Special Projects -
Atlantic Seal Research Program (A.S.R.P.)

On April 24, 2003, the Government of Canada announced the closure of three cod stocks in the Gulf of St. Lawrence and northeast of Newfoundland and Labrador. Recent scientific assessments of these stocks determined that they are at historically low levels and have shown little or no signs of recovery despite a decade of severe conservation measures. The scientific assessment concluded that predation by seals is a factor contributing to the high mortality of cod.

Three species of seals (harp, hooded, and grey) are generally considered within the context of seal predation on cod and other groundfish. The significance of their impact varies across regions. Harp and hooded seals are major predators off northeast Newfoundland and in the Gulf of St. Lawrence, while grey seals are also important predators in the Gulf of St. Lawrence and on the Scotian Shelf.

As part of this announcement, The Minister also announced a two-year $6 million science program to expand current research to advance our understanding of the complex interaction between seals and fish stocks.

This program had two main goals:

  • to provide current information on the extent of seal predation on cod,
  • to provide scientific advice on management actions that could reduce current and future levels of seal predation on cod.

To achieve these goals, the Department undertook research to determine:

  • the current population sizes of harp, hooded, and grey seals,
  • the areas where seals and cod co-occur,
  • the amount of cod consumed by seals,
  • the management tools that could reduce seal predation on cod.

Scientists and managers have worked together to address each of these requirements. Completion of this ambitious program involved considerable collaboration with other sectors (e.g., Canadian Coast Guard) and regions within the Department (e.g., Central and Arctic), international scientists (Norway) and scientists from other departments, universities (Dalhousie, Laval, Memorial), provincial governments, and fishermen and sealers.

Program Elements

Current Abundance of Seal Populations

Current Abundance of Seal Populations

Rationale - Current abundance is needed to effectively manage seal populations and to determine their role in marine ecosystems. However, the population estimates for all three seal species are dated. The most recent population estimate was conducted in 1990 for hooded seals, in 1997 for grey seals, and in 1999 for harp seals. There may have been large changes in population size since these surveys were conducted, particularly in the case of hooded and grey seals.

In the context of this program, current abundance of the three seal species is needed:

  • to determine the overall predation pressure on cod and other fish sepcies,
  • to provide a yardstick against which management actions to control seal populations can be judged.

Estimates of pup production, coupled with reproductive rates, and harvest levels are used to estimate total population size and predict population trends under differing management regimes. Surveys will be conducted using standard methods (i.e., large-format photography) to ensure continuity with previous surveys conducted by the Department. However, new approaches (e.g., digital imagery) will be used experimentally determine the feasibility of improving the quality and cost-effectiveness of future pinniped surveys.

Deliverables

  • 2004 pup production of harp and grey seals, 2005 pup production of hooded seals and associated estimates of total population sizes and trends,
  • results of digital imagery in comparison with aerial photography,
  • peer review of population estimates and digital imagery results at National Marine Mammal Review Committee
Seal Habitat Use and Co-occurence with Cod

Seal Habitat Use and Co-occurrence with Cod

Rationale - Seals are wide-ranging and mobile predators in eastern Canadian waters, capable of feeding on different cod stocks over a short period of time. Previous estimates of cod consumption have been based largely on assumptions about seal distribution. Seal distribution has been inferred from flipper-tag returns, which reflect hunting effort more than seal distribution. Thus, relatively little is know about the habitats used by seals and, with several exceptions, areas of co-occurrence by cod and seals also are poorly known. The development of satellite tags has revolutionized our ability to determine the foraging location of seals and the relative importance of different habitats. Although some satellite tags have been deployed previously on all three species, the number of seals tagged is too limited to provide reliable information on seasonal habitat use of the 6 million seals (all three species combined) inhabiting eastern Canada waters This information is necessary to determine where seal exclusion zones or other management tools could be implemented to reduce seal predation on cod.

Satellite tags will be deployed on harp, hooded and grey seals to:

  • identify for each seal species, areas of importance (hot spots), where seal exclusion zones or other management tools could be implemented to reduce seal predation on cod,
  • determine for each seal species, overall habitat use such that stock-specific consumption can be estimated.

Deliverables

  • significant areas and times of co-occurrence between grey, harp and hood seals and cod,
  • overall habitat use by each species to be used to estimate seal consumption on each cod stock,
  • prepare results for peer review by the National Marine Mammal Review Committee.
Seal Predation on Cod

Seal Predation on Cod

Rationale - Seal diets are known to vary significantly in both time and space. Therefore, estimates of what seals have eaten in the past may not be relevant today. Furthermore, reliable estimates of seal diets are not available for all areas used by cod. This program will use both traditional and new techniques to provide current estimate of seal diets. Quantitative fatty acid signature analysis (QFASA) is a new method of determining what seals eat that does not depend on the seal having eaten the head of the fish and integrates the diet over weeks to months providing a better understanding of the foods eaten by seals. This new technique will be used in collaboration with Dalhousie University in Halifax.

This program will:

  • provide current estimates the diet of each seal species to determine what proportion of the diet is cod,
  • provide better spatial and temporal coverage to reflect both inshore and offshore diets of seals,
  • determine that extent to which seals may be having indirect effects on cod by consuming the foods eaten by cod (such as capelin or sand lance),
  • synthesize existing and new data on seal predation and cod population dynamics across cod stocks to better understand the impact of seals on cod dynamics.

Deliverables

  • current estimates of the diet of harp, hooded, and grey seals,
  • current estimates of the proportion of cod in the diets of each species,
  • comparison across cod stocks of the apparent impact of seal predation,
  • prepare results for peer review by the National Marine Mammal Review Committee.
Management Tools

Management Tools

Rationale - Various management tools have been proposed to reduce seal predation on cod including increasing TAC for commercial sealing, implementing a cull, the establishment of seal exclusion zones, and seal contraception. There is no commercial harvest of grey seals. Seal exclusion zones and seal contraception are new concepts. The feasibility and effectiveness of both to achieve management goals with respect to seal predation on cod need to be evaluated.

Seal Exclusion zones (SEZ) have been proposed as a management tool to reduce seal predation on cod in specific areas, thereby promoting cod recovery. Smith Sound has been identified as one possible region, while bays along the west coast of Newfoundland, Miramichi Bay and Gaspé are other regions of potential interest.

This program will:

  • evaluate potential seal exclusion techniques (e.g. physical barriers, sound, hunting),
  • identify criteria for selection of exclusion zones,
  • identify performace measures for the likely benefit to cod given stated management objectives,
  • identify areas where large numbers of seals occur (consultations with fishermen, anecdotal information and satellite telemetry) and then to obtain samples to confirm that seals are preying on cod in these areas (diet),
  • conduct a pilot field study in Smith Sound, Newfoundland to determine if harp seals can be excluded from an area supporting a large over-wintering concentration of cod.

Contraception is effective in producing long-term infertility in seals. DFO Science and Dalhousie University developed the seal contraceptive vaccine through joint research during the 1990's. Field trials on Sable Island grey seals have shown that the vaccine is highly effective.

This program would:

  • conduct population model simulations to evaluate the effectiveness and costs of a contraception program to achieve different management goals with respect to grey seal population size.

Deliverables

  • evaluation of the feasibility of establishing Seal Exclusion Zones as a broadly applied management tool,
  • conduct a pilot SEZ study on harp seals in Smith Sound, Newfoundland,
  • evaluation of resource requirements and efficacy of immuno-contraception to control seal populations,
  • Working Group on Seal Exclusion Zone and other Seal Control management tools, including consultation the fishing industry and sealers,
  • prepare results for peer review by the National Marine Mammal Review Committee.

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