Is predation by grey seals a major component of the elevated natural mortality of cod in the Gulf of St Lawrence? ...

• Main Authors: Hammill, M. O., Swain, D., Stenson, G. B., Harvey, V., Benoit, H.
• Format: Conference Object
• Language: unknown
• Published: ASC 2010 - Theme session C 2024
• Subjects: Fisheries and aquaculture; Ecosystem observation, processes and dynamics; atlantic cod
• Online Access: https://dx.doi.org/10.17895/ices.pub.25068665; https://ices-library.figshare.com/articles/conference_contribution/Is_predation_by_grey_seals_a_major_component_of_the_elevated_natural_mortality_of_cod_in_the_Gulf_of_St_Lawrence_/25068665

No abstracts are to be cited without prior reference to the author.The southern Gulf of St Lawrence Atlantic cod fishery collapsed as a result of overfishing and a moratorium was declared in 1992. In spite of limited fishing, this stock has demonstrated no sign of recovery because of high M for large cod. Various hypotheses for the high M include dumping at sea, poor condition, fisheries-induced life-history changes, parasite infections, and predation by seals. Examination of the various hypotheses indicate that seal predation is the most likely source of high M because of the strong correlation between M and changes in the grey seal population size. Diet data suggest a strong cod component, but primarily of smaller fish, invoking the need for significant belly biting to account for consumption of sufficient numbers of large cod, but there are significant gaps in the spatial/temporal coverage of grey seal diet composition. A spatial analyses of the overlap between grey seals equipped with satellite ...