SCIENCE REVIEW 1987 - Bedford Institute of Oceanography

Research
regime to promote some stability in landing
patterns. Both measures are contributing to
a gradual restocking of the scallop beds.
Under this regime, not only is there an
upper limit to the quantities fished, but the
allocation of allowable catches to the
fishing enterprises involved assures them of
a certain level of landings and removes the
competition element (e.g. too many boats
chasing too few scallops). Some fluctuations
in TAC’s will occur because of the
great variability in the abundance of the
scallop age groups available to the fishery
in any one year. Biological advice on the
health of the fish stocks is a key element in
assisting industry in its efforts to achieve
the optimal use of annual yields and
available age groups. The EA program also
provides the incentive to reduce the
harvesting capacity through fleet streamlining
by downsizing and lessening of over
capitalization to improve economic
stability.
Another valuable invertebrate resource
exploited on Georges Bank is the lobster
(Homarus americanus), although at a
smaller scale. Once again, the ultimate
goals of resource management are conservation
and increased economic benefits to
the lobster industry. Since 1985, this stock
has also been managed by a TAC divided
into EA’s. A major management issue
which remains unresolved is the
relationship between inshore and offshore
lobster stocks.
Now that the ownership question is
settled, a new management issue to arise on
the Canadian sector of Georges Bank is
hydrocarbon exploration and potential
development. Texaco Canada Resources
Ltd. proposes to drill two exploratory wells
in Canadian territory near the northeast
peak (ref. to Figure 1). Other wells could
follow.
The management of hydrocarbon activities
off Nova Scotia will be the responsibility
of a joint federal-provincial board
established under the new Canada-Nova
Scotia Accord but DFO will continue to
supply advice and information. Many
studies of the environmental impacts of
offshore hydrocarbon exploration and
development have been conducted around
the world. The results available so far
suggest that in most instances the impacts
are restricted to a relatively small zone
around a rig. Less is known about recovery
16
after sites are abandoned. DFO has
recommended that further studies specific
to Georges Bank be undertaken to help
resolve present uncertainties regarding
hydrocarbon activities in this important
fishing area. Eight exploratory wells were
recently drilled on the US sector of
Georges Bank without known environmental
impact. The potential environmental
impacts of a production platform,
however, are greater. While not objecting
to hydrocarbon activities in other continental
shelf regions off eastern Canada, the
fishing industry has strongly opposed
exploratory drilling on Georges Bank, as it
also has in the US. This issue has temporarily
been set aside with the announcement
of a 12 year ban on drilling. Nevertheless,
the need for information to help resolve
this issue at a technical level remains. Some
environmental impacts could be
transboundary depending on the exact
location of drill sites and therefore, as with
fisheries, joint management programs
between Canada and the US are needed.
Research Programs
A large number of applied and basic
research programs in support of resource
management have been conducted or are
currently underway on Georges Bank by
DFO. While Georges Bank is relatively
well known compared to other offshore
areas, there remain important information
gaps.
For example, more detailed studies of
water mixing and turbulence are being
made across the seasonal tidal front along
the northern edge of the Bank. It is not yet
clear whether this front serves as a
boundary or allows the net transport of
water and associated plankton (including
larvae) off the Bank. Whether this front is
an area of convergence or divergence for
water and associated organisms, which is
important in predicting the fate of contaminants,
is also not known.
Studies of phytoplankton productivity
are designed to determine why Georges
Bank is so productive. The reasons appear
to be closely linked to physical processes,
especially in the vicinity of tidal fronts.
Feeding studies, particularly with scallops,
are aimed at obtaining a greater understanding
of the relationship between
phytoplankton productivity and potential
fish harvest. Chemical studies have estab-
lished the background levels of hydrocarbons
on Georges Bank. Surprisingly high
concentrations of low molecular weight
hydrocarbons in surficial sediments suggest
that natural seepage is common.
Research on Georges Bank fishery
stocks, both vertebrate and invertebrate,
has included all stages of life history.
Research in support of stock assessment
typically deals with adults and includes
annual surveys of abundance and distribution
using DFO vessels. Sampling is
conducted on a depth-stratified random
basis to allow unbiased estimates of stock
abundance. Estimates are then compared
with other indices of abundance such as
catch-per-unit effort statistics from the
commercial fishery during the stock
assessment process.
One particularly interesting aspect of
fisheries ecology has been the discovery of
a higher growth rate for cod and haddock
on Georges Bank compared with neighbouring
stocks, such as those on Browns
Bank. By age 3, haddock from Georges
Bank are 1.3 kg on average whereas those
from Browns Bank average less than 0.9
kg. For cod, the difference is even more
pronounced with respective values of 2.8
and 1.4 kg. A program under planning will
examine whether such differences are
caused by environmental or genetic factors.
The mechanisms causing the variation in
growth rate have significant implications
for both the management of wild stocks
and aquaculture.
Research programs are also evaluating
the factors that influence the survival of the
larval and juvenile stages of gadids. A
multidisciplinary program currently underway
will examine the implications of the
seasonal tidal front on Georges Bank on the
growth and distribution of fish larvae. One
of the objectives is to determine the
physiological condition of larvae across the
front with respect to the distribution of
their food supply. It has been hypothesized
that high concentrations of plankton in the
frontal area, upon which larvae feed, will
produce healthier larvae more likely to
survive than in mixed or stratified waters
on either side of the front.
It has been surmised that most mortality
affecting year-class strength occurs before
larvae metamorphosize into juveniles. It
remains unresolved whether surveys of
abundance of pelagic post-metamorphosis