'We could benefit from some new thinking on seals, and
a holistic reassessment of the roles played by seals in marine
environments must precede any experiments or new
initiatives that involve deliberately reducing their numbers.

Seal research has been an earlier focus of this committee(3),
and is currently at the forefront again, with the Minister’s
recent announcement of $6 million for a study on the
experimental use of “seal exclusion zones” in an effort to aid
the recovery of depleted cod stocks. Seal research is fine,
but any such proposed “experiments” must not be conducted
without the use of the appropriate scientific “controls.” And I
strongly suggest that this type of experimental seal research not
be undertaken before completing a holistic reassessment of the
roles played by seals in the larger marine ecosystem. Seals
have long lived in marine environments and their overall
contribution to these systems cannot have been negative (or
else they would have been eliminated millions of years ago(4)).
Therefore, although it is counterintuitive to many, the removal
of more seals at this point may not be without added risk to
the health of today’s declining fish stocks.

Positive contributions to ocean health that can be seen to be
made by seals include the production of zooplankton (via the
excretion of vast numbers of live worm eggs(5)), and the
scavenging consumption of dead or dying fish that might otherwise
undergo bacterial decay on bottom, with a resulting dangerous
depletion of oxygen from the water. In an oxygen stressed, low
zooplankton aquatic situation, air-breathing/zooplankton-excreting
marine mammals such as seals may therefore perform a unique
system-stabilizing role by consuming dead or dying fish, while
not removing oxygen from the water or succumbing to hypoxia
themselves.

These observations are intended to suggest some directions in
which the holistic effect of seals (and other marine mammals) on
ocean health might usefully be investigated. They also serve as
a warning of the nature of the adverse impacts on the marine
environment that may result from the removal of seals (less
zooplankton, less oxygen). Seals are an integral part of life in a
healthy ocean, and their actions today appear only to be part
of what naturally occurs when such a living system tries to
recover from damage inflicted on it. As fish eaters, the seals
will actively work towards the stabilization of an ocean
environment that supports fish…but the same cannot be said
for the bacteria that will break down dead fish in the absence
of larger animal consumers such as seals. The recent decision
to allow fishermen to shoot “nuisance seals,” as well as the
planned implementation of “seal exclusion zones” in Atlantic
Canada should be carefully reconsidered in this light. ..'

http://www.fisherycrisis.com/DFO/commons.htm