Research Document - 2012/062
Application of Ecosystem Research Results (ERI) to Fishery Management
By Claytor, R., and Leslie, S. (Editors)
Abstract
This Research Document presents results from the Maritimes Region Ecosystem Research Initiatives (ERI) that are applicable to fisheries management decisions. These initiatives were not specifically directed to address fisheries management decisions. Nevertheless, they provide insight and direction on a broad range of ecological interactions relevant to the application in fisheries management of Fisheries and Oceans Canada’s (DFO) precautionary approach (PA) framework. Presentations of ERI results are organized into three themes of relevance to fisheries management: Environmental Variability and Climate Change Considerations, Spatial Management Considerations, and Bycatch Considerations.
Environmental Variability and Climate Change Considerations
“Overview of Circulation in Maritime Canada Region” describes the major circulation features in the region and how they are interrelated, based on data and circulation model simulations. The importance of the North Atlantic Oscillation (NAO) to circulation properties in the shelf seas of Atlantic Canada is described.
“Climate Change on the Scotian Shelf: Recent Variability with a Future Outlook” provides a summary of observed and projected ocean climate changes on the Scotian Shelf. It indicates that changes are occurring in air and ocean temperature, stratification, sea level and ocean acidity that are consistent with expectations for anthropogenic climate change. However, natural variability associated with the NAO and other large-scale forcings remains an important contributor to changes in some variables.
“Climate Change Summary: State of the Scotian Shelf” explores potential changes to productivity, species distribution, timing of seasonal events, and ocean chemistry on the Scotian Shelf as a result of climate change.
“Zooplankton Variability in the Gulf of Maine and Scotian Shelf” identifies spatial, seasonal, and interannual variability patterns of zooplankton diversity and community composition, and their relationships with environmental variability, to develop a better understanding of how changes in circulation and the physical environment influence the feeding environment for fish.
“Ecosystem Responses to Climate Variability of the Atlantic Sea Scallop, Placopecten magellanicus”challenges previous assumptions on mortality and connectivity of scallop larvae on Georges Bank. By assessing the extent to which biological and physical factors affect retention and exchange among Georges Bank subpopulations, this work improves our understanding of the processes influencing connectivity and larval recruitment and explains the adaptive significance of spring spawned larvae in the life history of Georges Bank scallops.
“Common Large-scale Responses to Climate and Fishing across Northwest Atlantic Ecosystems” reports on a common pattern in the biological indicators responsible for the primary multivariate temporal trend in five northerly regions: an increase in abundance of phytoplankton, an increase in biomass at mid-trophic levels, and a decline in predatory groundfish size. While results are consistent with those observed under heavy fishing pressure, a more mechanistic understanding of how the climate affects lower trophic levels is needed to contextualize climate effects in heavily fished ecosystems.
Spatial Management Considerations
“Spatial Reference Points for Data-Poor Fisheries: A Case Study of Sea Cucumber” provides an example of how spatial reference points might be developed for fisheries management. Within a cluster in a lightly fished region, high density areas represent superior habitat simply because they support more individuals per unit area than low density habitat. These high density areas are also important to the reproductive cycle of broadcast spawners, and can be used to define fishing zones.
“Reference Points to Maintain Spatial Distribution: Sea Scallops” is another example of how spatial structure and habitat preferences can be used to derive reference points for fisheries management. The result of fishing down higher suitability areas to a more or less uniform density (and catch rate) over the entire fishing area creates an opportunity to use density changes rather than biomass as reference points. A lower reference point for the higher productivity areas could be based on mean density levels in the lower productivity areas.
Bycatch Considerations
DFO is developing a “Bycatch Policy” to ensure that Canadian fisheries are managed in a manner that supports the sustainable harvesting of aquatic species, minimizes the risk of fisheries causing serious or irreversible harm to bycatch and discard species, and accounts for total catch, including bycatch and discards. Scientific input will be required to support decisions on managing bycatch, and the type of information likely to be required is identified here.
“Preferred Habitat for Certain Species” links traditional assessment of bycatch issues through empirical, field-based studies in discrete areas, with habitat suitability measurements based on environmental data layers derived from multi-beam sonar data. These products, in combination with spatially explicit data on fishing pressure, could be used to assess potential conflicts in a multi-species context.
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