r
October - December 1993 Number 1007
_ Volume 118
Naturalist
A QUARTERLY JOURNAL OF NATURAL HISTORY FOR THE NORTH OF ENGLAND
Freshwater algae in Yorkshire — Gordon F. Leedale
Annual and long-term observations on the Cnidaria inhabiting
an intertidal mussel bed in Morecambe Bay, Lancashire —
David Jones
A review of the Grayling ( Thymallus thymallus L.) in Yorkshire
and some records of transfers of Fish and ova — Leslie Magee
Vegetation changes on Ilkley Moor between 1964 and 1984,
and possible environmental causes — W. H. G. Hale and
D. E. Cotton
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101
FRESHWATER ALGAE IN YORKSHIRE
Presidential Address to the Yorkshire Naturalists Union,
Wilton Castle, 5 December 1992
GORDON F. LEEDALE
Freshwater algal records for Yorkshire go back a long way but there have been relatively
few research investigations even though the county is rich in interesting lakes, meres,
ponds, marshes, rivers and streams. Accordingly, when I first came to Yorkshire in 1959 I
decided to make use of these habitats in my research which is mainly concerned with cell
structure of freshwater microalgae, especially plankton and, above all, Euglena. Taking
stock over thirty years later shows that these studies have utilised numerous sites but I shall
confine my remarks today to just two of the most interesting.
Those of my fellow naturalists who study beautiful birds, or wild flowers, or butterflies
and moths, or other marvels of natural history, may wonder why someone actually chooses
green slime! Well, as I hope to show you, providing one has access to good microscopes,
the algae are just as beautiful and fascinating as any other organisms.
Sawley Dene
My first site is Sawley Dene, a shallow eutrophic lake in North Yorkshire near Fountains
Abbey. This may sound familiar to some of you since I reported on the periodicity of
phytoplankton in this lake with two students, Helena Cmiech and Tony Rees, in The
Naturalist in 1984.
Two main peaks of biomass occur annually, diatoms in winter/spring and bluegreens in
late summer. One of my hobbies is trying to capture the beauty of these microorganisms by
colour photography in the light microscope and black-and-white photography in the
scanning electron microscope. What I intend to do today is pictorialise our 1984 account by
showing you some of the attractive algae that occurred. This will work well for my spoken
address but will not make much impact in the written version without the colour
photographs!
The lake is actually too shallow to stratify (become layered) and is really a large pond.
However, because there is virtually no inflow in the summer, the lake acts like the
epilimnion (top layer) of a stratified lake such as Esthwaite in the Lake District and nutrient
inflow in autumn acts like the overturn of a larger lake.
Asterionella and other diatoms peak in February, March and April, bluegreens in
September and October, and other algae mainly in summer, often just before the
bluegreens. These other algae include dinoflagellates, chrysophytes like Mallomonas, the
euglenoid Trachelomonas , and green algae such as Eudorina and desmids. The autumnal
bluegreens are dominated by blooms of Anabaena but large populations of
Aphanizomenon, Gomphosphaeria and other interesting genera also occur.
Helena Cmiech and I have written a long series of research papers on the cytological
changes in the bluegreens in natural conditions over several seasons in Sawley Dene. This
is the first study of its kind and Sawley Dene is now known worldwide. Electron
microscopy shows many changes in cell inclusions as filaments appear, grow, develop and
age. One new observation, among many, is that akinetes germinate immediately and serve
to take the bluegreens out of the plankton and into the mud, rather than being resting
spores.
Tholthorpe Village Pond
Our second destination is Tholthorpe in the Vale of York where, in the summer of 1980,
the village pond turned bright red and the Parish Council anxiously sought advice from
biologists at Leeds University. “Is it dangerous? Is it an act of God in retribution for village
Naturalist 118 (1993)
102
Freshwater Algae in Yorkshire
sins? Can it be got rid of?” The call for help was passed to me and after viewing the
phenomenon I said, “Don’t panic! Very interesting! May we study it over the next few
years, please?”
I was immediately interested because I realised that the redness was caused by an algal
bloom. What is more, the appearance of a surface skin on the water (looking as though
someone had thrown a pot of paint over the pond), bright red in full sunlight but turning
green in overcast conditions, recalled records from around the world of a red species of
Euglena, my favourite research genus.
A PhD student from South Africa, Heather Christie, was just starting to work with me
when the Red Pond of Tholthorpe manifested itself and it soon became her research topic.
After some preliminary studies, our main biological questions were (1) What causes the red
bloom? (2) Why has it suddenly appeared? (3) Why and how does it change from red to
green to red again? and (4) Why does it float?
Fortunately, the bloom appeared for three summers from 1980 to 1982, enabling us to
collect and study material by light and electron microscopy over a prolonged experimental
period. Yorkshire TV featured it as “The Traffic-Light Pond” and even the tabloid press
took up the story (“Red Cells in the Sunlight” - Ouch!). In my spoken address I can again
show you the beauty of the colour-changing cells of the red Euglena. In the written version
we will have to manage with black-and-white, including just a few of the many fascinating
electron micrographs from a very detailed study.
(1) The red colour was caused by a bloom of Euglena sanguinea, a rare microorganism.
In the floating mass the rounded cells lie in a raft of mucilage; transferred to clean water
they elongate and start to swim. The first record of “Bloody Euglena” perhaps occurs in
Exodus 7, 14-20:
The Lord said to Moses, “Tell Aaron to take his stick and hold it out over the
rivers and pools in Egypt. The water will become blood, and all over the land there
will be blood even in the wooden tubs and stone jars”. And Aaron raised his stick
and struck the surface of the river, and all the water in it was turned to blood. The
fish in the river died, and it smelt so bad that the Egyptians could not drink from it.
FIGURES 1 & 2
Living cells of Euglena sanuinea. Light microscopy. X 800.
Fig.l. Green cell in green bloom; the red droplets (H) surround the central
nucleus (N), the chloroplasts (Chi) are exposed.
Fig. 2. Red cell in red bloom; the red droplets are dispersed in the cell periphery,
the chloroplasts are hidden. P = paramylon (storage material).
Freshwater Algae in Yorkshire 103
In 1838, Ehrenberg considered this red plague was caused by E. sanguinea in shallow
pools following annual flooding of the river. Discovery of E. sanguinea in the Tholthorpe
pond enabled us to carry out the first modem study of its structure. Electron microscopy
revealed radiating chloroplast ribbons and many unique ultrastructural features.
(2) The organism appeared suddenly in Tholthorpe following pig-slurry manuring of the
surrounding farmland and a consequent huge increase of nitrate levels in the pond. It has to
be presumed that E. sanguinea was already present in the pond in small numbers. It has
never been recorded from anywhere else in Britain though it is known from Europe, China,
Argentina and Australia. Once the manuring stopped the blooms declined and by 1983 had
ceased altogether. However, scattered living cells of the red Euglena can still be found in
the pond’s mud to the present day.
FIGURE 3
Multiple electron micrographs montage showing a transverse section through a green cell
of Euglena sanguinea. As in Fig. 1, the red droplets (H) are in the centre, the chloroplasts
(Chi) are exposed between the paramylon granules (P). X 2000.
104
Freshwater Algae in Yorkshire
FIGURE 4
Electron micrographs montage showing a section through a floating cell of Euglena
sanuinea which is full of expanded mucilage bodies (MOe). X 5000.
Freshwater Algae in Yorkshire
105
(3) On cloudy days the floating bloom was green; in bright sunlight the bloom was red.
Change from green to red when the sun came out took about 20 minutes. When the pond
was green individual cells were green. Vast numbers of red pigment droplets congregated
in the centre of each cell while the green chloroplast ribbons were displayed around the cell
periphery for photosynthesis (Fig. 1). When the pond was red individual cells were red. In
bright light the red pigment droplets migrated to the cell surface and spread out as a screen
to protect the chloroplasts from damage (Fig. 2).
Electron microscopy of green cells showed huge numbers of carotenoid-containing lipid
droplets in the cell centre (Fig. 3); the cell periphery was occupied by chloroplasts, storage
granules of paramylon, and other organelles and inclusions. In red cells and cells turning
red, the pigment droplets were dispersed along tracks of microtubules and microfibrils to
become concentrated at the cell surface.
(4) Mature floating cells also became filled with a bubbly mass of expanded mucilage
bodies (Fig. 4). This is why the cells float. The internal changes of the mucigenic bodies
from very dense (Fig. 5) to fully expanded (Figs. 6-8) are unique to E. sanguinea. Most
planktonic organisms swim to the water surface in dull light and into the shade or deeper
water in full sunlight. Because E. sanguinea cells float they have evolved a unique method
of light protection. A mobile screen of hundreds of sunshade droplets that are centralised in
the cell when conditions are optimum for photosynthesis, spread out in sunlight to protect
the chloroplasts from sunburn.
Sawley Dene and Tholthorpe Pond are just two of the freshwater sites in Yorkshire that
have provided ideal situations for algal research. Studies will continue and I hope that
future generations of microscopists will be as enthralled as I have been by the intricate
structure, fascinating biology and supreme beauty of the microalgae.
FIGURES 5 & 6
EM sections of mucilage bodies of Euglena sanuinea. X 70,000.
Fig. 5. Condensed body (initial state), showing a dense granule and a membranous region.
Fig. 6. Body starting to expand; the membranous region is larger and more diffuse.
106
Freshwater Algae in Yorkshire
FIGURES 7 & 8
EM sections of mucilage bodies of Euglena sanguinea.
Fig. 7. Part of the membranous region has expanded into a
mucilaginous mass; the body is much larger. X 35,000.
Fig. 8. All the membraneous region is now bubbly mucilage but the dense
granule can still be recognised. X 50,000.
107
ANNUAL AND LONG-TERM OBSERVATIONS ON THE
CNIDARIA INHABITING AN INTERTIDAL MUSSEL BED
IN MORECAMBE BAY, LANCASHIRE
DAVID JONES
Institute of Environmental & Biological Sciences, Lancaster University,
Bailrigg, Lancaster LAI 4YQ
Introduction
Whilst there have been numerous studies of the flora and fauna of rocky, sandy and muddy
shores, usually over a relatively short time span, little has been published on the biota of
mussel beds, particularly that based on observations made over an extended period. This
paper describes the distribution in space and time of Cnidaria species on the Heysham
mussel bed (grid. ref. SD4163). The period of study was 1956-1990, excluding 1962,
September 1973-January 1976, and January 1979-1982.
Study Area and Methods
The study area and methods employed here have been fully described elsewhere (Jones &
Miller 1966; Jones & Clare 1977). The mussel bed is on an area of small stones, with
scattered large stones and boulders, and is exposed to strong tidal currents. The common
mussel, Mytilus edulis L., is widespread and abundant below MLWN, but more localised
above. Many pools are present on the mussel bed, which are submerged every day.
Each area of the shore was examined for about 2 hours, by walking a defined search path
and examining the same stones, boulders and pools each month. If conditions proved
unfavourable the nearest pools or boulders were examined. The tidal levels and vertical
ranges of these areas have been described elsewhere (Jones 1987). Search paths 1 and 2
were both recorded as high areas (the data from which were pooled), search path 3 as
middle area, search path 4 as low area, and search path 5 as LWS. The latter area presented
a special problem since during winter months complete daylight searches could not be
made; at such periods a torch was used. Partial examination did at times affect the recorded
abundance of certain species; on these occasions the abundance of organisms before and
after the partial examination was used to estimate the abundance for these months. The
abundance of species during the last 4 months of 1973 was estimated where necessary from
the results obtained in other years. The estimated values ranged from 0.1% of total
observations for Gonothyraea loveni (Allman) to 4.3% for Metridium senile (L.).
An arbitral system of recording population sizes was followed using the terms “rare” -
1-3 individuals or small colonies, “frequent” - more than 3, but inconspicuous, “common”
- conspicuous in some habitats, and “abundant” - conspicuous and using most habitats.
These categories were scored 1-5 respectively; 0=absent. While essentially subjective, this
method enables broad comparisons to be made between the abundance of species over
months and years. The temperature of the sea edge at low water was recorded on every
visit.
Throughout this paper the taxonomy and nomenclature of Haywood and Ryland (1990)
has been followed.
Results and Discussion
Hydroida
The following taxa were often recorded: Tubularia larynx (Ellis and Solander), Sarsia
tubulosa. (M.Sars.), Clava multicornis (Forskal), Hydractinia echinata (Fleming),
Bougainvillia ramosa (van Beneden), Gonothyraea loveni (Allman), Laomedea flexuosa
(Alder), Hartaubella gelatinosa (Pallas) and Obelia spp.. The vertical distribution of the
hydroids, annual variation in abundance and reproductive activity, and long-term changes
Naturalist 118 (1993)
108 Annual and Long-term Observations on the Cnidaria in Morecambe Bay, Lancashire
TABLE 1
Hydroid species infrequently or rarely recorded on Heysham mussel bed.
Species
Records
Reproduction
Corymorpha nutans M.Sars
First recorded 1970, then during 10
of the remaining years
May and June
Garveia nutans Wright
1956-61, 1968-90. Conspicuous
Nov-May
January-May
Dicoryne conferta (Alder)
Sept. 1966, Aug. 1969, Feb. 1970,
Aug. 1976.
Present on each
occasion
Clytia johnstoni (Alder)
First recorded Nov. 1966, then 7 of
the remaining years
Always present
Opercularella lacerata
(Johnston)
June 1977, Sept. & Nov. 1978,
Feb. & June 1979
June
Halecium halecinum (L.)
One recording June 1977
Present
Dynamena pumila (L.)
One recording August 1958
Present
Amphisbelia operculata (L.)
One recording Feb. 1973
Present
Rhizogeton nudum Broch
Every year since 1987
April-May
Hartaubella Sarsia
getatinosa tubulosa
(stage 1)
Tubularia Hartaubella
larynx gelatinosa
(stage 2)
I til
Hydractinia
echinata
Bougainvillia Metridium Sagartia
ramosa senile spp.
i I I
0 50 100
FIGURE 1
Vertical distribution of hydroid and anthozoan species on Heysham mussel bed.
Relative abundance shown as percentage of all records at each shore level.
H = high area; M = middle area; L = low area; LWS = low water springs.
Annual and Long-term Observations on the Cnidaria in Morecambe Bay, Lancashire 109
Hartaubella gelatinosa
(stage T)
Sarsia tubulosa
Tubularia larynx
XXX
Hartaubella gelatinosa
(stage 2)
Clava multicornis
XXXXXX
Gonothyraea loveni
* XXX
Obelia spp.
Laomedea flexuosa
Hydractinia echinata
Bougainvillia ramosa
Metridium senile
Sagartia spp
J FMAMJ JASOND J FMAMJ JASOND
FIGURE 2
Seasonal succession of hydroid and anthozoan species on Heysham mussel bed.
Mean abundance score (absent = 0, rare = 1, frequent = 2, common = 3, abundant = 4)
for all shore levels combined expressed as % maximum possible score.
• *■ Gonophores or gonothecae present, xxx mature gonophores or gonothecae present.
in abundance are summarised in Figures 1-3. Records of the occurrence and timing of
reproduction of other hydroid species are given in Table 1.
There was a clear pattern of vertical zonation (Fig. 1): G. loveni , L. flexuosa and
C. multicornis being particularly abundant at the highest areas searched, S. tubulosa,
B. ramosa, Obelia spp. and H. gelatinosa stages 1 and 2 mainly using the middle, low and
LWS areas, with H. echinata and T. larynx at the lowermost area. Generally the less
common species (Table 1) were found at the lowermost areas of the shore, the exception
being Clytia johnstoni (Alder) which occurred up to the middle search path, Rhizogeton
nudum Broch sharing the habitat of C. multicornis at middle and high areas, and
Opercularella lacerata (Johnston) found only in the high area.
There was a marked seasonal succession of abundance (Fig. 2). H. gelatinosa stage 1 and
S. tubulosa were the earliest hy droids to peak, in late winter, the last being B. ramosa in
autumn. Garveia nutans (Wright) (Table 1) attained maximum abundance in the late winter
and spring, Corymorpha nutans M. Sars. and Sertularia argentea L. in the early summer.
Hartaubella gelatinosa Sarsia tubulosa Tubularia larynx Hartaubella gelatinosa
(stage 1) (stage 2)
1 10 Annual and Long-term Observations on the Cnidaria in Morecambe Bay, Lancashire
aauepunqe %
FIGURE 3
Long-term patterns of abundance of hydroid and anthozoan species on Heysham mussel bed. % abundance as in Fig 2.
Annual and Long-term Observations on the Cnidaria in Morecambe Bay, Lancashire 111
Clava multicornis occurred on boulders, stones and shells. Colonies were always present
on some boulders. While occasionally hydranths were visible all year round, during the
autumn months they generally only existed in the form of a resting stolon. Colonies settling
on stones and shells did not become permanently established. Gonophores were found in
clusters behind the lower tentacles, becoming mature in April, May and June.
Gonothyraea loveni was found on boulders, stones and shells. Colonies on the high area
boulders were present throughout the year, while colonies on stones and shells on other
areas only occurred between April and July. These latter colonies were generally abundant
but did not occur every year. The gonothecae produced hanging medusae that were never
released.
Laomedea flexuosa formed permanent colonies on certain high and middle area
boulders, often extending onto mussels that were attached to the boulders.
Tubularia larynx continuously settled then disappeared from boulders, stones and shells,
never producing permanent colonies. It does not have a planktonic stage, the actinula larva
sinking to the substrate, where it moves around on its tentacles before eventually attaching
itself. Daughter colonies therefore would not be expected to settle very far from the parent
colony; this may explain why when T. larynx was lost after the cold winter of 1962-63 the
level of abundance recorded before 1963 was not restored until 1976 (Fig. 3).
Sarsia tubulosa was found in all months with the exception of July, August and
September. Settlement was on boulders, stones and shells. Free-swimming medusae were
produced during the first 4 months of the year (Fig. 2). Colonies appeared on the same
parts of some boulders most years, suggesting that a resting stolon may produce hydranths
the following season.
Spherical colonies of S. tubulosa appeared in 1969, becoming abundant during 1970.
They were common in 1978 and 1985, rare in 1972, 1977, 1979, 1984 and 1987. A
possible explanation for the formation of the rolling colonies is given in Clare et al. (1971).
The planula larva may have been affected by a chemical pollutant followed by recovery
and multipolar growth under natural conditions in the plankton.
Hartaubella gelatinosa stages 1 and 2 settled on boulders, stones and shells, but not on
the same ones season after season. It is therefore assumed that the littoral population is
maintained by settlement of larvae from the plankton. Gonothecae were rarely found on
stage 1, yet reproductive structures were always present on stage 2. Both stages appeared
without great variations in abundance every year of the study period (Fig. 3).
Only Obelia dichotoma (L.) was positively identified amongst the abundant Obelia
colonies that were present during the summer months, but other species may have been
present. Reproduction was by medusae with larval settlement from the plankton on
boulders, stones and shells. Colonies were not found on the same ones each year. No
obvious reason for the large variation in abundance (Fig. 2) could be found; however, their
settlement period of late spring and summer means that the demand for habitats is at its
greatest during settlement.
Active colonies of Bougainvillia ramosa were found on stones and shells during the last
5 months of the year, occasionally remaining in skeleton form until February.
Reproduction was by medusae during September, October and November (Fig. 2).
Hydractinia echinata was found mainly on gastropod shells occupied by the hermit crab
Pagurus bernhardus (L.), but colonies were occasionally found on stones and wood, and
on one occasion on the carapace of the shore crab Carcinus maenas (L.). No reason for the
steady decline in abundance of H. echinata (Fig. 3) could be found; the numbers of
P. bernhardus remained fairly constant throughout the survey. However once the decline
had commenced, the relative immobility of its larvae may have contributed to further
reduction in abundance, given the specialised nature of its microhabitat.
No data are presented for Sertularia argentea L., even though it was abundant during
some years, because many colonies remained in skeleton form for long periods and could
not be unequivocally separated in the field from living forms. It was recorded as frequent
every year from 1956-61, and rare from 1963-78, with the exceptions of 1966 and 1967
1 12 Annual and Long-term Observations on the Cnidaria in Morecambe Bay, Lancashire
when none were found. It was common or abundant from 1978 to the end of the survey.
Settlement from the plankton took place in July, August and September.
Of the hydroids that were infrequently or rarely recorded (Table 1), G. nutans was the
most consistent in occurrence although only found on one group of boulders at LWS. It
was active from November to the following May and gonophores were produced from
January to May (Table 1). During the remaining months it was present in a resting stage.
The colonies were lost after the cold winter of 1962-63 until 1968 when they returned.
Settlement was on the same boulders.
Rhizogeton nudum was recorded for the first time in the British Isles during this survey
(Jones 1992). It settled on boulders and mussel shells attached to these boulders, with
already established colonies of C. multicornis, in April and May of 1987 and each
subsequent year. In 1989 it also appeared in March. Gonophores were observed during
April and May. The ovoid female gonophores have ova which on release remain adhering
to the gonophore by mucus for some time. The immature male gonophore has a spadix; as
it matures it becomes white with sperm within. As R. nudum appeared at the same sites
each year, it seems likely that a resting stolon remains until conditions again favour
development.
Corymorpha nutans was only found from 1970, appearing in 10 of the remaining years.
Individuals were found between mussels, attached by a network of adhesive “rootlets” to
the muddy substrate. It was always recorded as rare and no specimens remained for more
than one month.
Clytia johnstoni was first found in 1966 and appeared in 7 of the remaining years. It was
found on stones, shells, seaweeds and the hydroid of S. argentea. It is not a conspicuous
hydroid, and colonies found in one month had disappeared by the next. C. johnstoni was
most likely to be found from July to November. Gonothecae were always present.
Opercularella lacerata was only found on one high area boulder and on mussels
attached to the boulder. Only 5 recordings were made between February and November.
Reproductive structures were present each time.
Dicoryne conferta was found on the shells of Buccinum undatum L. It is perhaps
surprising that only 4 sightings occurred during such long term observations because
substantial numbers of B. undatum were found, particularly during the winter months when
egg-laying was taking place.
Halecium halecinum, Dynamena pumila and Amphisbelia operculata each failed to form
permanent colonies, only one recording of each species being made throughout the survey.
The study period covers years when extreme temperatures were recorded, the lowest being
during the cold winter of 1962-63, when pools were covered with ice, and ice floes
occurred in the edge of the tide. In the winter of 1978-79 pools were again covered with ice
but the cold weather was not as severe or as prolonged. The warmest winter recorded was
1989-90, and the warmest summers 1976, 1983, 1984 and 1989. During the cold winter of
1962-63 two of the most abundant hydroids, H. gelatinosa stage 1 and S. tubulosa,
maintained their abundance (Fig. 3), and apart from T. larynx the species present during the
winter months generally showed little variation in abundance. Crisp (1964) found that the
cold winter of 1962-63 had little effect on hydroid species. It was noted, however, that taxa
which peak during the spring and summer, H. gelatinosa. stage 2 and Obelia spp., were less
abundant during 1963. This is surprising because when they settled temperatures were
close to normal. As these species do not develop each year from a resting stolon, perhaps
their parent colonies in the sublittoral zone, or the planktonic stages from these parent
colonies, were in some way affected. The cold winter of 1978-79 produced only a small
decline in the abundance of hydroid species from the previous year. The abundance of
hydroids was well maintained during the warm winter of 1989-90. While generally high
numbers occurred during the warm summer of 1976, it is unfortunate that no records are
available for the previous 3 years for comparison. However, abundances were also high
during the warm summers of 1983 and 1989.
Methods of reproduction have a bearing on the presence and yearly patterns of
Annual and Long-term Observations on the Cnidaria in Morecambe Bay, Lancashire 1 1 3
abundance of hydroid species. Clava multicornis, G. loveni and L.flexuosa were present on
some boulders throughout the study period. All have planulae that settle quickly in the
vicinity of parent colonies.
Several species of sea slug (Gastropoda: Opisthobranchia) were found on hydroids:
Tergipes tergipes (Forskal) and Eubranchus exiguus (Alder & Hancock) on Obelia spp.,
G. loveni and H. gelatinosa, Cuthona nana (Alder & Hancock) on H. echinata, Cuthona
concinna (Alder & Hancock) on H. gelatinosa and T. larynx and Doto coronata (Gmelin)
on S. tubulosa, S. argentea and C. multicornis. Sea slugs were seen to feed on hydroids, but
there was no evidence that such predation significantly reduced abundance. S. argentea
was occasionally covered with tiny mussel spat.
Actiniaria
The following taxa were recorded: Metridium senile L., Sagartia species: S. elegans var.
miniata Dalyell, var. nivea (Gosse) and var. rosea (Gosse), S. troglodytes var. decorata
(Price) and var. ornata (Holds worth). Other species recorded were Actinia equina L.,
Urticina felina L. and Diadumene cincta (Stephenson).
Metridium senile var. dianthus was readily identified, but only rarely recorded. The
abundances shown in Fig. 3 are of small forms of M. senile. They used all habitats, being
found on boulders, stones and shells and partly buried in the substrate with or without
attachment to a solid surface. During some summers abundant populations appeared in the
latter habitat at LWS. These were generally lost during the winter months when many
unattached specimens were found rolling in the tide. Colonies on boulders formed more
stable populations. One such colony existed beneath a boulder in the high area throughout
the study period, individuals never growing to more than 2 cm across the disc. The yearly
variations in abundance (Fig. 3) were mainly due to the arrival and eventual success of the
individuals using the substrate at LWS. Laceration of the base and budding were observed
as methods of reproduction.
Adult Sagartia species, with the exception of S. troglodytes var. ornata, were found with
their columns buried in the substrate. Juveniles were located beneath stones and shells.
Assessing their abundance was extremely difficult because specimens only occasionally
remained open when the tide receded, generally contracting and leaving a small hole in the
substrate to denote their presence. While their numbers were greatly reduced during the
cold winter of 1962-63, those found were healthy, and the less prolonged cold winter of
1978-79, had little effect on their abundance.
Although good numbers were again noted in 1967 it was not until 1979 that the level of
abundance recorded before 1963 was restored (Fig. 3). Sagartia species were recorded in
Morecambe Bay by Gosse (1860), but no details of abundance or distribution were given.
Sagartia troglodytes var. ornata was only found in the high area, and was not common.
Specimens were partly buried in the substrate or attached to stones or shells. They were
recorded each month from March 1957 to December 1960, but subsequently only 3
recordings were made, one in 1961 and two in 1971.
Recording of D. cincta was restricted to one colony. Although they were sometimes
found on a group of boulders at LWS it was not possible in the field to separate them from
small M. senile that shared this habitat. The recorded colony was a densely crowded cluster
beneath an overhang on a high area boulder. This colony persisted from January 1956 to
August 1964 when unfortunately the substrate accreted to cover the overhang.
U. felina was found partly buried in the substrate at LWS. It was present every year
throughout the study, being most frequent from 1956 to 1960, and 1983 to 1990. It did not
form obvious aggregations. No juveniles appeared in the population.
A. equina was most often recorded in the high area. Its appearance was sporadic;
individuals would appear one month only to disappear the next. However, 3 individuals
remained on a stone in one pool for 10 months.
The sea slug Aeolidia papillosa (L.) was seen attacking M. senile , Sagartia species, and
U. felina. The defence of M. senile was to extend the column and then detach itself.
1 14 Annual and Long-term Observations on the Cnidaria in Morecambe Bay, Lancashire
Sagartia species withdrew into the substrate, juvenile specimens beneath stones or shells,
expanding the column and ejecting acontia. U.felim. had no apparent defence.
The shore levels and microhabitats occupied by the anthozoans on the mussel bed are
consistent with those recorded by Stephenson (1928, 1935) and Manuel (1981).
Scyphozoa
Colonies of the scyphistoma of Aurelia aurita (L.) were found on boulders and stones at
LWS in January 1956 and July 1956, 57, 58 and 60. During 1958 they remained until
November.
Acknowledgements
I would like to express my gratitude to Dr T. G. Piearce for critically reading the
manuscript and offering valuable suggestions, Mr A. Dalton for help in the field,
Mr P. W. H. Flint for preparing the illustrations and to my wife Amy whose unending
patience and understanding have been invaluable.
References
Clare, J., Jones, D. and O’Sullivan, A. J. (1971) On the occurrence of detached spherical
colonies of the hydroids Sarsia tubulosa and Tubularia larynx in Morecambe Bay.
J. Mar. Biol. Ass., U.K. 55: 495-503.
Crisp, D. J. (1964) The effects of the severe winter of 1962-63 on marine life in Britain.
J.Anim.Ecol. 33: 165-201.
Gosse, P. H. (1860) Actinologia Britannica: a history of the British sea anemones and
corals. Van Voorst, London.
Hayward, P. J. and Ryland, J. S. (1990) The marine fauna of the British Isles and North-
West Europe , vols 1 & 2. Clarendon Press, Oxford.
Jones, D. (1987) Distribution and abundance of the starfish Asterias rubens L. on an
intertidal mussel bed in Morecambe Bay, Lancashire. Naturalist 112: 59-65.
Jones, D. (1992) Rhizogeton nudum (Cnidaria Hydroida) in the British Isles. J. Mar. Biol.
Ass., U.K. 72: 721-722.
Jones, D. and Clare, J. (1977) Annual and long-term fluctuations in the abundance of fish
species inhabiting the intertidal mussel bed in Morecambe Bay, Lancashire. Zool. J.
Linn. Soc. 60: 1 17-172.
Jones, D. & Miller, P. J. (1966) Seasonal migrations of the common goby Pomatoschistus
microps (Kroyer) in Morecambe Bay and elsewhere. Hydrobiologia 27: 515-528.
Manuel, R. L. (1981) British Anthozoa. Keys and notes for the identification of the species.
In: Synopses of the British Fauna (New series) No. 18. Academic Press, London.
Stephenson, T. A. (1928) The British Sea Anemones , Vol. 1 . The Ray Society, London.
Stephenson, T. A. (1935) The British Sea Anemones, Vol. 2. The Ray Society, London.
A REVIEW OF THE GRAYLING ( Thymallus thymallus L.)
IN YORKSHIRE AND SOME RECORDS OF TRANSFERS
OF FISH AND OVA
115
LESLIE MAGEE
4 Park Square, Pool-in-Wharfedale, Otley LS21 1LB
Introduction
The European grayling {Thymallus thymallus) is a salmonid fish which is found in cold
water between latitudes of 40° and 70° north. The very similar Arctic grayling T. arcticus
is widespread in suitable habitats in Asia and in North America. The grayling is instantly
distinguishable from all other salmonids by its very large erectable dorsal fin. The name
grayling is at least five centuries old and is believed to be a corruption of “gray lines”, a
name derived from the distinct pattern of dark longitudinal lines on its flanks. The
derivation of its other colloquial name ‘Umber’, now obsolete, is more obscure and various
theories have been put forward (Magee 1992).
The grayling is not an introduced species in England but whether or not it re-colonised
England from sub-arctic regions of Northern Europe, or from the Danube basin via the
east-flowing rivers of England while England was still joined to the European mainland
remains a matter of speculation (Platts 1939).
Historically, the grayling was thought to be confined to some rivers draining into the
North Sea and the English Channel but its distribution in the British Isles became better
understood and well documented during the 19th century. The main reasons for this were
the rapid growth of the railways from 1840 onwards, making regions formerly remote
readily accessible to sportsmen with the time and the means to travel, and the profusion of
angling literature after Waterloo, especially books on flyfishing and the development of
pisciculture, particularly trout breeding.
The grayling is considered to be an endangered species in Britain: it has become extinct
in some streams where it was formerly abundant and is declining in others. The causes of
the decline are various but pollution, water extraction, exploitation, habitat changes and
disease have all played some part (Magee 1992).
Habitats
The grayling does not occur in Ireland and does not naturally inhabit lakes but there are at
least two lakes, Gouthwaite Reservoir in Yorkshire and Llyn Tegid in Wales, where the fish
are known to migrate from the river to the lake and vice versa at different times of the year.
It has two distinct types of habitat in the British Isles and certainly has a preference for
alkaline waters. The first type of habitat is the mid-reaches of stony-bottomed spate rivers
which also have pools and glides with sand and gravel, such as the Wharfe and the Ure.
The second type is the so-called chalk streams of the lowlands which are spring fed and
have a less rapid descent from the sources, such as the Costa Beck (North Yorkshire) and
the Test in Hampshire.
Distribution
Grayling remains have been found in archaeological deposits in the York area dating
from the 1st to the 12th centuries (Jones 1988). This tends to confirm that the grayling is
indigenous to the Yorkshire Ouse river system, and that the historical records for the
Humber are correct, if one accepts that in that context ‘Humber’ refers to the system of
rivers draining into the Humber rather than the specific river. Taylor (1800), writing of
Yorkshire rivers, is precise: “This county is watered by an abundance of rivers; the principal
of which are the Humber , though this is not properly a distinct river, as not having a spring-
head of its own, but rather the mouth or receptacle of divers other rivers . . . especially the
Naturalist 118 (1993)
116
A Review of the Grayling in Yorkshire
Trent , the Ouse". Especially interesting is his mention of the Golden Umber. “The river
Humber is said to produce the greatest quantity of that sort of fish which in this part of the
country is called the Golden Umber, and in other counties the Grayling; and though some
are of the opinion that they really are a different species of fish, yet I am convinced that they
are not, but that different counties give them separate names.” One 20th century writer has
remarked on the variation in colouring of Yorkshire grayling: “some golden, some steely
and others lilac . . .” (Rhygini 1968). All the main rivers draining into the Ouse, with the
exception of the Calder, still have populations of grayling.
The earliest printed records of grayling in the British Isles are to be found in angling
literature, the first being that in A Treatise of Fysshinge wyth an Angle (1496) printed by
Wynkin de Word at Westminster. The second is that of Isaac Walton in The Compleat
Angler (1653) where he mentions its presence in “the Derbyshire Dove, the Trent and some
small rivers as that which runs by Salisbury”. This is the first mention that I have been able
to find of the grayling living in rivers draining into the Humber.
The first printed reference to the grayling in Yorkshire is that of John Aubrey in The
Natural History of Wiltshire (1660): “ ... it hath in it a rare fish called the Umber . . . This
kind of fish is in no other river in England except the river Humber in Yorkshire”. The next
record for Yorkshire rivers seems to be that of Dr Richard Brooks (1740): “They delight in
rivers that run through mountainous places and one to be met with in the clearest and
swiftest parts of those streams, particularly they are bred in the Hodder, Dove, Trent,
Derwent, Humber, Wye and the Lug”. [The Hodder and the Humber are Yorkshire rivers,
although the tidal Humber is an unlikely habitat.] The book ran to fourteen editions, the last
being in 1811; many authors of angling books quoted the same distribution almost verbatim.
According to The Sportsman s Dictionary (Anon. 1792), “The Grayling is found in
plenty in many rivers in the North, particularly in the Humber and in the Wye which runs
through Herefordshire and Monmouthshire into the Severn”. Whittaker (1818) mentions in
passing, “the beautiful river Hodder, famous for its Umber . . . rising near the Cross of
Crete”. Sir Humphry Davy (1828), the scientist and much travelled angler, wrote: “the
grayling is a rare fish in England and has never been found in Scotland or Ireland, I know it
no further west than the Avon in Hampshire ... In Derbyshire, Staffordshire, the Dove, the
Wye, the Trent, and the Blythe afford grayling; in Yorkshire, on the north coast, some of
the the tributary streams of the Ribble; and in the south, the Ure, the Wharfe, the Humber,
the Derwent, and the streams that form it, particularly the Rye”.
John Turton (1836) of Sheffield began flyfishing for trout on the head waters of the Don
around the turn of the century but wrote that there were no grayling there. Since he
describes in detail the Derbyshire and Staffordshire rivers in which he had found grayling
plentiful, it seems unlikely that they were present anywhere in the Don at that time. He
does mention the pollution from ‘manufactories’ which even at that date was becoming
widespread on the Don and the grayling is very susceptible to pollution in its many forms.
Ronalds (1836) quotes Sir Humphry Davy in full but acknowledges the author. Other
references are:
Yarrell (1836): “In Yorkshire, in the Derwent, the Ure, the Wharfe and the Whiske near
Northallerton”.
Shipley and Fitzgibbon (1838): “In Staffordshire in the Hodder [the Hodder is actually a
tributary of the Yorkshire Ribble] ... in Lancashire in the Ribble, ... in Yorkshire in the
Derwent, the Ure, the Wharfe, and the Whiske near Northallerton”. Pennell (1895) quotes
the above almost verbatim, with the same errors.
Hofland (1839) refers to Harewood on the Wharfe: “Here the grayling are much more
abundant than at Bolton. [Bolton Abbey, further upstream] I have seen shoals of them
swimming near the the sparlings of the bridge . . . during my residence at Harrowgate this
was a favourite resort of mine”.
Denny (1840): “ Thymallus vulgaris Rather local. Harwood, Bolton [Bolton Abbey]
Wakefield”.
Holland (1843): “The following fishes may be found in the Don and other streams in our
117
A Review of the Grayling in Yorkshire
locality . . . salmon , trout and grayling . . .
Since the list of 21 fishes which he said were to be found in the Sheffield district
includes the grayling, ‘The Sheffield district’ may well have included certain North
Derbyshire rivers where the grayling was abundant. Turton (1836) stated that for 30 years
he had travelled to Derbyshire for the fishing but he would hardly have done so if the local
fishing was as good as Holland seems to indicate.
Jackson (1854): “There are no grayling above Aysgarth . . . about Clifton trout and
grayling abound in considerable numbers and attain a good size . . . The Wharfe: Grayling
are found but are not very numerous at Grassington ... at Collingham the grayling are very
numerous and predominate over the trout . . . The Rye: At Rievaulx the grayling fishing
may be said to commence; the grayling are numerous and predominate over the trout”.
Clarke and Roebuck (1881): “[Grayling] Freshwater resident, found in varying
abundance in the middle waters of the Wharfe, Washburn, Nidd, Ure and Swale, also in the
Cover, Whiske and Codbeck, the Rye and other tributaries of the upper Derwent and in the
Scalby Beck near Scarborough. In the Tees it is very limited in numbers and it has been
introduced into the Esk. Formerly abundant in the Ribble and Hodder, their extreme
scarcity - if not extinction - being ascribed to the great increase in the salmon. It was also
formerly abundant in the Aire about Bingley but in 1824 all were destroyed due to the
bursting of a bog, subsequent attempts at re-introduction have as as yet proved ineffective”.
Pennell (1895), recommending streams where the grayling might be successfully
introduced, states (surprisingly for a stream noted for its large grayling), “Driffield Beck
below Wandsford Mill seems exactly fitted to carry grayling side by side with trout”.
Pritt (1886): “Kilnsey [Upper Wharfe] water holds no grayling”.
Pritt (1888): . . the grayling was formerly plentiful in the middle reaches of the Ribble,
about the Cistercian foundations of Sawley and Whalley. Of late years the fish had
practically disappeared from this river but careful nurturing and preservation between
Sawley and Gisbum have proved that the grayling will survive there as it did in ancient
days ... It is to be noticed that the grayling rivers of Yorkshire, some ten or eleven in all,
join their broad waters in the Humber . . . The best grayling river of Yorkshire is the
Costa”. [It joins the Rye at Howe Bridge, north of Malton.]
Pritt (1888): “There are many fine streams on the Western side of the country in which
it would prosper if it were properly introduced, ... as indeed it would in the Hodder, the
Lune . . .”.
Walbran (1895): “The river Wharfe from Otley down to Harewood used to abound with
grayling, but during recent years they have greatly decreased in numbers. Some 30 years
ago (1865) one angler killed 75 grayling in a single day with fly only . . . The sole reason
for the decline may be found at Ilkley and Otley where all the town’s sewage has hitherto
been turned direct into the river . . . There is also a large paper mill which has polluted the
stream”. [The Otley Angling Club was the first to successfully prosecute a local council for
pollution in 1897 but merely achieved bankruptcy] “In Yorkshire, the Wharfe, the Yore,
the Swale, the Derwent, the Costa and the Rye all abound with fine grayling”.
Minute Book, Appletreewick, Barden and Bumsall Angling Club (1889), referring to the
Wharfe: “There is a vast increase in the number of small grayling which is not looked upon
as at all satisfactory and that grayling have increased inordinately at the expense of the
trout”.
ABBAC Minute Book (1906): “1671 grayling were netted out and distributed to the
landlords and the tenants”.
ABBAC Minute Book (1928): J. Bazeley complained of excessive numbers of grayling
in the upper Wharfe, giving instances of 80 per day caught by individual anglers on rod and
line.
Yorkshire Post (1929): “Stocks of grayling on the upper Wharfe now very low”.
ABBAC Minute Book (1932): “It was decided that grayling should be netted out”.
ABBAC Minute Book (1968): “Disease was reported in the Aire and the Ure”. [This
proved catastrophic for grayling stocks on both these rivers as well as the Wharfe, and it
118
A Review of the Grayling in Yorkshire
was to be several years before there was a noticeable recovery, achieved mainly by
restocking with fish from the East Riding and restrictions on culling].
Briggs (1991 Pers. comm.): “Very rare in the Wharfe between Otley and Harewood
1940-1965”.
Grayling Introductions
Davy (1828) gives the first record of grayling being introduced into a river where they
were not previously known: “The grayling were recently [1816] introduced into the Test”.
They flourished in this famous chalk stream and some 50 years later fish between two and
three pounds were commonplace.
Turton (1836) gives the first note of grayling being introduced into ponds [in Darley
Dale ]: “We angled in three preserved dams, into one of which the owner had put many
fine greyling [sic] , - he being a young fly fisher himself. It was the only dam in which I
ever saw them”.
There are various contemporary accounts of the first grayling introductions into Scottish
rivers. The following is from Hutchinson (1904): “In 1855, 36 yearling grayling were sent
by mail train from the Derbyshire Wye to Abingdon on the Clyde”.
“In 1857, The West of Scotland Angling Club obtained 10,000 grayling ova from the
Derwent near Bakewell. The spawn was taken on 13th April 1857 and sent off the same
night in common wine bottles half filled with water to Abingdon on the Clyde, about 50
miles above Glasgow, where the club had prepared a rill for its reception ... It is a matter
of history that this simple method of transporting grayling ova stocked the Clyde with the
fish”. Grayling fingerlings from the above experiment were transfered to the river Nith in
1858. From this period onwards, the transfer of grayling from one river to another and to
higher reaches of the same river, where there were obstacles to upstream migration,
became a regular occurrence. Not all transfers were successful; grayling transferred from
the Costa Beck to the Yorkshire Esk in 1880 failed to survive. Transfers to the upper Aire
failed also, although they are now established in the main river in the Skipton area.
Pritt (1888): “. . . half a dozen grayling introduced into the Aire at Keighley 12 years
ago, have been sufficient to populate miles of good grayling water above the point at which
they were turned in. Previous to the introduction of these fish, grayling had become extinct
in the upper reaches of the Aire”.
No evidence of transfer of grayling into Yorkshire from outside the county has been
found to date; this is not surprising since grayling were to be had for the asking in a county
where the fish was numerous and was considered vermin by many proprietors of trout
streams. Large numbers of mature fish were transferred from East Yorkshire to the
tributaries of the Ouse, mainly to replace stocks which had been wiped out by pollution.
However, since the pollution was on-going, many of the introductions had to be regularly
repeated. The dates of the transfers, numbers of fish, sizes, origin and the receiving river
have survived in many instances and a list is given below, although it is not claimed to be
complete by any means.
DATE
SOURCE
NUMBER
RECEIVING RIVER
1876
Wharfe
6
Aire (above Keighley)
1931
Costa Beck
31
Wharfe (Kirby)
[Tagged fish]
November 1936
Golden Hill
Driffield
1170
Wharfe; Swale
Driffield
200
Nidd
1936
West Beck
200
Wharfe (Ulleskelf)
West Beck
300
Wharfe (Pool Bridge)
West Beck
250
Riffa Beck (Wharfe)
A Review of the Grayling in Yorkshire 1 19
1937
West Beck
800
Wharfe (Pool), Riffa Beck
1937
West Beck
800
Wharfe (Kirby Wharfe)
Aug/Sept 1937
Ure at Wensley and
Middleham
400
Nidd and Swale
Oct 1937
Wharfe (Bumsall)
[4oz to lOoz]
500
Lower Wharfe
Oct /Nov 1937
Driffield Beck
2400
Leeds ASA waters on
1939
West Beck
Part of 1500
Nidd and Wharfe.
(50% over one pound)
Wharfe
1940
West Beck
Part of 1600
Wharfe
1942
West Beck
Part of 1200
Wharfe
1943
West Beck
Part of 1000
Wharfe (Pool)
1945
West Beck
800
Wharfe (Boston Spa
1948
West Beck
400
and Wetherby)
Wharfe (Boston Spa)
1950
Aire (Broughton)
?
Wharfe
1956
Ure (Norton)
85
Wharfe
1958
Unknown
72
Wharfe (Harewood)
c.1960
Costa Beck
100
Aire (Keighley)
1961
Unknown
123
Wharfe (Harewood)
1962
Unknown
200
Wharfe (Harewood)
1963
Unknown
250
Wharfe (Harewood)
1965
Unknown
60
Wharfe (Harewood)
(In 1966 the Leeds Anglers’ Association felt that at long last the grayling had been re-
established in the Wharfe at Harewood and decided that members could take two brace per
day from the river between Oct 1 and Jan 31 if they so wished. However in 1968 ‘fungus’
disease wiped out the majority of grayling in the Wharfe from Burley to Boston Spa and
re-stocking commenced in 1971.)
1971
Unknown
190
Wharfe (Harewood)
‘Large fish’
1990
Reared from Nidd
ova by NRA.
100
Wharfe (Arthington)
Factors which have affected the Grayling populations
Pollution
The ‘grayling zones’ of several Yorkshire rivers, particularly the Tees, Aire, Wharfe, Nidd
and Swale, have suffered from pollution from lead mining for several centuries and the
destruction of the grayling as a result is well documented. The situation worsened in
Yorkshire from the beginning of the Industrial Revolution when noxious discharges came
from woollen mills, dyeing, tanning, mining and paper mills. In addition, until late into the
20th century raw sewage was discharged directly into the rivers.
Drainage
Many small tributaries were turned into canals by continuous dredging; the Costa Beck,
120
A Review of the Grayling in Yorkshire
once claimed to be Yorkshire’s finest grayling river, was permanently affected by drainage
operations.
Close Season
The brown trout has a close season lasting for six months, whereas the grayling close
season lasts only from March to mid-June since it is classed as a coarse fish. This would
not be so important except for the fact that grayling are killed for food and only the larger
fish are taken. It has been argued that this results in greater numbers of small fish but this
has not been substantiated in Yorkshire.
Owners and lessees of trout fisheries have until recent years encouraged the removal of
grayling in the interests of trout. Formerly netting was widely employed but more recently
electro-fishing has been used. Stock removed were given away as food, merely disposed
of, or transferred to other rivers when there was a demand. Some fisheries had rules that all
grayling caught by rod and line should be killed and encouragement was given to anglers to
capture the maximum number possible during the close season for trout. Mottram (1928),
writing of trout fisheries, says, “As regards grayling, if as usual, they are looked upon as
vermin, then the rules should be that every grayling caught should be killed”.
Impounding and Water Extraction
The tendency to augment water supplies by river transfer, in conjunction with extraction by
pumping from downstream, is increasing and has changed the character of some grayling
zones. As a result, the grayling stocks have become almost extinct on the upper Wharfe.
Insufficient research has been done to determine the reasons but it is well known that
mature and immature fish of all species as well as invertebrates are drawn into the pumps
and destroyed. No successful method of preventing this has been found to date and the
effect of extraction by pumping has been little studied.
Flora and Fauna of Grayling Zones
There has been a great reduction in the distribution of aquatic plants in some Yorkshire
rivers during the post-war years, with a consequent reduction in the numbers of aquatic
invertebrates. The density of grayling per hectare in the grayling zones appears to be
directly related to the presence of aquatic plants (Magee 1992).
There is little evidence that disease has had a serious effect on grayling stocks in Yorkshire
with the exception of the outbreak of fungal disease in 1967. This outbreak reduced stocks
on the River Wharfe and some tributaries to very small numbers and upstream of
Addingham they have never recovered. The existing populations are healthy and spawning
does take place but the stocks are very low. Following the outbreak no attempts were made
to re-introduce grayling of breeding age into the Upper Wharfe as was done on the mid-
Wharfe.
Yorkshire Grayling Rivers
Main River Tributary
Culling
Disease
Tees
Esk
Ribble
Not common
- Hodder
Wharfe
Virtually extinct upstream of Buckden
A sparse population
At confluence with main river
At confluence with main river
- Skirfare
-Dibb
- Washburn
121
A Review of the Grayling in Yorkshire
Aire
Upstream of Keighley
Derwent
- Rye
- Seven
-Dove
- Costa Beck
- Pickering Beck
- Thornton Beck
- Ricall
Upper reaches
Swale
- Cod Beck
- Whiske
- Bedale Beck
Upper reaches
Ure
- Cover
- Skell
- Laver
As far down stream as Ripon
Don
Introduced into upper reaches
Hull
Nidd
- Driffield canal
- Driffield Beck
- Gouthwaite Reservoir
The stocks appear to be most vulnerable and variable in the tributaries, where the effects of
an occasional chemical, farm, or sewage pollution can be severe. This is particularly so
during low summer levels or during a period of drought.
Conclusion
Axford (1991) stated at a seminar on ‘Yorkshire Grayling’, “The rarity of the grayling
seems to be a natural characteristic, probably related to habitat restrictions and the grayling
are naturally succeeded by trout in the upper reaches. The environmental requirements of
the grayling which cause this restriction are not known’’. He went on to enumerate some of
the possible factors.
At the same seminar Crisp said, “The general message which we get from the scientific
literature is that when the environment of the grayling deteriorates, the juveniles and young
die and the adults move away to more favourable living conditions (Jankovic 1964)”.
The author has closely observed the fluctuations of the grayling stocks on the Wharfe
(and to a lesser extent on some other rivers) since 1968. Since 1984 angling interests and
the National Rivers Authority have been collecting data which it is hoped will give a better
understanding of the ecological requirements of the grayling and enable steps to be taken
which will preserve this truly wild fish as a denizen of Yorkshire rivers.
Acknowledgements
The author acknowledges the assistance of Mr C. A. Howes for his encouragement, advice
and the provision of certain obscure references previously unknown to him and Mr H.
Briggs, Dr S. Axford (National Rivers Authority) and Dr Ross Gardiner (The Grayling
Society) for suggestions and comments on the manuscript.
References
Anon. ( 1792 ) The Sportsman s Dictionary. London.
Appletreewick, Barden & Bumsall Angling Club, Minute Books (1889-1968).
Aubrey, J. (1660) The Natural History of Wiltshire. Davy, London.
Axford, S. (1991) River Wharfe Grayling. Seminar, ‘Yorkshire Grayling’, River Wharfe
Anglers’ Association, Bolton Abbey.
122
Book Review
Bazeley, J. (1928) Letter to Bumsall Angling Club. ABB AC Minute Book.
Berners, J. (1496) A Treaty se ofFysshing wyth an Angle. Wynkin de Word, Westminster.
Brooks, R. (1740) The Art of Angling. Lowndes, London.
Clarke, W. E. and Roebuck, W. D. (1881) A Handbook Of the Vertebrate Fauna of
Yorkshire. Lovell Reeve, London.
Crisp, T. (1991) Grayling. Seminar ‘Yorkshire Grayling’, River Wharfe Anglers’
Association, Bolton Abbey,
Davy, Sir Humphry (1828) Salmonalia, or Days and Nights of Fly-fishing. White, London.
Denny, J. (1840) Sketch of the natural history of Leeds and its vicinity for twenty miles.
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Hofland, T. C.(1839) The British Angler s Manual. Whitehead, London.
Holland, J. (1843) The Vital Statistics of Sheffield. Tyas, London.
Hutchinson, H. G, ed. (1904) Fishing. Country Life Library of Sport, Vol.l: 496-499.
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Jackson, J. (1854) The Practical Fly-Fisher. Farlow, London & Leeds.
Jankovic, D. (1964) Synopsis of Biological Data of the European Grayling ( Thymallus
thymallus), FAO Fisheries Synopsis 24.
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York. In: The Exploitation of Wetlands. (P. Murphy and C. French, eds). Symposia for
the Association of Environmental Archaeology No. 7. British Archaeological Reports,
British Series 186: 1 13-127.
Magee, L. (1992) The grayling: an endangered species. Bulletin Yorkshire Naturalists’
Union 17: 1-3.
Magee, L. (1992) The Caddis Fly Brachycentrus subnubilus. Bulletin Yorkshire
Naturalists’ Union 17: 10-11.
Mottram, J. C. (1928) Trout Fisheries: their care and preservation. Jenkins, London.
Pennell, H. C. (1889) Fishing - Salmon and Trout. Longmans, London.
Platts, W. C. (1939) Grayling Fishing. Adam & Charles Black, London.
Pritt, T. E. (1886) North-Country Flies. Sampson Low, London.
Pritt, T. E. (1888) The Book Of the Grayling. Goodall and Suddick, Leeds.
Rhygini, R. (1968) Grayling. Macdonald, London
Ronalds, A. (1836) The Fly-fisher’s Entomology. 10th edition, Longmans, London.
Shipley, W. & FitzGibbon, E. (1838) A True Treatise on the Art of Fly Fishing , London.
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Turton, J. (1836) The Angler’ s Manual. Groombridge, London.
Walbran, F. M. (1895) Grayling and How to Catch Them. The Angler Co, Scarborough.
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BOOK REVIEW
A Field Guide to the Shallow-water Echinoderms of the British Isles by Bernard E.
Pickton. Pp. 96 + 66 full colour illustrations. Marine Conservation Society. Immel
Publishing, London, £15.95 paperback.
The information contained in this Marine Conservation Society account of the sea lilies,
starfish, brittle stars, sea urchins and sea cucumbers is remarkable. Species descriptions are
accompanied in all cases by colour photographs taken from life, the quality of which reflect
the author’s international reputation as an underwater photographer. Whilst aimed at those
who dive our coastal waters, most of the species can be found between tides in rock pools
and the like. A book which all who have an interest in marine life should have on their
bookshelf. Taking into consideration the quality of the illustrations, it is not overpriced.
DTR
123
VEGETATION CHANGES ON ILKLEY MOOR BETWEEN
1964 AND 1984, AND POSSIBLE ENVIRONMENTAL CAUSES
W. H. G. HALE and D. E. COTTON
Department of Environmental Science, The University, Bradford BD7 1DP
Introduction
In recent years there has been concern about the decrease in the quality and quantity of
Britain’s heaths and moorlands. This concern has prompted attempts to monitor change in
moorland vegetation, and programmes of action designed to halt the decline, both
nationally and locally (Bunce, 1989; Hudson & Newborn, 1989a).
In northern England the decline has been brought about partly by a reduction in the areal
extent of the moors but mainly by changes in their species composition, with Calluna
vulgaris (L.) Hull (heather) declining and grasses, Empetrum nigrum L. (crowberry) and
other species increasing. These changes have been attributed to changed management
practices, such as less effective burning regimes and increased sheep grazing (Bunce,
1989). However, there are few detailed quantitative studies of long-term vegetation change.
This paper draws upon historical records to determine the nature and extent of change in
the vegetation of Ilkley Moor over a twenty-year interval.
4 08
16
448
Key
Study Area
□ Sample Areas (a - d)
Transect Lines (1 and 2)
Pr Panorama Reservoir
Rr Reva Reservoir
Wr Weecher Reservoir
W Whetstone Gate
H Hawks worth Moor
Contours (metres)
4|j|||j| Urban Areas
441
Location map showing the positions of the transect lines ( 1 and 2) and sample areas
(a-d) mentioned in the text. The numbers on the edges relate to the National Grid.
Naturalist 118 (1993)
124
Vegetation changes on Ilkley Moor over 20 years
In 1974 when Bradford Metropolitan District Council acquired responsibility for the
management of the common land on Ilkley Moor, there was general disquiet about the state
of the moor. Based on a vegetation survey undertaken in 1964, it was contended that
Pteridium aquilinum (L.) Kuhn (bracken) and Empetrum were rapidly spreading and that
Calluna was in decline (Fidler et al. , 1970). Because of this concern, a new vegetation
survey was made of the area in 1984 to provide more recent information about the plant
communities on the moor, and to enable comparisons to be made with the earlier survey.
This paper analyses the changes which have occurred on the moor in the period 1964-1984
and evaluates possible causes of the observed change such as variation in sheep numbers
and climatic trends.
Physical Background
Ilkley Moor and the integral contiguous area of Hawks worth Moor occupy about 10km2 of
the upland area which separates the rivers Wharfe and Aire (Fig. 1). The underlying
geology consists of an alternating sequence of coarse sandstones and shales of
Carboniferous age (Lamming, 1969) which dip gently towards the south (Fig. 2). Coarse
sandstones cap much of the gently undulating upper portion of the area, which attains a
maximum height of 402m close to the moor’s southern boundary. Shales are more
abundant in the northern, lower portion of the moor where the land slopes steeply into the
valley of the river Wharfe. The lowest portion of the moor has an elevation of 160m.
During the Devensian glaciation the area was scoured by ice which moved down the
Wharfe valley. The beds of shale were preferentially eroded, steepening the lower, northern
slopes of the moor. On the moor’s northern flank, landslipping has occurred due to glacial
oversteepening. In the mid and upper portions of the moor, glacial erosion produced a
number of small sandstone scarps. Sandstone beds also underlie the ill-drained almost
horizontal areas which make up large tracts of the moor. Glacial debris, in the form of a
calcareous lateral moraine, forms a small but notable feature in the eastern section of the
moor (Fig. 2a), but apart from this little glacial debris is in evidence though deep
solifluction debris is present on many slopes. Over the sandstone beds the soils are
generally thin and stony with a pH of 3.0 to 5.5. Near the crests of the sandstone scarps
drainage is good, but waterlogged soils and thin peat deposits occupy much of the flatter
dipslope areas. These thin peats are underlain by a mineral soil typically comprising
mostly coarse and fine sands (44% and 53% by weight respectively) with a small
quantity of silt and clay materials (1% and 2% respectively).
Though meteorological data are not available for the moor itself, data drawn from
stations within 9 km indicate that the area has a seasonally well-distributed annual
precipitation of 800 to 900 mm. Mean winter temperatures on the moor average about 2°C
and mean summer temperatures 13°C. Only during the three summer months will frosts
usually be completely absent.
Vegetation Records
In 1903 William Smith published a map of Ilkley Moor as part of his 1:126,720 scale
vegetation map of Yorkshire (Smith & Moss, 1903). On this map the upper moor is
depicted as ‘heather moor ( Calluna dominant)’, with the scarps supporting Vaccinium
myrtillus L. (bilberry); Empetrum is also mentioned as being present. By 1960, however,
Calluna cover had apparently declined and vegetation changes were attracting the attention
of the local naturalists. A map of the vegetation produced in 1964 by the Wharfedale
Naturalists, and papers published at that time, highlight the spread of Empetrum on the
upper moor and Pteridium in the lower areas (Dalby, 1961; Dalby et al., 1970; Fidler et al.,
1970). They suggested that these changes arose either from excessive grazing by sheep or
from the moor drying out following the excavation of shallow ditches which were intended
to improve the drainage.
Since the 1960s the vegetation of the moor has continued to change (Cotton & Hale,
1989). This paper quantifies some of the changes and discusses possible causes for the
FIGURE 2
Composite cross sectional transects of Ilkley Moor showing topography, generalised geology and vegetation communities as mapped in
1964 and 1984. The letters within each community type give an approximate indication of the relative abundance of the species present.
The locations of the transects are given in the text and in Figure 1 .
1 26 Vegetation changes on Ilkley Moor over 20 years
changes between 1964 and the period 1983-1984, when the moor’s vegetation was
resurveyed.
Data Collection and Methods of Analysis
The 1984 map was produced at a scale of 1:500 to match the 1964 map, a copy of which
had been obtained from the Wharfedale Naturalists. Details of the recording procedure in
1984 are given in Cotton and Hale (1989), but in summary involved the following. Ten
community categories were used. Six of them were based on the relative proportions of the
Ericales species ( Calluna , Empetrum and Vaccinium ) where these occupied between them
over 50% of the vegetation cover. The four remaining categories related to dominance by
Pteridium, Eriophorum species (E. angustifolium Honck. and E. vaginatum L.) and grass
and J uncus species (particularly J. effusus L.). Percentage cover of a species was not
recorded directly, but since the categories were decided using relative abundance of species
the approximate cover value of the key species in each category was known. With the 1964
map categories, based largely on dominance of key species, assumptions had to be made
about the percentage cover values for each category. For example, in categories where two
species were named, it was assumed that the first-named was dominant with a cover of
60% and the second-named was subsidiary with 40% cover.
Quantitative data were extracted from both the 1964 and 1984 maps by superimposing a
regular rectangular grid with a line spacing of 33.3m, providing almost 9,000 sample points
per map. This gave a sample density of nine points per hectare. At each sample point the
vegetation community recorded on the map was noted. The frequency of these community
records then enabled estimates of the percentage cover of the moor by different plant
species to be calculated for both surveys, as indicated above.
Due to some uncertainty about the most appropriate percentage cover values to apply to
the 1964 map categories, it was decided to check the sensitivity of the results under
different assumptions. Consequently, the vegetation categories on the 1964 map were
assigned to the closest matching category from the 1984 survey, and the percentage cover
value for each species in 1964 was then calculated in accordance with the procedures used
for the 1984 results. If the results are robust with respect to the different assumptions used,
this would give greater confidence in the accuracy of the results estimated. The results
presented are therefore of two types: (1) the percentage of the moor occupied by the major
species from the 1964 and 1984 surveys as originally classified, and (2) data obtained from
the 1964 survey as reclassified.
Composite transects showing the relationship between geology, topography and
vegetation in 1964 and 1984 were constructed using the 1934 1:10,560 scale geological
maps and the original 1:500 scale vegetation maps (Fig. 2). Both are North-South profiles,
located as shown in Fig. 1; one is of the eastern section of the moor and runs from near the
Cow and Calf rocks (44/130469) to Hawksworth Moor; the other traverses the western
portion of the moor from Panorama Reservoir in the north (44/101469) to Whetstone Gate
on the moor’s southern boundary.
Spatial change in small areas of vegetation was also evaluated for four markedly
different moorland environments. The locations of four illustrative areas are depicted in
Figure 1. They comprise portions of the upper moorland plateau; the upper sandstone
scarp; the poorly-drained plateau of the middle moor; and the steep slopes of the lower
moor. Maps have been drawn for both 1964 and 1984 for each of these 25x25m tracts of
vegetation (Fig. 3a-d respectively), so that the frequency of the species symbols creates a
visual impression of the relative abundance of the species in each of the mapped
communities. Comparison between the 1964 and 1984 maps therefore gives a direct
impression of estimated species changes.
Data were also obtained on the climatic conditions which have prevailed over the period
1964-1984 in order to determine if there were any trends which may have influenced
vegetation change. Precipitation data were obtained for Reva and Weecher Reservoirs,
which lie less than 2.5 km from the moor’s southern edge (Fig. 1). Further information on
127
Vegetation changes on Ilkley Moor over 20 years
precipitation, bright sunshine and temperatures were obtained for Lister Park in Bradford,
which is less than 9 km from the moor. Data from these three sources have been combined
to provide a more complete picture of conditions on the moor than would be given by
information from any one recording station.
Records of sheep numbers between 1950 and 1988 were obtained from the Ministry of
Agriculture, Fisheries and Food (MAFF) annual June returns. These provide details of
livestock numbers on agricultural holdings within all the parishes which together constitute
the moor. Records of sheep numbers actually on Ilkley Moor came from direct counts
made between 1974 and 1978, and were obtained from Bradford Metropolitan District
Council.
Results
Table 1 provides data for the estimated percentage areas of the moor occupied by major
plant species. The reclassified 1964 data show very little difference (<3%) in the indicated
species abundances from the data obtained with the original categories - compare columns
(b) and (c). This contrasts with the marked differences between the 1964 and 1984 data -
compare columns (b) and (a). This gives confidence that the differences are not merely an
artefact of using different mapping procedures in the two surveys.
It is apparent that the estimated cover value for Calluna has increased appreciably (from
8.2% to 25.9%) whilst those for Vaccinium and Pteridium have also increased but by a
smaller absolute amount (from 2.5% to 8.4% and 17.3% to 22.5% respectively). However,
in percentage terms Vaccinium has increased even more than Calluna (Table 1). Empetrum
and Eriophorum species have decreased considerably (by an estimated 13.4% and 10.8%
respectively). Whilst there is an indication that Gramineae and Juncus species have each
decreased slightly, the decrease is close to the 3% variation associated with the community
reclassification and therefore should be interpreted with caution.
Notable tracts (30ha in total) of the whole moor were recorded as bare ground or burnt
areas in 1964, probably reflecting a more active burning regime at that time. By 1984 these
had been colonised by vegetation, and no bare ground or burnt areas were recorded. For
these colonised areas, Empetrum accounted for an estimated 33% of the new cover, Calluna
for 28% and Vaccinium for 16%; the remaining species each had 10% cover or less.
TABLE 1
Percentage of vegetation cover (excluding bare ground) accounted for
by species and higher taxa in (a) 1984, (c) 1964 and (b) 1964 as reclassified.
Percentage change calculated by ((a)-(b)/(b))xl00.
Species
1984
categories
(a)
1964 re-
classified
(b)
1964
categories
(c)
%
change
Calluna
vulgaris
25.9
8.2
7.2
+216
Pteridium
aquilinum
22.5
17.3
16.3
+30
Empetrum
nigrum
19.0
32.4
35.2
-41
Eriophorum
spp.
13.5
24.3
24.3
-45
Vaccinium
myrtillus
8.4
2.5
2.1
+238
Gramineae
6.6
10.1
7.3
-35
Juncaceae
4.1
5.2
7.8
-21
128
Vegetation changes on Ilkley Moor over 20 years
Figures 2a and 2b illustrate the relationships between topography, the underlying
geology and the vegetation communities. Pteridium is associated with the moor’s lower
scarps and Calluna is prevalent on the level tracts of the eastern portion of the upper moor.
Over the twenty year period, Calluna has increased markedly on Hawksworth Moor and on
the central plateau. In contrast, Eriophorum species are now abundant only on the western
(a) UPPER MOOR
G.R. 130440
340m AO.D.
to) UPPER SCARP
G.R. 093458
390m AO.D.
(c) MIDDLE MOOR PLATEAU
G.R. 118458
350m AO.D.
(d) LOWER MOOR
G.R. 099467
270m AO.D.
1964
KEY
p
Pteridium aquiiinum
(Bracken)
R
Eriophorum spp.
(Cotton grass)
E
Empetrum nigrum
(Crowberry)
G
Gramineae
(Grasses)
C
Calluna vulgaris
(Heather)
J
Juncus spp.
(Rushes)
V
Vaocinium myrtillus
(Bilberry)
0 25m
Scale I i i i i I
FIGURE 3
Vegetation maps of selected 625m2 portions of Ilkley Moor in 1964 and 1984.
The lines demarcate the mapped vegetation communities and the letters
schematically depict the most abundant species in each community
Vegetation changes on Ilkley Moor over 20 years
129
(a)
Total yearly number of frost days
1964 - 1983
(b)
1500 _
Total yearly precipitation
1964 - 1983
160 _
*
X
150 _
1400 _
140 _
*
E
£
x
130 _
8 1300 _
X
120 _
X x
O
0.
* X
1 10
X
8
*
X X
a 1200 _
* x
100 _
X X * x X X
I
X
90 _
x
1100 _
*
80 _
x
70
X | r 1 1—
A'X !OA7 1071 1071; 1070 lOQ^
1000
1 1 r~ 1 m
1971 1975
years
(c) Total yearly hours of bright sunshine
1964 - 1983
1200
1100 _ *
fc2 X
I 1000 * XX*
.8
J 900 - * *
D XX
I 800 _
700 - x X
1963 1967 1971 1975 1979 1983
years
FIGURE 4
Variations in yearly values for (a) number
of frost days, (b) precipitation and
(c) bright sunshine over the
twenty-year period 1964-1983.
There is a significant trend
(p<0.05) only in (a).
section of the central plateau, and have diminished particularly in the upper portion of the
eastern moor. Empetrum has also declined on the upper moor, but the relationship with
relief is less clear. Vaccinium has increased on the upper areas of the moor, particularly in
the west. Pteridium has not extended beyond the lower portions of the moor, but in some
areas it has been ousted by Calluna and Empetrum whilst elsewhere it has expanded at the
expense of the Empetrum- grass community. Maps showing changes in the spatial
distribution of the species on the moor are given in Cotton and Hale (1989).
Comparison of the vegetation maps of different portions of the moor in 1964 and 1984
reveals many changes. On the upper moor (Fig. 3a), Calluna has become much more
abundant, having spread into large areas that were formerly dominated by Empetrum and
Eriophorum. Empetrum now only occurs rarely in the area. On the upper sandstone scarp
changes are equally pronounced (Fig. 3b). Vaccinium has spread along the crest of the
scarp and in 1984 formed a distinct zone. Calluna too has become more abundant, with
both species occupying areas where Eriophorum and Empetrum were formerly abundant.
On the poorly drained plateau of the middle moor (Fig. 3c), ericaceous species have spread
into areas formerly occupied by Eriophorum. Juncus species have decreased in the area.
The biggest change on the lower moor (Fig. 3d) is the general increase in the abundance of
Pteridium. However, locally Gramineae and Juncaceae have become more abundant and
Empetrum has declined in the lowest portions of the area.
130
Vegetation changes on Ilkley Moor over 20 years
Analysis of the climatic data for the twenty year period revealed marked fluctuations in
most of the climatic elements, but statistically significant trends were confined to the
incidence of ground frost. Though there were no significant trends in overall yearly
temperatures, the incidence of both spring and autumn frosts increased significantly
(p<0.05) and the annual incidence of frosts also showed a significant increase (p<0.05; Fig.
4a). Though the summer of 1976 was the driest since records began in 1908, the overall
annual precipitation showed no significant trend (Fig. 4b). Sunshine data (Fig. 4c) revealed
no apparent trend in annual totals over the period, even though the implementation of the
Clean Air Acts might have been expected to influence this parameter.
1950 1955 I 960 1965 1970 1975 1980 1985 1'
Years
FIGURE 5
Total numbers of sheep recorded by
MAFF June returns for all the
parishes which include portions of
Ilkley Moor. The heavy line depicts
the principal study period.
The records of sheep numbers in the moorland parishes indicate that sheep numbers in
the area have increased dramatically since 1950 (Fig. 5). In the 20 year period (1964-84)
numbers rose from 26,102 to 48,758. Counts of sheep actually on the moor between 1974
and 1978 revealed that numbers varied from approximately 1200 to 1700, suggesting that
about 5% of the total sheep population of the parishes was present on the 1000 hectares of
moorland.
Discussion
Stocking Density and Effects on Vegetation
The stocking density revealed by sheep counts on Ilkley Moor during the 1970s indicates
that at that time there were between 1.2 and 1.7 sheep per hectare. If the numbers of sheep
actually on the moor is a constant proportion of sheep numbers in the moorland parishes,
then grazing pressure doubled, from about 1 to around 2 sheep per hectare, over the period
1955 to 1980. Similar shifts in stocking density have been associated with changes in the
nature of moorland vegetation cover at many sites in Britain (Rawes, 1983; Hobbs &
131
Vegetation changes on Ilkley Moor over 20 years
Gimingham, 1987). Hudson and Newborn (1989a) maintain that, as a rough guide, a
grazing density of 1 sheep per hectare is the maximum that will normally allow Calluna to
maintain itself in the vegetation; while the Nature Conservancy Council have given
predictions for heather moorland condition at different stocking densities (Cranbrook,
1991). They predict that heather moorland should be in ‘good’ condition (i.e. >50% heather
cover) when stocked, on average, at <2 ewes per hectare; in ‘poor’ condition (25-50%
cover) at 2-3 ewes per hectare; ‘suppressed’ (<25% cover) at 3-4 ewes per hectare; and
absent at >4 ewes per hectare. They suggest that heather moorland would be likely to
disappear in the longer term if stocking rates persist at >2 ewes per hectare . Ilkley Moor
therefore had, by 1984, reached a stocking rate at which some deleterious vegetation
changes might be expected to occur.
Our results indicate that pronounced vegetation changes have occurred on Ilkley Moor in
the period 1964 to 1984. However, the nature of these changes differs from the response to
similar increases in grazing intensity recorded elsewhere. When sheep are present at
densities of over 1 per hectare, Calluna decline has been associated with the spread of
Nardus stricta L. and other less palatable species such as Empetrum (Welch, 1984). In
contrast, on Ilkley Moor our data indicate that Calluna, Pteridium and Vaccinium have
increased while Empetrum and Eriophorum species have declined. Examination of the
changes in the plant communities on Ilkley Moor (Fig. 3a-d) reveals that different
moorland habitats have changed in different ways. Hence, it is probably unwise to regard
Ilkley Moor as one single unit when making comparisons with other findings. Clearly,
erroneous conclusions could be reached by assuming that observations on change on one
moor are directly applicable to the whole of another moor where the habitats may differ.
Possible explanations for the observed changes in individual species abundance and
distribution on Ilkley Moor are given separately below.
Empetrum Decline
The decrease in Empetrum on most of the moor might have arisen from climatic change.
On Ilkley Moor Empetrum is close to its south-eastern limit of distribution within Britain
(Bell & Tallis, 1973). Consequently, any tendency toward warming or drying might be
expected to affect it adversely on this site, particularly on the lower slopes of the moor
where a marked decrease was noted (Fig. 3d). The annual climatic data, however, show no
systematic tendency for change in bright sunshine, temperature or precipitation. There was
a slight increase in the number of frost days, but it is unlikely that this would have caused a
decline in a species with a northerly distribution. The increase in stocking rates probably
would not have led to greater grazing pressure as Empetrum is relatively unpalatable.
However, increased sheep numbers could have led to an increase in trampling to which this
species, with its prostrate stems, would be particularly susceptible (Dalby, 1961; Rawes,
1983).
Pteridium Consolidation
The distribution of Pteridium on Ilkley Moor is thought to be limited by altitude and
exposure (Fidler et al., 1970). Over the 20 year period the upper limit of the major areas of
Pteridium has remained below the 350 metre contour, though it has consolidated its hold
within the areas it occupied previously. This increased occupancy may be because
increased sheep grazing pressure does not greatly affect Pteridium due to its unpalatability,
and its spread has been widely recorded in other upland areas of Britain (Anderson &
Yalden, 1981; Hudson & Newborn, 1989b).
Eriophorum Decline
It is known that sheep have distinct grazing preferences for different species at different
times of the year (Hunter, 1962). Therefore, replacement of the Eriophorum species by
Calluna in parts of the moor may well be associated with preferential seasonal (summer)
grazing. However, details of such preferences are not entirely understood (Grant et al..
132
Vegetation changes on Ilkley Moor over 20 years
1976), and also it is not known how grazing pressure varied seasonally on Ilkley Moor
during the period. Anderson and Yalden (1981) reported that under a regime of increased
sheep grazing Calluna expanded into areas of Eriophorum. They suggest that this spread of
Calluna might be due to gully-erosion caused by excessive stocking or the digging of
drainage ditches. Fidler et al. (1970) have also suggested that Ilkley Moor might have been
drying out, and that this would adversely affect the Eriophorum species. However, these
explanations do not seem appropriate to the changes reported here. Drainage ditches only
affect the vegetation immediately adjacent to the ditch and are of questionable value in
changing plant communities (Stewart & Lance, 1983; Coulson et al., 1990), and indeed on
Ilkley Moor such attempts at drainage have long been abandoned. Moreover, there is
virtually no evidence of active gully erosion on the middle and upper moor where
Eriophorum has experienced major decline (Figs. 3a-c). Nor was there any trend to reduced
precipitation over this period which might have led to the moor drying out.
A more likely possibility is that the frequency of burning on the moor has declined.
Though there are no comprehensive records of past burning, the 1964 map records that
large areas of the upper moor had been burned at that time. In contrast, no such extensive
areas were recorded on the 1984 map, and field observations from the 1970s suggest that
burning did not feature strongly in the management regime in the period between the two
surveys. As Eriophorum species are known to be early colonisers of newly burned areas
and to decline when Calluna fully establishes itself (Hobbs & Gimingham, 1980; Hobbs,
1984), the reduced burning may well have reduced the opportunities for Eriophorum
colonisation and consequently effected a reduction in its abundance.
Calluna Increase - A Delayed Effect?
Calluna has increased over much of the moor, but particularly on the higher areas (Fig. 2).
On the upper moor it has expanded into areas that were formerly bare ground and has
displaced both Empetrum and Eriophorum (Figs. 3a, b). Though it has been reported that
Calluna may be stimulated when low grazing pressures are slightly increased (Welch,
1984), this is probably not an explanation for the major expansion of Calluna in this
period, particularly as the stocking rates are such that Calluna decline might be expected. It
is possible that other competitor species may have been worse affected by stocking density,
for example Eriophorum by summer grazing and Empetrum by trampling. Alternatively,
the observed increase in Calluna may reflect the long-term effects of the extensive burning
which was recorded on the 1964 map. Burning is an effective treatment which stimulates
the growth of almost pure stands of Calluna (Gimingham, 1972). Moreover, the
widespread extent of the burned areas would have reduced localised grazing pressures on
the young Calluna and this, coupled with the relatively low number of sheep in the area in
the 1960s, would have facilitated the establishment of Calluna at that time. Twenty years
later, these Calluna stands would have reached the most vigorous and dominant phase of
their life cycle, and other species would consequently have been adversely affected.
Conclusions
The records of vegetation on Ilkley Moor present a rare opportunity to observe vegetation
changes throughout the twentieth century, and the existence of two detailed vegetation maps
allows the quantification of such changes to be made over a twenty year time interval.
Between 1903 and 1964 Calluna declined in abundance, but increased substantially from
the mid-1960s to 1984 despite an increase in sheep numbers. Though several suggestions
may be advanced to explain the observed vegetation change, we consider it most likely that
the recent changes are related to the extensive burning which occurred twenty years ago.
Climatic parameters over the period 1964-1984 show little consistent variation and are not
likely to be the major instigators of vegetation change; neither are the ineffective attempts
to drain the moor by digging ditches. The spread of Pteridium may be associated with
rising sheep numbers in this period, but without further information on seasonal numbers
their probable effect on Calluna, Empetrum and Eriophorum cannot be determined.
133
Vegetation changes on Ilkley Moor over 20 years
Notable differences in the fate of species within different communities have been observed
in different sections of the moor. Consequently, regarding a moor as one uniform whole
may be inappropriate.
Variations in the burning management regimes may account for many of the vegetation
changes on the moorland, its current vegetation communities probably reflecting the
extensive disturbance that was recorded in the 1960s. Current management practice in
operation since 1984, which includes the reduction of grazing pressure, may not maintain
the presently improved moorland quality. Indeed, it is possible that the relative
abandonment of Calluna burning since the 1960s may lead to a deterioration of the
vegetation in the coming decades despite the reduced grazing unless there is further active
management.
Summary
Records of the vegetation of Ilkley Moor date back to 1903. Detailed maps of the
vegetation of l,000ha of the moor, completed in 1964 and 1984, were compared using a
grid of almost 9000 points to determine the vegetation change, notably of the species
Calluna vulgaris (L.) Hull, Empetrum nigrum L., Pteridium aquilinum (L.) Kuhn,
Vaccinium myrtillus L., Eriophorum angustifolium Honck. and Eriophorum vaginatum L.
Although different community classifications were adopted in the two surveys, data
derived from the two maps could be compared directly without undue distortion of results.
Comparison of the two surveys indicated marked increases in percentage occupancy of C.
vulgaris , V. myrtillus and P. aquilinum , and decreases of E. nigrum and Eriophorum
species. The specific changes also varied on different parts of the moor.
Trends in various environmental parameters over the period 1964 to 1984 were assessed
to try to explain these changes. There is no evidence to show that drainage operations have
been an important factor, nor that there have been any consistent climatic trends that might
have affected the vegetation composition. The vegetation changes cannot be explained
solely in terms of alterations in grazing pressure by sheep, although the local sheep
numbers were found to have increased substantially over this period. Possible effects from
trampling by sheep, seasonal grazing, species unpalatability and past burning regime are
discussed.
Acknowledgments
Thanks are due to the members of the survey group, Mr P. Baker, Mr A. Bradford, Mr J.
Brown, Mr S. Pickard and Mr S. Short, for much of the fieldwork and the Manpower
Services Commission for financial support. Bradford Metropolitan District Council
provided data on sheep numbers on the moor during the 1970s, Dr J. E. P. Currall helped
supervise the survey work, Mrs J. E. Duncan provided information about the earlier
Wharfedale Naturalists survey, Mr S. Davidson drew the figures, Dr D. J. Hambler made
helpful comments on a draft of this paper and Yorkshire Water provided precipitation data
for Reva and Weecher Reservoirs.
References
Anderson, P. and Yalden, D. W. (1981) Increased sheep numbers and the loss of heather
moorland in the Peak District, England. Biological Conservation 20: 195-213.
Bell, J. N. B. and Tallis, J. H. (1973) Biological flora of the British Isles: Empetrum
nigrum L. Journal of Ecology 61: 289-305.
Bunce, R. G. H., ed. (1989) Heather in England and Wales. ITE Research Publication
No. 3, HMSO, London.
Cotton, D. E. and Hale, W. H. G. (1989) Vegetation changes on Ilkley Moor 1964-1984.
Naturalist 114: 109-1 14.
Coulson, J. C., Butterfield, J. E. L. and Henderson, E. (1990) The effect of open drainage
ditches on the plant and invertebrate communities of moorland and on the decomposition
of peat. Journal of Applied Ecology 27: 549-561.
134
Book Reviews
Cranbrook, Earl of (1991) Upland heather: international importance and objectives for
nature conservation. In: Heather (ed. R. W. Brown). Proceedings of the National Heather
Convention. Seale Hayne Faculty, Polytechnic South West, Devon.
Dalby, M. (1961) The ecology of crowberry (. Empetrum nigrum ) on Ilkley Moor 1959-60.
Naturalist 86: 37-40.
Dalby, M., Fidler, J. H., Fidler, A. and Duncan, J. E. (1971) The vegetative changes on
Ilkley Moor. Naturalist 96: 19-56.
Fidler, J. H., Dalby, M. and Duncan, J. E. (1970) The plant communities of Ilkley Moor.
Naturalist 95: 41-48.
Gimingham, C. H. (1972) Ecology of Heathlands. Chapman & Hall, London.
Grant, S. A., Lamb, W. I. C., Kerr, C. D. and Bolton, G. R. (1976) The utilization of
blanket bog vegetation by grazing sheep. Journal of Applied Ecology 13: 857-869.
Hewson, R. (1977) The effect on heather Calluna vulgaris of excluding sheep from
moorland in north-east England. Naturalist 102: 133-136.
Hobbs, R. J. (1984) Length of burning rotation and community composition in high-level
Calluna-Eriophorum bog in N. England. Vegetatio 57: 129-136.
Hobbs, R. J. and Gimingham, C. H. (1987) Vegetation, fire and herbivore interactions in
heathland. Advances in Ecological Research 16: 87-173.
Hudson, P. and Newborn, D. (1989a) The conservation of heather moorlands. The Game
Conservancy Review 1988: 111-117.
Hudson, P. and Newborn, D. (1989b) The environmental impact of bracken. The Game
Conservancy Review 1988 : 1 17-119.
Hunter, R. F. (1962) Hill sheep and their pasture: a study of sheep-grazing in south-east
Scotland. Journal of Ecology 50: 651-680.
Lamming, P. D. (1969) The geology of Ilkley Moor. Naturalist 94: 53-54.
Rawes, M. (1983) Changes in two high altitude blanket bogs after the cessation of sheep
grazing. Journal of Ecology 71: 219-235.
Rawes, M. and Hobbs, R. (1979) Management of semi-natural blanket bog in the northern
Pennines. Journal of Ecology 67: 789-807.
Smith, W. G. and Moss, C. E. (1903) Geographical distribution of vegetation in Yorkshire.
Part 1 - Leeds and Halifax District. Geographical Journal 21: 375-401.
Stewart, A. J. A. and Lance, A. N. (1983) Moor draining: a review of impacts on land use.
Journal of Environmental Management 17: 81-99.
Welch, D. (1984) Studies in the grazing of heather moorland in north-east Scotland. III.
Floristics. Journal of Applied Ecology 21: 209-225.
BOOK REVIEWS
The Freshwater Crustacea of Yorkshire: A Faunistic and Ecological Survey by
Geoffrey Fryer. Pp. 312, with 58 figures. Yorkshire Naturalists’ Union and The Leeds
Philosophical and Literary Society, 1993. £16.00 paperback.
This remarkable book is, in my opinion, essential reading for all freshwater ecologists. It is
a detailed account of the distribution of Yorkshire’s freshwater crustaceans based primarily
on the author’s own meticulous observations made over several decades. This work is
unique in its scope - in the number of sites examined, the number of samples taken, the
precision and number of measurements made of environmental parameters, and in the
wealth of background information provided on the geology, fauna and flora of the region.
The core of the book is the analysis of distribution patterns, both by habitat type and by
species, but it also includes short chapters on classification and taxonomy, biogeographical
factors and conservation issues. The text is well organised and amply supplied with
distribution maps and line drawings of the species.
The regional nature of the work does not, however, mean that the results are only of
Book Reviews
135
regional, or even national interest. In fact, this work clearly demonstrates the paramount
importance of making observations at a scale appropriate to the organisms concerned, and
raises numerous points of general biological significance:
1 . The concept of ubiquity in the distribution of particular organisms has previously been
considered on anthropomorphic scales; on the microhabitat scale appropriate to small
crustaceans the concept requires much qualification.
2. Acidity is a great restricter of diversity and can exclude a sensitive species from one
water body only metres away from another where it breeds successfully.
3. The dispersal ability of freshwater microcrustaceans is emphasised by the temporal
dimension of the data.
4. The extraordinary persistence of individual species at given microhabitats, such as a
seepage by the side of the road, is demonstrated over extended periods of time.
5. It points to the relative importance of factors such as altitude, soil type and water
chemistry in determining distributions of small aquatic organisms.
6. There is a link between small scale distribution patterns and the behaviour of species.
This work is not, to use the modem jargon, big science but it shows that a big
contribution to scientific progress can still be made by genuine natural historians. It
reminds us that, however much we are able to explain the distributions of living organisms
and relate them to environmental parameters, they are not entirely predictable and there
will always remain a few occurrences that are inexplicable. I found this book fascinating
and I recommend it, as an invaluable reference work, to those working on the ecology of
freshwater organisms and to all natural historians interested in the diversity of life. The
price is very reasonable and the attractive cover and layout of the text make it suitable as a
present.
GAB
Biogeography and Ecology of the Rain Forests of Eastern Africa, edited by Jon C.
Lovett and Samuel K. Wasser. Pp. x + 341 with numerous line drawings & tables. 1993.
Cambridge University Press. £75.00 hardback.
Tropical rain forests are disappearing at an alarming rate, and no more so than in eastern
Africa. As pointed out by Rodgers in the final chapter of this book, there is a dearth of
information on forest conservation; although it is increasingly understood by administrators
and planners that forests are essential for our survival, resulting in some cases, e.g.
Tanzania, in policies and action plans for long-term sustainable use and conservation of
forest resources, this realization has coincided with a period of extreme economic
difficulty. There are no local funds to implement enlightened policies, so forest
conservation must therefore depend largely on foreign aid.
It is hoped that Rodger’s thought-provoking chapter will impress on politicians and
donor organizations the necessity of such assistance, but the chapters preceding it are quite
clearly aimed as a scientific audience. Short introductory chapters on the geological
evolution, climatic history and general biogeography and ecology of east African rain
forests are followed by two chapters detailing the flora. The remaining chapters (with the
exception of that on conservation) are concerned with forest millipedes, Linyphiid spiders,
mountain butterflies, herpetofauna, avifauna and mammals (mainly monkeys). Each
chapter reveals the exceptional biodiversity and the high level of endemism within East
African rain forests, and together they provide a unique insight into tropical evolutionary
processes and the need for effective management practices if they are to be successfully
conserved.
It is ironic that the very high price of this important volume will preclude its purchase by
those at the sharp end of the problem, namely East Africans, and by students; one can only
hope that it will find its way into many libraries so that its research data, and the underlying
conservation messages therein, can reach the widest possible audience.
MRDS
136
Book Reviews
Red Data Books of Britain and Ireland: Stoneworts by N. F. Stewart and J. M.
Church. Pp. 143, including numerous line drawings & 8 pages of colour plates. 1992.
Available from: Publications Branch, Joint Nature Conservation Committee, Monkstone
House, City Road, Peterborough PEI 1JY. £15.00 (hardback), plus postage & packing.
As well as providing an important conservation database for a group of plants severely
threatened by the continual disappearance or modification of suitable water systems, this
book is also a useful reference guide and should stimulate greater interest in these
fascinating plants. Despite the regrettable lack of detailed knowledge of the distribution of
many species, the authors have assembled distributional maps and ecological information
which present a reasonable picture of the status and vulnerability of 21 out of a total British
and Irish charophyte flora of 33 species - obviously a remarkable state affairs when two-
thirds of a flora need to be listed in a Red Data Book! The usefulness of this slim volume is
extended by the presence of a key to all species and a section on the more general habits
and habitats of the group. A pity such a high price is levied on publications of such vital
importance to understanding and solving conservation problems.
MRDS
Stewart & Corry’s Flora of the North-east of Ireland, edited by Paul Hackney, with
the assistance of Stan Beesley, John Harron and Doreen S. Lambert. Pp. xi + 419
(including numerous line drawings & b/w plates), plus 8 pages of full colour plates. 1992.
Institute of Irish Studies, The Queen’s University of Belfast, Belfast BT7 INN. £17.50,
plus £1.00 post & packing.
This completely revised and remodelled edition of S. A. Stewart and T. H. Corry’s Flora is
a worthy successor to the two earlier editions (1888, 1938) and maintains the very high
standard of recent local floras which are a hallmark of British and Irish botany.
The Flora, which covers the counties of Down, Antrim and Londonderry, includes
introductory chapters on the history of the study of the flora (8pp.), some comparisons with
the floras of adjoining areas (4pp.), history of the vegetation and influence of man (19pp.),
topographical and climatic details (30pp.) and an edited section (8pp.) of Robert Lloyd
Praeger’s ‘Botanist’s Guide’ from the 1938 edition. The Flora is richly illustrated
throughout with line drawings (mainly maps) and excellent photographic plates (some in
colour), mainly of plants and their habitats.
The major section of the Flora (283pp.) is devoted to inventories of vascular plant and
charophyte records, the former based mainly on the nomenclature of Clapham, Tutin and
Moore (1987), giving detailed data on localities, recorders and dates, as well as succinct,
but useful, information on ecology and abundance of each species. Synonymy is provided,
but its usefulness in the text is limited by the index (14pp.) which provides full common
English names, but Latin names to generic level only. An extensive gazetteer (31pp.) is a
particularly helpful feature of the volume.
The editor and his assistants, those who contributed introductory chapters, the many
botanists involved in its compilation and the publishers are all to be congratulated on
providing a comprehensive source of information which is also very attractively presented.
MRDS
Green Roads in the Mid-Pennines by A. Raistrick. Moorland Publishing. Paperback
edition 1991. £6.99.
The title and cover of this slim paperback by the late Arthur Raistrick will be inviting to
many people who enjoy walking in the Yorkshire Dales. However, the unwary reader may
be in for a surprise. Originally published in 1962 as Green Tracks in the Pennines, this
book has been little altered since the 1978 edition and in many ways falls short of what is
expected from a modem guidebook. The introductory chapter is interesting and readable
Book Reviews
137
but extremely brief (five pages). The majority of the following chapters consist of
descriptions of the routes taken by the old roads, with insufficient historical and descriptive
detail to make the narrative come alive. As the author admitted, many of the tracks are now
‘macadamised’, which renders the term ‘green roads’ somewhat euphemistic.
Scant attention is paid to the many changes in the Pennine landscape which have
occurred since Raistrick’s original fieldwork was carried out. The descriptions of the routes
rely entirely on the names of villages, streams, inns, etc, without the benefit of grid
references. This makes the text extremely difficult to follow, even with a large-scale map
to hand, except for those who already possess an intimate knowledge of the area. The maps
in the book are very poor, sketchy affairs, and of little use for illustrating the routes in
question. The photographs and drawings, by contrast, are delightful and informative.
In short this book is disappointing in that it provides neither a practical guide for those
wishing to walk the green roads nor a detailed historical account of their development for
those wishing to learn more about them from the comfort of their armchairs. It may have
broken new ground when it was originally published in 1962, but thirty years later the book
has a quaint, old-fashioned feel to it. Styles of writing and presentation have changed
almost as much as the green roads themselves. The reader of the 1990s is looking for
something more modem and ‘user-friendly’ to guide him or her through the by-ways of old
England.
MA
Coppiced Woodlands: their management for wildlife by R. J. Fuller and M. S.
Warren. 2nd edition. Pp. 34 (including 9 figures), plus 4 pages of colour plates.
Woodland Rides and Glades: their management for wildlife by M. S. Warren and R.
J. Fuller. 2nd edition. Pp. 32 (including 9 figures), plus 4 pages of colour plates. 1993.
Joint Nature Conservation Committee, Peterborough. £3.50 (plus postage) each, paperback.
Available from: Natural History Book Service Ltd., 2-3 Wills Road, Totnes, Devon TQ9
5XN. (£2 is charged for postage & packing on orders below £10.)
These useful booklets on woodland conservation, first published in 1990 (see Naturalist
117: 62), quickly went out of print due to popular demand. Their return, in revised and
expanded form, will be widely welcomed.
The Beast of Exmoor and other mystery predators of Britain by Di Francis. Pp. 150,
with 4 pages of photographs. Jonathan Cape. 1993. £14.99 hardback, £7.99 paperback.
Initially, I was uncertain whether this book was suitable for review in The Naturalist.
However, on reading it through I realised it contained a considerable amount of
information about large wild cats, such as pumas, tigers and leopards, and their taxonomy,
habits and habitat, which any mammalogist would find of interest. Most of the book, which
is anecdotal, is about large wild cats roaming the British countryside, causing considerable
damage to farming stock, especially sheep. The story starts with the spring of 1983, when
farmers on the southern fringes of Exmoor began losing their sheep and lambs at an
alarming rate. Local farmers, police and a detachment of marines failed to track down
the mystery predator. According to the authoress, Di Francis, who is described as a
naturalist, water colour artist and journalist, various expert zoological opinions have been
sought and expressed within the book on the possible predator involved. Unfortunately, no
satisfactory answer has been found to date, as physical evidence of these elusive predatory
cats is very limited. In some ways the book can be described as a naturalist’s ‘who done it’,
and would make suitable reading for a long train journey, for, at times, I found it very
captivating.
MJAT
138 Book Reviews
Journey into Dolphin Dreamtime by Horace Dibbs. Pp. 208 with 22 colour plates. 1993
Jonathan Cape, £8.99.
This is the latest in a long list of successful contributions on dolphins and dolphin therapy
by Horace Dibbs. The author introduces the reader to several situations where dolphins not
only show a positive empathy to man but also on numerous occasions have a positive
therapeutic affect, particularly in areas such as clinical depression. The explanation for this
the author locates in the Australian aboriginal ethos and philosophy of spatial identity with
the environment, or their dreamtime. The author’s arguments are at times difficult to follow
although the overall presentation is interesting and stimulating.
MJD
The Golem. What everybody needs to know about science by Harry Collins and
Trevor Pinch. Pp. xii + 264, including line drawings & tables. Cambridge University
Press. 1993. £10.95 hardback.
A series of case studies for different scientific disciplines are fascinatingly portrayed by the
authors, who show that science is not “the straightforward result of competent theorization,
observation and experimentation”. Of particular interest to readers are the chapters on
‘edible knowledge’ (the chemical transfer of memory in planarians), ‘the germs of dissent’
(spontaneous generation of life) and ‘the sex life of the whiptail lizard’ (pseudocopulatory
behaviour and its possible role in priming reproductive mechanisms). Written in a lively
style, but one all too typical of the social scientist, this work will make stimulating reading,
with such interpretive gems as . . 17000 trained goldfish gave their lives in the
production of 750 grams of colour discriminating brains . . .” (p.23) and . . the number of
‘love bites’ the lizards underwent and whether or not they waved their hands as a sign of
sexual submission both became important” (p.l 17).
IJH
Microscopic Life in Sphagnum by Marjorie Hingley, illustrated by Peter Hayward and
Diana Herrett. Pp. 64, with 4 colour plates and numerous b/w illustrations. Naturalists’
Handbook no. 20. Richmond Publishing, Slough. 1993. £13.00 hardback, £7.95 paperback.
Many naturalists and academics will find this book an inspiration for further studies into
the various forms of life found in and amongst the leaves of Sphagna (bogmosses). It
briefly covers the type and variety of habitat in which species of Sphagna are found and
their physical and chemical environment. The comprehensive review of the life forms
found in and on their leaves is clear and concise. The excellent illustrations and key can be
used to identify some of the life forms at least to genus level. The book includes the
following: algae, cyanobacteria, flagellates, naked amobae, helizoans, testate rhizopods,
ciliates, rotifers, flatworms, nematodes, segmented worms, gastrotrichs, Crustacea and
mites. One of the strengths of this small book lies in the many projects or investigations
that it could generate, with suggestions on how they can be carried out with little expense
other than a good microscope. I would highly recommend this title to both botanists and
zoologists.
ADH
The Earth as Transformed by Human Action: Global and Regional Changes in the
Biosphere over the Past 300 years edited by B. L. Turner, W. C. Clarke, R. W. Kater,
J. F. Richards, J. T. Mathews and W. B. Meyer. Pp. xvi + 713, including numerous
black and white illustrations and photographs. Cambridge University Press. 1993. £27.95
paperback.
The reviewer must admit to not having read all of this book, and most probably never will
read every word; however, he does expect to go on referring to it for the rest of his
Contributors
139
professional life! The Earth as Transformed by Human Action is a monumental book both
in size and inclusiveness, with 713 pages of very small print. It contains 42 chapters each
written by acknowledged experts plus Foreword, Preface and Postscript.
The work is very much in the vein of the influential and authoritative work Man s Role in
Changing the Face of the Earth (W. L. Thomas, 1956, Chicago University Press). The
work under review arose from a meeting convened by the Geography Department at Clark
University in 1987 as part of the universities centennial celebrations. As such the
contributions have a strong ‘geographical flavour’ which makes the important
environmental issues covered amenable to the lay reader. After a thoughtful introduction
by the principal editors, the volume is divided into four sections: Changes in population
and society (7 chapters); Transformations of the global environment, sub-divided into
Land, Water, Oceans and atmosphere. Biota, and Chemicals and radiation, (19 chapters);
Regional studies of transformations (12 chapters) and Understanding transformations (3
chapters). Among the many stimulating chapters those covering carbon (by R. A.
Houghton and David Skole), sulphur (by R. B. and J. D. Husar) and nitrogen and
phosphorous (by V. Smil), are notable as models of clarity and conciseness.
This is a blockbuster of a book, excellently produced, with good clear illustrations, and
modestly priced. It should be read by all who have an interest in man’s effect on the
environment, and like Man s Role in Changing the Face of the Earth is likely to be a
standard source of ideas and examples for many years to come.
DEC
CONTRIBUTORS
Angus, R. B. 26-27
Archer, M. E. 13-15,26,37-44
Atherden, M. 92-93, 94, 136-137
Barker, A. 100
Bamham, M. 47-53
Blackburn, J. M. 99-100
Blocked, T. L. 96-97
Boatman, D. J. 71-78
Boxhall, G. A. 134-135
Brightman, F. H. 30
Caulton, E. 79-85
Chicken, E. 24-25,91-92
Cotton, D. E. 32, 1 23- 1 34, 1 38- 1 39
Crackles, F. E. 21
Crossley, R. 17-18, 55-60, 87-89
Cudworth, J. 95
Dale, J. E. 9-12
Delany , M. J. 45-46, 89-90, 1 38
Denton, M. L. 95-96, 98
Duncan, J. E. 21-25
Fiskin, J. 79-85
Flint, J. H. 18-20
Foggitt, G. T. 47-53
Gilbert, O. L. 3-8, 70
Godfrey, A. 15-16
Goulder, R. 85-87
Grant, D. R. 22-23, 94, 96, 99
Hale, W. H.G. 90, 123-134
Hambler, C. 27-28
Hambler, D. J. 28-29
Headley, A. D. 20, 29, 138
Henderson, A. 54, 92
Hinton, V. A. 30
Hodgkiss, I. J. 138
Horsman, F. 60-61
Howes, C. A. 31,61-63,67-70
Jones, D. 107-114
Lawson, R. 27
Leedale, G. F. 101-106
Limbert, M. 44-45
Lloyd-Evans, L. 100
Lunn, J. 9-12
Magee, L. 23-24, 97, 98-99, 115-122
Marsh, R. J. 64, 99
McKean, D. R. 12
Medd, T. F. 21-22,24
Millward, D. 99
Norris, A. 17,95
Pashby, S. 91
Payne, J. 91,93-94,95,96,98
Payne, K. G. 53-54
Phillips, S. 67-70
Potter, T. 31
Ratliffe, L. V. 47-53
Richardson, D. T. 98-99, 122
Seaward, M. R. D. 16, 31, 32, 78, 94,
97, 100, 135, 136
Skidmore, P. 61-63
140
Index
Sykes, M. 97, 100
Thompson, M. J. A. 46-47, 137
Varty, C. G. 63-64
Wallis, A. J. 93
Wardhaugh, A. A. 33-37
Watling, R. 29-30
Yalden, D. W. 65-67
Yeates, C. S. V. 91-100
INDEX
Algology
Freshwater algae in Yorkshire, 101-106
Aquatic Ecology
Aquatic vegetation and resumption of flow after drought in a Wold winterbourne, 85-87
Book Reviews
12, 16, 20, 26-32, 45-47, 53-54, 64, 70, 78, 89-90, 100, 122, 134-139
Botany
Botanical reports for 1992, 21-25; Backhouse and the Killamey Fern, 60-61; Vegetation
changes on Ilkley Moor between 1964 and 1984, 123-134
Conchology
Pisidium tenuilineatum new to Yorkshire, 17
Entomology
Aculeate Hymenoptera in Yorkshire and the development of a quality scoring system, 13-
15; Systenus pallidus in Yorkshire, 15-16; Trifid Bur-marigold and associated flies, 17-
18; Entomological reports for 1987-1992: Hymenoptera, 18-20; Aculeate wasps and
bees of Duncombe Park, 37-44; Recent changes in butterfly distribution in the Harrogate
district, 47-53; Notes on the Empidoidea of the Lower Derwent Valley, 55-60; Bat-flies
in Yorkshire, 61-63; Sciomyzidae of the Lower Derwent Valley Nature Reserve, 87-89
Fish
The Grayling in Yorkshire, 115-122
Historical Ecology
History and status of North Cliffe Wood, 71-78
Lichenology
The lichen flora of Derbyshire - supplement 3, 3-8
Mammals
Bats and their roosts in Cleveland II, 33-37; Chad’s shrews, 65-67; Yorkshire Cetaceans:
strandings and sightings 1985 to 1992, 67-70
Marine Ecology
Observations on the Cnidaria inhabiting an intertidal mussel bed in Morecambe Bay, 107-
114
Obituary
Margaret Revell Sanderson, 63-64
Ornithology
Breeding activities of Parrot Crossbills in South Yorkshire in 1983, 9-12
Palynology
Pollen diagrams from 17th century turf roof, Rosslyn Chapel, 79-85
Personalia
Portrait of Thomas Bunker of Goole, 44-45
Yorkshire Naturalists’ Union
Excursions in 1992, 91-100
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SMITHSONIAN INSTITUTION LIBRARIES
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Latest publication of the Yorkshire Naturalists’ Union
THE FRESHWATER CRUSTACEA OF YORKSHIRE
a faunistic & ecological survey
by
GEOFFREY FRYER
The crustacean fauna of Yorkshire reflects the great physiographic diversity of the
region. Adopting an ecological approach, this book considers the Yorkshire fauna in
relation to climate, topography, geology, soils and water chemistry, always keeping in
mind that it is dealing with living organisms whose habits, requirements and
physiological limitations determine exactly where they live.
Matters covered include the ecological background; faunal assemblages and their
regional attributes; an analysis of the factors that determine distribution patterns, many
of which are mapped; wide geographical aspects; and conservation. Large areas, such
as the Pennines, Howgill Fells, North Eastern uplands and the lowland plains are
surveyed. So too are localised regions including Whemside, the Malham area, lowland
heaths, and the largest lakes, as well as habitats such as upland tarns, seepages, cold
springs, small lowland ponds, inland saline waters. Notes are given on every species
recorded, including parasitic forms.
Price £16.00 (plus £2.00 per copy p.&p.) Special offer to member of the Yorkshire
Naturalists’ Union £13.50 (plus £2.00 p.&p.)
Please make cheques payable to Yorkshire Naturalists’ Union.
Available from: Professor M. R. D. Seaward, Department of Environmental
Science, University of Bradford, Bradford BD7 1DP.
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