![[Orconectes virilis]](ovirilis.jpg)
Orconectes virilis
Virile Crayfish
DESCRIPTION
The Virile crayfish, Ecrivisse
virile, is a medium to large crayfish. It is
distinguished from similar species (the
Papershell Crayfish) by broad flattened
tuberculate chela with straight margin of
dactyl, and male gonopod morphology. It has
a olive-brown body that is dappled with dark
brown, abdominal segments with dark brown
medial spots and chelae and legs that are
distinctly blueish with yellow tubercles. Blue
colour morphs of this species have been
recorded on occasion (Momot and Gall, 1971).
HABITAT
Found in rivers, streams, lakes and ponds. The Virile Crayfish is able to survive severe
weather conditions in the northern parts of its range.
DISTRBUTION
Canada/Ontario
The
Virile Crayfish is the most widely
distributed crayfish species in Canada. It is
found from eastern Alberta (Beaver, Amisk,
North Saskatchewan and Battle Rivers),
through Saskatchewan (Qu'apelle,
Assiniboine River, Churchill and South
Saskatchewan drainages), Manitoba
(Assiniboine River, Lake
Winnipeg, Manitoba and
Winipegosis drainages),
Ontario (Great Lakes to
Hudson Bay) to Quebec
(Ottawa River, St. Lawrence
River drainage and north)
(Rawson and Moore, 1944; Aiken,
1968; Crocker and Barr, 1968;
Vermeer, 1972; Talbot, 1985;
Sawchyn, 1986; Clifford, 1991;
Somers and Green, 1993; David et al.,
1994, 1997; Dube pers. comm.). It is worth
noting that Amisk River record in Alberta
(54¡ 27' 00" N-111¡ 46' 00" W) is the
northern-most record for any crayfish
species in North America to date.
North America Ð This species is wide
ranging in North America where it occurs
in Quebec, Ontario, Manitoba,
Saskatchewan, Alberta, New York, Michigan,
Ohio, Kentucky, Illinois, Indiana,
Minnesota, Wisconsin, Iowa, Missouri,
Arkansas, Nebraska, Oklahoma, Texas, North
Dakota, Kansas, Wyoming, Montana,
Colorado and Utah. It has also been widely
introduced throughout the United States
(Alabama, Arizona, California, Connecticut,
Maine, Massachusetts, Mississippi,
Tennessee, Vermont, Virginia, West Virginia,
New Hampshire, New Jersey, New Mexico,
Pennsylvania and Rhode Island) as well as
Mexico (Chihuahua) and Europe (France
and Sweden) (Hobbs, 1989; Hobbs III et
al., 1989; Taylor et al., 1996).
HABITAT AND ECOLOGY: It is
usually not found in swift flows or
rapids (Berrill, 1978). This species
occurs most often on rocky substrate
but it can also be found in slower
flowing rivers on mud, silt and sand as
well as in weedy soft bottomed lakes
(Berrill, 1978; Crocker and Barr,
1968).
ECOLOGY
The Virile Crayfish lives in excavations
under rocks but occasionally constructs
extensive burrow networks in the banks of
rivers such as those observed in the
Wanapitei River (Hamr, pers. comm.). On the
Ontario Precambrian Shield, this species has
been found in lakes with higher pH (> 5.7)
(David et al., 1997). It can also occur in deep
water (up to 10 m/33 ft.) (Crocker and Barr,
1968). The Virile Crayfish is able to survive
severe weather conditions in the northern
parts of its range. Survival in these conditions
is not due to any special physiological
adaptations but rather migration into deeper
water and it is dependent on the presence of
habitat where water does not freeze to the
substrate at any time of year (Aiken, 1968).
Immature individuals apparently suffer higher
winter-kills than adults because they do not
migrate into deeper water like the adults.
Laboratory studies have shown this species to
have a preference for soft substrates and a
fairly low station holding ability (28 cm/sec
or 10.9 in./sec) in fast currents (Maude and
Williams, 1983). The Virile Crayfish appears to
be most active from May to September and
their trapability is influenced by water
temperatures and presence of predatory fish
(Collins et al., 1983; Somers and Green, 1993).
This species has been found together with
the Appalachian Brook Crayfish, the Robust
Crayfish, the Northern Clearwater Crayfish,
the Papershell Crayfish, the Obscure Crayfish
and the Rusty Crayfish.
LIFE HISTORY
In Ontario, Quebec,
Saskatchewan and Alberta, the Virile
Crayfish mates from July to September and
perhaps again in the spring. Eggs are laid
from late May to early June and hatch in
July (Sawchyn, 1986; Talbot, 1985; Weagle and
Ozborne, 1972). Young moult 5 times in the
first summer and 3-4 times in the second.
Crayfish mature within the first or second
year. Mature males moult from Form I to
Form II in mid-June and back again to Form
I in early August. Mature females moult
once only in July when their young leave.
The average life span is 3 years and
maximum size is 55 mm CPL at about 3-4
years of age (Sawchyn, 1986; Talbot, 1985;
Weagle and Ozborne, 1972).
CONSERVATION STATUS This species is
widespread and common especially in the
western parts of Canada. In Alberta, where
the species apparently occurred naturally in
the Beaver River drainage, it has been
introduced by baitfishermen into water
bodies up to 400 km (249 mi.) from the
nearest possible source (Hanson et al.,1990)
and crayfish have been reported recently
from the North Saskatchewan and Battle
Rivers (Saffran, pers. comm.).
On the other hand, the Virile Crayfish is
locally threatened in many watersheds in
eastern Canada. It is presently being
displaced by the introduced Rusty Crayfish
in many areas of southern and northern
Ontario (Berrill, 1978; Momot, 1997). Local
declines may also be due to air and water
pollution and associated chemical changes
in watersheds. A study of crayfishes in lakes
of the Canadian Shield in Ontario found a
decline in the Virile Crayfish as well as
other native species. It was suggested that
these declines may be linked to low pH and
high aluminum concentrations (David et al.,
1994). Acidification of lakes has been
shown to cause reductions in the fecundity
of this species and it was concluded that
reproductive failure could cause the
disappearance of crayfish populations long
before water becomes acidic enough to
cause direct mortality. A pH of more than
5.8 is apparently needed for successful egg
attachment (France, 1987a). Acidification
also results in reduced carapace rigidity
which makes crayfishes more vulnerable to
predation and mechanical stress.
The Virile Crayfish has been shown to be a
good indicator of mercury contamination in
water bodies in Ontario and Manitoba
(Vermeer, 1972). Studies in the Sudbury area
where emissions of heavy metals remain
high showed that, although metals were
accumulated, the species appeared to be
tolerant to copper, cadmium and nickel
(Bagatto and Alikhan, 1987). A study of the
potential for commercial exploitation in
various Saskatchewan rivers and lakes
showed that the levels of heavy metals
(mercury, arsenic, lead, copper etc.) and
organic compounds (e.g. PCB, DDT,
dieldrin) were at least an order of
magnitude lower than levels accepted for
human consumption (Sawchyn, 1986).
This species has been the subject of
numerous studies in Canada and, as a
result, a good database dealing with its
biology, ecology and physiology exists in
the literature. The main gaps in knowledge
remain in the documentation of its
distribution, particularly in the most
northern regions of its distribution and its
interaction with introduced or expanding
species. Despite local extinctions, the Virile
Crayfish is still common and has a very
extensive distribution (with many "safe"
populations outside of the range of the
introduced species) and must therefore be
considered to have a "Currently Stable"
status in Canada.
(Used by permission: text by Premek Hamr, adapted from "Baitfish of North America"2007
painting by Aleta Karstad)
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