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Lingcod (Ophiodon
elongatus)
By Dr. Abby L.
Schwarz
Lingcod Identification
The lingcod is the only genus in the greenling fish family (Hexagrammidae),
a small group of North Pacific cold-water marine species. It
is not a true cod, although its common names - buffalo cod,
blue cod, green cod, leopard cod, cultus cod - give that
impression. It is the most commercially important of the
Pacific greenlings, so that considerable research has been
focused on its life history and distribution.
Females mature at 3-5 yrs and may live to 20 yrs, reaching a
maximum size of 120 cm. Males mature at 2 yrs, may live up
to 14 yrs, and reach a maximum size of about 90 cm. Males can
be distinguished from females of similar size by a small
conical papilla behind the vent. Both sexes are slender,
mottled grey and brown with a long continuous dorsal fin
(spiny and soft portions are connected). They have enormous
mouths and prominent teeth.
Lingcod Distribution and Migration
Lingcod are found only on the west coast of North America,
from Alaska to Baja California (Mexico). Their centre of
abundance is off the B.C. coast. The adults are benthic,
typically found in rocky areas at depths of 10-100 m. Tagging
studies have shown that lingcod are largely non-migratory;
colonisation and recruitment occur only in localised areas.
Lingcod Life History, Behaviour and Research
Lingcod are voracious predators, eating invertebrates and many
fishes (e.g. Pacific herring, Clupea harengus, Pacific
hake, Merluccius productus, and rockfish, Sebastes
spp.). However, Department of Fisheries and Oceans Canada (DFO)
studies indicate that
severe over-fishing has reduced their abundance and the
impact of their predation in British Columbia.
Mortality is highest in the larval and early juvenile stages,
as egg masses are guarded by the males; as well, late-stage
juveniles and adults have few predators (mainly marine mammals
such as sea lions and harbour seals).
Starting in October, lingcod migrate to nearshore spawning
grounds. The males arrive first and establish nest sites in
areas of strong current, on ledges or in crevices in rocks.
Recent DFO research on nest site selection suggests that the
males exhibit both nest site affinity (the same nest site area
is selected each year, but by different lingcod) and nest site
fidelity (when the same male selects exactly the same nest
site each year). The possibility of cultural transmission of
spawning site locations, as shown for bluehead wrasse by
Warner and his colleagues, has not been examined in lingcod.
Spawning occurs from December through March, but peaks from
mid-January to mid-February. Females lay demersal eggs at
night and then leave the spawning area. DNA analysis
indicates that each egg mass contains eggs from only one
female, and that a female lays only one egg mass in a given
area. This suggests that a female will only spawn once in a
season, at least within the study area, and has implications
for management of the lingcod fishery, as well as for the
maintenance of genetic diversity of lingcod populations.
Multiple males, sometimes up to 5, may contribute to an egg
mass. Males also contribute to more than one egg mass,
although each male actively defends only one nest from
predators. The eggs will not survive without male protection.
As they grow, lingcod undergo several habitat shifts,
particularly in their first few months of life. The eggs
hatch in early March through late April. The larvae are
initially pelagic, and in the Strait of Georgia peak abundance
in the water column occurs in mid-April. In early May, the
larvae begin a short-lived juvenile pelagic stage, finally
metamorphosing and settling to the bottom in late May and
early June. At first they inhabit eelgrass beds and kelp
beds, but by July they move to deeper, flat, sandy areas.
They finally settle in rocky habitat similar to that of older
lingcod, but remain at shallower depths for several years.
Research is ongoing at DFO on the effects of currents on
larval distribution, and on the effects of larval dispersal on
young-of-the-year lingcod distribution.
Lingcod Conservation and Management
Lingcod have been fished for thousands of years, starting with
First Nations some 5000 years ago. The Canadian commercial
lingcod fishery began around 1860, primarily hook and line (in
the Strait of Georgia) and trawl (outside the Strait). By the
1940s lingcod were ranked fourth in economic importance behind
salmon, herring and sardines (pilchards).
In 1996, a number of stock-preserving practices were
introduced: on-board vessel observers, bycatch limits for
halibut, and the provision that all catches of quota species,
including discards, would be counted against individual vessel
quotas. This changed the groundfish trawl fishery in BC and
resulted in reduced targeting on lingcod. Nevertheless, in
the Strait of Georgia, the overall lingcod catch has decreased
steadily since the 1950s, so that the commercial fishery for
lingcod was closed in 1990 and the recreational fishery was
closed in 2002.
The Lingcod Management Framework Committee was formed in
2004. Members included federal and provincial fisheries,
representatives from the recreational and commercial fishery
sectors, and conservation groups. The committee developed an
age-structured stock assessment model to estimate lingcod
biomass. As of 2005, projections suggest that there is a 50%
probability that by 2013, the stock will be at 43-44% of
historic biomass.
DFO monitored egg masses in 1990, 1991 and 1994, and every
year from 2001-2007 at a reference site (Snake Island reef) in
the Strait of Georgia. In some years additional egg mass
surveys were done at other sites. The results suggested that
the spawning stock biomass had not improved significantly
since the commercial fishery for lingcod was closed in the
Strait of Georgia in 1990.
(NOTE: Offshore lingcod are caught primarily by trawlers,
primarily from the SW coast of Vancouver Island and followed
by Queen Charlotte Sound. In 2005, DFO considered offshore
lingcod stocks to be at a moderate level of abundance.)
References
King, J.R. and A.M. Surry, 2001. Lingcod stock assessment and
recommended yield options for 2001. Cdn Stock Assessment Sec.
Res. Doc. 2001/164. 50 pp.
King, J.R. and R.E. Withler, 2005. Male nest site fidelity
and female serial polyandry in lingcod (Ophiodon
elongatus,
Hexagrammidae). Molec. Ecol. 14: 653-660.
King, J.R., G.A. McFarlane and A.M. Surry, 2003. Stock
assessment framework for Strait of Georgia lingcod. DFO Cdn
Science Advisory Sec. Res. Doc. 2003/062. 64 pp.
Logan, G., W. de la Mare, J. King and D. Haggarty, 2005.
Management framework for Strait of Georgia lingcod. Can.
Sci. Advisory Sec. Res. Doc. 2005/048.
Withler, R.E., J.R. King, J.B. Marliave, B. Beaith, S.Li, K.J.
Supernault and K.M. Miller, in press. Polygamous mating and
high levels of genetic variation in lingcod (Ophiodon
elongatus)
of the Strait of Georgia, British Columbia. Env. Bio. Fish.
Abstract.
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