Fisheries Oceanography
Numerous studies conducted over past years have indicated there are potential connections between the spatial and temporal patterns in physical oceanographic conditions and the population structure, distribution, abundance, growth, availability and catchability of fish and invertebrate species. Changes in these oceanographic conditions can therefore potentially influence the sustainability of the region's harvest fisheries, the perception of the resource status and the accuracy of the resource projections.
Research is focused on quantifying these connections and incorporating them into the resource assessment, conservation and management processes. From a harvesting viewpoint, such knowledge may improve efficiency and hence profitability and competitiveness.
The specific research goals are to identify and assess the linkages between the physical and biological oceanographic conditions, the fisheries and their supporting ecosystems. Activities include statistical analysis of associations between fisheries and environmental variables, monitoring of the environmental variability in key areas, and the development of models and statistical tools to study the ecological linkages between fish and the environment.
Surveys Provide Resource Data
As part of the DFO harvest fisheries assessment program, Page and Losier work with SABS and BIO colleagues to describe the water temperatures and salinities encountered during fisheries resource monitoring surveys. The resource surveys monitor the abundance, distribution and health of the major commercial fishery resources in the Maritimes Region.
Annual reports on the environmental conditions are presented at regional DFO Resource Assessment Program meetings and the annual DFO Atlantic Canada Fisheries Oceanography Committee (FOC) meeting. Similar reports for other surveys are generated by colleagues from other parts of the Atlantic region. These reports are used to form part of the Canadian perspective on oceanographic conditions within Atlantic Canada and how they influence fishery resources.
Ocean Conditions Affect Populations
For conservation and management purposes, the associations between the hydrographic conditions, the water temperatures and salinities, and distribution, catchability and availability of fish need to be identified and methods developed so these relationships can be incorporated into the resource assessment and management processes. In other words, how much of the variation that is seen in commercial and resource monitoring survey catches of fish is due to real changes in fish abundance and how much is due to changing environmental conditions such as those induced by climate change?
To help address these questions, statistical associations between the catches of fish and environmental conditions are sought. This work, conducted with Mr. Stephen Smith (BIO) has indicated that several species of fish are not distributed randomly with respect to water temperatures, salinities and depths. This suggests that some changes in ocean conditions may influence, at least in part, the distribution, catchability and availability of the fish. The study is continuing to search for relationships for other fish species and to determine how this information can improve assessments of fish abundance. This may aid fishermen in their harvesting efficiencies, profitabilities and competitiveness. In fact, some fishers are already using indices of the ocean environment, mainly temperature, to guide their fishing practices.
3D Computer Models Developed
Page and Losier are helping to develop an understanding of how changes in the water circulation and hydrography (water temperature and salinity) influence the distribution and survival of early life stages of living resources, particularly those of commercially important fish species such as cod, haddock, lobsters and scallops.
The work has emphasized the statistical analyses of distribution and abundance data and the use of three dimensional computer circulation models of Georges Bank, Gulf of Maine, Bay of Fundy and Scotian Shelf. This is a collaborative study with Canadian and American universities and government laboratories.
The computer models generated have been used to investigate the physical influence on the timing and location of cod and haddock spawning on Georges Bank and the distribution of their pelagic early life stages. The team has found, for the most part, that spawning does not occur in areas where the water tends to leave the Bank quickly, i.e.within 30-40 days. They have also found that the distribution of the eggs and early larvae derived from plankton surveys is consistent with the pattern estimated from the circulation-based models, at least up to an age of about 60 days.