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1991

LITERATURE REVIEW ON CRAYFISH ECOLOGY AND MANAGEMENT METHODS

Prepared for: Montana Department of Fish, Wildlife, and Parks
1420 E. 6th Avenue
Helena, Montana 59620

By: Ginger Thomas, Fisheries Consultant
521 Hartman Street #7
Missoula, Montana 59802

June 3, 1991

STATE DOCUMENTS COLLECTION

2 3 1992

MONTANA STATE LU3RARY
ISIS 0th AVE.
HELENA, MONTANA 59620

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INTRODUCTION

The commercial harvest of crayfish began in Montana in 1988.
Prior to that time, crayfish were harvested on a small scale for
personal use. Crayfish are a popular food in Europe, especially
Sweden. The Swedes eat 4 to 6 million pounds of crayfish per
year (Larson 1989) . A fungus has wiped out European crayfish
populations and stimulated the market for American crayfish. The
native western Montana species, Pacifasticus leniusculus
resembles the European species and is especially favored in the
European markets.

At the time that the commercial crayfishery started to
develop in Montana, the Montana Department of Fish, Wildlife, and
Parks (MDFWP) had no regulations on the harvest of crayfish.

There is concern among many sportsmen that a commercial
crayfishery will have a negative impact on game fish. Montana
declared the crayfish to be a non-game species in need of
management so that regulations could be developed. In 1989, the
Montana legislature directed that the MDFWP develop regulations
governing the commercial harvest of crayfish, mysis shrimp, and
other aquatic organisms. Current Montana crayfish regulations
were developed under this statute. Interest in the commercial
fishery continues to grow, as does the public controversy
surrounding this fishery.

In addition, Montanans are also concerned about interactions
between a non-native crayfish, Orconectes virilis. and the native
Pacifasticus . Orconectes is a widely distributed species whose
native range extends into eastern Montana. It has been
introduced into western Montana and deliberately dispersed by the
Montana Department of Fish, Wildlife, and Parks and probably by
anglers (Sheldon 1989) . There is concern that Orconectes may
replace Pacifasticus in some areas. For a complete review of
this issue, see Sheldon (1989).

In March 1991, the Montana Department of Fish, Wildlife, and
Parks contracted with Ginger Thomas to prepare a literature
review on crayfish ecology and management. The purpose of this
report is to provide the MDFWP with information that will be
helpful in making management decisions for the Montana commercial
crayf ishery .

The report covers three areas: 1. A review of the recent
scientific literature concerning the population dynamics and
ecology of crayfish populations with emphasis on Orconectes and
Pacifasticus so. Special emphasis is given to studies that have
evaluated exploited populations. 2. A review of the scientific
literature concerning the importance of crayfish in the diet or
food chain of fish, aquatic birds and mammals, with an emphasis
on Montana species and 3. A narrative and tabular summary of
information concerning commercial crayfishing activities in the
Pacific northwest states and provinces.

Digitized by the Internet Archive
in 2017 with funding from
Montana State Library

https://archive.org/detaiis/iiteraturereview1991thom

THE POPULATION DYNAMICS AND ECOLOGY OF

PACIFASTICUS SP, AND ORCONECTES

Pacifasticus sp.

Life history

Pacifasticus are members of the family Astacidae, which
includes many of the European crayfishes. Fertilization and egg
laying take place in the autumn in response to shortening day
length and falling water temperatures (Hogger 1988) . In British
Columbia, mating occurs when water temperatures are less than
14oC during periods of shortening day length (Mason 1975) . Eggs
are carried over the winter by the female, with hatching
occurring the following summer (Hogger 1988) .

Pacifasticus leniusculus has a life span of from 48 - 132
months and age 8+ crayfish reach a carapace length (CL) of 47 -
54 mm (Momot 1988) . However, Sheldon (1989) reported male
Pacifasticus exceeding 70 mm CL in his report on western Montana
crayfish populations. He also reported that most of his catch was
greater than 45 mm CL, the approximate commercial minimum.

The growth rate of Pacifasticus varies with water
temperature and is density dependent. However, it is clear that
Pacifasticus grows faster than many other North American
temperate zone species and may achieve a larger final size
(Lowery and Holdich 1988) . Males typically grow faster than
females (Sheldon 1989, Abrahamsson and Goldman 1970). Growth
rates for Pacifasticus have been studied in Lake Tahoe,

California and the Sacramento River, California. Growth rates in
the Sacramento River are faster, probably due to warmer water
temperatures. Young-of-the-year (YOY) Pacifasticus reach an
approximate carapace length of 20 - 27 mm in the Sacramento
River, as compared to 15 - 22 mm in Lake Tahoe. The Sacramento
River populations remain larger at a given age compared to the
Lake Tahoe populations throughout their life cycle. The average
molt increment in the Sacramento River is 2.3 mm, compared to 2.0
mm in Lake Tahoe (Shimizu and Goldman 1983, Flint 1975a).
Sheldon's (1989) preliminary analysis of Pacifasticus growth
rates in Montana found them to be comparable to the Sacramento
River population, however the sample size was small.

The age at maturity varies depending on the growth rate.

They may mature the first summer, although the second summer is
more usual. In Lake Tahoe, the males mature in the third summer,
and females the fourth summer (Lowery and Holdich 1988) . The age
at maturity may also vary from year to year within a water body,
especially for females. For example, McGriff (1983) reported
that the percentage of mature 2+ female Pacifasticus leniusculus
varied from 80.2% in 1977 to 36.8% in 1979 in the Sacramento-San
Joaquin Delta.

3

The average size at maturity has been reported to be 40-50
mm (McGriff 1983) . Flint (1975b) found a difference in the size
at maturity among crayfish taken from the three transects he
studied in Lake Tahoe. He attributed smaller size at maturity to
lack of suitable cover for larger individuals and greater
population density which resulted in a population of stunted
adults. Sheldon (1989) reported only one berried female in his
samples from Montana waters at the relatively large size of 63 mm
CL. However, he comments that the biased sex ratio of this
sample suggests that many berried females were inactive and
unavailable to his sampling gear.

The mean number of eggs per female is 110 to 280 (Momot
1988) . The mean number of eggs per female varies by the size and
age of crayfish, and with the year. Larger and older crayfish
tend to carry more eggs (McGriff 1983) .

Pacifasticus leniusculus are reported to have standing crops
from 132 to 622 kg/hectare (Momot 1988) .

Habitat requirements

The habitat preference of Pacifasticus is for slower moving
streams. However, the range and diversity of habitat occupied by
this genera has been extensively modified by man. They are found
to occupy clear, shallow, coastal streams; reservoirs and lakes;
and turbid, saline delta regions (Hogger 1988) . The juveniles
seem to favor fast flowing shallow regions, moving to deeper slow
moving pools as they grow up (Lowery and Holdich 1988) .

Crayfish in general are very sensitive to changes in water
quality and habitat changes, particularly as they are slow moving
bottom dwellers, confined to a relatively narrow littoral zone.
The crayfish is as demanding as salmonid fish in its requirements
for dissolved oxygen in water. They do not thrive in waters with
a pH value below 6.0, although they can withstand a pH of 4.0 and
even lower for short periods of time. The ability of crayfish to
withstand increases in suspended solids is little understood
(Westman 1985) .

Rock size is an important factor in determining crayfish
density and distribution. Unlike many other species, Pacifasticus
is a non-burrowing species that prefers areas which provide
suitable cover. Rocky substrate provides crevices for crayfish
to use as cover. Shimizu and Goldman (1983) in their study of
Pacifasticus in the Sacramento River found that crayfish
distribution was primarily influenced by substrate. Rocky areas
provided 87% of their catch, while the other 13% was taken from
traps set on sand and mud-silt areas. Flint and Goldman (1977)
found that the larger the crayfish, the larger the rocks used for
cover. However, open sandy areas support lower numbers of
crayfish but larger sized individuals. Larger crayfish can live

4

in these areas as their large size protects them from fish
predation (Hogger 1988) .

In regions with stones of suitable size, the animals may
become so abundant that they are stunted (Lowery and Holdich
1988) . Studies of crayfish from different areas of Lake Tahoe
have shown that there is a large variation in the density and
average body length of these animals. One transect in Lake Tahoe
which had an abundant, stunted population of crayfish had a large
percentage of cobble-boulder substrate, large percent of shallow
water, a high level of periphyton growth, but a smaller mean rock
size than other areas of the lake. High densities of crayfish on
this transect caused overcrowding resulting in competition for
food and suitable cover resulting in a stunted population
(Abrahamsson and Goldman 1970, Flint and Goldman 1977) .

In Lake Tahoe, crayfish are confined to the depth of less
than 40 m, regardless of the substrate. This seems to be because
Pacifasticus eggs do not hatch at cold water temperatures. In a
laboratory experiment oviferous females were held in a fluvarium
from the beginning of May until mid-September without any eggs
hatching. During this time the water temperature ranged from 5.8
to 8.6°C, and averaged 6.8°C (Abrahamsson and Goldman 1970).

Additionally, crayfish in Lake Tahoe undertake extensive
seasonal migrations. During the summer and autumn, the peak
distribution of crayfish is in shallow near-shore waters. In
autumn the population migrates into deeper waters. It is
supposed that the migration is an adaption of the species to
avoid winter storms that cause high rates of mortality among
members of the population living in shallow water (Flint 1977) .

Orconectes sp.

Life history

The typical Orconectoid crayfish life cycle is about three
or four years. Females, which move in shore in early spring,
produce only one brood per year. The female Orconectes virilis
(the species found in western Montana) attach eggs to their
pleopods in early spring, i.e. April or May. The young are
usually attached for one to three weeks, and depending on
temperature, hatch in May or June. The young of the year then
frequent the littoral zones of lakes or ponds or the riffle areas
of rivers or streams. The young remain attached to the female
through two molts and leave after the second molt (third instar)
(Momot 1988) .

Adult males are usually larger than females of the same age.
Male members of this family of crayfish come in two forms. The
Form I male is sexually competent. When their post-reproductive
moult occurs, the males turn into the sexually incompetent Form

5

II (Hogger 1988) . The mature animals usually mate in late summer
or early spring. The male transfers the sperm to a receptacle in
the abdomen of the female (Momot 1988) . The females of O.
virilis migrate to deeper water during the summer. This is due
either to increased aggression by males or to environmental
triggers to facilitate gonadal maturation. Gonadal maturation
occurs only in total darkness at temperatures less than 10°C
(Momot and Cowing 1972) .

Orconectes virilis has a maximum life span of 40 months. An
age 3+ O. virilis reaches a mean length (CL) of 40 - 44 mm.
Sheldon (1989) reported catches of larger than average Orconectes
in McGregor Lake and Cabinet Gorge Reservoir (46 and 47 mm CL
respectively) . The average growth increment has been reported to
be 2.0 to 2.7 mm per moult, depending on age and sex (Weagle and
Ozburn 1972). The mean number of eggs per female is 86 - 214.
Larger females generally carry more eggs. They are reported to
have standing crops from 5.5 to 142.9 kg per hectare (Momot
1988) .

Habitat requirements

The genus Orconectes is considered to be tertiary burrowers.
That is, they burrow only during drought conditions, and in some
cases during their breeding cycle. Orconectes occur in both
lotic and lentic habitats under rocks, in vegetation, among the
roots of riparian trees, in leaf litter and in gravel beds
(Hogger 1988) .

Role of crayfish in the ecosystem

Trophic status

Crayfish are polytrophic ,* that is they are herbivores,
omnivores, and detritivores . Their diet is largely plant
detritus although the main nutritional value of this food is
derived from the epiphytic fungal and bacterial organisms
involved in decomposition. Crayfish also eat macrophytes,
invertebrates, small fish, and other crayfish. The food of
animal origin usually constitutes the smallest part of the diet
but it provides essential organic compounds (Hogger 1988)

The crayfish's popular image is as a scavenger. This is
mainly an opportunistic role which is greatly exaggerated.
Circumstances such as fish kills can make scavenging important,
but in the crayfish's day-to-day role in the community it is far
less important than many of its other activities (Momot et al
1978) .

The position of crayfish as consumers on several trophic
levels means they perform a vital function within the aquatic

6

ecosystem. Crayfish biomass tends to be high relative to other
consumers which can not readily utilize detritus and living
vegetation so they transfer energy directly to higher trophic
organisms (Hogger 1988) . Not only do crayfish utilize the
microorganisms in detritus, but they also break it down into
finer particles more easily attacked by decomposers. Crayfish
could also be considered to be acting as decomposers (Momot et al
1978) .

Without crayfish, much of the energy in the food cycle would
be short-circuited into dead ends leading to an overall decrease
of energy cycling, community productivity, and food availability
to higher trophic levels in the system (Momot et al 1978) .

However, it should be noted that the role of crayfish in the
ecosystem varies by the species of crayfish. In Wisconsin, the
introduction of the rusty crayfish (Orconectes rusticus) into
waters where it was not native has resulted in a short -
circuiting of the ecosystem. The rusty crayfish consume the
plants that fuel the production of insects and small fish. In
addition, rusty crayfish also feed on the remaining snails and
insects. Through the consumption of those invertebrates and of
fish eggs, as well as destruction of habitat, crayfish are
replacing small fish, and ultimately bass, walleye, and
muskellunge as the top predators. Much of the problem with rusty
crayfish comes from its very agressive behavior which makes it a
difficult prey item for fish (Lodge at al 1985) .

Crayfish tend to be most important in lakes with low
phytoplankton production. In such lakes, detritus and benthic
algae, both of which are ingested by crayfish, are important
sources of energy. Since crayfish are a major consumer of
benthos, they provide a key link in the food web by interacting
with species ranging from large benthic invertebrates and
submerged higher aquatic plants and animals to the periphytic
microcommunity. In low nutrient lakes, due to their functional
role and biomass dominance, the role of crayfish is more
significant than is assumed from their occurrence in fish diets
(Momot et al 1978) .

Crayfish can also have an impact on the behavior of other
animals in their environment. Rahel and Stein (1988) report that
johnny darters (Etheostoma niarum) were more active in the
presence of smallmouth bass and crayfish than they were in the
presence of bass alone. Crayfish increased the vulnerability of
darters to bass by evicting them from shelters and causing
increased activity. Conversely, bass increased the vulnerability
of darters to crayfish by forcing them to seek cover under
shelters occupied by crayfish.

Impact on aquatic vegetation

7

Crayfish have an impact on their environment. There is
considerable documentation of crayfish reducing the abundance of
aquatic macrophytes. The introduction of Pacifasticus into a
previously crayfish free water resulted in a significant
reduction of aquatic macrophytes in England (Hogger 1984) . The
same phenomenon was reported by Taub (1972) , who observed that
plant growth during his study of a small Ohio pond was inversely
proportional to crayfish density. In Wisconsin, densities of
rusty crayfish of one per square yard - a density often exceeded
in nature- reduced the biomass of aquatic plants by 40% (Lodge et
al 1985) .

There has been some interest in using crayfish as a
biological control for aquatic weeds. Dean (1969) found that the
crayfish Orconectes causeyi is useful in controlling submerged
aquatic plants in shallow trout lakes in the southwestern United
States. This control is probably self-limiting however, as
crayfish use plants not only for food but also for cover. If the
plant density is reduced too far, then predation on crayfish
increases (Saiki and Tash 1979) . In addition, emergent shoreline
vegetation serves as a nursery area for newly hatched Orconectes
virilis . A decrease in vegetation could result in lower
recruitment (Momot and Cowing 1983) .

An over abundance of crayfish can result in increases in
turbidity from the lack of vegetation and from crayfish activity.
Increased turbidity can, in turn, reduce the photic zone and
increase the rate of absorption of solar energy. These effects
may offset each other (Rickett 1974) .

In Sweden, lakes which lost crayfish populations to plague
suffered increased eutrophication and growth of aquatic
macrophytes (Abrahamsson 1966, Abrahamsson 1973).

Crayfish must be above a certain density before vegetation
is reduced. Below this density, grazing may actually increase
plant growth (Lorman and Magnuson 1978) .

Clearly, the ideal situation is to maintain a balance
between crayfish densities, vegetation, and the predator
population .

Population dynamics of exploited populations

The effect of exploitation on wild crayfish stocks has been
examined with regard to Orconectes virilis in two sets of lakes.
North Twin and West Lost Lakes, Michigan and Dock and Shallow
Lakes, Ontario (Momot 1985) . In the Michigan study, the two
populations were managed using the maximum sustained yield model
(MSY) (Ricker 1975) . After harvesting all crayfish greater than
6 cm TL with traps at the MSY rate for three years, fishing
effort was then increased four-fold in West Lost Lake for two

8

successive seasons, while in North Twin Lake the MSY was
retained .

In West Lost Lake, yields were stable during MSY, but
increased with over-exploitation during which both growth and
recruitment declined. Distortions then occurred in the age
composition of the population. In North Twin Lake, this same
pattern was repeated even though the population was fished at the
prescribed MSY rate. In the last year of the fishery the catch
drastically declined even though harvest had not been increased
over the MSY. Because of a dramatic decrease in recruitment.
North Twin had been greatly over-fished by 1975 (the last year of
the study) .

The assumption of relatively constant recruitment of the
Ricker model was not met. Decreased recruitment in both lakes
was attributed to two factors: 1. a decrease in the survival of
hatchlings in both lakes due to a loss of nursery habitat caused
by natural factors and 2. an increase in the density of sub-adult
females as a result of the fishery being mainly directed toward
males over 6 cm TL. There is also a possibility that the
predation by sub-adult male and female crayfish on young may have
been a factor as well.

Yields were not a good indicator of the impact of the
fishery since yields in North Twin remained high just prior to
the collapse (Momot 1988) .

The experiment on the Ontario lakes was somewhat different
as these two lakes are eutrophic. Nutrient rich lakes were
selected so that a density-dependent growth response could be
documented. In addition the low oxygen content of the deep
waters of Dock Lake kept female crayfish confined to shallow
waters. This avoided the problem of selective harvest of males.
Shallow Lake was left unexploited in this experiment.

In the Dock Lake experiment, yields remained steady and
increased with effort. Production increased through a shift in
survival rates and age at maturity to compensate for the
increased rate of removal. The question remains as to how much
more of the stock can be harvested without causing a sudden stock
collapse (Momot 1988) .

While fin fishes typically respond to exploitation through a
growth or fecundity adjustment, crayfish adjust to exploitation
principally through a shift in survival rates and age at
maturity. Both of these responses are much more difficult to
estimate (Momot 1988) . The absence of dramatic density dependent
compensation in growth and a limited fecundity response inhibits
early detection of growth over-fishing in orconectid crayfish
populations, especially in northern latitudes. If such
populations were subjected to a succession of years exhibiting

9

poor climatic conditions for optimum cohort recruitment, wide
oscillations in production and yield might result. Since growth
over-fishing cannot be easily detected, recruitment over-fishing
remains a distinct threat.

McGriff's (1983) study of the crayfish fPacifasticus
leniusculus) of the Sacramento- San Joaquin delta confirms that
crayfish tend to adjust survival rates and age at maturity in
response to higher mortality. Both 1976 and 1977 were severe
drought years in California. The data indicate that the 1976 and
1977 year classes may have been weakened by decreased survival of
juveniles during the adverse conditions. The 1978 year class
compensated for the decreased fecundity during the drought with
increased survival of juveniles when conditions improved. In
addition, although significantly fewer eggs per female were
produced in 1977, there was a higher level of maturity among
smaller sizes and younger ages that year. Therefore, the
absolute fecundity level, in total eggs produced Delta-wide, may
not have been reduced. Commercial fishing does not seem to have
had an impact on the fecundity of the Delta population (McGriff
1983) .

Crayfish management has been of interest to the Swedes for
many years as crayfish are a favored food in Sweden. Svardson
(1949) examined whether the stunted crayfish (Astacus fluvialtis)
population of Lake Alkvettern, Sweden was due to overfishing,
overpopulation, or genetic growth capacity. He concluded that
the small size of the population was due to overpopulation. He
based his conclusions on evidence of slow growth of the Lake
Alkevettern population, and faster growth when crayfish from this
lake was transplanted to other lakes. His recommendation to
increase the size of the crayfish was to increase harvest of the
smaller crayfish, or to re-introduce eels, which prey on
crayfish. However, he does not report if his recommendations
were acted upon or whether they were effective in increasing the
average size of crayfish.

Catch per unit effort is not a reliable indicator of
population density. In a study of Donner Lake and Lake Tahoe,
Goldman and Rundquist (1977) found through mark and recapture
studies that Lake Tahoe had a higher density of crayfish than
Donner Lake. However, based on the average catch/trap data
alone, one might conclude that the two populations were very
similar. Predator density is one factor that influences
trapability. Rock bass in particular have been found to reduce
the trapability of crayfish (Collins et al 1983) .

It should be noted that commercial harvesting of crayfish is
size selective. Since large individuals are more herbivorous and
less carnivorous than small individuals, changes in the
population structure could modify the role of crayfish population
in the system (Lorman and Magnuson 1978) .

10

Siunmary

The population dynamics of exploited populations is not well
understood. The quantitative research done to date has been
primarily on Orconectes populations. Several generalities can be
made. Crayfish populations tend to respond to exploitation
through a shift in age at maturity and survival rates. These
changes are relatively difficult to detect. Catch per unit
effort is not a reliable indicator of population density.

Catches can remain high until the population collapses. Crayfish
populations are sensitive to environmental conditions which makes
accurate calculation of MSY difficult. In addition, commercial
harvest of crayfish is sex selective in most situations. This
can result in unexpected changes in the structure of the
population .

However, this information comes primarily from experimental
research. In actual commercial crayf isheries, such as in Oregon
and California, no substantial biological problems have been
noted.

IMPORTANCE OF CRAYFISH AS FOOD FOR OTHER SPECIES

Crayfish are preyed upon by a wide range of organisms of
both terrestrial and aquatic origin. Rarely do they form more
than a minor part of the overall diet of the predator. The most
vulnerable periods are the juvenile stages and the immediate
post-molt period when the exo-skeleton is still soft. The
importance of crayfish as a food is often seasonal (Hogger 1988) .

Trout

Brook trout

Benson (1953) studied eastern brook trout ( Salvelinus
f ontinalis) food habits from April to September 1952 in the
Pigeon River, Otsego County, Michigan. The frequency of
occurrence of crayfish in brook trout stomachs varied from 3.2%
(June 24 to July 4) to 35.1% (May 24 to June 6). The percent
composition of crayfish in the stomachs varied from 0.4% (July 19
to Aug 1) to 39.8% (May 24 to June 6). Mayflies and caddisflies
tended to have a higher frequency of occurrence than crayfish,
but crayfish were clearly an important component of the diet in
terms of the volume of food.

Larger brook trout (over 9" in length) were found to feed
heavily on crayfish in West Lost Lake, Michigan in the late
summer (July - October) and winter (December - March) . Trout
were effective predators only on 1/2 to 1 year old crayfish.
Apparently crayfish more than a year old were too large to be
captured by trout. It is believed that crayfish were more
available to trout in these two seasons for the following

11

reasons: 1. in the spring the crayfish young-of-the-previous-year
were larger than the maximum size consumed by trout, 2. the
young-of-the-present-year had not yet hatched and were
unavailable to trout in the spring and 3. in the fall, trout eggs
were more important in the trout diet. Brook trout under 9" were
found to feed on crayfish only sporadically and in small amounts
(Momot 1965, Momot 1967).

On an annual basis, brook trout utilized only 2.9% of the
total net production of crayfish biomass in West Lost Lake (Momot
1965, Momot 1967) . In this lake, trout predation acted as a
compensatory form of mortality in that trout ate crayfish that
would have died of other causes. Trout predation had no impact
on the crayfish population (Cowing and Momot 1979) .

Rainbow trout

Predation of rainbow trout (Oncorhvnchus mykiss) on crayfish
(Orconectes virilis) was studied from 1983 to 1985 in Newcastle
Reservoir, Utah. This predation was found to be seasonal,
occurring only during June-December . It was greatest during June
- August, when up to 100% of fish stomachs contained crayfish.
Crayfish were consumed up to a size of 38 mm in carapace length
(CL) . Relative sizes of predators and prey helped limit crayfish
consumption by fish, but seasonal behavior and distribution of
crayfish also influenced their availability. Rainbow trout
growth declined after crayfish became abundant in the reservoir.
Crayfish changed the reservoir ecosystem by altering the food web
and thereby reducing the energy transfer to trout (Hepworth and
Duffield 1987) .

Parson (1955) studied food habits of rainbow trout in a tail
water fishery below Dale Hollow Reservoir. He found that algae
and associated organisms and snails were the most important food
for all sizes of trout. Terrestrial insect forms and crayfish
were more common in larger trout than smaller trout. Of the
rainbow less than 12" in length, none had crayfish, but 11% of
the rainbow greater than 12" had crayfish in their stomachs.

There were sharp differences in the consumption of crayfish
by rainbow trout from year to year in Birch Lake, Michigan.
Crayfish and scuds were 3% of the diet over a six year period,
but were completely absent from the stomachs from 1941-1943.
Rainbow under 12" only occasionally utilized crayfish, whereas
10% of the rainbow trout over 12" contained crayfish. The
average number of crayfish per stomach was 1.5, with the maximum
number being 8 per stomach (Leonard and Leonard 1946) .

Lake trout

A study of the food of lake trout (Salvelinus namavcush) in

12

Lake Tahoe (Frantz and Cordone 1970) , found that crayfish
('Pacif asticus leniusculus) were the only invertebrate that is of
importance in the diet of larger lake trout. Crayfish were not
found in the stomachs of lake trout smaller than 10.0" (FL) .

Lake trout stomachs from fish 10.0" to 14.9" contained 2.0%
crayfish by weight (3.3% frequency). Crayfish were more common
in the lake trout from 15.0" to 19.9": 12.6% frequency, 11.7% by
weight. Lake trout over 19.9" contained 8.8% crayfish by weight,
17.1% frequency.

The importance of crayfish in the diet varied seasonally.
Generally, crayfish were utilized most heavily in the summer.

The exception to this is the 10.0 to 14.9" lake trout which
utilized crayfish more heavily in the spring (5.7% frequency,

2.6% by weight) than in the summer (2.9% frequency, 0.4% by
weight) . This size class of lake trout utilized crayfish
lightly in the autumn (2.0% frequency, 2.1% by weight), and not
at all in the winter. The other size classes utilized crayfish
moderately and in approximately the same amounts in the spring
and fall, and the least in the winter. The highest percent
frequency of occurrence was with lake trout over 19.9" in the
summer (30% frequency of occurrence, 19.8% by weight). For this
size class and season, crayfish were the second most important
food .

Not surprisingly, the mean and maximum length of the
crayfish ingested increased with size of fish. The mean length
of the crayfish ingested by the 10.0" to 14.9" fish was 1.6",
with the maximum length being 1.8". Lake trout over 19.9" ate
crayfish of a mean length of 2.9", with a maximum size being 4.3"
(Frantz and Cordone 1970) .

In contrast, lake trout in Birch Lake, Michigan were not
found to be feeding on crayfish (Leonard and Leonard 1946) .

Other trout

Neither brown trout (Salmo trutta) nor cutthroat trout
(Oncorhynchus clarki) were found to contain crayfish in a study
of food habits of fish in the Pend Oreille River (Barber et al
1990)

Lowery (1966) did find crayfish in the diets of cutthroat
trout, but their occurrence was limited to a short period of time
in the spring. The sample taken on May 18 found 19.6% occurrence
by dry weight. The sample taken June 1 found 46.2% occurrence by
dry weight. None of the other samples taken contained crayfish.
The author noted that the June 1 sample contained larger fish
than any of the other samples, in line with the observation that
larger fish tend to utilize crayfish more heavily than small
f ish .

13

Leathe and Graham (1982) did not detect crayfish in the
diets of fish in Flathead Lake, Montana.

Largemouth bass

Dubets (1954) studied the food habits of largemouth bass in
four lakes in Illinois. In lakes that contained gizzard shad,
this was the most popular food item and the frequency of
occurrence of crayfish was low (1% to 10% of the fish contained
crayfish) . However, in Christopher Reservoir, which did not
contain gizzard shad, crayfish was the most popular food item.

Of the 12 stomach examined from this lake that contained food,

50% contained crayfish.

A study of the food habits of largemouth bass from Crab
Orchard Lake, Illinois found that the most important food item
was gizzard shad. Crayfish were found in 15% of the stomachs.
Only 10% of the fish contained more than one forage item. Of the
fish that did contain more than one forage item, 46% contained at
least one crayfish (Lewis et al 1974) .

Snow (1971) found an average of 1.4 crayfish per bass
stomach and 1.2 fish per bass stomach in Murphy Flowage,
Wisconsin. There were no gizzard shad in this lake.

Lewis et al (1961) in their study of the food choice of
largemouth bass as a function of availability and vulnerability
of food items, found that the utilization of crayfish was quite
variable. In some trials, crayfish were not used at all, while
in two trials crayfish were preferred to bullfrogs and tadpoles.
In their tests, golden shiners seemed to be the preferred prey.
Largemouth bass also preferred leopard frog tadpoles to crayfish.
Green sunfish and bullfrog tadpoles were eaten in preference to
crayfish in one trial, but in another trial they were eaten only
50% as well.

Crayfish (Pacif asticus sp.) were found in the stomachs of
age 3+ largemouth bass during the summer in Lake Pend Oreille
(Barber et al 1990). However, they were only in 2.3% of the
stomachs examined for this age class of fish. No other age class
of largemouth bass were found to be eating crayfish, and no age
3+ bass were found to be eating crayfish during the spring and
fall.

An interesting study of crayf ish-largemouth bass
interactions in a small Ohio pond was done by Taub (1972) . In
this study, a small pond was located which contained large
populations of the burrowing crayfish Cambarus diogenes. and no
fin fish. An estimate of the crayfish population at the start of
the study found an estimated population of 37,000 crayfish +

2,000 at the 95% confidence level.

14

Largemouth bass were then stocked at a rate of 770 per
hectare. Attempts to estimate the crayfish population during the
two years after bass were introduced were unsuccessful due to the
low density of crayfish. However, largemouth bass continued to
utilize crayfish as prey throughout the course of the study
despite their low numbers in the pond. In the first year after
bass introduction, 69% of the bass stomachs contained crayfish.
During the second year this dropped to 54%. Largemouth bass
growth was good throughout the study.

The author comments that it was surprising to find even
moderate use of crayfish by bass after 24 months because seining
indicated a low crayfish population 12 months after the bass
introduction. This suggests that largemouth bass are highly
effective predators of crayfish. These results should be applied
with caution in Montana however, since the species of crayfish in
this study is a burrowing crayfish (Taub 1972) .

Mullan and Applegate (1970) studied the food habits of
largemouth bass during the filling of Beaver Reservoir. Bass
smaller than 100 mm TL did not utilize crayfish. Bass that were
101 mm to 200 mm TL ate crayfish in small amounts during the
spring and fall (percent of total volume varied from 1.2% in
November to 14.2% in April).

Bass larger than 200 mm TL ate crayfish during the winter,
spring, and fall. The percent of total food volume made of
crayfish varied considerably from month to month. Crayfish were
not utilized in the summer months (June, July, August) . During
the other 9 months crayfish composed from 1.3% of the total food
volume (January) to 71.9% of the total food volume (September).
The authors stated that as young shad diminished in abundance and
in stomach contents as the summer progressed, largemouth bass
larger than 200 mm TL included more crayfish in their diet.

This differs somewhat from the result of the research done
by Rickett (1974). He found bass as small as 41 mm utilizing
crayfish, although bass larger than 100 mm ate crayfish more
frequently than did smaller bass.

Smallmouth bass

In Lake Sammamish, Washington, the major prey of smallmouth
bass (Micropterus dolomieui) were juvenile salmon, crayfish, and
sculpins. The young smallmouth bass fed primarily on smaller
versions of the same prey types that the adults fed on, rather
than different food types. The number of juvenile salmon in
smallmouth bass stomachs was highest in May, during the peak of
the salmon out migration. In the other months studied (March
through August) , crayfish and sculpins were the most important
food. Smallmouth bass in Lake Sammamish are apparently feeding
generalists, feeding on prey items as they are encountered. The

15

more numerous the prey is in the environment, the more numerous
it is in the stomachs (Pflug and Pauley 1984) .

Investigations of smallmouth bass food habits in Dworshak
Reservoir, Idaho, found decapods to be a small portion of the
diet (7.7 % frequency of occurrence, 9.3 % by volume) (Stabler
1990) .

Emery (1975) concluded that stunting of a smallmouth bass
population in Lake Opeongo, Ontario, was the result of
competition with cisco fCoreqonis sp.) and a limited supply of
crayfish for adult bass. The average intake of food items on a
volume basis was 69.1% crayfish over the years of the study. The
range of values was 38% in 1956 and 74% in 1971. He estimated
that bass constitute a mortality factor of approximately 70% on
Orconectes sp. . as compared to an overall mortality rate of
75.5%. It appears that bass are responsible for a major part of
the mortality of Orconectes in this system.

Emery (1975) also noted competition for crayfish between
divers and smallmouth bass. Bass took the crayfish as the SCUBA
divers chased them in an attempt to capture them for the research
project. He also said that the bass could easily be fed 10
crayfish from a diver's hand. Up to 5 crayfish per stomach and
an average of 2.5 crayfish per stomach were found in bass
stomachs in 1972. Smallmouth bass showed a distinct preference
for Orconectes over Cambarus in this lake. This may be due to
bass being crepuscular feeders, and Cambarus are primarily active
at night. Orconectes is relatively active in the daytime, and is
quite active at dusk when the bass are feeding.

Other fish

Maloney and Johnson (1955) studied the food habits of
walleye (Stizostedion vitreum) and yellow perch (Perea
f lavescens) in two Minnesota lakes. Food of young of the year
walleye was almost entirely fish in both lakes. Young of the
year perch fed on plankton crustaceans and insects. In Mille
Lacs Lake yearling yellow perch ate 24% crustaceans, including
hyalella, cladocerans, and a few crayfish. In Lake
Winnibigoshish yearling yellow perch ate crustaceans and insects
in late June but by late July crustaceans had been replaced by
fish .

Jeppson and Platts (1959) commented that perch fed mostly on
crayfish and insects in the three northern Idaho lakes they
studied. In Cocalella Lake, 98% of the perch food volume was
crayfish. In Lake Pend Oreille, none of the perch had eaten
crayfish, all of the perch were eating insects. In Hayden Lake,
87% of the perch food volume was crayfish.

Bonde and Maloney (1960) studied winter food habits of

16

burbot (Lota lota) in Mills Lakes, Minnesota. In 1949, 4.2% of
the burbot contained crayfish. In 1958-59, 9.4% of the burbot
contained crayfish. The primary winter food of burbot was found
to be perch, with darters, cyprinids, sculpins, crayfish, and
mayflies of secondary importance.

Burbot were also reported to feed on Cambarus at night in
Lake Opeongo, Ontario (Hackney 1973) .

A study of the food habits of northern squawfish
CPtychocheilus oreaonensis) in northern Idaho found that 8.1" to
12.0" squawfish contained 30% crayfish by volume. The 16.1" to
20.0" squawfish contained 6% crayfish by volume. Other sizes of
squawfish did not contain crayfish (Jeppson and Platts 1959) .
However, the importance of crayfish in the diet varied
considerably between lakes. In Hayden Lake, 18% of the squawfish
food volume was crayfish, whereas in Lake Pend Oreille only 1% of
the squawfish food volume was crayfish. In Lake Cocalalla
squawfish were not found to eat crayfish.

A study of the fisheries of Lake Roosevelt, Washington did
not find crayfish to be an important food item in the diet of any
of the fishes reviewed. No crayfish were found in the stomachs
of lake whitefish (Coreaonis clupeaformis) . northern squawfish,
or yellow perch. A small percentage of the walleye stomachs
contained crayfish during July (1.9% frequency of occurrence, 0.8
% by weight and volume) , but not during May, June, August, or
September (Nigro et al 1983) .

Observations of the food habits of fish in the Clark Fork
River, Montana indicates that crayfish are an important component
of the diet of northern squawfish (Berg pers. comm. 1991) .
However, the study was limited to spring time food habits,
primarily the month of May.

In Nigro 's (1990) study of the status and habitat
requirements of the white sturgeon (Acipenser transmontanus) in
the Columbia River downstream from McNary Dam, he found that
17.2% of the white sturgeon stomachs contained Pacifasticus sp.
The number of Pacifasticus so. in the stomachs varied from 1 to
17, with the mean being 3. Pacifasticus comprised 26.5% of the
food volume by weight.

A study of the food habits of the fish of the Pend Oreille
River found crayfish in the stomach of 100% of the age 7+ yellow
perch in the summer (Barber et al 1990) . However, the sample
size was only one fish. They found no crayfish in the stomach of
any other yellow perch during any other season. They also did
not report crayfish being utilized by mountain whitefish
fProsopium williamsoni) , black crappie (Pomoxis niaromaculatus) .
kokanee (Oncorhvnchus nerka) , pumpkinseed (Lepomis aibbosus) .
tench (Tinea tinea) , largescale sucker fCatostomus macrocheilus) .

17

long nose sucker fCatostomus catostomus) , northern squawfish,
peamouth CMvlocheilus caurinus) , or black bullhead f Ictalurus
melas) .

Allen (1939) studied the food habits of pike in Lake
Windermere and found they fed almost exclusively on fishes,
mostly perch.

Black bullheads (Ictalurus melas) were found to consume
crayfish by Rickett (1974), although they preferred artificial
fish food, vegetation, and mayfly nymphs.

Wading birds

The principal avian predators on crayfish are wading birds
such as ibises, herons, and egrets. As much as 90 - 95% of the
diet of yellow crowned night herons (Nvctianassa violacea)
consists of crayfish, whereas they comprise 45-50% of the diet of
the little blue heron (Florida caerulea) (Huner and Barr 1984) .

Collazo (1985) studied the food habits of great blue herons
in Idaho. He found that the primary food were brown bullheads
(Ictalurus nebulosus) and tench. Only one crayfish was found in
a great blue heron stomach over a two year study.

Other birds

Ducks will occasionally eat crayfish. Kimble and Ensminger
(1959) mention crayfish as ranking 13th in importance in the diet
of ducks (out of 15 items) in Louisiana after a hurricane. Ducks
not reported to be eating crayfish prior to the hurricane.

Crayfish play an important role in the diet of eastern
belted kingfishers (Mecracervle alcyon alcvon) during a short
period during the young bird's development. After learning to
catch insects, young kingfishers spend the 5th to the 10th day on
the wing exclusively learning to capture crayfish. Broods in
this period show a striking uniformity of behavior. It is the
latter part of the second week on the wing when kingfishers learn
to catch fish. The frequency of occurrence of crayfish in the
diet of kingfishers was found to vary from 14.3% (on trout
rearing waters) to 59.1% on non-trout streams
(Salyer and Lagler 1946) . Kingfishers seemed to eat more
crayfish from streams than from lakes, perhaps due to the greater
proportion of shallow water in streams.

Eipper (1956) studied the food habits of eastern belted
kingfishers and found that crayfish composed 49.5% of the
remains from two kingfisher nests. Orconectes made up two-thirds
of the stream samples, but was not found in nests remains. The
nests remains were 100% Cambarus. The reason may be that
Cambarus breeds in both the spring and fall. The spring breeding

18

behavior may increase the crayfish's vulnerabilty to kingfisher
attack.

Bald eagles will occasionally eat crayfish, although they do
not constitute a major portion of the diet (Becker 1991 pers.
comm. )

Mink

Mink fMustela vison) tend to be opportunistic feeders with a
varied diet (Linscombe et al 1982) . Crayfish are frequently used
by mink. Korschgen (1958) stated that crayfish occurred in mink
stomachs 19.9 % of the time (9.3% of the food volume by weight)
during the winter in Missouri. He noted that mink predation on
crayfish increased during drought periods, which made crayfish
more available to mink. In addition, crayfish were more common
in mink stomachs taken from southern Missouri than those taken
from northern Missouri. Waller (1962) found crayfish more
abundant in scats collected during summer and fall months and in
areas where crayfish were most plentiful. Crayfish constituted
22.3% of the food of mink in summer in an Iowa marsh (Waller
1962) . Erlinge (1969) did not mention crayfish as being a
component of the diet of mink in Sweden. However, he does state
that he observed mink catching more prey, including crayfish,
than they immediately require and then storing it.

Gerell (1967) studied the food habits of mink in Sweden and
found that crayfish were found in the diet primarily in the warm
months. The low activity and more hidden mode of life in the
cold months kept crayfish less vulnerable to predation. In August
1963, the crayfish were killed by the crayfish plague. In the
first half of August 1963, crayfish amounted to 85% of the mink
diet. In the second half of August this number went down to 31%,
and then by September to 0. After the crayfish plague killed off
the crayfish, mink switched to rodents and frogs for food.

Burgess and Bider (1980) studied the effects of stream
habitat improvements on invertebrates, trout populations, and
mink activity. They found that habitat improvement resulted in
trout population and biomass increases. Crayfish (Cambarus
bartoni) biomass was also greater in the improved section. Mink
activity was 52.5% higher in the area surrounding the improved
section. However, mink did not respond to the trout biomass
increases, nor was mink activity correlated with activity
patterns of any terrestrial prey species. Analysis of mink scats
revealed that crayfish occurred in 20% of all scats found, and
50% of those from the study area. Thus, habitat improvement and
the resulting increases in crayfish production resulted in
greater use of that area by mink.

Raccoon

19

Raccoons are omnivorous and opportunistic feeders. Hundreds
of species of plant and animal food have been recorded from scats
and stomachs, and the relative proportions of different foods
vary with the locality and season. In most habitats, plants are
generally more important than animals in the raccoon's diet. The
most important animal food is crayfish (Kaufmann 1982) .

Raccoons in most habitat throughout their range follow the
same general pattern of diet changes. Only in the spring do most
raccoons eat more animal food than plant food. Crayfish are the
most important food at this time, followed by insects and small
vertebrates. In the summer raccoons eat primarily fruits, but
crayfish continue to be the most important animal food item
(Kaufman 1982). Dearborn (1932) found that crayfish made up 59%
of the summer diet in one area of Michigan. Dorney (1954) found
that muskrats and crayfish provided most of the diet in a
Wisconsin marsh.

River otters

Most authors have found the primary food of river otters
(Lutra canadensis) to be fish. However, the importance of food
items other than fish should not be underestimated. Liers (1951)
reported that captive otters fed a basic diet of live fish often
did poorly.

Several authors have reported that crayfish is the second
most important food for river otters (Knudsen and Hale 1968,
Hamilton 1961, Ryder 1954, 1955). Lauhachinda and Hill (1977)
report that fish were the most important food, with crayfish
recovered from 62.5% of the digestive tracts that contained food
remains, and 58.3% of the scats. Their study was of river otters
in Alabama and Georgia.

In Montana, Greer (1955) did not identify crayfish as being
in the diet of river otters in the Thompson Lake region, however,
it is not clear if those lakes contain crayfish. This is the
only food habits study reviewed by Toweill and Tabor (1982) that
did not list crayfish in the diet of otters.

The importance of crayfish in the diet of otters varies
seasonally. In a study of Wisconsin otter scats, crayfish were
most common in summer and winter, and least common in spring
(Knudsen and Hale 1968) .

Other mammals

Coyotes have been reported to consume crayfish in trace
amounts (Korschgen 1957) .

Summary

20

From the above information it is clear that the importance
of crayfish in the diet of fish, birds, and mammals varies by
season, species of crayfish, geographic location, year, and
availability of other prey. Some generalizations can be made
however. Many species of fish, birds, and mammals have been
reported to eat crayfish, but there does not appear to be any
species which feeds exclusively on crayfish in all localities.
Large fish utilize crayfish more than small fish. Small
crayfish, and crayfish that have recently molted are more
vulnerable than large, hard shelled crayfish. In cold climates,
crayfish are usually most important as a prey species during the
summer when they are more active and therefore more vulnerable.

Crayfish can be extremely important in fish diets in some
localities. In particular, yellow perch and largemouth and
smallmouth bass have been reported to utilize crayfish in large
amounts. The importance of crayfish in fish diets varies greatly
by location and seems to depend primarily on what other sources
of food are available. Trout also utilize crayfish in their diet
in some locations. Even lake trout, primarily considered to be
fish eaters, will utilize crayfish in some situations. Other
species of fish reported to utilize crayfish include burbot,
northern squawfish, black bullheads, and white sturgeon.

The primary avain predators on crayfish are wading birds
such as ibises, herons, and egrets. Ducks and bald eagles will
also take crayfish occasionally. Eastern belted kingfishers feed
on crayfish, especially during the second week of life.

Mink and raccoons seem to be the primary mammalian predators
on crayfish. However river otters will also use crayfish
seasonally if they are available. Even coyotes make take an
occasional crayfish. This list of species which utilize crayfish
as a food source is not necessarily exhautive, but rather
summarizes the most important predators and gives a picture of
the range of animals that utilize crayfish.

MANAGEMENT OF PACIFA8TICUS SP. IN THE WESTERN

UNITED STATES AND CANADA

Montana

The 1991 Montana commercial crayfishing regulations require
that commercial crayfish anglers have a Class B commercial
fishing license (cost : $200.00) and post a $1,000.00 corporate
surety bond. Usually only one commercial crayfish permit is
issued for each body of water. However, the Montana Department
of Fish, Wildlife, and Parks (MDFWP) may issue additional permits
on other waters if the aquatic resource or recreational use of
the water will not be affected. The MDFWP may also close waters
at any time, after demonstrating the need to protect the aquatic
resource, recreational use, or to protect human health and

21

safety .

There are no season restrictions in Montana. The minimum
size for harvest of Pacifasticus is 3 5/8 inches and for
Ocronectes the minimum size is 3 inches. Undersized and berried
females must be returned to the water immediately following the
emptying of any single trap or trap line.

There are restrictions on the type of gear that may be used
on the frequency with which the gear must be tended. All gear
must be disinfected before it can be used. In addition, all
traps, rings and live cars must be marked with the angler's name,
address, and permit number.

The angler is required to submit monthly reports on his
operations and transacions.

Idaho

About 3 to 4 years ago, there was a great deal of interest
in commercial crayfish harvest in Idaho. At that time, Idaho
added crayfish to the commercial fishing regulations. It now
cost $100.00 to get a commercial crayfish license in Idaho, and
each trap must be marked with an identification tag which costs
$1.00 per pot. There is a 3 5/8" minimum size limit and reporting
requirements. Since these regulations have been implemented,
there has been a decline in the number of people interested in
crayfishing. At this point the fishery is limited to "serious"
anglers, with the casual operator being discouraged by the
license cost (Van Vooren, per. comm. 1991) .

There are currently about 4 anglers fishing for crayfish in
Idaho. Most of the crayfishing activity is confined to
reservoirs on the main stem of the Snake River. Idaho has not
conducted any studies of the impact of the crayfish fishery, but
I was told that their qualitative observation is that there has
been a downward shift in the size and age structure of the
population. It is Idaho's view that the impact of this shift is
probably either neutral or beneficial to the fishery. Larger
numbers of small crayfish provide more available prey for the
coolwater species that inhabit these waters (Van Vooren pers.
comm. 1991) .

Idaho has had minimal problems with non-target species being
caught in the traps. There has been a little incidental catch of
yellow perch or bullheads but not enough to cause a concern.

There have been some enforcement problems with traps being
stolen. Overall, the number of complaints they have received
from other user groups has declined since the regulations went
into effect.

A1 Van Vooren ' s advice to Montana officials is to charge a

22

substantial fee for the commercial crayfishing licenses to weed
out the irresponsible or non-serious anglers.

Washington

Prior to 1990, there were 26,000 pounds of crayfish
harvested commercially in Washington each year. Washington
requires that each angler obtain a $50.00 shellfish pot license
for commercial crayfish harvest. The state publishes a list of
waters that are open to commercial harvest. The general
regulation is a limit of 400 pots per angler but each body of
water has a maximum pot number which may be less than 400 per
angler (Wood pers. comm. 1991) .

The minimum size of crayfish is 3 1/4" from the tip of the
rostrum to the tip of the tail. Undersized and berried females
must be released. In the Columbia River and its tributaries the
season is early April to the end of October. In the rest of the
state the season is May to October. There is no bag limit.

Sometimes anglers will want to harvest crayfish in a water
body that is not on the list of open waters. They may apply for
a commercial crayfish permit which will be reviewed to determine
if there are potential conflicts such as high recreational use.

If the conflicts are determined to be low, then a permit may be
issued, usually for specific areas within the water body.

Anglers must fill out a crayfish log and submit the log
monthly. There is no mesh size or size limit on the pots. A
buoy brand number (issued by the state) and the angler's name
must be put on unattended pots. Buoys must be of indestructible
material and the number of pots held by each buoy must be
recorded.

The fishery in Washington has not gotten alot of attention.
The biologist I spoke with was not aware of any over-fishing
problems. He stated that their system has been pretty successful
in mitigating the conflicts between user groups. He also stated
that their fishery seems to be a lot of work for the number of
pounds harvested and there is a lot of turnover among the
anglers. It is also a lot of administrative work for the staff
(Wood pers. comm. 1991).

Oregon

Oregon has a large and active commercial crayfish fishery,
managed by the Oregon Department of Fish and Wildlife. The
statewide season in Oregon is April 1st to October 30th. The
reason for this season is that is when the crayfish are
catchable. Their regulations require that anglers use pots or
rings only. There is no size or number restriction on traps.

Most anglers fish a maximum of 80 to 100 pots per person per day.

23

They have a minimum size limit of 3 5/8" measured from the
tip of the bony spike to the tip of the telson. The reason for
this size limit is that most females have spawned at least once
by the time they reach that size. All berried crayfish must be
released and possession of berried females is illegal (Smith
pers. comm. 1991).

Oregon requires that all fishing gear be identified with an
identification tag. This includes boats, buoys, live boxes,
bags, etc. The purpose of this regulation is to aid law
enforcement and also to protect the angler in case of theft.

The entire state is open to commercial crayfish harvest
except for a few areas which have been closed due to conflicts
with sport crayfishing or sport trout fishing. They occasionally
get complaints from sport crayfishers about the activities of
commercial crayfishers, but there do not appear to be too many
other conflicts (Smith pers. comm. 1991).

Oregon monitors the commercial crayfishery by requiring
anglers to report their catch to the Oregon Department of Fish
and Wildlife when the crayfish are sold commercially. The report
must state the number of pounds harvested by water body. In the
case of large rivers, the location of the catch must be
identified. Anglers are required to purchase a commercial
fishing license (price $40.00), but they do not need a commercial
boat license. There is no restriction on the number of licenses
issued (Smith pers. comm. 1991) .

It was the opinion of the biologist from the Oregon
Department of Fish and Wildlife that I spoke with that the
minimum size restriction is adequate to protect the fishery. He
was unaware of any over-fishing problems that had occurred. He
said they do occasionally get complaints from the commercial
anglers that certain specific areas are being fished too heavily
and they occasionally request entry limitations. Oregon has only
recently begun collecting data on their crayfishery. Three years
ago they began sampling the catches to look for any changes in
average size. To date no changes have been detected. They also
did some tagging to monitor crayfish movements. They have just
completed analyzing that data, which indicates that crayfish did
move from other areas into the areas which were being harvested.
This data collection was undertaken primarily out of curiosity,
not because they have concerns about the fishery (Smith pers.
comm 1991) .

It was Mr. Smith's recommendation to the Montana Department
of Fish, Wildlife, and Parks that anglers be required to report
the number of traps fished and the time they were fished in
addition to the number of pounds harvested. This would give
Montana an estimate of the catch per unit effort without using
much staff time to monitor the fishery in the field. In

24

addition, Mr. Smith recommended that anglers be required to be
specific about the location of the catches, especially on large
river systems. He also expressed some concern about crayfish
picking up pollutants such as dioxin. He suggested that any
questionable waters be tested for crayfish toxicity (Smith pers.
comm. 1991) .

British Columbia

In British Columbia there is both a recreational and a
commercial crayfishery. Neither fishery has been given much
attention by the British Columbia Ministry of Environment. The
biologist I spoke with stated that they do not even know for
certain how much of the province is occupied by crayfish (Sunde
pers. comm. 1991).

Recreational anglers are allowed to trap crayfish if they
are in possession of an angling license. There is no season or
limits, however, they are requested to release berried females.
The biologist I spoke with has no idea how many recreational
crayfish anglers there are in British Columbia (Sunde pers. comm.
1991) .

The province of British Columbia issues approximately 20 to
30 commercial crayfish licenses every year at a cost of $5.00 per
license. A separate license is needed for every water body to be
fished. There are no seasons or limits, and the license is valid
from the date of issuance until December 31st. The minimum size
is 9 cm measured from the rostrum to the tip of the tail.

Berried females must be released. Traps must be designed to
impound rather than entangle, i.e. no gill nets are allowed
(Sunde pers. comm. 1991) .

British Columbia does not provide licenses for every water
body. Some waters, that are used heavily by recreational
crayfish anglers, are closed to harvest. To date, the province
has closed approximately 2 to 3 rivers and 3 to 4 lakes to
commercial harvest (Sunde pers. comm. 1991) .

Commercial fisherman are required to report information
about their catch to the provincial government. About half of
those who are issued licenses submit their reports. (It is
assumed that the others did not fish or were unsuccessful) . They
are required to state the number of pounds harvested, the number
of undersized crayfish released, the number of berried females
released, the number of traps-nights fished, and the bait used.
Generally, anglers harvest crayfish by the hundreds of pounds (as
opposed to thousands of pounds) . Mr. Sunde was unaware of any
problems that have occurred due to over-fishing. He stated that
the data that comes in on the angler's reports is so sparse they
have made no attempt to do any type of analysis of the data.

25

California

The commercial crayfish fishery began in California in 1970.
From 1970 to 1975 the fishery was unrestricted and the mean
length of crayfish caught declined from 104 mm to 90 mm. In 1975
regulations were imposed including a minimum size of 92 mm total
length with the catch sorted on the boat, and undersized crayfish
returned to the water immediately. In addition, restrictions
were put on the use and design of transport boxes in an attempt
to increase transport survival. By 1976 the minimum size of the
animals sent for processing was raised to 102 mm. Following the
establishment of these practices the yield and size was
maintained until 1980, which suggested that the area was not
being over-fished (Lowery and Holdich 1988) . The fishery
harvests 500,000 pounds per year.

There is a long set of complex regulations which govern the
fishery (Appendix E) , however the biologist I spoke with felt
that they really do not have a good handle on the resource
(Cordone pers. comm. 1991) . The state did attempt to study the
crayfish fishery in the Sacramento delta, but had only limited
success due to the difficulty of working with crayfish and the
difficulty of working in the delta.

Mr. Cordone stated that when the fishery first got started
there were numerous social conflicts between anglers and
crayfishers. However, the number of complaints has gradually
declined until now there are hardly any problems.

The crayfishers periodically request that the fishery be
made a limited entry fishery. The state has declined to do this
because of the administrative problems of these types of
fisheries. In addition the crayfishers also periodically request
that the lakes and reservoirs be opened to commercial harvest.

The state has consistently denied this request because of
pressure from the black bass anglers who feel that this would be
detrimental to their interests. Mr. Cordone did not feel there
was any real biological reason why some of these lakes could not
be opened on an experimental basis.

Utah

Utah has no commercial crayfish fishery. Recreational
crayfishing is allowed and there are no regulations governing
this activity (Shaddick pers. comm. 1991).

Crayfish distribution and composition in Utah are poorly
documented. It appears that Utah has only one native crayfish
species, and that only north of Salt Lake County. However, in
recent years crayfish have been introduced into numerous waters
around the state. The state is concerned primarily with
gathering more information about their crayfish populations and

26

with controlling illegal introductions (Johnson 1986) .

Wyoming

Wyoming does not have a commercial crayfish fishery, nor do
they have any regulations on recreational harvest. In Wyoming,
crayfish are considered to be a valuable fish forage in most
waters where they occur, but several potential problems with
introduced crayfish are of concern to fisheries managers. These
concerns include possible impacts to native species, possible
forage imbalance in some trout fisheries, and the loss of aquatic
macrophytes in aquatic systems where plants are ecologically
important (Hubert 1988) .

Alberta

Alberta has no commercial or recreational crayfishery.
Crayfish are believed to be native to the Beaver River system in
northeastern Alberta only. Alberta biologists are also aware of
one illegal introduction of crayfish near Grand Prairie. All the
crayfish in Alberta are small and do not attract any interest as
a human food (Watson pers. comm. 1991) .

Summary of western crayfish management

A minimum size limit seems to be standard for all the states
and provinces which have a commercial crayfish harvest. The
biological basis for the minimum size limit is that it allows the
crayfish the opportunity to spawn at least once before it is
harvested. However, this limit also closely correlates to the
minimum size that is acceptable for the market.

Some areas have seasons but California and British Columbia
do not. Since crayfish are not vulnerable to trapping during the
cold months, a season restriction is probably not necessary.

All the agencies I spoke with require the release of berried
females. Since the Scandinavians will not accept berried females
anyway, this is no great hardship on the anglers. The primary
benefit of this regulation (as with the minimum size limit) is
that the anglers are required to sort their catch at the time of
harvest and release undersized and berried females alive.

It is also apparent that this fishery is not getting very
much attention. Although none of the biologists I spoke with
were aware of any biological problems that have occurred from
commercial crayfish fishing, none of the states have really
gathered any data which provide any solid evidence one way or the
other. Most of the problems that have arisen have been between
competing user groups or sometimes between competing commercial
crayf ishers .

27

Of the states I contacted, only Oregon and California have a
significant crayfish harvest. In the other states, the interest
in crayfishing fluctuates with the market price, however it is
not a major fishery at any time.

28

COMMERCIAL CRAYFISH REGULATIONS IN THE WESTERN U.S. AND CANADA

JUNE 1991

Commercial

License Min. Collection Transport Special

State Require. Season Size Method Restrict. Regula.

MT

Class B

Year

3 5/8"

crayfish

May

Undersized

commerci

round

for

or minnow

transpo

and berried

al

Pacif as

traps not

rt only

females

license :

ticus

> 3' dia.

between

immediately

$200/yr

and 3"

Crab

the

released.

+ free

for

rings, by

areas

Sorting

crayf ish

Orconec

hand.

harvest

error 5%.

permit

tes

hook and

ed and

Traps

for a

line, or

the

disinfected

specific

experimen

point

& tended

water +

tal gear

of

every 72

$1,000.

as

sale.

hrs. All

surety

approved

holding

gear must

bond

by MDFWP

, or

have gear

process

tags. Only

ing.

one permit
per water
body (with
exceptions)

No gear
within 100

yds of any
public boat

ramp or
dock .

Monthly

reports

required.

29

II

' "L TO,.

•v-i V ■ ,-^,v ■“

'■ " ■• «■■'«;:■• '■': ”"

sik'^.ta‘

’■ ' '5;-- a: '

.1

■?SJ'

'■'Jl" ■■' a' ,'■ ( 5.

'r -■' - ,

o, ■> %? . t i

... '* :»■ L

.,. ‘i

.?*•?? V I g iiS,

■ .' I

— 4‘ 3-

•3. ,.

; js' ,

'■ I't

\n0¥;^'

^:4.:rsl.

:fri".t.aq
:!A/i
‘'1^^

;■ ' r ilia

•'.'tcsi'

->. ■

^■ir. ■'

I: . .- . '•- W ;/ ;'.
-AU- ;:rH • ."••,J_ s ,

.•••■.% .. .•■•• ,•

- ■■ '

V . ; . ■

’4i ‘1

J?'’

ID

Commerci
al fish
license
$100. +
gear tag
$1 . 00/po
t

4/1

to

10/31

3 5/8"

Attended
seines or
crayfish
or minnow
traps not
> 3' dia.

Trans-
port
from
capture
area to
point
of sale

or

holding

only

Undersized
and berried
females
released
immediately
Only
certain
waters
open. No
fishing
within 100
yds of any
public boat
ramp or
dock. Must
have gear
tags. Traps
checked
every 96
hrs.

Monthly

report.

WA

Shell-
fish pot
license
$50.

1st

Mon

in

May

to

Oct

31.

Some

excep

tions

3 1/4"

Crayfish
pots or
rings
only

400 pot max
per person.

No fishing
within 1/4
mi of
developed
parks. Only
certain
waters
open, with
max number
of pots
allowed.

Must

maintain

harvest

log.

Immediate
release of
berried
females and
undersized
crayfish.

30

OR

Commer-

cial

fishing

licence

$40.

4/1

to

10/31

3 5/8"

Pots or

rings

only

Need

trans-

port

permit

Undersized
and berried
females
released.

Some waters
closed. All
gear must
be labeled
with

identifica-
tion
number .

BC

Crayfish

license

$5.00

Year

round

9 cm

Gear

which

impounds

rather

than

entangles
is legal

No

trans-
plantin
g from
water
body to
another

Catch

record must

be turned

in when

license

expires.

Undersized,

berried

females,

and game

fish

released

unharmed

31

ir,-1 1

*' < I ^'1 *7 •• S’'‘J ^•,

.■■ iV. 'f-Ji j

! ■ ; \ -■ i: ■

. -^ « • •• ■

■■ -M ■

CA

Commerci

Year

3 5/8"

Hand,

Contain

Immediate

al fish

round

on

hook &

ers

return of

license

Pacif as

line, dip

vented

undersized

($40.) +

ticus

net not

at

and berried

free

only

>6 ' or

bottom.

females .

crayfish

trap not

depth

10% sorting

permit.

> 3 '

of

error

crayf is

allowed.

h not >

Traps must

13"

be tagged
with permit
number .
Trapping
area must
be

buoyed. Trap
s must be
checked
every 72
hrs. All
lakes and
reservoirs
are closed.

Only some
counties

are open.

32

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34

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38

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