The IUCN/SSC Shark Specialist Group
Shark News 12: November 1998
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Management and Perceptions of Spiny Dogfish in Atlantic Canada
Christina Semeniuk, Concordia University, Canada, and
Thomas Hurlbut, Assessment Biologist, Department of Fisheries and
Oceans, Canada
Spiny dogfish Squalus acanthias off the east coast of North America
may be in trouble. A recent (1997) assessment by the United States'
National Marine Fisheries Service indicates that the spiny dogfish stock
in the Northwest Atlantic has begun
to decline due to recent increases in
exploitation. Furthermore, it was
shown that minimum biomass
estimates of mature females have
dropped by nearly 50% since 1990,
a higher proportion of males are now
being fished, mean lengths have
rapidly begun to decline, and fishing
mortality rates are much higher than
what is considered sustainable.
Lack of management
Although these findings are mainly based on data from fisheries
and surveys in US waters, they have serious ramifications for spiny
dogfish that migrate into Canadian waters because all dogfish in
the west Atlantic are considered to be a unit stock, and because
Canadian fishers have their own view of the fishery and its status.
There are no quotas or TACs to limit fishing for spiny dogfish in
Atlantic Canada, or elsewhere, throughout the rest of the
management unit (nor have there ever been).
Source: David Wrobel. Copyright © 1997 Discovery Communications, Inc.
Figure 1. NAFO subareas 2-6.
In the southern Gulf of St Lawrence, where directed fishing for
spiny dogfish began to increase in the mid-1980s, management
measures have mainly been limited to the establishment of minimum
fish sizes, minimum mesh and hook sizes, and daily by-catch limits
for cod and white hake. Moratoria and quota reductions on the
fisheries for traditional groundfish species in the southern Gulf and
along the Scotian Shelf (i.e. cod, white hake, haddock, etc.) may have
contributed to this increase in fishing effort directed at spiny dogfish
[ as is the case in US waters to the south - Editor].
In these two areas (NAFO subareas 4TVWX - see Fig. 1),
landings of spiny dogfish have averaged about 950 tonnes per year
since 1990, compared to the average 30 tonnes being landed
annually during the early 1980s. Moreover, if more groundfish
fisheries are closed, it is conceivable that fishing pressure will
continue to increase on spiny dogfish - once considered the 'unlimited resource'.
The Pest and the Predator
Another serious threat to dogfish is their perception by fishers. Spiny
dogfish are considered a nuisance by Atlantic fishers due to their
destructive impact on fishing gear and predation and competition on/
with commercially valuable groundfish species. Some Atlantic fishers
believe that spiny dogfish may be responsible for the slow recovery
of groundfish stocks that are under moratoria. Some also feel that
dogfish have driven traditional groundfish species from some areas by
either dispersing the stock, or, as is more widely believed, by eating
a significant quantity of mature or pre-recruit fish [ there are data to
refute this assertation - Editor].
In essence, there are many commercial fishers that feel the
numbers of dogfish should be reduced, either by means of eradication
or a sustained dogfish fishery. Yet, as news from across the border
informs us that spiny dogfish numbers are low, an eradication
procedure seems unreasonable. And what exactly is a sustainable
fishery for dogfish in Canadian waters? Needless to say, more biological
data needs to be compiled, and joint assessment and management of
this resource by Canada and the US needs to be considered.
Canadian Action
For its part, the Department of Fisheries and Oceans (DFO) is
presently trying to dispel/validate the claim that spiny dogfish predation
negatively impacts groundfish species by carrying out stomach content
analyses on dogfish collected during groundfish surveys in the NAFO
4TVWX subareas. Preliminary results of this study suggest that spiny
dogfish in Atlantic Canada are primarily benthic, invertebrate feeders.
As a more complete picture is formed, it is possible that some of the
negative opinions and perceptions held by Canadian fishers will be
changed, allowing for a more satisfying management plan to be
devised for all parties involved - especially the spiny dogfish.
Further Reading
Hurlbut, T., G. Nielsen, R. Hébert, and D. Gillis. 1995. The Status of Spiny Dogfish (Squalus acanthias, Linnaeus) in the Southern Gulf of St. Lawrence.
DFO Atlantic Fisheries Research Document 95/42.
Rago, P., and K. Sosebee. 1997. Spiny dogfish (Squalus acanthias). SAW-26
SARC Working Paper D1. NMFS Northeast Fisheries Science
Center, Woods Hole, MA.
Christina Semeniuk, Concordia University, Canada
Email: ca_seme@alcor.concordia.ca
and
Thomas Hurlbut, Assessment Biologist,
Department of Fisheries and Oceans, Canada
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