of species-rich or economically important groups

group common spp __ distribution ecology
name no.
Charophyta stoneworts 440 cosmopolitan freshwater
Pteridophyta
Salviniaceae water ferns 10 tropical, warm temperate freshwater, free-floating, some
ornamentals, includes Salvinia auriculata a
major weed pest in Africa, Sn Lanka and
elsewhere
flowering plants
Acoraceae sweet flag 2 Old World, N America aromatic marshland emergent herb,
rhizomes widely used medicinally, leaves
for scent, etc
Haloragidaceae water 145 cosmopolitan, especially freshwater aquatics or in moist areas, some
milfoils, etc southern hemisphere shrubs, mostly herbaceous
Hydrocharitaceae waterweed, 90 cosmopolitan, mainly freshwater, some marine’ includes
frog’s bit, tropical important aquarium plants and a some
etc major weeds eg. Elodea canadensis
Nymphaeaceae water lilies 75 cosmopolitan freshwaters only; some ornamentals, some
yield edible seeds and rhizomes
Podostemaceae 280 tropical, many species are _—_ moss-like herbs of stony rivers, including
narrow endemics hill torrents
Pontederiaceae water 34 tropical freshwater, includes the world’s most
hyacinth widespread and pestilential aquatic weed
Eichhomia crassipes
Potamogetonaceae pondweeds 100 cosmopolitan fresh and brackish waters, food source for
animals and sometimes humans
Trapaceae water 15 Old World freshwaters only, free-floating, fruits a
chestnut staple food in parts of Asia

ncn = ase nse ren aURE RTOS RE SECIS SS NRA SO PP NOOR EPSP MASRS CESAR

Note: This table includes basic information on a small selection of the few plant families that include
freshwater species.
Source: based on data in Sculthorpe (1967) and Mabberley (1997).

Several species of aquatic plant, particularly free-floating species able to spread
rapidly by vegetative growth, but also other forms, have dispersed widely over the
globe and become major pest species. They block drainage channels, sluices and
hydro-electric installations, impede boat traffic, and hinder fishing. In recent
decades the question of how best to control or eradicate pest species has been the
foremost issue in conservation and management of aquatic plants.

Animal species are considerably more diverse and numerous in inland waters than
plants. Most of the major groups include terrestrial or marine species as well as
freshwater forms. Apart from fishes, important groups with inland water species
include crustacea (crabs, crayfishes and many smaller organisms), molluscs

21

Freshwater Biodiversity: a preliminary global assessment

(including mussels and snails), insects (including stoneflies Plecoptera, caddisflies
Trichoptera, mayflies Ephemoptera), sponges, flatworms, polychaete worms,
oligochaete worms, numerous parasitic species in various groups, and numerous
microscopic forms. Palmer et al. (1997) provide a review of diversity and the
ecological réle of microorganisms and microinvertebrates in freshwater sediments.

DISTRIBUTION PATTERNS OF FRESHWATER ORGANISMS

Freshwater lineages that originated within continental water systems may show
general patterns of distribution similar to terrestrial groups, corresponding more or
less to broad biogeographic realms. Lineages of marine origin may remain
restricted to peripheral systems corresponding to the area where the ancestral
forms moved into freshwater.

Unlike many terrestrial species, that can disperse widely in suitable habitat, the
spatial extent of the range of strictly freshwater species tends to correspond to
present or formerly continuous river basins or lakes; these species include fishes
and most molluscs and crustaceans. Watersheds between river basins are the
principal barriers to their dispersal between systems, and their ranges are extended
mainly by physical changes to the drainage pattern (eg. river capture following
erosion or uplift can allow species formerly restricted to one system to move into
another), or by accidental transport of eggs by waterbirds, or by flooding.

In many instances, the range within a system will also be restricted by particular
habitat requirements (variations in water turbulence or speed, shelter, substrate,
etc). These frequently differ between different stages in the life cycle (eg. in fishes,
different conditions and different sites are often required for egg deposition and
development, for early growth of fry, and for feeding and breeding of adults).

Many cave or subterranean freshwater aquatic species (eg. of fishes, amphibians
and crustaceans) have very restricted ranges, perhaps consisting of a single cave or
aquifer, and very limited opportunities for dispersal, depending on the surrounding
geology and the consequent morphology of the water system occupied.

Insects with an aquatic larval phase but a winged adult phase are often restricted to
particular river basins (even if adults disperse widely, they may not find suitable
habitat), but in general are much less restricted in this way than entirely aquatic
species. A relatively large number of species, particularly of crustaceans, occupy
temporary pools and have a desiccation-resistant stage that can undergo long-range

passive dispersal between drainage basins; some such species are thus widely
distributed.

22

2. Biodiversity in freshwaters

Vascular plants are essentially terrestrial forms, and existing aquatic species are
derived from terrestrial ancestors; several different lineages include aquatic
species and this transition has therefore occurred several times. Most inland water
plant species are relatively widespread, ranging over more than one continental
land mass; many are cosmopolitan, occurring around the world and on remote
islands. Of the widespread forms, some are essentially northern temperate species
extending to a great or lesser extent into the tropics; some are mainly tropical.
Tropical regions of Asia, Africa and South America appear to be most rich in
species restricted to a single continent, or to a single country or smaller area
(Sculthorpe, 1967).

The Podostemaceae is particularly noteworthy for its many monotypic genera, and
a large number of narrowly endemic species, in at least one instance with several
forms restricted to different stretches of a single river; tropical South America,
Madagascar, Sri Lanka, India, Myanmar, and Indonesia hold such localised
species (Willis, in Sculthorpe, 1967).

A large number of species have been spread by intentional or accidental human
introductions to areas beyond their native range, and in many cases have occupied
vast areas and had serious ecological impacts.

SPECIES DIVERSITY

The general goal of biodiversity conservation is to minimise loss of irreplaceable
biodiversity. This not only includes individual species, but also habitats and
ecosystems where these are known to be unlikely to regenerate naturally or
difficult to restore artificially. The first step in planning for biodiversity
conservation at any geographic scale is to assess the diversity of natural resources
present and identify those which are most important, or in this context, most
irreplaceable.

The species diversity of an area can be evaluated in different terms:

* an area with a large number of species (high species richness) can be described
as more diverse than an area with fewer;

* an area with more species restricted to it (ie. more endemics), includes more
diversity than one with few or none,

* an area with representatives of more higher taxa (ie. groups higher than species
level, such as genera, families, or classes), is more diverse than one with fewer

23

Freshwater Biodiversity: a preliminary global assessment

e an area with more phylogenetically ‘primitive’ taxa (eg. lungfishes or sturgeon
among fishes) is more diverse than areas with representatives only of more
recent radiations.

A collation and analysis of expert opinion on the location of areas of special
importance for inland water biodiversity, assessed in terms of species richness and
endemism, is provided in Chapter 4 of this document.

Species diversity is not the sole criterion to be used in prioritising species or sites
for conservation action. Human attitudes and values also determine the
significance attached to elements of biodiversity: areas supporting species
threatened with extinction, or which are consumed or which yield important
commodities, may with justification be rated more highly than areas not
supporting such species.

24

3. STATUS, TRENDS AND THREATS

THE STATUS OF FRESHWATER BIODIVERSITY

Awareness has been growing during the past decade of the unique nature of much
freshwater biodiversity, of the array of factors that in the past and at present have an
impact upon freshwater species, and the extent to which real damage has already
been done (recent reviews: Abramovitz, 1996, McAllister et al. 1997). The evidence
is uneven in geographic scope, but decline in habitat quality and species populations
is typical in the countries and regions where good field information is available, and
real concern for the status of freshwater species worldwide is justified. While much
general interest has been stimulated in the more spectacular of the terrestrial habitats
and species, knowledge of the diversity and importance of the species hidden
beneath the surface of freshwaters has remained very largely within the academic
scientific community.

Many human activities tend to promote fragmentation of natural and often species-
rich habitats (eg. floodplain rivers) and the spread of highly-managed species-poor
habitats (eg. channelised rivers and reservoirs). Small isolated populations tend to be
more sensitive than larger connected ones to demographic factors (eg. random
events affecting the survival and reproduction of individuals) or environmental
factors (eg. spread of disease, changes in food supply). The risks of this kind of
distribution pattern may be compounded by other external threats, such as excess
exploitation, introduced predators or pollution events.

In a first attempt to obtain an overview of global trends in inland water biodiversity,
qualitative information on population trends (ie. whether increasing, stable or
decreasing) in a sample of more than 200 freshwater, wetland and water margin
vertebrate species has been collated. This is represented in summary form in Figure
1. Most species in each decade are in decline. Although the sample size is very small
in earlier decades, the proportion of species with an increasing trend has grown
somewhat during the 1990s. Quantitative time-series population data are extremely
scarce, but could be found for a subset of 70 species. An index generated from these
data (Figure 2) shows a decline of around 50% from the 1970 baseline, seemingly
ample justification for recent concern about the health of inland water ecosystems
and the status of their biodiversity.

25

Freshwater Biodiversity: a preliminary global assessment

Figure 1. Population trends in sample of inland water species

100% 7 --p—- - -- ees
Qe spe slh oles seo | ee ess
80% + - - Aimed - - -- - Ge - - -
70% + - - Ramm - - - - ~*~ =~
al |6hlh Gincreasing

Ostable
Midecreasing

50% + - - fim - - - - - GM - ~~

40% + - - (RM - - - - - Gee -

30% + - - fem - --- - Ge - - -

20% + - - Mime ---- - Ge - - - -

10% + - - MMMM - - - - - GM -

0% +

pre 1970s 1970s
n=8 n=14

Notes: derived from qualitative trend information on freshwater and wetland species (19 mammals, 92 birds, 72
reptiles, 44 fishes).
Source: prepared by WCMC for WWF Living Planet Report 1998 (Loh et al., 1998); modified from Fig. 10.

Figure 2. Inland water biodiversity index

index value

(@) - T T T T =I
1970 1975 1980 1985 1990 1995
period

Notes: derived from quantitative trend information on freshwater and wetland species (3 mammals, 49 birds, 8
reptile, 10 fishes).

Source: prepared by WCMC for WWF Living Planet Report 1998 (Loh et al., 1998); modified from Fig. 2b.

26

3. Status, trends and threats

THREATENED FISHES

The distribution and systematics of fishes are inadequately known, although they are
certainly the best-known species-rich and cosmopolitan group in freshwaters; their
conservation status may exemplify the situation in other groups of organisms.
Recent experience is that wherever fish faunas are studied, more species than
suspected turn out to be threatened, or cannot be re-recorded at all (example
reviews: Moyle and Leidy, 1992; Stiassny, 1996; Reinthal and Stiassny, 1991,
Kirchhofer and Hefti, eds., 1996, and see IUCN, 1996).

Table 9. Numbers of threatened freshwater fishes in select countries

total threatened percent
species species threatened
USA 822 120 15
Mexico 384 77 20
Australia 216 27 13
South Africa 94 25 27
Croatia 64 20 31
Turkey 174 18 11
Greece 98 16 16
Madagascar 41 13 32
Papua New Guinea 195 12 6
Hungary 79 11 14
Canada 177 11 6
Spain 50 11 22
Romania 87 11 13
Italy 45 9 20
Moldova 82 9 11
Portugal 28 9 32
Bulgaria v2 8 11
Sri Lanka 90 8 g)
Germany 68 1 10
Slovakia 62 7 11
7 4

Japan 150

Notes: These are the 20 countries whose fish faunas have been evaluated completely, or nearly so, and which
have the greatest number of globally-threatened freshwater fish species.

Source: The threatened species data in this table were collated for The 1996 IUCN Red List of Threatened
Animals. The estimates of total fish species present are all approximations.

27

Freshwater Biodiversity: a preliminary global assessment

Table 9 shows a selection of the very few countries where the status of the native
fish fauna has been fully evaluated using the new IUCN threat category system. The
countries are those with the twenty highest counts of globally-threatened species (ie.
the entire species is at risk of extinction). In several countries 20-30% of the fish
species present are threatened at this level; the mean for all 20 countries listed is
around 17% (see Figure 3). This is certainly an underestimate because it covers only
the species that meet the criteria for Critically Endangered, Endangered or
Vulnerable listing under the new category system; it does not include those that are
declining in parts of the range but are not yet threatened as a species, nor those that
lack the information needed to make an assessment.

Among other freshwater groups, four of the five river dolphins and two of the three
manatees are threatened, as are several smaller aquatic mammals, also around 40
freshwater turtles, more than 400 inland water crustaceans, and hundreds of bivalve

and gastropod molluscs.

Figure 3. Freshwater fish species: percent threatened in selected countries

percent of species

Mexico pean

Madagascar [iii
South Africa
Italy

Greece |

USA
Hungary
Australia
Romania
Turkey
Moldova
Bulgaria
Slovakia
Germany
Sri Lanka

Note: these are the 20 countries with the highest numbers of globaily threatened fish species, selected from the
few countries where the fish fauna has been comprehensively assessed.
Source: based on data compiled by WCMC, in part for The 1996 IUCN Red List of Threatened Animals.

EXTINCT FISHES

A species is extinct when the last individuals have died without leaving offspring
(or, in a different sense, may be termed extinct when over evolutionary time a given
lineage has branched into two or more lineages). The fossil record suggests that
extinct species greatly outnumber living ones, perhaps by one thousand to one; this,
and evolutionary theory, suggests that extinction is probably the ultimate fate of all
species.

28

3. Status, trends and threats

Most extinctions indicated in the fossil record have taken place during about five
geologically very short periods; a corollary of this is that extinction rates have been
relatively low over geological time in general. The average lifespan of a species in
the fossil record is 5-10 million years, and if 12-13 million species now exist, the
general background extinction rate may be between one and three species per year.
For mammals, the average lifespan of species in the fossil record is one million
years, which suggests one natural extinction every 200 years among the
contemporary fauna.

Recent extinctions are likely to be recorded with significant accuracy either where
circumstances favour preservation of hard remains in good number or where
naturalists of the past century recorded the fauna or flora with sufficient care that
they set a firm baseline against which the composition of the modern biota may be
assessed. It is exceptional to observe the actual process of extinction. Typically,
many years elapse before sightings of a species become sparse enough to generate
concern, and many more years are likely to pass before negative evidence (ie. failure
to find the species) accumulaies to the point where extinction is the most probable
explanation.

Table 10. Freshwater fish extinctions: number of known species extinctions by
decade

1890s 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s

number 2 1 0 4 2 3 4 1 8 53 3
total 3 3 7 9 12 16 17 25 78 81

Notes; Data refer to globally extinct species, not national or geographic populations. 91 fish species were
listed as extinct in the wild in 1996; this table includes 50 Lake Victoria cichlids all treated here as becoming
extinct during the 1980s, and 31 other species for which estimated extinction times are available. A further 10
species could not be assigned to a decade.

Source: based on data compiled by WCMC, in part for The 1996 IUCN Red List of Threatened Animals.

Evidence for extinction of aquatic species is even less likely to be available than in
terrestrial environments. However, some 81 fish species are recorded to have
become extinct during the past century, and a further 11 are extinct in the wild but
remain as captive populations (see Table 10 and Figure 4). This is far higher than
estimated background animal extinctions. A major proportion of known
extinctions have resulted from the ecological effects of the apparently deliberate
introduction of the Nile Perch Lates niloticus into Lake Victoria in the mid-20"
century. The state of knowledge of freshwater fish faunas is so incomplete that
other species could well have been lost before being discovered by scientists and
formally described.

29

Freshwater Biodiversity: a preliminary global assessment

Figure 4. Freshwater fish extinctions: graph to show known species
extinctions by decade

number extinct

1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s
decades

Notes: Data refer to globally extinct species, not national or geographic populations. 91 fish species were
listed as extinct in the wild in 1996; this table includes 50 Lake Victoria cichlids all treated here as becoming
extinct during the 1980s, and 31 other species for which estimated dates are available. A further 10 species
could not be assigned to a decade.

Source: based on data compiled by WCMC, in part for The 1996 IUCN Red List of Threatened Animals.

GLOBAL CHANGES TO FRESHWATER SYSTEMS

Changes to the structure and quality of the freshwater environment are brought
about by many different human activities. Many such changes are sufficiently large-
scale and radical as to be obvious to a human observer (eg. dam construction);
others occur on a much smaller scale and without visible effect (eg. release of
sublethal pollutants). It is now clear that multiple habitat changes can have a
cumulative impact on freshwater species, and there is evidence of a widespread and
often severe decline in freshwater biodiversity.

External factors affecting populations of freshwater species include:
e simple habitat loss resulting from withdrawal of water for human use,

° a variety of changes in habitat condition as a direct or indirect effect of human

activities, including competition or predation by introduced non-native species,
and

e direct exploitation.

Although humans have always made use of freshwater systems and species, the last
200 years (the Industrial Revolution, the growth of cities, the spread of high-input
agriculture) have brought about transformations on an unprecedented scale. The rate

30

3. Status, trends and threats

of water withdrawal rose steeply at the start of the present century, and further after
mid-century. Over the same period the volume of river water polluted to some
degree by waste water has similarly risen.

Major changes in the distribution of water on the continents has resulted mainly
from withdrawals for irrigation, and secondarily from domestic and industrial use
(L’Vovich, et al., 1990). Other factors are impoundment, wetland drainage and
flood control. These physical changes have consequences for aquatic species: many
large reservoirs have been created, river systems have been heavily disturbed,
wetlands have been drained and the load of inorganic and organic pollutants in
flowing waters has increased. From a water quality viewpoint, the major challenge
is to address the increasing volume of polluted waste water from industrial and
agricultural processes.

The various anthropogenic factors that impact upon freshwater systems can
usefully be classified according to spatial scale and the location of effects (Table
11). As a general rule, wherever impacts have been investigated and changes in
biological diversity demonstrated, multiple factors are involved.

Table 11. Scale and source of factors impacting freshwater biodiversity (rivers)

spatial scale source of impact
Supra-catchment Acid rain
Inter-basin water transfer
Catchment Deforestation, afforestation
Urbanisation

Agricultural development
Land drainage

River corridor Flood protection
Flow regulation; dams, weirs,
channelisation
Riparian vegetation removal
Dredging, mining

In-stream Material pollution; organic, inorganic
Thermal pollution
Abstraction
Navigation
Exploitation of native species
Introduction of alien species

Source: after Boon (1992).

Acid deposition through precipitation has been recognised as a regional
transboundary phenomenon since the 1960s. Industrial emissions of sulphur and
nitrogen oxides (SO,, NO,), mainly a result of fossil fuel combustion, are the
principal source of acid rain. Most evidence of acid rain and its effects relates to

31

Freshwater Biodiversity: a preliminary global assessment

North America and Europe, but emission rates are rising steeply in rapidly
industrialising countries elsewhere. Acid rain in one country may be a consequence
of compounds released into the atmosphere by industry in another country hundreds
of kilometres distant. The geology, soil and vegetation of drainage basins will
strongly influence the acidification process: coniferous forests (with acidic leaf
litter) over granitic rocks will tend to promote acidification, whereas calcareous soils
over limestone will exert a strong buffering effect on percolating water. Acid rain
has been shown to decrease species diversity in lakes and streams. It has not been
implicated in any recorded species extinction nor any major species decline. It has
not yet been shown to be a significant issue in tropical freshwaters, where global
freshwater diversity is concentrated.

Removal or extension of forest cover, or any anthropogenic interference with soils
and land cover (eg. agriculture, urbanisation, road construction, mining), will
modify the rate of runoff from catchment slopes and also the density of particles
carried in the drainage system. All moving waters will carry some mass of
suspended material, and there is considerable natural variation in this in space and
time, but logging can increase sediment load by up to 100% for a short period, and
20-50% over the longer term. Sediment reaching lakes will be deposited and in
effect enter long-term storage; depending on water velocity, sediment in rivers will
settle out on floodplains or other parts of the course, or be carried into the coastal
marine environment.

Increased sedimentation can have several effects on aquatic biodiversity: deposition
can radically change the physical environment of species restricted to particular
conditions of depth, light penetration and velocity; it is a major carrier of heavy
metals, organic pollutants, pathogens and nutrient; it can interfere mechanically with
respiration in gill-breathing organisms; and it can damage coral reef systems in the
coastal environment.

Floodplain areas of large rivers tend to be regarded as wasteland suitable for
draining and agricultural development; this destroys highly productive floodplain
fisheries and modifies flow in the main course.

Dam construction and channelisation also strongly disrupt natural production cycles,
including migration of fishes that ascend rivers from downstream areas or the sea in
order to spawn. A review of hydrological change in the northern hemisphere as a
result of dams and flow regulation is provided by Dynesius and Nilsson (1994). Fish
production can be maintained or increased in some circumstances, in reservoirs or
floodplain canals, although natural aquatic biodiversity is expected to decrease. For
example, dam construction has so severely disrupted flow in the Colorado River

32

3. Status, trends and threats

(USA) that all native fishes in the lower reaches are in decline or extirpated (Moyle
and Leidy, 1992).

Dam construction is the prime cause of extinction in the gastropod fauna of the
Mobile Bay drainage in USA. Historically, the freshwater snail fauna of Mobile Bay
basin was probably the most diverse in the world, followed by the Mekong River.
Nine families and about 118 species were known at the turn of the century to occur
in the Mobile Bay drainage. Several genera and many species were endemic,
particularly in the Pleuroceridae. Recent surveys suggest at least 38 species are
extinct (32%); decline in species richness ranges between 33% and 84% in the main
river systems. The richest fauna was in the Coosa River and this system has
undergone the greatest decline (from 82 to 30 species). Almost all the snail species
presumed extinct were members of the Pleuroceridae and grazed on plants growing
on rocks in shallow oxygen-rich riffle and shoal zones. The system has 33 major
hydroelectric dams and many smaller impoundments, as well as locks and flood
control structures. A combination of siltation behind dams, and submergence of
shallow water shoals has removed the snails' former habitat. Where habitat remains
it has diminished in area and become fragmented.

Globally, pollution and habitat modification are the most widespread and pervasive
factors known to cause decline in fisheries. Water quality maintenance has generally
been given much lower priority than industrial growth, and many river systems in
developed countries are degraded as a result. Some countries have devoted resources
to habitat restoration, with recent evidence of success. For example, the Rhine was a
wild salmon-rich river two centuries ago, but by the 1970s, heavy pollution
(combined with dam construction, channelisation, floodplain modification, and
introduction of non-native fishes) led to marked decrease in populations of many
fish species and collapse of fisheries. Since the end of the 1970s, water quality has
improved and the decline in populations has slowed or reversed (Lelek, 1989, 1996).

Many smaller lakes have been affected, particularly by domestic and industrial
wastes, and fisheries have declined or disappeared. Low levels of nutrient
enrichment may stimulate production. There is growing concern for larger lakes,
including the Rift Valley system in eastern Africa, where increased urbanisation and
agricultural development are affecting catchment areas, with eg. increased sediment
loads entering lake waters locally. The impact of these developments on biodiversity
and fisheries is not known in detail.

There are major regional differences in the present and expected future impact on

biodiversity and fish production of habitat degradation. Some of the most developed
countries appear to have passed the peak of freshwater habitat modification, and are

33

Freshwater Biodiversity: a preliminary global assessment

investing in water quality controls and rehabilitation measures. Some of the
countries that are now undergoing rapid industrial development are a considerable
distance from this state, and their freshwater habitats are likely to come under
increasing pressure in coming years. The heaviest impacts are likely to be felt in
eastern Europe, South and South-east Asia, with increasing industrial effluent and
hydroelectric development, and in Africa, where water extraction and agricultural
development for increasing human populations may be the principal impacts.

Unplanned or poorly planned introduction of non-native species and genetic stocks
is a major threat to freshwater biodiversity (eg. Moyle, 1996). Such introductions
can have negative or positive effects on fishery production. Table 12 and Figure 5
show the scale of introductions in recent decades; it is a reasonable assumption that
all successful introductions will have an impact on existing population levels and
community structure, and many changes are likely to be undesirable.

Lake Victoria, the largest tropical lake in the world, provides a classic example of
the potential negative impacts of species introductions. Until some 30 years ago,
when the large top predator, the Nile Perch Lates niloticus, was introduced, the lake
supported an exceptional 'species flock’ of around 300 species of haplochromine
cichlid fishes as well as smaller numbers from other families. Not all the species
have yet been formally described; many of these are known among aquarists and
others only by informal common names. At least half and up to two-thirds of the
native species are believed to be extinct or so severely depleted that too few
individuals exist for the species to be harvested or recorded by scientists. The
evolutionary processes behind this adaptive radiation, involving an immense variety
in teeth and jaw morphology and feeding niches, have been the subject of
considerable scientific research which has contributed to development of modern
theories of evolutionary diversification. Additional factors in decline of the Victoria
cichlids are excess fishing pressure, already evident before introduction of Nile
Perch, and possible competition from tilapiine cichlids that were also introduced.
The lake itself has now become depleted of oxygen, and a shrimp tolerant of
oxygen-poor waters provides a major food source for the Nile Perch. In recent years
the Nile Perch, and one of the introduced tilapiines form the basis of a high-yielding
fishery, and an important national and export trade. It is unlikely that such high
yields will be maintained.

Although it is of interest to distinguish the general factors that adversely affect
freshwaters and their biodiversity, it is more useful from a management viewpoint to
distinguish the various specific types of impact and the specific human activities that
generates those impacts. Richter et al. (1997) termed these ‘stressors’ and ‘sources’
respectively, and analysed expert opinion on their identity in relation to more than

34

3. Status, trends and threats

100 threatened aquatic species in the USA. Some 40 individual stressors were
identified, grouped into six principal classes.

Table 12. Fish introductions: inland species by continent and decade

decade Africa Asia+ Europe Mid NAm _ Oceania S Am " decade running

‘USSR East total total
ancient 0 1 4 0 1 1 Olan 7,
pre (0) 4 9 0 0 0 0 13 20
1850
1850 2 0 0 0 0 0 2 4 24
1860 1 0 2 0 0 5 1 9 33
1870 0 3 9 0 0 6 2 20 53
1880 0 2 27 0 3 0 1 33 86
1890 2 1 27 0 4 0 4 38 124
1900 3 6 14 ) 1 10 17 51 175
1910 6 11 5 0 1 0 5 28 203
1920 19 6 14 1 2 9 8 59 262
1930 16 11 14 1 1 17 65 327
1940 12 10 4 1 0 21 53 380
1950 67 21 11 1 9 13 44 166 546
1960 44 37 40 7 10 21 41 200 746
1970 35 20 43 1 3 11 175 921
1980 1 7 14 0 2 37 62 983

“total 208 140 ey ae 35 80 271 983

Source: compiled from data in Welcomme (1988).

Figure 5. Fish introductions: graph to show known inland species introductions by
decade

:

teem decade total
—@— cumulative total

number of species introduced

Source: compiled from data in Welcomme (1988).

35

Freshwater Biodiversity: a preliminary global assessment

The threat classes identified were reported to arise from a relatively small number of
primary sources, chiefly from different kinds of land use. Analysis of reported
stressors and their sources for all 135 threatened species assessed indicates that three
fundamental threat sources are most important (1-3 in Table 13). However, there
was significant variation in results with respect to the groups of organism assessed,
their geographic origin within the USA, and to historic versus current conditions. An
important conclusion from this analysis is that it is not possible to derive a single
global ranking of threats and their effects to guide conservation action; it will always
be essential to evaluate local history, local conditions and individual species ecology
in order to focus management efforts.

Table 13. Summary of sources of stressors affecting threatened aquatic species in
USA

primary source of threats

1 Agricultural land use

2 Power generation

3. Exotic species

threat classes

agricultural non point source
pollution

impoundment operations for
hydroelectric and agricultural
purposes

introduced non-native species

effects

Streambed sedimentation,
suspended sediment loading,
nutrient loading

altered hydrology, habitat
destruction and fragmentation

competition, genetic alteration,

parasitism, predation

4 Municipal land use pollution, land/waterway

conversion

Note: information relates to analysis of species in USA.
Source: summarised from text in Richter et al., (1997).

THE STATUS OF LAKES

Although there is much evidence for widespread decline in the health of many
freshwater habitats, this is very variable in scope and quality. We have attempted to
derive a semi-quantitative global assessment of change over recent decades in the
condition of freshwater lakes. The study is based on Project Aqua, a project initiated
by the Societas Internationalis Limnologiae in 1959, with the aim of documenting
information on more than 600 water bodies judged worthy of conservation. A
provisional list was issued in 1969 by the International Biological Programme, and a
revised enlarged version was published with the additional support of IUCN in 1971
(Luther and Rzéska, 1971). So far as possible, data on each system were collated by
national or regional specialists and presented in a standard numbered format; the
information relates essentially to the 1960s.

36

3. Status, trends and threats

A substantial number of systems treated in Project Aqua are also treated in later
information sources, and in these cases it is often possible, taking the 1960s data as a
baseline, to make an assessment of condition at a later time point and determine the
direction of change. Of later sources, we have relied mainly on volumes such as The
Directory of Asian Wetlands (Scott, 1989) and companion works dealing with other
continents. The directories in many cases contain information relating to the 1980s
and 1990s. We have also extracted information, often from the 1990s, from the
Lakes Database (see references for web address) maintained by the International
Lake Environment Committee Foundation. We have compared available entries (at
least two, sometimes three) for 93 systems and scored each according to whether its
condition appears to have deteriorated (or impacts have increased), improved, or no
change is reported (this can mean ‘no new information’).

Table 14. Change in lake condition: a preliminary assessment

number in worse és better
sample
AFRICA 20 8 i 1
ASIA 24 16 fl 1
CENT & S AMERICA 9 7 2 0
AUSTRALIA 3 1 2 0
EUROPE 37 23 13 1

total 93 55 35 3

Note: sample of 93 lakes (and a small number of other wetland types); “worse” = condition deteriorated or
impacts increased; “*?” = no change reported; “better” = condition improved or remedial measures reported.
Source: data sources cited in text; prepared by WCMC for WWF Living Planet Report (Loh et al., 1998).

Figure 6. Changes in condition in a sample of lakes worldwide

100%
90%
80%
70%
60%
50%
40%
30%
20%
10%

0%

Eibetter
oO?
@iworse

percent In each category

Se ae ea

AFRICA ASIA CENT&S AUSTRALIA EUROPE
AMERICA

Note: sample of 93 lakes (and a small number of other wetland types) ); “worse” = condition deteriorated or
impacts increased; “?” = no change reported; “better” = condition improoved or remedia! measures reported.
Source: data sources cited in text; prepared by WCMC for WWF Living Planet Report (Loh et al., 1998).

37

Freshwater Biodiversity: a preliminary global assessment

The results are based on uneven sampling and non-standard reporting, but may be
taken as valid indication of the general direction of change in recent decades (see
Table 14). Most lakes in the sample have declined in quality, particularly those in
Asia. However, not all remedial measures taken within the past ten years or so, or
their beneficial effects, will have been reported in the information sources used. The
data are graphed as percentages in Figure 6.

38

4. IMPORTANT AREAS FOR FRESHWATER
DIVERSITY

If sites or areas of high diversity, often termed ‘hotspots’, can be identified, there
is an opportunity to implement measures to conserve biodiversity and manage land
use in a concerted and cost-effective manner. In the context of biological diversity,
the word ‘hotspots’ was originally applied during the late 1980s to areas in tropical
forest regions that each supported high concentrations of plant species found
nowhere else, and which in most cases were also suffering higher than average
rates of deforestation (Myers, 1988, 1990). The central point was that, although
not necessarily small in absolute terms (the hotspots included entire islands, such
as New Caledonia and Madagascar, and large sections of countries, such as all of
Peninsular Malaysia) they included so many endemics that they collectively
supported a large proportion of the world’s total flora on a relatively small
proportion of the world’s surface. The term ‘hotspots’ is now widely applied to
any area that appears to be of especially high biodiversity value.

Considerable interest remains in identifying hotspots. This is partly because of the
scientific interest attached to the search for natural patterns in the distribution of
species, but primarily because conservation measures undertaken in ‘hotspot’ areas
can in theory be extremely cost-effective because of the amount of biodiversity
that can be maintained per unit cost.

Large and long-lived lakes have long been known to support high diversity in
fishes, molluscs, crustaceans and others, sometimes in several groups (see Table
15). As sources of unique lineages, these lakes are indeed ‘hotspots’, and are the
aquatic equivalents of islands such as Hawaii or the Galapagos.

However, lake sites are relatively easy to assess and compare, simply because
lakes typically have clear and permanent boundaries. It is a much greater challenge
similarly to identify, delimit and compare other areas important for freshwater
biodiversity. This is in part because geographic boundaries are diffuse or otherwise
difficult to determine, and in part because available diversity data are very sparse
and have not been collected in a manner that allows standardised comparisons to
be made.

For the present study, we have collated the preliminary views of a number of leading
systematists and aquatic biologists (see Acknowledgements) on the identity of areas
of special importance for a selection of key animal groups (freshwater fishes,
molluscs, crayfish, crabs, and fairy shrimps). This ‘expert opinion’ approach is

39

Freshwater Biodiversity: a preliminary global assessment

Table 15. Physical and biodiversity features of major long-lived lakes

Lake

Baikal

Largest, deepest,
oldest extant
freshwater lake

(20% of all liquid
surface fresh water on
Earth)

Tanganyika

Victoria

world’s second largest
freshwater lake (area)

Malawi

Titicaca
world’s highest

navigable lake

Biwa

Ohrid

fed mainly by
subterranean karst
waters

country

Russia

Burundi,
Tanzania,
Zambia, Zaire

Kenya,
Tanzania,
Uganda

Malawi,
Mozambique
Tanzania

Bolivia, Peru

Japan

Albania,
Macedonia
(FYR)

age
(mill.
yrs)

25-30

20

>47?

>>2

max
depth
(m)
1,637

1,470

/ 70

780

295

vol.

(km’)

23,000

18,880

2,760

890

674

50

biodiversity

very high spp richness, exceptional ‘endemism
in fishes and several invertebrate groups

total animal spp: 1,825 endemic: 982

fishes: 56 spp., 27 endemic

very high spp richness, high endemism,
especially high among cichlid fishes

total animal spp: 1,470 endemic: 632

fishes: 330 spp., 241 endemic
high spp richness, especially of fishes
exceptional endemism among cichlid fishes

many fish endemics depleted or extirpated
following introduction of Nile Perch

fishes: ca 290 spp., ca 270 endemic
very high spp richness, high endemism,
especially high among cichlid fishes

fishes: ca 640 spp., >600 endemic

more fish species than any other lake

moderate species richness ‘and endemism
(highest among fishes)

total animal spp: 533 endemic: 61

fishes: 29 spp., 23 endemic

moderate species richness and endemism
(highest in gastropod molluscs and fishes)

total animal spp: 595 endemic: 54

fishes: 57 spp., 11 endemic

moderate species richness, exceptional
endemism in several groups (planarians,
oligochaetes, gastropod molluscs, ostracod
crustaceans)

fishes: 17 spp., 2 endemic

Notes: 1) A few other lakes have notable endemism among fishes, molluscs, crustaceans or other groups —
among these are lakes Inle (Myanmar), Lanao (Phillippines); Malili (Indonesia) and the Cuatro Cienegas basin
(Mexico) — but their ages are not yet firmly established. 2) Qualitative remarks (eg. “very high”, “low”) in the
‘biodiversity’ column are related to long-lived lakes, not to lake systems in general.

Source: collated from data in Martens er al., 1994.

40

4. Important areas for freshwater diversity

valuable in making effective use of readily available information, and although
preliminary, has yielded the first global overview of freshwater biodiversity
hotspots. Kottelat and Whitten (1996) have reviewed many aspects of freshwater
biodiversity in Asia, including discussion of taxonomy, hotspots and policy.
Regional assessments for Latin America (Olson et al., 1997) and North America
(Abell, et al., 1998) are now available.

Although this indicative synthesis has a real heuristic value, it has not yet been
possible to evaluate candidate areas against a globally consistent set of spatial and
diversity criteria. A more comprehensive global analysis will require development
of such criteria, and a prolonged phase of research and international consultation;
we believe this is well justified by the results of the present study.

Table 16 lists in summary form some of the sites and areas that have been
identified as of special importance for more than one of the groups (fishes,
molluscs, crabs, crayfish, fairy shrimp). It is not intended to be a comprehensive
global listing: it omits the large but imprecisely defined areas of known high
diversity as listed more fully in Table 17; it omits diverse taxa not covered in this
assessment (eg. amphipods, copepods, etc); and it does not mention sites of key
importance mainly for one group of animals. See Maps 2-5; Map 2 shows the
general location of areas noted in Table 16.

The fact that only two regions in South America are listed reflects the continuing
lack of detailed information for taxa other than fishes. On the evidence of fishes
alone the Amazon basin is likely to be exceptionally rich in other freshwater
groups, but although known to be rich in freshwater crabs, for example, it is not
possible to delimit special areas within the basin. However, this table is a valid
reflection of current information and begins to meet the need for global
information on the relative importance of hotspots of freshwater biodiversity.

This summary should be consulted in conjunction with Table 17, which outlines

biodiversity and geographic information distilled from the material provided by
contributors.

41

Freshwater Biodiversity: a preliminary global assessment

Table 16. Partial list of global hotspots of freshwater biodiversity

continent area name groupl # group2 # group3 #

Africa 1 L Malawi fishes 15 molluscs 27 i cr

Africa 2 L Tanganyika fishes 17 molluscs 28 crabs 1

Africa 3 L Victoria fishes 19 molluscs 29

Africa 4 Madagascar fishes 20 molluscs 31 crabs 3

Africa 5 Niger-Gabon fishes 21 crabs 4

Africa 6 Upper Guinea fishes 2 molluscs 32 crabs 6

Africa 7 lower Congo fishes 9 crabs 2

Eurasia. 8 SE Asia and Lower fishes 71 molluscs 89 crabs 48

Mekong River

Eurasia 9 Balkans (southwest) fishes Uy molluscs 82

Eurasia 10 L Baikal fishes 60 molluscs 84

Eurasia 11 L Biwa fishes 61 molluscs 85

Eurasia 12 LInle fishes 63 molluscs 86

Eurasia 13 L Poso fishes 65 molluscs 88

Eurasia 14 Malili Lakes fishes 72 molluscs 88

Eurasia 15 Sri Lanka fishes 78 crabs 51

Eurasia 16 Western Ghats fishes 81 molluscs 90 crabs 50

Aus 17 SE Australia & Tasmania _ fishes 40,42 molluscs 46 crayfish a

Aus 18 SW Australia fishes 41 fairy 35
oe SDEIND oo

N Am 19 East Mississippii drainage _ fishes 96 molluscs 109 crayfish 92

(Ohio, Cumberland,
Tennessee rivers)

NAm 20 Mobile Bay drainage fishes 104 molluscs 108 crayfish 92

NAm 21 western USA fishes 93 molluscs 105 fairy 93
shrimp

S Am 22 L Titicaca fishes 119 molluscs 134

S Am 23 La Plata drainage fishes 118 molluscs 135,136

Notes: this table includes sites and areas noted in Table 17 (important areas...) that are identified as of
particular importance for more than one of the groups discussed; see relevant entries in Table 17 for
description; # - key to area code number in Table 17; the table is not intended to include all areas of global
importance for freshwater diversity

Sources: See sources cited at end of Table 17.

42

4. Important areas for freshwater diversity

Table 17. Important areas for freshwater biodiversity

area name

AFRICA

L. Tanganyika

group

crabs

remarks

Lake Tanganyika is the only East African Great Lake where
endemic species of freshwater crabs occur: of the 9 species and 2
genera present, one genus and 7 species are endemic. [NC/RvS]

lower Congo

crabs

Diversity is marked in the Congo river basin, but appear highest in
two areas, the lower parts of the basin (including Congo, Cabinda
and former Zaire) and the upper reaches (including

Madagascar

Four genera and 10 species of freshwater crabs, all endemic, occur
in Madagascar. [NC/RvS]

Niger-Gabon

crabs

Southeast Nigeria, southern Cameroon, and Gabon: 3 endemic
genera and more than 10 endemic species of freshwater crabs
(Cumberlidge, 1998). [NC/RvS]

upper Congo

crabs

Diversity is marked in the Congo river basin, but appear highest in
two areas, the lower parts of the basin (including Congo, Cabinda
and former Zaire) and the upper reaches (including
Rwanda/Burundi and parts of former Zaire). [NC/RvS]

Upper Guinea

crabs

Upper Guinean rainforest, centred on Guinea, Sierra Leone, Liberia,
and western Cote d'Ivoire (including Mount Nimba): 2 endemic
genera and 5 endemic species of gecarcinucids (Cumberlidge,
1996a,b, 1998; Tiirkay & Cumberlidge, 1998). [NC/RvS]

southern Africa

2 endemic genera, 45 species, 38 endemic.South Africa proper: 34
species, 22 endemic. [DB]

Cape rivers

With 4 families and 33 species the fish fauna of Southern Africa is
rather poor in comparison with most other parts of the continent;
most species are cyprinids. However, there is marked local
endemism; most rivers in the southern Cape region have three or
four native endemics (several species are threatened). [WCMC]

Congo (Zaire)
basin

fishes

General region of very high richness; second only to the Amazon
basin in species richness. 25 families and 686 species have been
reliably reported from the Congo/Zaire basin, excluding Lakes
Tanganyika and Moero (Teugels and Guegan, 1994). Around 548 of
the species present (c 70%) are endemic to this basin. The basin can
be divided into four sections: Upper Lualaba, Cuvette Centrale,
Luapula-Mweru, and the rapids.. [WCMC]

10

Congo 'cuvette
centrale’

fishes

High richness plus marked endemism.. Around 690 species occur in
the Congo system; the Cuvette Centrale section possibly has the
highest species richness owing to the great diversity of freshwater
habitats available. [WCMC]

43

Freshwater Biodiversity: a preliminary global assessment

area name group remarks

11 Congo rapids fishes High richness plus marked endemism. The rapids between Kinshasa
and the sea have a high concentration of fish species (150 species),
34 of which are endemic to this section. The caves near Thysville
are fed by the Congo system and support one of Africa’s few true
hypogean fishes Caecobarbus geertsi. Caecomastacembelus
brichardi and Gymnanallabes tihoni, not strictly cave fishes, have
been collected in the Stanley Pool in riffles under flagstones or in
crevices. [WCMC]

12 Cross River fishes Nigeria-Cameroon. 42 families, 166 species (Teugels et al., 1992);
very high species diversity compared to the relatively modest
catchment area, and marked endemism. Transitional ichthyofauna
between the Nile-Sudan province and the Lower Guinea province.
[WCMC]

13 L. Barombi-Mbo fishes This small (c 4.5 km2 ) crater lake in Cameroon has 15 species
(plus another two present in the inflow stream, not the lake proper).
At least 12 of the species are endemic, notably the 11 cichlids that
form one of the two recorded ‘species flocks’ in West Africa. 4 of
the five cichlid genera are endemic: Konia, Myaka, Pungu and
Stomatepia. This very important site is at risk from over-fishing, the
effects of introduced crustaceans and fishes, siltation from local
deforestation and water pollution. [WCMC]

14 L. Bermin fishes A very small (c 0.5 km2) crater lake in southwest Cameroon with 2
non-endemic fishes and a remarkable species flock of 9 tilapiine
cichlids. The cichlids are very small in size and not exploited; they
are at some risk because of the very small distribution and
deforestation in the surrounding area. [WCMC]

15 L. Malawi fishes 30,800 km2.12 families, more than 645 species, most of them
endemic to the lake. Rich species flocks among Cichlidae, and a

16 L. Tana fishes The fish fauna of this large (3,150 km2) lake includes 21 species in
4 families and is dominated by lake endemic cyprinids. The large
Barbus cyprinids form one of two recorded cyprinid species flocks
(the other being that of Lake Lanao in Philippines, many species of
which are severely threatened). [WCMC]

17 L. Tanganyika fishes 32,000 km2. In the lake itself, 16 families, more than 165 species of
cichlids and 72 non-cichlid species. Several ‘species flocks’ are
present not only in Cichlidae, but also among Clariidae, Bagridae,
Mochokidae, Centropomidae, Mastacembelidae. In the whole
Tanganyika basin, there are 21 fish families (7 endemic to Africa),
at least 185 cichlid species (180 endemic), and 145 non-cichlids (61

18 L. Turkana fishes 6,750 km2. 51 species, 35 genera, 17 families. High family and

generic diversity, many of the species are lake endemic; cyprinids
form the most diverse family. [WCMC]

44

4. Important areas for freshwater diversity

area name group remarks

19 L. Victona fishes 68,800 km2. 12 families, 238-288 species (many undescribed).
High species diversity dominated by cichlids. The majority of
species are lake endemic. [WCMC]

20 Madagascar fishes Around 140 fish species have been recorded from brackish and
freshwaters of Madagascar (Stiassny & Raminosoa, 1994), although
species richness is not remarkable, endemism is high. Two endemic
families (Bedotiidae and Anchariidae) have been recognised in
Madagascar, as well as 13 endemic genera and 43 endemic species.
Most endemic species are restricted to freshwater habitats, mainly
in eastern forested regions. About one quarter of endemic species
are known only from the type locality. Blind cave fishes have been
described from Madagascar: the gobiid Glossogobius ankaranensis,
and the elotrids Typheleotris madagascarensis and T. pauliani.

21 Niger basin fishes General region of high richness. 36 families, around 243 species,
with 225 primary freshwater species (Teugels and Powell, 1993 and
unpublished data). Endemism moderate: 20 species endemic to
Niger. The basin includes 11 of the 13 primary freshwater families
that are endemic to Africa. Teugels and Powell (1993 and
unpublished data) reported 164 primary freshwater fishes from the
Niger delta in Nigeria, based on reference specimens for each
species; the high diversity (73 % of the freshwater species in the
entire basin) in this area is seriously threatened by oil-pollution.
[WCMC]

DD Ntem River fishes Cameroon. High richness for area, plus marked endemism. 16
families, 94 species, 8 endemic. [WCMC]

23 Ogooue (Ogowe) fishes Gabon. High richness for area, plus marked endemism. 23 families,
River 185 species, 48 species endemic to Ogowe. A relatively small

drainage basin with a very high concentration of species. Many of
the families represented are endemic to Africa. Available data
certainly underestimate actual diversity (several new species are
now being described, resulting from a collaborative project of
Tervuren Museum, the American Museum of Natural History and
Cornell University). [WCMC]

24 Sanaga River fishes Cameroon. 21 families; high concentration of species in a small
river basin; probably at least 135 (and this figure is believed to be a
significant underestimate) (Teugels and Guegan). Between 10 and
18 species endemic to the Sanaga. [WCMC]

25 Upper Guinea fishes High richness for area, plus marked endemism. The Upper Guinea
rivers province includes coastal rivers from south of the Kogon River in

Guinea, to Liberia, and has faunal affinities with the lower Guinea
province and the Congo/Zaire. The fauna includes many taxa
endemic to the area (Lévéque et al., 1989; Lévéque et al., 1990,
1992). Many small river basins, many of them still poorly
investigated. Konkoure River (Guinea): 19 families, 85 species, at
least 10 endemic species. Kolente or Great Scarcies River (Guinea-

45

Freshwater Biodiversity: a preliminary global assessment

area name group remarks

Sierra Leone): 19 families, 68 species. Jong River (Sierra Leone):
20 families, 94 species. Saint-Paul River (Liberia): 19 families, 76
species. Cess-Nipoué River (Liberia-Cote d'Ivoire): 20 families, 61
species. [WCMC]

26 Volta basin fishes General region of high richness. 27 families, about 139 species, 8
endemic to Volta basin. High species richness with 9 of the 13
African endemic primary freshwater fish families represented
(Lévéque, 1997). [WCMC]

27 L. Malawi moll. Gastropods: 28 species, 16 endemic; 7 Endangered, 1 Vulnerable in
1996. Bivalves: 9 species, 1 endemic. [MSG]

28 L. Tanganyika moll. Gastropods: 68 species, 45 endemic. 32 Endangered. Bivalves: 15
species, 8 endemic. [MSG]

29 L. Victoria moll. Gastropods: 28 species, 13 endemic; 5 Endangered, 1 Vulnerable in
1996. Bivalves: 18 species, 9 endemic. [MSG]

30 Lower Congo moll. The region downstream of Kinshasa in Congo and Congo (DR)
basin (former Zaire). Gastropods: 96 species, 24 endemic, 1 Endangered,
2 Vulnerable.Endemic Gastropods are almost all prosobranchs; 5
endemic 'rheophilous' (specialised for life in the rapids) genera,
belonging to the Bithyniidae (Congodoma, Liminitesta) and
Assimineidae (Pseudogibbula, Septariellina, Valvatorbis).
Bivalves: no data. [MSG]

Si Madagascar moll. Gastropods: 30 species, 12 endemic, of which 1 Endangered. Genus
Melanatria endemic. Bivalves: no data. [MSG]

32 Western lowland moll. Upper Guinea region in Ghana, Cote d'Ivoire, Sierra Leone, Liberia,

forest and Volta Guinea. Around 28 gastropod species of which 19 endemic (and 9
basin near-endemic). 2 species ranked Critically Endangered in 1996.

Bivalves: no data. [MSG]

AUSTRALASIA
33 New Guinea- crabs The Mollucas, New Guinea and northern Australia: more than 30
Australia species of freshwater crabs belonging to 5 genera, all in the
Parathelphusidae. [NC/RvS]
34 SE Australia Cray large area of high richness and endemism, centred on Victoria, 35

fish spp. and Tasmania, 19 spp. [KC]

35 SW Australia fairy 19 species, 12 endemic. [DB]

46

4. Important areas for freshwater diversity

area name group _—s remarks

36 Fly River fishes High species richness, 103 species in Fly proper, and high local
PNG endemism, 12 endemics in system. [GA]

3i7/ Kikori River fishes Headwaters of Kikori and Purari systems, with Lake Kutubu. High
Lake Kutubu, richness, 103 species and high endemism, 16 species in Kikori; plus
PNG 14 species in Lake Kutubu. [GA]

38 Kimberley fishes 14 endemic species (a density second only in Australia to Tasmania
District, WA and equal to southwest Western Australia), including 5 species

within Prince Regent Reserve and 4 in the Drysdale River area); and
47 species in total. [GA]

39 Aikwa (Iwaka) R. fishes River near Timiki, Irian Jaya. High species richness: around 78
Irian Jaya species. [GA]

40 SE Australia fishes 11 endemic species occur in coastal southeast Australia, a lower
count per area than the other three areas cited here, and 42 species
in total. [GA]

41 SW Western fishes There are 9 endemic species (ie. density similar to the Kimberleys),
Australia and 14 species in total. [GA]
42 Tasmania fishes 12 endemic species, a greater number per area than anywhere else

in Australia, including 6 concentrated in the Central Plateau area;
and 24 species in total. [GA]

43 Vogelkop, fishes Moderate richness with high local endemism, around 14 endemic

Irian Jaya species, including Triton and Etna Bay lakes. [GA]

44 Great Artesian moll. Springs and underground aquifers. Important area of gastropod
basin, Australia diversity. Bivalves: no data. [MSG]

45 New Caledonia _— moll. Springs and underground aquifers. Gastropods: 81 species, 65
endemic; 40 Vulnerable, 3 Endangered, 1 Extinct. Bivalves: no
data. [MSG]

46 Western moll. Springs and underground aquifers. Important area of gastropod
Tasmania, diversity. 4 species Extinct. Bivalves: no data. [MSG]
Australia

EURASIA

47 Indonesia crabs The area comprising Sumatra, Java, Borneo, Sulawesi and the

southern Philippines has the greatest freshwater crab diversity in
Indo-Australia, with representatives of the Parathelphusidae (10
genera and 71 species) and the Gecarcinucidae (5 genera and 21
species). [NC/RvS]

47

Freshwater Biodiversity: a preliminary global assessment

48

49

50

51

53

54

55)

area name

Myanmar-
Malaysia

south China

south India

Sri Lanka

Italy

Borneo highlands

Caspian Sea

Central Anatolia

group

crabs

crabs

crabs

crabs

fairy
shrimp

fishes

fishes

fishes

remarks

Northeast India (Assam), Myanmar, Thailand, the Mekong basin in
southern Indochina, to the Malaysian peninsula and Singapore. In
this region there are an estimated 30 genera and over 100 species of
freshwater crabs in three families, the Potamidae, the
Parathelphusidae and the Gecarcinucidae (Alcock, 1910; Bott,
1970b; Ng, 1988; Ng & Naiyanetr, 1993). [NC/RvS]

Only the Potamidae occur in China, but more than 160 species and
subspecies in 22 genera are present, most of which are endemic.
The southern provinces of China represent the hotspot of
biodiversity for this country (Bott, 1970b; Ng & Dudgeon, 1991;
Dai, Zhou, & Peng, 1995; Tiirkay & Dai, 1997; Dai, 1997; Dai &
Tiirkay, 1997). [NC/RvS]

The freshwater crabs of the Indian peninsula south of the Ganges
basin are all endemic to the subcontinent and belong to two
families, the Gecarcinucidae and the Parathelphusidae (Alcock,
1910; Bott, 1970b). The west coast of the peninsula and the south
show most diversity: an estimated 7 endemic genera and about 20
endemic species in two families (the Parathelphusidae and the
Gecarcinucidae). A third freshwater crab family, the Potamidae, is
found only in northern India but is not represented in the Indian
Peninsula. [NC/RvS]

Sri Lanka: some 16 endemic species of freshwater crabs belonging
to three genera, one of which (Spiralothelphusa) is endemic to the
island (Bott, 1970c; Ng, 1995). [NC/RvS]

16 species, 7 endemic. [DB]

The fish fauna of the highlands of Borneo seems to be poor in
absolute number of species, but many of them have developed
specialisation for hill-stream habitats and are endemic to single
basins. The area is still largely unsurveyed. About 50 known
endemic species, but actual figure might be over 200 (Kottelat ef
al., 1993). [MK]

Moderate species richness; although many species are shared with
the Black Sea region, and/or the Aral basin, there is marked
endemism, including the monotypic lamprey Caspiomyzon, around
one dozen gobies, including monotypic genera Asra and
Anatirostrum, also 3 Alosa. [WCMC]

An arid plateau with several endorheic lakes. About 20 endemic
species, apparently underestimated by inadequate taxonomy.
Adjacent areas also have a number of endemics. In urgent need of
critical reassessment, probably one of the most poorly known fish
faunas in Eurasia. [MK]

48

56

57

58

59

60

61

62

63

area name group
Coastal

peatswamps and
swamp forests of

fishes

Malaysia, Sumatra
and Borneo

Coastal rain forest fishes
of southeast Asia

High Asia. fishes
Karstic basins of __ fishes
Yunnan, Guizhou

and Guangxi

L. Baikal, fishes
Siberia

L. Biwa, fishes
Japan

L. El'gygytgyn, fishes
Siberia

L. Inle fishes
Myanmar/Burma

L. Lindu, fishes
Sulawesi

4. Important areas for freshwater diversity

remarks

Includes Bangka island. Extent along eastern coast of Borneo not
known. Probably formerly present on Java but apparently cleared.
About 100 endemic species in peat swamp forests, an habitat type
often restricted to a narrow fringe along the coasts, still largely
unsurveyed. Although peat swamps are traditionally considered as
an habitat with poor diversity, good data for limited areas in Malay
Peninsula and Borneo indicate that up to 50 species may be found
within a small area (less than 1 km2), about half of them endemic
and stenotypic. Mosi species have small distribution ranges (some
possibly only a few km2) (Kottelat et al., 1993; Ng, 1994; Ng et al.,
1994; Kottelat & Lim, 1995). [MK]

Thailand, Cambodia and southern Vietnam. Southern extent not
known accurately. This habitat is largely destroyed in Thailand, and
virtually unsurveyed in Cambodia and Vietnam. Endemic species
expected in peat swamp forests (Kottelat, 1985, 1989). [MK]

Boundaries not known with accuracy; includes the Tibetan plateau
and probably parts of Chinese Turkestan. Distribution and
ecological data are sparse outside the Chinese literature. About 150
known fish species, about half of them endemic to this area (Wu &
Wu, 1992). Survey probably still superficial as a result of
difficulties of access. [MK]

Boundary not known with accuracy. About 14 known species of
cave fishes. Survey is still superficial and numerous additional
species are expected (Chen & Yang, 1993, updated). [MK]

A species flock of 36 species of the family Cottidae (sculpins)
(including the endemic "family" Comephoridae), 4 "ecologically
differentiated stocks" (many probably endemic species using
western concepts) of Coregonus, 2 of Thymallus, 2 of Lota (Smith
& Todd, 1984). Endemic molluscs, gammarids, sponges, and Baikal
seal. [MK]

Reportedly 4 endemic species (counted in Masuda et al., 1984).
[MK]

An old lake formed on the site of a meteorite crater. 113 km2. Total
fish diversity: 5 species, including an endemic genus and species
(Salvethymus svetovidovi), an endemic species (Salvelinus
elgyticus), and one species endemic to eastern Siberia (Salvelinus
boganidae). Endemic diatom species and apparently endemic
invertebrate(s) (Chereshnev, 1992; Chereshnev & Skopets, 1990).
[MK]

About 25 native fish species, about 10 of them endemic, including 3
endemic genera (Annandale, 1918; Kottelat, 1986). [MK]

Very limited information. One native and endemic species; others
might be expected (Kottelat, 1990a). [MK]

49

Freshwater Biodiversity: a preliminary global assessment

65

66

67

68

69

70

71

area name group
L. Poso, fishes
Sulawesi.

L. Thingvalla, fishes
Iceland.

Lakes of British _ fishes
Isles.

Lakes of Central fishes
Yunnan, China

Lough Melvin, fishes
Ireland.

lower Danube fishes
Mainland South _ fishes

East Asian hills.

remarks

10 native and endemic species, 2 endemic genera (both extinct ?)
and with lake Lindu comprises the entire known distribution of the
subfamily Adrianichthyinae (Kottelat, 1990a-c, 1991). Additional
species might still be expected. [MK]

5 native fish species, including 3 endemic Salvelinus (recent
summary in Kottelat, 1997). [MK]

A number of lakes host | or 2 species of Salvelinus, although
information on individual lakes is usually inadequate. At the
beginning of the century up to 14 species were recognised;
although generally not accepted under later systematic
conceptsmostly, recent work suggests that this figure may be
underestimated. Also at least 5 endemic Coregonus, 1 endemic
Clupeidae and potential for endemic Salmo (recent summary in
Kottelat, 1997). [MK]

Lakes Dianchi, Fuxian, Er Hai, Yangling, Yangzong, Xingyun, etc.
have a distinctive fauna; despite the lakes being now in different
river basins (Mekong, Yantgtze, Nanpangjiang), they have similar
fauna, characterized by numerous endemic species in the genera
Cyprinus, Schizothorax, Anabarilius and Yunnanilus. Exact up-to-
date figures of the number of species are difficult to extract from the
Chinese literature, but we have the following data: Dianchi: 25
native species, 11 endemic of which apparently all but 2 are extinct.
The lake basin has 2 other endemics (Kottelat & Chu, 1988,
updated); Fuxian: 25 native species, 12 endemic, + 2 endemic
shared only with lake Xingyun (Yang & Chen, 1995); Er Hai: 17
Native species, 9 endemic, several apparently extinct (Li, 1982,
updated); Yangzong has (had) at least two endemics, Yangling and
Xingyun at least one each. [MK]

Three endemic species of Salmo (recent summary in Kottelat,
1997). [MK]

The lower Danube basin has a relatively richer fauna (especially
more diverse communities) than any European river. Endemics:
about 6, possibly underestimated (counted in Kottelat, 1997). [MK]

Northern boundary not clear as published data on actual fish
distribution (and actual ground surveys) in southern China are too
scanty. Could be subdivided into a) upper Song Hong (includes hills
of Hainan and southern Nanpang Jiang); b) Annamite cordillera; c)
upper Mekong, Chao Phraya and Mae Khlong basins; d) Salween,
upper Irrawaddy, and southeastern Assam (including Tenasserim).
Recorded fish fauna estimated to be over 1000 species (with an
estimated 200-500 species still awaiting discovery), with 500
endemic to this area. Includes about some 400 known species
endemic to head waters of individual sub-basins. The fauna of the
lower reaches of the main rivers (excluded from this polygon) is
richer (in terms of the number of species which can be observed at a
given locality) but most have wide distributions crossing several

50

72

73

74

75

76

77

area name group
Malili lakes, fishes
Sulawesi.

Maros karst, fishes
Sulawesi

Mindanao, fishes
Philippines

Northwest Medi- fishes

terranean drainage

Palawan, fishes
Philippines

southwest Balkans fishes

4. Important areas for freshwater diversity

remarks

river basins (Kottelat, 1989, 1990d, 1998). [MK]

Most important single site for aquatic biodiversity in Asia. A
complex of 5 lakes (Towuti, Matano, Mahalona, Wawontoa,
Masapi) with endemic radiations of fishes of the families
Telmatherinidae (3 genera, 15 species, all but one endemic),
Hemiramphidae (3 endemic species), Oryziidae (3 endemic
species), Gobiidae (at least 8, all but one endemic), prawns (about
12 species ?), crabs (4 species ?), molluscs (about 60 endemic
species), etc. The distribution of the fishes is not uniform within the
lakes, all but one of the species of lake Matano are endemic, while
the others (and 2 genera) are endemic to Towuti, Mahalona,
Wawontoa. Masapi has not yet been surveyed. Only 2 species of the
Telmatherinidae are known outside this area. [MK]

One endemic genus (possibly an artefact of limited collection; more
surveys might show it to be present outside this area) and about’6
endemic species, including a cave species (Kottelat et al., 1993,
updated). [MK]

About 30 endemic species of cyprinids fishes, including about 18
endemic species of Puntius in Lake Lanao (all but 2 or 3 reportedly
extinct) (Myers, 1960; Kornfield & Carpenter, 1984). Cyprinids are
fishes which live only in freshwater and cannot disperse in marine
environment; several other families also occur in the island's
freshwaters, but all are able to disperse through the seas. [MK]

Includes Spain, Portugal, southern France and northern Italy. The
total diversity in the whole area is quite low, the communities are
quite poor, but this area holds 55 endemics, many with small
distribution ranges. 3 of the Rhone endemics extend almost to the
northern extremity of the basin. Endemics: | Petromyzonidae, 1
Acipenseridae, 1 Clupeidae, 34 Cyprinidae, 5 Cobitidae, 6
Salmonidae, 1 Valenciidae, 1 Cyprinodontidae, 2 Cottidae, 1
Percidae, and 4 Gobiidae (counted in Kottelat, 1997). [MK]

About 10 recorded species of cyprinid fishes, actual figure probably
higher. [MK]

The total diversity in the whole area is quite low, the communities
are quite poor, but the area holds 84 endemics, most of them with
restricted or very restricted distribution ranges: 1 Petromyzonidae, 2
Clupeidae, 48 Cyprinidae, 8 Cobitidae, 1 Balitoridae, 1 Siluridae,
13 Salmonidae, 1 Valenciidae, 1 Gasterosteidae, 1 Percidae, and 7
Gobiidae. The systematics of many groups is still very poorly
known and more species will be be recognised or even discovered
in the future (possibly 10-20). Noteworthy are lake Ohrid with
apparently 4 endemic Salmo, lake Prespa with apparently 7 endemic
species and the Vardar basin with at least 8 endemic species
(Kottelat, 1997). [MK]

51

Freshwater Biodiversity: a preliminary global assessment

78

79

80

81

82

83

84

85

86

87

88

area name

southwest Sri
Lanka

Subalpine lakes

Sundaic foothills
and floodplains

Western Ghats,
India

Balkans region

Chilka Lake
[brackish water]

Lake Baikal

Lake Biwa

Lake Inle

Lake Ohrid and
Ohrid basin

Lake Poso and
Malili Lakes
system

group

fishes

fishes

fishes

fishes

moll.

moll.

moll.

moll.

moll.

moll.

moll.

remarks

28 of the 91 native fish species of Sri Lanka are endemic to this
area. Several of the species traditionally given the same name as
Indian species are being revised and turn out to be specifically
distinct, so that the figure will rise (Pethiyagoda, 1991, 1994). [MK]

Stretches from lake Bourget in the West to Traunsee in the East.
Numerous endemic Coregonus (possibly >27, several already
extinct), at least two endemic Salvelinus and possibly some
endemic Salmo. Some lakes have more complex communities, e.g.
lake Konstanz with 4 Coregonus, 2 Salvelinus, 1 Salmo and several
other species (recent summary in Kottelat, 1997). [MK]

Probably formerly present on Java, but is mostly cleared. About 400
known species. Most of the floodplain species are widely
distributed over the whole area, while those of foothill streams have
a more localised distributions and are of greater interest in terms of
endemicity. Northern limit: Tapi basin in Peninsular Thailand
(Kottelat et al., 1993; Kottelat, 1989, 1995). [MK]

About 100 endemic fish species (estimated from Talwar &
Jhingran, 1991, updated; Pethiyagoda & Kottelat, 1994, ms.).
Difficult to give accurate figures. Many wide ranging "species" of
fishes in South Asia in fact are complexes of species, so that the
actual number of species is likely to increase significantly after
adequate systematic revision. [MK]

Former Yugoslavia-Austria-Bulgaria-Greece. Springs and
underground aquifers. Gastropods: c 190 species, some 180
endemic; 3 Extinct, 9 Critically Endangered, 10 Endangered, 3
Vulnerable. Bivalves: no data. [MSG]

Gastropods: 28 species, c 11 endemic. Bivalves: 43 species, 25
endemic. [MSG]

Gastropods: 147 species, 114 endemic. Bivalves: 3 species, 13
endemic. [MSG]

Gastropods: 38 species, 19 endemic. Bivalves: 16 species, 9
endemic. [MSG]

Gastropods: 25 species, 9 endemic. Bivalves: 4 species, 2 endemic.
Bivalves: 4 species, 2 endemic. [MSG]

Gastropods: 72 species, 55 endemic, 1 Extinct. Bivalves: no data.
[MSG]

Sulawesi. Gastropods: c 50 species , c 40 endemic. 1 Extinct.
Bivalves: 5 species, 2 endemic. 1 Extinct. [MSG]

52

area name

89 Lower Mekong
River

90 north Western

Ghats
91 Zrmanja River,
Croatia
NORTH AMERICA

92 southeast USA

93 western USA

94 Bear Lake

95 Colorado basin

96 Cumberland
Plateau
(Cumberland
+Tennessee rivers)

group

moll.

moll.

moll.

cray
fish
fairy
shrimp

fishes

fishes

fishes

4. Important areas for freshwater diversity

remarks

Lower Mekong in Thailand-Laos-Cambodia. River habitat. Only ca.
500 km of the lower Mekong main course (with the tributary Mun
River) has been well-studied. Gastropods: 121 species, 111
endemic. Two rissoacean groups dominate this entirely
prosobranch assemblage of over 120 species, the pomatiopsid
Triculinae (92 endemic species, 11 endemic genera) and the
Stenothyridae (19 endemic species). Bivalves: 39 species, 5
endemic. [MSG]

River habitat. Gastropods: c 60 species,10 endemic.2 endemic
genera Turbinicola, Cremnoconchus. The succineid genus Lithotis
is known from two species: L. tumida not collected since its
description in 1870, and L. rupicola only known from a single
locality. The highly localised genus Cremnoconchus is the only
littorinid living in a freshwater/terrestrial environment. Bivalves: 11
species, 5 endemic. [MSG]

Gastropods: all are hydrobioid snails, 11 species, 5 endemic.
Bivalves: no data. [MSG]

large area of high richness and endemism at generic and species
level; including the eastern and southem Mississippi drainage (Ohio
R, Tennessee R, to Ozark and Ouachita Mtns); 72 species in
Alabama, 71 Tennessee. [KC]

26 species, 13 endemic. [DB]

This lake is part of the Bonneville river basin and contains | local
endemic (Prosopium gemmiferum); and 2 species that are now
restricted to this site (Prosopium spilonotus and P. abyssicola)
(Minkley et al, in Hocutt & Wiley, 1986). [WCMC]

The largest basin of the west USA, this has high species richness
and endemism, including 5 endemic genera of which only
Plagopterus is monotypic (Banarescu, P. 1991). About one third of
the ichthyofauna of the Colorado is threatened, endangered or
extinct due to dams and introduced species (Carlson, C.A., Muth,
R.T. in Dodge, D.P. ed. 1989); 8 species appear in the 1996 IUCN
Red List. [WCMC]

This area, consisting of the Tennessee and Cumberland river
systems, has both the highest species richness and local endemism
in North America. It is part of the highly diverse Mississippi basin,
with some 240 species in total, 160 of which are present in both the
Tennessee and Cumberland drainages, and 14 of these are endemic
to the two basins. Of these 14, 10 are darters, 3 are minnows and 1
is a topminnow. The Tennessee has the greatest species diversity
with 224 species including 25 endemics (as well as 64 not found in
the Cumberland). The Cumberland has 176 native species,

53

Freshwater Biodiversity: a preliminary global assessment

area name

group remarks

including 9 endemics and 16 species not shared with the Tennessee
(Starnes& Etnier, in Hocutt & Wiley, 1986). [WCMC]

97

Death Valley
region

fishes There is a high level of local endemism associated with the
dispersed pattern of springs and marshes. 4 families are present
(Cyprinidae, Catostomidae, Cyprinodontidae and Goodeidae) with 9
species including an endemic species of Catostomidae (Minckley er
al, in Hocutt & Wiley, 1986). Several are globally threatened,
including 2 out of the 5 Cyprinodon species (Cyprinodom radiosus
and C. diabolis) which are listed as endangered and vulnerable
respectively in the 1996 IUCN Red List. [WCMC]

98

eastern USA

fishes This is a general area of high species richness and endemism which,
with the possible exception of the incompletely known East Asian
fish species, represents the most diverse of all the freshwater faunas
of the temperate zone (Banarescu, P. 1991). This includes a) the
Ozark Plateau, b) the Ouachita Mountains, c) the South Atlantic
Central Plain and d) The Tennessee-Cumberland Plateau. [WCMC]

99

100

Klamath-upper fishes The Klamath river basin contains 28 species in total with relatively

Sacramento

high endemism. The 6 endemic species include 2 Catostomus, one
Chasmistes and one Gila (Minckley et al, in Hocutt & Wiley,
1986). The ichthyofauna of the Sacramento differs from that of the
Klamath and contains 4 genera that are confined to this river and a
few neighbouring drainages (Banarescu 1991). [WCMC]

Ouachita Mtns fishes This area includes parts of the lower Red and Ouachita rivers, each

containing 133 species. The Ouachita and the Red River system
both contain 18 endemic species (Cross, F.B. et al in Hocutt &
Wiley, 1986). [WCMC]

Ozark Plateau

fishes The Ozark Plateau is an area of high species diversity and
particularly high local endemism in the southeast USA; it represents
a concentration of the species-rich southwestern Mississippi
drainage (more than 30 endemic fish species) (Banarescu, P. 1991).
[WCMC}

102

Rio Grande-Pecos fishes The Rio Grande basin overall has over 60 endemic species

confluence

S Oregon-

(Banarescu, P., 1991) and the Pecos, a tributary, has 5 (Smith, M.L,
Rush Miller, R. in Hocutt & Wiley, 1986). Many of the endemics
occur at the confluence of the two rivers, and many are listed as
globally threatened in the 1996 IUCN Red List. [WCMC]

fishes These rivers share few family similarities with the eastern USA and

California rivers have about 25% of the number of species but the region is high in

local endemism. [WCMC]

southern Atlantic fishes This includes the Alabama-Tombigbee river basin with a species-

coastal plain

rich fauna, including about 40 endemic taxa (Swift, C.C. et al. in
Hocutt & Wiley, 1986). This region also contains the Pearl River,
with 106 species (Swift et al in Hocutt & Wiley, 1986), and the
species rich lower Mississippi. [WCMC]

54

area name group

105 arid/semi-arid moll
Western USA

106 Cuatro Cienegas_ moll.
basin, Mexico

107 Florida, USA moll.

108 Mobile Bay basin moll.

109 Ohio-Tennessee
rivers

SOUTH AMERICA

110 Central America

111 S America

crabs

crabs

4. Important areas for freshwater diversity

remarks

Springs and underground aquifers. Gastropods: all are hydrobioid
snails, c 100 species, at least 58 endemic. Great radiation in genus
Pyrgulopsis. 3 extinct species, and all other are candidates for
listing by USFWS. Bivalves: no data. [MSG]

Springs and underground aquifers. Gastropods: all are hydrobiids;
12 species, more than 9 endemic, | Critically Endangered, 3
Vulnerable in 1996. 5 genera (Nymphophilus, Coahuilix,
Paludiscala, Mexithauma, Mexipyrgus) are endemic to this small
area of 30 x 40 km. Bivalves: no data. [MSG]

Springs and underground aquifers. Gastropods: mostly hydrobiid
snails. 84 species, c 43 endemic. No bivalves. [MSG]

Tombigbee-Alabama rivers. River habitat. Gastropods: 118 species,
110 endemic; 6 endemic genera; greatest species richness (76 spp)
in Pleurocercidae. 38 of the gastropod species believed extinct, 1
Endangered, 70 candidates for listing by USFW. Bivalves: 74
species, 40 endemic, 25 extinct. [MSG]

Eastern Mississippi drainage. River habitat. High species richness
and endemism. 16 Extinct bivalves. [MSG]

The freshwater crabs of Central America belong to families (the
Pseudothelphusidae and the Trichodactylidae) both of which are
exclusively Neotropical. The region of Central America from
Mexico to Panama, including some of the Caribbean islands holds
at least 22 genera and over 80 species of pseudothelphusid crabs,
and 4 genera and about 10 species of trichodactylids. The Isthmus
of Tehuantepec in central Mexico is a hotspot of biodiversity for
freshwater crabs in Central America (Alvarez & Villalobos, 1991;
Rodriguez, 1986), and richness declines toward to the south and
north. The seven species of freshwater crab belonging to a single
genus found in Cuba are all endemic to that island (Chace & Hobbs,
1969). [NC/RvS]

Two freshwater crab families (Pseudothelphusidae,
Trichodactylidae) endemic to the Neotropics occur in South
America. The former family includes air-breathing forms restricted
to cooler stream habitats, often in mountain regions; the latter are
gill-breathing and flourish in warmer lowland rivers. Freshwater
crabs do not extend to southern Chile or southern Argentina. There
are an estimated 17 genera and over 90 species of
pseudothelphusids, found mainly in the highland regions of Peru,
Ecuador, Colombia, Venezuela and the Guianas, and on the islands
of the southern Caribbean, and 12 genera and over 40 species of
trichodactylids found in the Amazon basin. The Cordilleras of
Colombia (Rodriguez & Campos, 1989; Rodriguez & Pereira,
1992), coastal Venezuela and the Guianas (Rodriguez, 1986;
Rodriguez & Pereira 1992), and the highland areas of Ecuador and

55

Freshwater Biodiversity: a preliminary global assessment

area name group remarks

Peru (Rodriguez & Sternberg, 1998) are all diversity hotspots for
freshwater crabs. The Amazon basin is rich in species(Rodriguez,
1982, 1992; Magalhaes & Tiirkay, 1996a,b,c), but most are
widespread in the basin, and it is not possible yet to delimit special
areas. [NC/RvS]

112 southern S fairy 18 species, 14 endemic. [DB]

America shrimp
113 Altiplano of the fishes Species flock of Orestias with 43 or more species, representing an
Andes endemic subfamily, Orestiinae, of the Cyprinodontidae. [SK]

114 Amazon River fishes The Amazon (with adjacent Tocantins) basin probably has about
basin 3000 species, and is one gigantic hotspot. The Amazon fauna equals
or exceeds other continental faunas in species richness. Endemism
in tributaries and subtributaries makes up most of the overall
diversity, rather than the main Amazon itself. Only a few of the
constituent rivers have been studied in any detail. [SK]

115 Aripuana River, a fishes A tributary of the Madeira; known to have a highly endemic but still
tributary of the little studied fauna upstream of the lowermost falls, with at least 10
Madeira endemic species, some restricted to rapids. [SK]

116 Central America fishes
between the
Isthmus of
Tehuantepec and
Isthmus of
Panama

117 Iguacu River fishes Rio Iguacu, on the border between Argentina and Brazil, tributary
to the Rio Parana. Its fish fauna is separated from the Rio Parana by
the Iguacu Falls, which do not permit any migration. The fish fauna
is highly endemic, with about 50 endemic species out of a total of
65 species (ca 80%). There are considerable difficulties with the
nomenclature and systematic status of the Iguacu fish species, most
belonging to groups that have never been revised. Nonetheless, the
high endemism will probably remain above 50%. The endemic
fauna, mainly a running water one, is highly endangered by
hydroelectric power projects, pollution and introduced species. The
fauna is not protected. Basic information can be obtained from
Agostinho and Gomes (1997). [SK]

118 La Plata basin, fishes Comprising the Uruguay, Paraguay and Parana rivers, with mainly
comprising the endemic species, including numerous local endemics, and marked
Uruguay, by numerous waterfalls providing isolation. Number of species
Paraguay and unknown, but estimated fewer than 1000, possibly about 600. Taken
Parana rivers together, the tributaries of the Parana down to about Encarnacién

have a very high number of local endemics, often restricted to a
single river, most of which are separated from the Parana by one or
more waterfalls near the mouth. Many of these have not been
described or examined by a specialist, but are known only from

56

area name

group

4. Important areas for freshwater diversity

remarks

occasional collections made before the Itaipu, Acaray and Yacyreta
dams were constructed. Unfortunately, EIA for those dams did not
result in any significant collections to show what species were in the
area before the dams were built. A lesser collection of pre-dam
fishes is available in MNHNP (Paraguay) and the Muséum
d'Histoire naturelle de Genéve (Switzerland). [SK]

119

Lago Titicaca

fishes

Lago Titicaca and smaller lakes of the Altiplano extending from
Chile to Peru, hold a large number of species of the genus Orestias
(Cyprinodontidae), 23 are endemic to Titicaca. The genus, with a
total of 43 species has a narrow range from northem Chile to
southern Peru. The lake species flocks may not be monophyletic
(Parenti 1984), but the group certainly attained its present species
richness in the area. The sister group are the North American
Cyprinodontidae. Other highland Andean fish families include the
Astroblepidae, ranging from Bolivia across Peru and Ecuador into
Colombia, and many trichomycterid fishes (Trichomycteridae)
occur. Lago Titicaca with its Orestias fauna is the only identifiable
‘hotspot’. [SK]

120

Marowijne/Maroni fishes

River drainage

Marowijne/Maroni River drainage in Guyana and Surinam: known
to have many endemic species above the falls, with the same genera
as in the rest of the Guianas area. [SK]

121

Mata Atlantica.

fishes

The Mata Atlantica has numerous endemic species, in small
mountain streams or in the few major river systems, most
incompletely known. The Rio Ribeira has 77 species, and similar
numbers appear to be in the other rivers. The Jequitinhonha is
notable for several endemic species, including one of Rhamdia,
which is otherwise represented by only a few widespread species in
South America. The Mata Atlantica fauna extends to eastern
Uruguay and southeastern Paraguay as numerous fragmented
habitat patches, and although not high in species richness (perhaps
around 150), has a large number of locally restricted species, with
related species replacing each other from one river to another. [SK]

122

Mazaruni and
Potaro Rivers in
the Guyana
highlands

fishes

Mazaruni and Potaro Rivers in the Guyana highlands: separated
from the rest of the Essequibo system by falls, with several endemic
species, but little explored. [SK]

123

Mesa Central,
Mexico

fishes

Endemic subfamily Goodeinae of family Goodeidae with about 36
species. [SK]

124

Mexican Plateau

fishes

125

Negro River and
upper Orinoco
River

fishes

Negro River and upper Orinoco River in Brazil, Colombia and
Venezuela, with at least 700 species, probably nearer to 1000, many
of which are endemic to the clear and black waters distinguishing
the basin. [SK]

57

Freshwater Biodiversity: a preliminary global assessment

126

area name group

Nicaraguan lakes fishes

remarks

The Nicaraguan Great Lakes (Nicaragua and Managua) in the San
Juan Basin do not have great numbers of species (about 16
cichlids), but endemism is high (9 endemic species, 2 endemic
genera). [SK]

127

Orinoco River fishes

basin

More than 1000 species, most of which may be endemic. There is
much local endemism as habitats vary considerably, including
lowland inundation savannahs, fast flowing mountain rivers, etc.
Includes thus different biogeographic regions. [SK]

Oyapock River fishes

Shared between Brazil and French Guiana, known to have many
endemic species, especially rheophilic, from the lowermost falls
upstream. Still little studied. [SK]

129

130

Pacific Coast of fishes
Colombia and
Ecuador

Although a high-rainfall region there are few large rivers. The fauna
is poor, but species are highly endemic to the region and to
particular rivers or portions of rivers. In particular, the Baud6 River
and San Juan River in Colombia seem to have numerous endemics.
Possibly the Atrato River should be included. [SK]

Patagonia fishes

Rio Panuco Basin fishes

Upper Uruguay _fishes

River

Argentina and Chile, from around the R Negro southward (except
the most arid areas). Low diversity but endemic relict fauna of more
general southern hemisphere type, with families such as Geotriidae
and Galaxiidae, and also the endemic catfish family Diplomystidae
with six species, the monotypic catfish family Nematogenyidae, and
four species of the percoid family Percicihtyidae. This is not a
hotspot of species richness, but a region of considerable local
endemism, and a fauna completely different from that of the rest of
South America. The Nematogenyidae are related to the Loricariidae
and Trichomycteridae of northern South America (the Brazilian
fauna), but the Diplomystidae are the most primitive living catfish
family. The scaleless characid Gymnocharacinus bergti represents
the Brazilian fauna, but lives isolated in one Patagonian locality in
the Sumuncurd mountain which maintains about 22.5°C water
temperature year-round. [SK]

A small drainage with about 75 species, c 30% endemic, including
several closely related species of Herichthys (Cichlidae). eastern
Mexico, about 25 endemic out of about 75 known species. [SK]

The river is relatively well known from collections made by teams
of the Museu de Zoologia of the Pontificia Universidade Catdlica
do Rio Grande do Sul during environmental impact assessment in
the area, which is destined for numerous hydroelectric power plants.
The MCP collections concern the middle and upper portions,
located in Brazil. More than 130 species of fish are recorded from
the middle and upper Uruguay, and the number is likely to rise to
over 150 at least. About half of those may be endemic. Lucena &
Kullander described 11 species of Crenicichla from the Uruguay
River, and noted that this is double the number of a similar
Amazonian river. Six of the species form a species flock originating
on site and diversifying by trophic adaptation similar to cichlids of

58

4. Important areas for freshwater diversity

area name group remarks

East African Lakes. The lower Uruguay river, along the
Argentinian-Uruguayan border is very little studied, and may have
fewer endemics. [SK]

133 Western fishes Lowland Amazonian Peru, Ecuador and Colombia, and parts of
Amazonia Brazil, representing a large expanse of lowland Amazonia, very rich
in species, but not well studied. Work in Peru and Ecuador suggest
that there may be at least 1000 species in the area, and at least half
may be endemic. [SK]

134 Lake Titicaca moll. Gastropods: 24 species, 15 endemic. Bivalves: no data. [MSG]

Lower Uruguay moll. Argentina-Uruguay-Brazil. Gastropods: 54 species, 26 endemic.
River and Rio de Bivalves: 39 species, 8 endemic. [MSG]
la Plata

136 Parana River moll. More the 7 species, 7 endemic, of which 3 are extinct in the wild.

Bivalves: no data. [MSG]

Notes:

1) This table presents information on areas identified as of special importance for diversity (species
richness, and/or endemism) in the inland water groups treated (fishes, molluscs ['moll.’ in table] , crabs,
crayfish, fairy shrimps).

2) This is a preliminary synthesis, designed to represent expert opinion on relative levels of diversity for
each taxon at continent level. In the absence of global criteria for relative importance, areas on different
continents do not represent strictly equivalent levels of diversity.

3) The rows of data in this list are sorted first by continent, and secondly by the taxon concerned.

Sources: information has been derived from a number of sources, mainly as indicated by letters in square
brackets in the 'remarks' text. GA - Gerald Allen, in litt. March 1998; MK - Maurice Kottelat, report compiled
for this document; SK - Sven Kullander, report compiled for this document; MSG - report adapted by
IUCN/SSC Mollusc Specialist Group, primarily by Philippe Bouchet and Olivier Gargominy, also Arthur
Bogan and Winston Ponder; KC - Keith Crandall, information on distribution of crayfish genera and species;
DB - Denton Belk, summary of fairy shrimp distribution patterns; NC/RvS - Neil Cumberlidge and R von
Sternberg, report compiled for this document. For North American and African fishes, where source is
WCMC, information has been extracted from available literature, with additional data and advice for Africa
from Christian Lévéque and Guy Teugels. In most instances (MK, SK, MSG, NC/RvS, DB) contributors
indicated the approximate location of the important areas concerned on a series of A3 sized base maps
provided. These areas, and those identified from literature by WCMC were digitised as a basis for data
presentation and future analysis.

59

5. DIVERSITY, RISK AND PRIORITIES:
A FRAMEWORK FOR ANALYSIS OF RIVER BASINS

This chapter develops a global analysis of fish diversity at catchment level as the
main element in an outline assessment of pressures and the relative global
importance of river basins. An overall measure of relative wilderness value is used
to estimate the magnitude of high-level regional and landscape scale effects on the
current condition of catchment basins. Estimates of future pressures on water
resources at national level are then used to indicate possible trends in catchment
condition. These two factors are then evaluated together with fish diversity data in
order to suggest levels of priority at global scale.

FRESHWATER FISHES: ANALYSIS OF GLOBAL DIVERSITY

A first step in planning for improved biodiversity management is to assess the
biological resources present, and at local or national level it is important to consider
this information in a continental or global context. With this in mind, we have
assembled a database of estimates of the number of fish species in a large number of
river basins.

The data have been gathered from a wide range of sources, including published
literature and unpublished data supplied by colleagues (please refer to
Acknowledgements, above). Figures are available for 166 basins, of which 107 are
amongst the 151 mapped in the present analysis (Map |, and Annex 1). Fish species
included are those that spend a significant part of their life within river systems
(including anadromous and catadromous species, that is those that migrate up or
down rivers to breed); introduced species and marine species that enter estuarine
waters only have been excluded where possible.

For most catchment basins actual counts of species are included; however in the
case of a small number of very large tropical catchments (the Amazon, Mekong and
Congo/Zaire) where it is known that species counts are very incomplete, expert
assessments of likely overall numbers are included. The figures for the Mekong and
Zaire are believed to be fairly reliable; for the Amazon the figure used (2,500) is
certainly a very rough estimate. A number of rivers, particularly larger tropical ones,
are incompletely known and the totals given are likely to under-represent the true
figure somewhat. The number of native fish species per catchment ranges from 5 to
an estimate of 2,500 for the Amazon system.

61

Freshwater Biodiversity: a preliminary global assessment

Figure 7. Relationship between species number and basin area

Ln no. of fish species

4 6 8 10 12 14 16 18
Ln catchment area (square km)

Notes: log-log plot, see Annex 2, dashed lines indicate 90% confidence limits.

Figure 8. Relationship between species number and basin discharge volume

Ln no. of species

2.0 2.5

Ln river discharge

Notes: log-log plot, see Annex 2, dashed lines indicate 90% confidence limits.

62

5. Diversity, risk and priorities...

Figure 9. Species richness against basin latitude

Relative fish species richness

Degrees from equator of centroid of catchment

Notes: this graph plots species richness relative to number of species expected on basis of basin size against
latitude of centroid of basin (dashed lines indicate 90% confidence limits).

The readily available estimates of fish richness have resulted from studies made at
various times and reflect different approaches to fish taxonomy, so the dataset is
uneven in quality. However, both the low intensity of field survey work and the
slow rate at which the few experienced systematists can deal with available
specimens imply that the available global dataset is unlikely to be greatly improved
in the near future.

The number of fish species in the 151 basins included in this analysis is shown in
simplified form in Map 6, and fish species richness (in terms of actual number
versus number expected on basis of basin area) in Map 7.

As might be expected from the classic species-area relationship (ie. that other things
being equal, the number of species present increases with increasing area), there is
overall a strong correlation between the size of a river and the number of fish
species present (Figure 7). The ‘size’ of a river can be represented by the area of the
basin, or by the volume of water flowing through the river system in any given
period; the latter is a better predictor of fish species richness than is basin area
(Figure 8). See Annex 3 for a note on methodology. Similar observations were
reported in more detail by Oberdorff er al. (1995) and Guégan et al. (1998),
including discussion of the rdle of energy availability.

63

Freshwater Biodiversity: a preliminary global assessment

By fitting a regression line through a log-transformed plot of species number against
catchment area and measuring the distance from this line of each point (ie. the
residual of each point), we estimate whether any given river is richer or poorer in
species than would be expected on the basis of its size alone. A plot of these
residuals (a measure of fish-species richness) against latitude (taken as the latitude
of the centroid of each catchment) demonstrates overall a strong inverse correlation
between latitude and species richness (Figure 9), so that in general the lower the
latitude of the river, the richer in species it is. This is a clear manifestation of the
most well known global diversity gradient, namely that species diversity increases
with decreasing latitude. Analysis by Guégan et al. (1998) appears to indicate that
latitude may be a surrogate measure for productivity within the basin.

Fish family diversity

In general, at any site there are certain to be far fewer families (or other higher taxa)
present than individual species, and so it is usually quicker and easier during field
collection at new sites, and subsequent museum study of samples, to determine how
many families are present than how many different and perhaps undescribed species.
So the question whether higher taxon richness is a valid surrogate of species
richness is an important one in the context of biodiversity assessment. With this, and
the incomplete and uneven nature of the fish diversity dataset in mind, we have
examined family richness in fishes.

Distribution maps from Berra (1981) for the 142 fish families recognised by him
with representatives in freshwater have been digitised. Although there have been
some changes to the names and content of families mapped by Berra, and the maps
themselves are coarse in scale, we have taken this source to represent a reasonable
consensus view of fish families.

We have included all primary freshwater families and the inland areas of all those
peripheral and secondary division families that extend significantly beyond estuarine
waters into inland systems (primary families are strictly freshwater, secondary
families are mainly freshwater but have some salt tolerance, peripheral groups occur
mainly or partly in freshwater but are clearly derived from marine ancestors). From
the digitised maps, a global density surface of numbers of freshwater fish families
has been prepared (Map 8). By overlaying the outlines of the river catchments
mapped in this analysis, the number of fish families in each of these basins has been
estimated (Map 9).

The number of families per basin ranges from two in the Dra river in southern
Morocco to 49 in the Amazon as a whole. This range is clearly far smaller than the

64

5. Diversity, risk and priorities...

range in fish species diversity (a 25-fold increase from least to most diverse,
compared with a 250-fold for species). As with fish species, there is a clear, but less
strong, relationship between the number of fish families in a catchment and the size
of catchment. Again, as with fish species, the relationship with discharge is clearly
better than that with catchment area. However, as data for discharge are incomplete,
we have used catchment area in this analysis.

Map 10 shows the relative richness in families of the 151 river catchments mapped.
The most obvious observation is that the richest rivers are all found in the tropics,
most notably in northern and central south America. There are lesser centres of fish
family diversity in western Africa and southeast Asia. This well reflects the
density/contour map of fish family diversity. Of further note, by far the most diverse
area outside the tropics or subtropics is eastern North America, where family
richness calculated in this way is comparable to that in much of Africa and in the
Indian sub-continent. This is reflected also in the species-richness of river
catchments in this area (Map 7). It is likely that this effect is at least in part because
catchment area has been used to calculate relative richness rather than discharge or
runoff: rivers in much of Africa in particular have far lower runoff that would be
expected from the size of their catchments, and therefore would be expected to have
fewer fish species and families in them than predicted from the size of the catchment
and its latitude.

Because of the relatively coarse level of resolution of the source data for fish family
distribution, it is likely that the number of families in some smaller rivers,
particularly in the tropics, has been overestimated. That is, it has not been confirmed
that every catchment within the delimited range of a given family contains
representatives of that family. Clearly this may alter results to some extent but is
unlikely to have significantly distorted the overall picture.

How well does fish family richness indicate fish species richness?

A simple plot of number of fish species in a river catchment against estimated
number of fish families demonstrates a correlation between the two (Figure 10).
With the exception of a small number of catchments with a very large number of
species (the Amazon, Congo/Zaire, Mekong and Yangtze, each with over 300
species), the relationship between fish species and fish numbers is a close one. At
first inspection it appears to be roughly linear, with around five fish species for each
family represented. In the four very species-rich rivers, there are over twice this
number of fish species per family.

65

Freshwater Biodiversity: a preliminary global assessment

Figure 10. Relationship between number of fish species and fish families in
catchment basins

1600 f+

1200) pen

No. of fish species in catchment

No. of fish families in catchment

Notes: species richness estimates derived from literature and personal communications; number of fish
families per basin calculated from GIS overlay of fish family ranges on our sample catchment outlines. The
outlying point is the Amazon basin.

Fitting a series of curves to the plot indicates that, in fact, the relationship between
fish species and fish family richness is probably not strictly a linear one. The best fit
of an exponential or power series curve is derived from a power series in which
number of species is related to number of families to the power of 1.5 (Figure 10).
Using this relationship, family number can explain over 80% of the variation in
species number between river catchments. However, even then three of the most
species rich rivers (in this case the Amazon, Zaire and Yangtze) deviate
considerably from the relationship, with between from nearly three to nearly seven
times the number of species predicted by family number (although the highest
anomaly is for the Amazon, where the species estimate is very approximate). There
is however,apparently no significant relationship between latitude and number of
species per family, indicating that speciation at this level is similar in the tropics and
in temperate regions.

There is still overall considerable variation in the relationship between number of
species and number of families in different catchments. Because of uncertainties in
some of the underlying data, it is difficult to tell how much of this is an artefact and
how much reflects real differences. Of some note are the two catchments in New
Guinea mapped in this study, the Fly and the Sepik. Both these are depauperate in fish
families, as may be expected from the geographical position and geological history of

66

5. Diversity, risk and priorities...

the island, which is isolated from major continental centres of freshwater fish
diversity. They are also apparently depauperate in number of species, compared with
that to be expected of rivers of that size and at that latitude. However, both have
considerably more numbers of species per family than predicted from the overall
relationship set out above (130% and 80% more respectively), indicating that those
families that have colonised these catchments have undergone a higher degree of
speciation than normal.

It seems likely that as the data are refined, through more accurate counts of fish
species and fish families and use of discharge rather than catchment area, the fit will
improve somewhat and more interesting individual patterns will emerge.

Overall, however, it is clear that even with the variable quality of the existing data,
at a global level fish family diversity is a good surrogate for fish species diversity, in
that the general patterns in one are well reflected in the other.

INDICATORS OF HABITAT CONDITION IN RIVER CATCHMENTS.

Wilderness

A measure of wilderness in each of the catchments analysed has been derived, based
on the Wilderness Index developed by the Australian Heritage Commission (R.
Lesslie, in litt., 30 May 1998). The wilderness value of any given point is essentially
a measure of remoteness from human influence and is assessed on the basis of:
remoteness from settlement (settled land or points of permanent occupation), from
access (constructed vehicle access routes), and apparent naturalness (remoteness
from permanent manmade structures) (Lesslie and Maslen, 1995). The analysis is
carried out on a grid, using data from the Digital Chart of the World (DCW), and
remoteness is measured as a distance from each grid point to the nearest feature of
each class within a given radius (generally 30 km). Wilderness value is the sum of
standardised values for each indicator class. The value used here is the mean
wilderness value for all points within the catchment; this dataset is represented in
simplified form in Map 11.

Water resource vulnerability

A measure of water resource vulnerability for each catchment has been calculated
following Raskin et al. (1997). This team compiled a novel Water Resource
Vulnerability Index (WRVI) for each country on the basis of three water resource
stress indices: reliability; use-to-resource; and coping capacity.

67

Freshwater Biodiversity: a preliminary global assessment

“Reliability” incorporates three separate factors: storage-to-flow (national reservoir
storage capacity in relation to average annual water supply; annual coefficient of
variation of precipitation (ie. long-term predictability of rainfall); and import
dependence (the percentage of a national water supply that flows from external
sources). ‘““Use-to-resource ratio” is a measure of annual water withdrawals divided
by annual renewable water resources. “Coping capacity” is GDP per capita and
serves as a proxy for a nation’s capacity to cope with water problems and
uncertainties, and to deliver basic water services to its citizens.

For each measure, including the three separate factors in “reliability”, four classes
(from “no stress” to “high stress”) have been designated in Raskin (1997). A
compound WRVI (model I) for each country is derived by giving equal weightings
to each of the three stress indices (Model I).

We have calculated a measure of vulnerability for each catchment by measuring that
proportion of each catchment which lies within any given country and weighting
this proportion by the WRVI of that country. This analysis is represented in Map 12.

Water resource vulnerability and wilderness are both high-level measures of the
state of water catchments and the pressures exerted on them. The extent to which
they can provide actual insight into the state of riverine ecosystems in individual
catchments is a matter of great interest.

In particular, the former is a measure of the extent to which water supply is or may
be expected to become a problem to the human population in a country and is
therefore only indirectly a measure of vulnerability of or degree of threat to riverine
ecosystems. Further, being derived from country-level indices, it may be expected to
provide only a limited insight into the state of individual catchments. Indeed, Raskin
(1997) notes that “Ideally, the analysis would be conducted at the river catchment
level where the relationship among water resources, human requirements and
ecosystems is most direct. But a comprehensive global assessment that is built from
numerous river catchments would be a problematic undertaking due to the sheer
scale of effort and to the lack of a comprehensive water data-base organised by
catchment.”

Nevertheless, inspection of the map of water resource vulnerability shows good
agreement with what may intuitively be expected at a global level, namely that the
most vulnerable catchments overall are in South Asia, which has very high human
population density, and in the northern half of Africa where rainfall is generally low
and unpredictable. In contrast, the least vulnerable catchments are in high latitude
countries with predictable rainfall and low population densities (Canada and

68

5. Diversity, risk and priorities...

Finland). Some evident anomalies arise, of which perhaps the most noticeable are
the two Alaskan catchments (the Yukon and the Kuskokwim). These may intuitively
be expected to be of very low vulnerability, essentially in the same class as adjacent
catchments such as the Mackenzie in Canada. However, because by this system the
value for the USA as a whole has been applied, they are classified as of somewhat
higher vulnerability.

The wilderness estimate is derived from data mapped by grid-squares rather than at
country level, and is therefore of a much finer resolution and can be applied as a
direct measure for each catchment. Again in general the map (Map 12) gives good
overall agreement with what may be intuitively expected. Major apparent anomalies
include the relatively low wilderness value ascribed to the Zaire catchment and the
relatively high value ascribed to the Yangtze. The former is probably because the
base data, taken from the Digital Chart of the World (DCW) are not completely
standardised across the globe. Thus in parts of Central Africa several low-grade
forms of access (tracks, trails and footpaths), and the settlements associated with
them, that are not normally marked on DCW maps, are marked. This will tend to
decrease the apparent wilderness value of the area compared with other regions (R.
Lesslie, in litt., 30 May 1998). In contrast, the Yangtze catchment, despite much of it
lying in one of the most densely populated parts of the world, contains significant
areas of montane regions with little marked access, so that the catchment as a whole
has a higher wilderness value ascribed to it than might be expected.

Further refinements of the base-line information used to generate the wilderness
index should resolve many of these apparent anomalies. However, the most
important caveat to use of the wilderness index in this context is that it is a measure
of the amount of wilderness in the land area of the catchment as a whole and does
not directly reflect the condition of riverine ecosystems. Reasonably, other things
being equal, it would be expected that there would be a good correspondence
between the two, in that a catchment with a high wilderness rating should be
relatively undisturbed and therefore have at least a proportion of its riverine
ecosystems also relatively undisturbed. However, this may be expected not strictly
to hold in arid and semi-arid areas (in this case most notably in northern Africa).
Here, the wilderness measure for the catchment is often high because large areas of
desert or subdesert hinterland are very sparsely inhabited, but the rivers themselves
may be expected to be disproportionately affected by human activity (ie. should in
fact have a low wilderness measure) because this is were the bulk of the human
population in the catchment is settled.

Despite these problems, the measure does seem to provide a good starting point for
assessing how disturbed or impacted the world’s major catchments are overall.

69

Freshwater Biodiversity: a preliminary global assessment

A good overall impression of stress to or probable impact on riverine ecosystems
can be gained by combining the water resource vulnerability index with the negative
of the wilderness index (i.e. a measure of the absence of wilderness in a catchment).
This has been done by normalising the two, so that all values for each lie between 0
and 1, and subtracting wilderness value from the water resource vulnerability index.
Both indices have essentially the same spread of values (approximately four-fold
increase from the lowest value to the highest), so that each contributes equally to an
overall value for threat calculated in this way.

Map 13 shows an overall vulnerability or impact value for the river catchment as
calculated in this way. Interestingly, combining these two independent measures
appears to have the effect of mitigating some of the more obvious anomalies found
for each of the measures separately (discussed above). Overall, the pattern mapped
agrees well with what might intuitively be expected, with few evident anomalies.
This is particularly noteworthy because neither of the two indices used to generate
this measure includes direct measures of the state of the riverine ecosystems
(although the use-to-resource ratio, used as part of the Water Resources
Vulnerability Index provides some insight into this in that it estimates what
proportion of river water is physically removed).

Using these measures, the most stressed catchments are to be found in South Asia
(the Indian subcontinent), the Middle East and western and north-central Europe.
The least stressed are those in the north-western part of North America.

Clearly, this methodology represents a preliminary assessment, at a coarse level, of
likely major impacts on catchments. Further refinement of the system should take
into account measurable impacts on individual catchments. Two major factors that
should be considered in trying to obtain more direct measures of impacts on riverine
ecosystems are dams and pollution.

Dams

Dams, particularly large dams, self-evidently have a major impact on the rivers they
are built on. They affect flow regimes, often dramatically, and destroy large areas of
existing habitat while creating new ones (eg. Dynesius and Nilsson, 1994). They
have particularly significant impacts on catadromous and anadromous fishes (those
that migrate down or up river systems to breed). Dams, particularly those used for
generating hydroelectric power, may be, and indeed often are, built in areas that are
not heavily populated or under major water stress. It may be expected therefore that
their presence will not accurately be reflected in the indicators outlined above.
Preliminary analysis of data on large dams shows that these are very unevenly

70

5. Diversity, risk and priorities...

distributed across the world’s major catchments, with an enormous concentration in
North America, particularly within the contiguous states of the USA, where at least
eight catchments have over one hundred large dams in each. Clearly, such
information should be incorporated into any further assessment of threats to
catchments.

Pollution

The degree of pollution in a basin may be expected to be reflected to some extent
both in the amount of wilderness in the basin and the measure of water resource
vulnerability. However the connection is likely not to be straightforward. Point
sources of pollution may have major impacts on river systems that are otherwise
relatively undisturbed and therefore have a high wilderness value (as reportedly with
the Fly River in New Guinea, which is affected by pollution from mining within its
catchment). Furthermore catchments in areas of low water vulnerability (often in
developed, temperate countries), may be expected to be particularly susceptible to
pollution. This, however, is likely to be reflected in a low wilderness measure.

A FRAMEWORK FOR PRIORITISATION

Despite the various caveats, the measures for fish family richness and overall stress
elaborated above do appear to be reasonable indicators respectively of biodiversity
in riverine systems and the threats to it. Combining these can give some indication
of global level priorities for the maintenance of riverine biodiversity. Figure 11
shows a scatter-plot of these two measures.

We suggest for this preliminary approach that highly diverse and highly stressed
river systems (ie. those towards the top, right-hand part of the graph) should be
accorded highest priority and systems with low diversity and low stress (ie. those
towards the bottom left-hand part of the graph) should be accorded lowest priority.

There is no single a priori way of ranking the others, which may have high diversity
and low stress, low stress and high diversity or moderate measures of both.
However, simply allotting equal weight to richness and stress (i.e. normalising and
averaging the two) allows a single measure to be derived for each catchment that
can be used to identify three groups: high priority; intermediate priority; lower
priority. The division between these three groups is arbitrary, particularly as there is
very little numerical difference between many of the catchments of intermediate

value.

71

Freshwater Biodiversity: a preliminary global assessment

The results are shown in Map 14. For clarity we have chosen to show the top thirty
as high priority and the bottom thirty as lower priority, with the remaining 91 basins
as intermediate. The 30 high priority basins are represented by a black marker in
Figure 11 and named in Table 18.

This preliminary analysis of diversity and risk analysis could be further developed
by inter alia the following steps:

il Use discharge data, as a better predictor of fish richness than catchment area.
2. Verify and expand the dataset on fish species per catchment.
3), Revise fish family taxonomy and occurrence, and seek field data on fish

richness per family, particularly for smaller river basins.

4. Most importantly, include system-specific information on river condition:
dams; pollution; abstraction of water for irrigation; canalisation, etc.

Figure 11. Scatter diagram of fish family richness per basin against vulnerability

30

20

Family richness

-10

-0.8 -0.6 -0.4 -0.2 0.0

Overall vulnerability

72

5. Diversity, risk and priorities...

Table 18. Thirty high priority river basins

Ca Magdalena Perak

Cauvery Mahanadi Salween

Chao Phraya Mekong Sao Francisco
Gambia Narmada Senegal
Ganges-Brahmaputra Niger Sittang

Godavari Nile Song Hong (Red)
Indus Pahang Tapti

Irrawaddy Parana Tembesi-Hari
Krishna Parnaiba Uruguay

Ma Penner Volta

Notes. These are thirty river basins that support high biodiversity (assessed as fish family richness) and are
most vulnerable to future pressures (have a low wildemess score, and high water resource vulnerability index).
See text for further explanation. Basins are listed in alphabetical sequence.

73

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81

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ANNEX 1

LARGER RIVERS OF THE WORLD, INCLUDING A LIST OF BASINS
ANALYSED IN THIS REPORT AND A PRELIMINARY REVISED LIST
OF INTERNATIONAL BASINS

Part 1: basins included in the analytic phase of this report (sorted by approximate
area of basin).
Part 2: other larger basins, not yet included in the analysis (sorted by approximate
area of basin).

NB: international basins have more than one country listed in the 'Countries'

column.

Part 1. Basins included in the analytic phase of this report.

Continent

South America

Africa

N+C America

South America
Africa

Asia
Asia
Asia
Africa

Asia
Asia
N+C America

Asia

Africa

Europe

N+C America
Australia & NZ

N+C America

Asia

River
Amazon (with Ucayali)

Congo

Mississippi (with Missouri)

La Plata (with Parana and
Uruguay)

Nile (with Kagera)

Ob (with Irtysh)
Yenisey (Yenesei)
Lena

Niger

Amur
Yangtze
Mackenzie (with Athabaska)

Ganges-Brahmaputra
Zambezi

Volga

St. Lawrence
Murray-Darling

Nelson (with Saskatchewan)

Indus

Countries

Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru,
Venezuela

Angola, Burundi, Cameroon, Central African
Republic, Congo, Congo (DR), Rwanda, Tanzania,
Zambia,

Canada, USA

Argentina, Bolivia, Brazil, Paraguay, Uruguay

Burundi, Congo (DR), Egypt, Ethiopia, Kenya,
Rwanda, Sudan, Tanzania, Uganda

China, Kazakhstan, Russia
Mongolia, Russia
Russia

Algeria, Benin, Burkino Faso, Cameroon, Chad, Cote
d'Ivoire, Guinea, Mali, Nigeria, Niger

China, Mongolia, Russia
China
Canada

Bangladesh, Bhutan, China, India, Nepal

Angola, Botswana, Malawi, Mozambique, Namibia,
Tanzania, Zambia, Zimbabwe

Russia
Canada, USA
Australia
Canada, USA

Afghanistan, China, India, Pakistan

83

area (sq. km)
"5,870,000

3,720,000

3,250,000

3,200,000
3,030,700

3,010,000
2,530,000
2,490,000
2,200,000

1,900,000
1,800,000
1,800,000

1,600,400
1,419,960
1,360,000
1,280,000
1,060,000

990,000

980,000

Freshwater Biodiversity: a preliminary global assessment

Continent

South America
Africa

Asia

Africa

Europe

Asia

Africa

N+C America
Asia

Asia

Asia
N+C America

N+C America
South America
N+C America

Europe
Asia

Europe
Asia
Asia
Africa

Africa

Asia

Europe

Africa

South America
Asia

Asia

N+C America
Asia

South America
Europe

Asia

Asia

Africa

River
Orinoco

Orange

Shatt-al-Arab (Tigris and
Euphrates)

Chari

Danube

Mekong

Juba (with Shaballe)
Yukon

Hwang Ho

Amu Darya

Kolyma

Colorado (State of Arizona)

Columbia

Sao Francisco

Countries

Colombia, Venezuela
Botswana, Lesotho, Namibia, South Africa

Iran, Iraq, Syria, Turkey

Cameroon, Chad, Central African Republic

Albania, Austria, Bulgaria, Czech Republic,
Germany, Hungary, Italy, Moldova, Poland,
Romania, Slovakia, Switzerland, Ukraine,
Yugoslavia,

Cambodia, China, Laos, Myanmar, Thailand, Viet
Nam,

Ethiopia, Kenya, Somalia

Canada, USA
China

Afghanistan, Kyrgystan, Tajikistan, Turkmenistan,

Uzbekistan

Russia
Mexico, USA

Canada, USA
Brazil

Bravo del Norte (Rio Grande) Mexico, USA

Dnepr
Syr Darya

Don
Irrawaddy
Helmand

Limpopo

Volta

Indigirka
Northern Dvina
Senegal
Parnaiba
Godavari
Salween
Fraser
Krishna
Magdalena
Ural

Liao Ho
Kura-Araks

Ogooue/Ogowe

Belarus, Russia, Ukraine
Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan

Russia, Ukraine

China, India, Myanmar

Afghanistan, Iran, Pakistan

Botswana, Mozambique, South Africa, Zimbabwe

Benin, Burkino Faso, Céte d'Ivoire, Ghana, Mali,
Togo

Russia

Russia

Guinea, Mali, Mauritania, Senegal

Brazil

India

China, Myanmar, Thailand

Canada, USA

India

Colombia

Kazakhstan, Russia

China

Armenia, Azerbaijan, Georgia, Iran, Turkey

Cameroon, Congo, Equatorial Guinea Gabon

84

area (sq. km)
"966,000
950,000

884,000

880,000

796,250

786,000
766,500

765,000
745,000
653,000

647,000
615,000

610,000
600,000
550,000

504,000
429,134

422,000
396,000
386,000
385,000

379,000

360,000
357,000
353,000
325,000
314,000
270,000
260,000
256,000
240,000
237,000
231,000
225,000

220,700

Continent

Europe
Africa
Asia

Europe

Asia

South America
Europe

South America
Africa

Asia

Europe

N+C America

Europe
N+C America

N+C America
N+C America
South America

Africa

N+C America
Africa

Asia

N+C America

Europe
Europe
Africa
Europe
Europe

N+C America
Europe
Africa
Europe
Africa

Asia

Africa
Europe

Asia

N+C America
N+C America
Europe

Asia

Asia

N+C America
Asia

River

Wisla/Vistula

Rufiji

Hong Ha (Red River)

Rhine

Chao Phraya/Menam

Essequibo
Elbe

Chubut

Sanaga

Mahanadi

Oder

Rio Grande de Santiago

Loire
Gnijalva (with Usumacinta)

Mobile (Alabama)
Brazos

Lakes Titicaca — Poopo
system

Cunene/Kunene

Balsas

Save (Sabi)

Narmada

Colorado (State of Texas)

Rhone
Douro/Duero
Tana

Westem Dvina
Ebro

Panuco
Tejo/Tagus
Dra

Seine
Sassandra
Kyzy] Irmak/Kizil Irmack
Gambia

Po

Murgab
Sacramento
Susquehanna
Dnestr

Sepik

Hari Rud/Tedzhen
Yaqui

Fly

Annex 1

Countries area (sq. km)

Belarus, Poland, Slovakia, Ukraine ; ; ss 193,000
Tanzania 178,000
China, Laos, Viet Nam 169,600
Austria, Belgium, France, Germany, Liechtenstein, 168,757

Luxembourg, Netherlands, Switzerland

Thailand 160,000
Guyana, Venezuela 147,000
Austria, Czech Republic, Germany, Poland 144,500
Argentina 138,000
Cameroon, Central African Republic 135,000
India 133,000
Czech Republic, Germany, Poland 126,000
Mexico 125,000
France 120,000
Guatemala, Mexico 120,000
USA 115,000
USA 114,000
Bolvia, Chile, Peru 114,000
Angola, Namibia 112,000
Mexico 106,000
Mozambique, Zimbabwe 103,000
India 102,000
USA 100,000
France, Switzerland 95,300
Portugal, Spain 94,500
Kenya 91,000
Belarus, Latvia, Russia 87,900
Andorra, France, Spain 84,440
Mexico 84,000
Portugal, Spain 82,000
Algeria, Morocco 80,500
France 78,600
Céte d'Ivoire, Guinea 77,500
Turkey 75,800
Gambia, Guinea, Senegal 75,760
Italy, Switzerland 74,300
Afghanistan, Turkmenistan 73,000
USA 73,000
USA 72,500
Moldova, Ukraine 72,100
Indonesia, Papua New Guinea 71,000
Afghanistan, Iran, Turkmenistan 70,600
Mexico, USA 70,000
Indonesia, Papua New Guinea 67,000

85

Freshwater Biodiversity: a preliminary global assessment

Continent

South America
South America
Asia

Europe

Africa

Europe

N+C America
N+C America
Europe
Europe
Europe

Africa

Europe
Europe

N+C America
Asia

N+C America
South America
Europe

Asia

N+C America

River
Maroni
Colorado
Yalu
Guadiana
Lurio
Guadalquivir
Stikine
Skeena
Garonne
Weser
Kemi/Kemijoki
Omo

Terek

Glama
Papaloapan
Ma

Hudson
Atrato

Countries

French Guiana, Surinam
Argentina

China, Korea (PDR)
Portugal, Spain
Mozambique

Spain

Canada, USA
Canada

Andorra, France, Spain
Germany

Finland, Russia
Ethiopia

Georgia, Russia
Norway

Mexico

Laos, Viet Nam
USA

Colombia

Sweden

Laos, Viet Nam
USA

Part 2. Larger basins not analysed in this report.

Africa

Asia

Africa

Asia

Asia

Asia

Europe
Australia & NZ
Europe

N+C America
Asia

Asia

Asia

Africa

Asia

Asia

Asia

Africa
Australia & NZ
Asia

Africa
Australia & NZ
N+C America
N+C America
N+C America
Australia & NZ

Lake Chad basin

Tarim (Yarkend)
Kavango (Cubango)
Chutsyan

His

Khatanga
Pechora
Coopers Creek
Neva
Churchill
Yana

Hwai Ho
Olenek

Lake Turkana
Anadyr
Pyasina

Ili

Ruvuma
Diamantina
Taz

Cuanza
Fitzroy (Qld)
Thelon
Albany
Koksoak
Burdekin

Cameroon , Central African Republic, Chad, Niger,

Nigena, Sudan
China, Kyrgyzstan

Angola, Botswana, Namibia

China, Viet Nam
Russia

Russia

Australia

Russia

Canada

Russia

China

Russia

Ethiopia, Kenya, Sudan, Uganda
Russia

Russia

China, Kazakhstan
Malawi, Mozambique, Tanzania
Australia

Russia

Angola

Australia

Canada

Canada

Canada

Australia

86

area (sq. km)

66,000
65,000
64,500
61,400
57,600
57,100
56,700
54,900
53,425
52,800
51,500
46,700
43,200
40,500
37,400
36,000
35,000
32,200
29,000
28,500
27,200

1,910,000

980,000
785,000
437,000
436,000
364,000
322,000
285,000
281,000
281,000
238,000
220,000
219,000
203,300
191,000
182,000
176,000
166,500
156,000
150,000
149,000
143,000
142,000
134,000
133,000
131,000

Continent

South America
Africa

Asia

Asia

Africa

Asia

N+C America
N+C America
Australia & NZ
N+C America
N+C America
Asia

Africa

N+C America
Africa

N+C America
South America
Australia & NZ
Europe

Asia

Australia & NZ
Asia

South America
N+C America
N+C America
Australia & NZ
Europe
Australia & NZ
Africa

Europe

Africa

Asia

South America
N+C America
Australia & NZ
Australia & NZ
N+C America
Asia

Africa

Africa

N+C America
Asia

Asia

Africa

N+C America
Asia

Asia

Asia

South America
Europe

Africa

Europe

River

Rio Negro
Cuvelai-Etosha
Taimyr
Kerulen
Awash

Pur

Moose
Hayes
Flinders
Back
Severn
Anabar
Guir

Fort George
Bandama
Saguenay
Meanm
Fitzroy (WA)
Neman
Hari
Ashburton
Sarysu
Doce

San Joaquin
Churchill (Hamilton)
Gascoyne
Mezen
Victoria
Kam
Vuoksa
Komoe
Penzhina
Courantyne
Kazan
Mitchell
Murchison
Winisk
Lake Ubsa
Baraka
Daoura
Nottaway
Alazea/Alazeya
Nadym
Kouilou
Copper
Uda

Atrek

Chu
Paraiba
Kuban
Cross
Onega

Countries

Brazil, Colombia, Venezuela
Angola, Namibia

Russia

Mongolia

Djibouti, Ethiopia

Russia

Canada

Canada

Australia

Canada

Canada

Russia

Algeria, Morocco

Canada

Cote d'Ivoire

Canada

Brazil

Australia

Belarus, Lithuania, Poland, Russia
Afghanistan, Iran, Turkmenistan
Australia

Kazakhstan

Brazil

USA

Australia

Russia

Australia

Nigeria

Finland, Russia
Burkino Faso, Cote d'Ivoire
Russia

Guyana, Surinam
Canada

Australia
Australia

Canada

Mongolia, Russia
Ethiopia, Sudan
Algeria, Morocco
Canada

Russia

Russia

Congo

Canada

Russia

Iran, Turkmenistan
Laos, Viet Nam
Brazil

Russia

Cameroon, Nigeria

Russia

87

Annex I

area (sq. km)

130,000
126,000
124,000
120,000
118,500
112,000
108,000
108,000
108,000
107,000
101,000
100,000
98,500
97,700
97,000
90,100
89,700
86,500
86,300
84,000
82,000
81,600
81,300
80,100
79,800
79,000
78,000
77,500
76,500
76,000
75,000
73,500
72,100
71,500
69,300
68,300
67,300
67,000
66,200
65,700
65,000
64,700
64,000
62,000
61,800
61,300
61,000
60,800
59,000
57,900
57,000
56,900

Freshwater Biodiversity: a preliminary global assessment

Continent
Asia

Europe
Europe

Asia

South America
Australia & NZ
Africa

N+C America
N+C America
N+C America
Europe

N+C America
N+C America
Africa

N+C America
Asia

Africa

N+C America
N+C America
N+C America
N+C America
N+C America
Asia

Africa

N+C America
Europe

Asia

Africa

Africa

Asia

South America
Asia

Africa

Africa

Africa

Africa
Europe
Africa

N+C America
South America
N+C America
N+C America
Africa

N+C America
N+C America
Africa

Africa
Europe
Africa

South America
Africa
Europe

River
Sakarya
Narva
Maritsa
Kamchatka
Lagoon Minm
Fortescue
Moulouya
Saint John
Apalachicola
Attawapiskat
Klaralven
Eastmain
Manicouagan
Oueme
George
Saigon
Gounits
Humboldt
Rupert

Great Whale
Leaf

St. Maurice
Kaladan
Sebu

San Juan
Kiumi

Dasht
Medjerda
Chelif

Han
Catatumbo
Tumen
Oum-er-Rbia
Maputo
Pangani
Niem
Tome/Tomio
Gash

Weiss
Oyapock
Penobscot
Potomac
Buzi
Harricanaw
Connecticut
Kovali/Cavally
Lake Natron
Kem
Nyanga
Baker

Mono

Oulu

Countries

Turkey

Estonia, Russia
Bulgaria, Greece, Turkey
Russia

Brazil, Uruguay
Australia

Morocco

Canada, USA

USA

Canada

Norway, Sweden
Canada

Canada

Benin, Nigeria, Togo
Canada

Cambodia, Viet Nam
South Africa

USA

Canada

Canada

USA

Canada

India, Myanmar

Costa Rica, Nicaragua

Iran, Pakistan

Algeria, Tunisia

Algena

Korea (PDR), Korea (R)

Colombia, Venezuela

China, Korea (PDR), Russia
Morocco

Mozambique, South Africa, Swaziland
Tanzania

Cameroon, Gabon, Equatorial Guinea
Finland, Sweden

Ethiopia, Sudan

Brazil, French Guiana
USA

USA

Mozambique, Zimbabwe
Canada

Canada, USA

C6te d'Ivoire, Guinea, Liberia
Kenya, Tanzania

Russia

Congo, Gabon
Argentina, Chile

Benin, Togo

Finland, Russia

88

area (sq. km)
~56,500
56,200
56,000
55,900
55,700
55,000
52,000
51,800
51,800
50,200
47,000
46,400
45,600
45,500
44,800
44,000
44,000
43,900
43,200
43,200
43,000
42,700
40,000
40,000
39,350
37,800
36,000
36,000
35,000
34,700
34,480
34,400
34,400
33,963
33,800
33,000
32,400
32,000
31,300
30,270
30,000
30,000
29,500
29,300
29,000
28,800
28,500
27,700
26,000
25,700
25,600
25,000

Continent

N+C America
South America
Europe

Europe

Africa

South America
South America
Europe

Africa
Australia & NZ
Europe

Asia

Europe

Africa

Europe

Africa

Europe

Africa

Europe
Europe
Europe

Europe

Asia

South America
Europe

Africa

Europe
Europe

South America
Africa

Europe

Africa

South America
Africa

Europe

Africa

Asia

Africa

Europe

South America
Africa

N+C America
Africa

South America
Africa

Asia

South America
South America
South America
Asia

Africa

River
Coco (Segovia)
Bio Bio
Vardar
Tuloma
Cavally
Lauca
Patia
Jucar
Corubal
Ciutha
Sevem
Coruh
Olanga
Moa
Pregel
Atui
Pasvik
St Paul
Minko/Mino
Tiber
Dnn
Schelde
Suyfun
Chira
Segura
Benito
Shannon
Thames
Aysen
Little Scarcies
Struma

Tano

Pascua

Geba

Minho

St John

Asi (Orontes)
Bia

Tana

Palena
Utamboni
Motagua
Cestos
Gallegos-Chico
Lofa

Jordan
Valdivia
Mira

Yelcho
Sembakung
Chiloango

Annex 1

Countries area (sq. km)

Honduras, Nicaragua
Argentina, Chile

Greece, Macedonia FYR
Finland, Russia

Cote d'Ivoire, Guinea, Liberia
Bolivia, Chile

Colombia, Ecuador

Spain

Guinea, Guinea-Bisseau

New Zealand

UK

Georgia, Turkey

Finland, Russia

Guinea, Liberia, Sierra Leone
Poland, Russia

Mauritania, Western Sahara
Finland, Norway, Russia
Guinea, Liberia

Portugal, Spain

Italy

Albania, Macedonia FYR
Belgium, France, Netherlands
China, Russia

Ecuador, Peru

Spain

Equatorial Guinea, Gabon
Ireland

UK

Argentina, Chile

Guinea, Sierra Leone
Bulgaria, Greece, Macedonia FYR, Federal Republic of
Yugoslavia

Céte d'Ivoire, Ghana
Argentina, Chile

Guinea, Guinea-Bissau, Senegal
Portugal, Spain

Guinea, Liberia

Lebanon, Syria, Turkey
Ghana, Cote d'Ivoire

Finland, Norway

Argentina, Chile

Equatorial Guinea, Gabon
Guatemala, Honduras
Liberia, Cote d'Ivoire, Guinea
Argentina, Chile

Guinea, Liberia

Israel, Jordan, Lebanon, Syna
Argentina, Chile

Colombia, Ecuador
Argentina, Chile

Indonesia, Malaysia

Angola, Congo, Congo (DR)

89

24,800
24,300
24,000
23,600
23,500
23,500
22,540
22,400
22,000
22,000
21,000
21,000
20,700
20,000
19,700
19,500
19,300
18,000
17,700
17,200
17,100
16,500
16,500
16,220
16,100
15,900
15,700
15,300
15,300
15,000
14,500

14,000
13,840
13,700
13,500
13,500
13,300
13,100
13,000
13,060
12,800
12,570
12,500
12,240
12,000
11,500
11,280
11,200
11,145
11,000
11,000

Freshwater Biodiversity: a preliminary global assessment

Continent
N+C America
Asia

South America
Africa

N+C America
South America
Africa

South America
Africa

South America
N+C America
Africa

N+C America
N+C America
Europe

N+C America
Asia

Europe

N+C America
South America
South America
Europe

South America
Asia

Europe
Europe
Europe

N+C America
Asia

N+C America
N+C America
Europe

N+C America
Africa

N+C America
N+C America
Europe

N+C Amenica
N+C America
South America
South America
South America
Asia

Europe
Europe

N+C America
Europe
Europe

South America
Europe
Europe

South America

River
Candelaria
Kamafuli
Amacuro
Mano-Morro
Lempa
Serrano
Tafna

Puelo

Great Scarcies
Barima

St. Croix
Umbeluzi
Artibonite
Belize
Vijose
Choluteca
Tiban

Bann

Hondo

Rio Grande
Lake Gagnano
Eme
Tumbes
Tami

Foyle
Naatamo
Lima
Sixaola
Pakchan
Changuinola
Negro
Isonzo
Goascoran
Akpa
Suchiate
Sarstun
Yser

Paz

Tijuana
Carmen Silva
Zarumilla
Zapaleri
Golok

Lake Prespa
Muga
Coatan-Achute
Rezvaya
Veleka
Mataje
Bidasoa
Roia

Cullen

Countries
Guatemala, Mexico
Bangladesh, India
Guyana, Venezuela
Liberia, Sierra Leone

EI Salvador, Guatemala, Honduras

Chile, Argentina
Algeria, Morocco
Argentina, Chile
Guinea, Sierra Leone
Guyana, Venezuela
Canada, USA,

Mozambique, South Africa, Swaziland

Dominican Republic, Haiti
Belize, Guatemala

Albania, Greece

Honduras, Nicaragua

Yemen

Ireland, UK (Northern Ireland)
Belize, Guatemala, Mexico
Argentina, Chile

Argentina, Chile

Ireland, UK (Northern Ireland)
Ecuador, Peru

Indonesia, Papua New Guinea
Ireland, UK (Northern Ireland)
Finland, Norway

Portugal, Spain

Costa Rica, Panama
Myanmar, Thailand

Costa Rica, Panama
Honduras, Nicaragua

Italy, Slovenia

El Salvador, Honduras
Cameroon, Nigeria
Guatemala, Mexico

Belize, Guatemala

Belgium, France

El Salvador, Guatemala
Mexico, USA

Argentina, Chile

Ecuador, Peru

Argentina, Bolivia, Chile
Malaysia, Thailand

Albania, Greece, Macedonia FYR

France, Spain
Guatemala, Mexico
Turkey, Bulgaria
Bulgaria, Turkey
Colombia, Ecuador
France, Spain
France, Italy
Argentina, Chile

90

area (sq. km)

10,800
10,500
10,260
10,000
9,870
9,100
8,800
8,800
8,500
8,400
8,100
8,000
7,900
6,960
6,900
6,260
6,200
5,800
5,600
4,830
4,820
4,750
4,655
4,600
4,000
3,700
3,400
3,300
3,100
3,060
2,830
2,800
2,500
2,150
1,840
1,800
1,700
1,650
1,635
1,620
1,570
1,565
1,500
1,400
1,300
1,250
1,100
1,000
870
820
750
735

Continent
Nec America
South America
N+C America
N+C America
South America
Europe
Europe
Europe

River
Jurado
Chuy
Massacre
Pedernales
San Martin
Jacobs
Fane

Meuse

Countries

Colombia, Panama

Brazil, Uruguay

Dominican Republic, Haiti

Dominican Republic, Haiti

Argentina, Chile

Norway, Russia

Ireland, UK (Northern Ireland)
Belgium, France, Germany, Netherlands

Annex 1

area (sq. km)
620
500
480
450
370
240
190

Notes: the estimates of basin area are from two different sources, sometimes with significant differences for
the same system; the country information is preliminary and entirely unofficial and implies no expression of
opinion on the part of WCMC, UNEP or any collaborating organisation about the legal status of any country,

territory or area concerning the delimitation of boundaries of nations or catchment basins.

Sources: expanded from:
Anon. 1978a (Centre for Natural Resources, Energy and Transport of the Department of Economic and Social
Affairs, United Nations). 1978. Register of International Rivers. Water Supply and Management. 2: 1-58.

(Special Issue). Pergamon Press.

Anon. 1978b. World water balance and water resources of the Earth. USSR Committee for the International
Hydrological Decade. Studies and reports in hydrology NO. 25. UNESCO.

91

ANNEX 2

RIVER BASIN ANALYSIS: SELECT DATA FROM WCMC
FRESHWATER BIODIVERSITY DATABASE

93

Freshwater Biodiversity: a preliminary global assessment

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101

ANNEX 3

TECHNICAL NOTES

Catchment basin boundaries

The catchment basin boundaries used were based initially on the global dataset on
the GlobalARC CR-ROM made available by CERL (the US Army Corps of
Engineers Construction Engineering Research Laboratories). This is generated
from a relatively coarse elevation model. Data for North America and Africa were
replaced with improved boundaries generated by the United States Geological
Survey (USGS). The most inclusive basin boundaries, ie. the entire drainage
system passing through one river mouth (or delta region) to the sea were used in
the analysis, selected to provide a reasonable sample from each continent. A very
few internally draining systems were also included. In addition, and particularly
outside N America and Africa, the major catchment boundaries were inspected by
eye against appropriate paper maps, and adjustments made. USGS hydrological
data are available from:
http://edcwww.cr.usgs.gov/landdaac/gtopo30/hydro/index.html.

Fish diversity analysis

The number of native fish species per catchment ranges from 5 to an estimate of
2500 for the Amazon system. Because of this very wide range in numbers, the data
are easier to manage when log-transformed; that is, the natural logs of both the
species number and the measure of river size are used. The size of the river can be
expressed both in terms of the size of the catchment and of the mean annual
discharge (essentially a measure of the volume of water in the river). As confirmed
by Guégan et al. (1998) where data for both these are available, the latter is a
considerably better predictor of fish species number than the former (r=0.49 in the
case of catchment area, r=0.67 in the case of discharge for log-transformed data,
n=69, p<0.0001 in both cases). As might be expected, discharge and catchment
area themselves are strongly correlated (r=0.74, n=69, p<0.0001), with the major
deviations being large rivers (e.g. the Niger and Nile) whose catchments lie mainly
in arid regions and which thus have less discharge than expected from the size of
the catchment. However, because we have data for catchment area for considerably
more rivers than we have data for discharge (data on species number and catchment
size available for 166 rivers, compared with data on species number and discharge
for 69 rivers), we have used the former as an imperfect surrogate for the latter, in
order to maximise our use of information.

103

Freshwater Biodiversity: a preliminary global assessment

Because the range of values for fish families is much smaller than for fish species,
these data can be analysed without log-transforming them (although, as in all
species-area relationships, the log of the area concerned is used, rather than the
absolute value). A comparison of the logged and unlogged data shows that the two
yield similar results. For this reason, and because unlogged data are intuitively
easier to understand, we have used these.

104

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