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All:
As a the former chair of a three-member Eminent Panel [it is to blush]
on Seal Management that submitted a lengthy report the Minister of
fisheries in 2001 I thought I?d weigh in on seals vs. fisheries. We
concluded then that evidence for then the efficacy of culls
(essentially of Gray and Harp Seals) in restoring fisheries was
inadequate. I?m not going to commit myself on current issues issue.
I?d have to do a great deal of work and preferably get paid for it .
Inevitably, public at large and naturalists in particular want to and
should speak out on issues of seals and fisheries. However, I think
that as a group with some understanding of how things work in nature,
it might be good if positions were based on some knowledge of the
issues, data, and analyses. You can get a vast amount of scientific
information from the web, Some of it is in the (correctly) vaunted
form of refereed scientific papers. It is also an unfortunate, but
unavoidable feature of science, including fisheries science, that
detailed studies supporting certain conclusions can be pretty opaque
to the lay reader: biological terminology, statistical analysis,
mathematical modelling, etc.
It is perfectly valid to hold a moral view that animals (or wild
animals, or animals like mammals with which we might claim some
affinity) should not be killed in our interests. Another moral view
might be that we should ?correct? consequences of our former
mismanagement of wild animals by readjusting (culling) some
populations; no thoughtful fisherman that we spoke to during our Panel
enquiries blamed seals for the collapse of fisheries, but some argued
that seals were preventing those devastated stocks from recovering.
That is the argument made by the recent DFO panel for stocks of
Atlantic Cod in the Gulf (White Hake, and others also in trouble).
That report made the same kind of analysis that is routinely used to
adjust (and sometimes to close) fisheries, but in this case concluded
that cod were experiencing negligible fisheries mortality, but very
high and increasing mortality natural mortality, and found no evidence
for causes other than seal predation.
But, positions for or against a cull should not use false information.
An example of is in the recent press statement by Rebecca Aldworth
listed as executive director of Humane Society International/Canada
(from the Can. Press site). "A cull of 70 per cent of the population
would not be sustainable and could lead to the extrication [sic] of
this species off our east coast," Aldworth said Thursday. "The fact
the FRCC would call for such a reckless move . . . speaks to the
political motives of the FRCC . . . and is, in my opinion, the fishing
industry attempting to divert attention from the irresponsible fishing
practices that continue today." ___ She insists there is a lack of
scientific evidence to suggest that the grey seal population has a
negative effect on the health of groundfish stocks and that
overfishing remains the largest threat against cod and other fish in
the region.
Her problem is that no-one has argued that 70% of the East Coast
population would be removed and there is NO commercial fishing for cod
?that continue[s] today? in the southern Gulf. It has been closed for
some years.
There has also been some confusion about numbers seals, size of mooted
culls, and between earlier talk of a large cull (or sterilization) of
Gray Seals on Sable Island and the recent consideration of more
focussed culls in the Gulf (perhaps even in a small area of northern
Cape Breton in winter). Also, a recent study has been quoted
indicating modest recent recovery of cod on the Scotian Shelf,
possibly because pelagic fish (more important sad seal prey) have
declined as predators of young cod (although I attended a recent talk
that indicated a current downward turn of cod again). But the Gulf
situation is not the same as that of the Scotian Shelf.
A balanced, evidence-based, and scientifically cautious statement has
been made by Jeff Hutchings, a biology professor at Dalhousie
University. (Again from Can. Press. I placed dashes between originally
separate paragraphs.)___ He was part of the workshop that concluded
grey seals may be hindering the recovery of groundfish in the southern
Gulf. ___"There was some pretty careful analysis," he said in an
interview. "It is a scientifically defensible position to say that the
elevated levels of natural mortality may well be caused by predation
by grey seals." However, he said more research needs to be done to
justify a cull. The problem, he said, is that a crucial piece of
evidence ? an analysis of grey seal stomach contents taken off the
north coast of Cape Breton ? has yet to be repeated. ___"It's one year
of data," Hutchings said. "Any scientist would tell you that you would
want to repeat that sampling to see whether it holds up in other
years." ___ "Even if you have all of these (monitoring) criteria in
place, the suggestion that we will know precisely what the
consequences of the removal will be is simply not a statement that
would receive strong scientific support," he said."
The last statement is certainly true; nor can we know precisely the
consequences, e.g., of restored populations of the World?s large
sharks that are so badly in need of protection from shark-finning for
soup ? all fisheries and wildlife management is like this.
For information on numbers of Gray Seals the following is informative.
Again, Fig. 2 summarizes the results. The overall Atlantic Canada
population is estimated currently (with 95% probability) to lie
between about 405,000 and 445,000 (my approximations from Fig. 2).
Note, that the largest fraction is found on the Scotian Shelf (and
Sable Island). All populations are increasing, but now at a lower per
capita rate than in the past.
<http://www.dfo-mpo.gc.ca/CSAS/Csas/publications/sar-as/2010/2010_071_e.pdf>
For information on Gray Seal diets, a number of studies recently have
used sophisticated analysis of ?fatty acid signatures? in blubber
(sampled relatively unobtrusively on Sable Island). This integrates
diets of seals that have fed over a wide range and for some time, and
gives the best overall view of possible impacts. See, e.g., Fig. 2 and
3 in:
<http://bowenlab.biology.dal.ca/data/Beck%20Hg%20diets%20JAE%202007.pdf>
Obviously cod only make up a relatively small proportion of their
overall diets, although there are many seals, so it adds up.
Finally, the data, analyses, and conclusions on seals and fish in the
Gulf are in this recent report.
<http://www.dfo-mpo.gc.ca/Csas-sccs/publications/resdocs-docrech/2011/2011_041-eng.pdf>
That?s the one to read for focus on the issues at hand. The study
uses stomach contents, which have their shortcomings, but, unlike
fatty acid signatures, give information on what?s being eaten on the
spot, at the time by a particular segment of the seal population ? for
example off the northern coast of Cape Breton, where high predation on
larger cod is supposed to occur.
Ian McLaren
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