Grey seals and cod
Learn about the effect of grey seals on cod, including research into grey seal eating habits, cod stock recovery and seal culls.
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Grey seal eating habits
We’re studying the relationships between grey seals and other parts of the Atlantic ecosystem, including Atlantic cod. With independent scientific experts and the fishing industry, we’ve conducted several studies on grey seal diet using different methods, including analyses of:
- fatty acids
- stomach contents
The amount of cod in a seal's diet varies widely between locations, seasons, age, sex and individuals. Based on data from several studies using traditional methods, a single adult grey seal can eat up to 2 tonnes of prey per year. Cod can represent up to 50% of this diet.
The lack of cod recovery in the southern Gulf of St. Lawrence appears to be due to high mortality of larger cod. Predation by grey seals may account for up to 50% of natural cod mortality, making them a major factor limiting this specific stock’s recovery.
We’ll continue to study the interactions between grey seals and cod in Quebec and Atlantic Canada. This information will be used to inform management of seal harvest and cod fishery.
Cod stock recovery
We’ve made changes to the management measures in place for cod and other fisheries that incidentally catch cod, including:
- investments in scientific research programs
- gear modifications to limit the bycatch of cod
- increased at-sea observer coverage in fisheries
- fishing gear restrictions that limit the harvest of small fish
- mandatory dockside monitoring for almost all groundfish landings
- limiting participation in some fisheries to fixed gear only (no trawling)
- closing fishing areas when cod are spawning or where juvenile fish are known to be found
- implementing maximum incidental catch of cod (by percentage or weight) in other fisheries
We’ll use a balanced approach that considers the health of Atlantic cod stocks and the grey seal population. This will benefit important marine ecosystems and the fishing communities that depend on them.
There are currently no plans to conduct a program for the removal of grey seals. If we consider such a program, we’ll consult with scientific experts and affected stakeholders to ensure that any measures:
- are achievable, humane and responsible
- will ensure the sustainability of the grey seal population
- will have a tangible, long-term impact on the recovery of important fish stocks
- Feeding by grey seals on endangered stocks of Atlantic cod and white hake
- Impacts of Grey Seals on Fish Populations in Eastern Canada. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2010/071.
- Covariation between grey seal (Halichoerus grypus) abundance and natural mortality of cod (Gadus morhua) in the southern Gulf of St. Lawrence
- Seals, cod and forage fish: A comparative exploration of variations in the theme of stock collapse and ecosystem change in four Northwest Atlantic ecosystems
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