Pelagic fishes and the cod recruitment dilemma in the Northwest Atlantic

Like most other stocks of Atlantic cod (Gadus morhua) in the Northwest Atlantic, cod in the southern Gulf of St. Lawrence declined to low abundance in the early 1990s. Recovery has been slow in contrast with the rapid recovery from similar levels of abundance in the mid-1970s. This difference reflec...

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Bibliographic Details
Published in:Canadian journal of fisheries and aquatic sciences 2000-07, Vol.57 (7), p.1321-1325
Main Authors: Swain, D P, Sinclair, A F
Format: Article
Language:English
Subjects:
Agnatha. Pisces
Animal and plant ecology
Animal behavior
Animal populations
Animal, plant and microbial ecology
Animals
Applied ecology
Biological and medical sciences
Cod
Demecology
Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.)
Fish
Fishery economics
Fundamental and applied biological sciences. Psychology
Herring
Mackerel
Supply
Vertebrata
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Summary:Like most other stocks of Atlantic cod (Gadus morhua) in the Northwest Atlantic, cod in the southern Gulf of St. Lawrence declined to low abundance in the early 1990s. Recovery has been slow in contrast with the rapid recovery from similar levels of abundance in the mid-1970s. This difference reflects remarkably high prerecruit survival of cod in the earlier period of low abundance rather than unusually poor survival in the 1990s. The period of high prerecruit survival of cod coincided with the collapse of herring (Clupea harengus) and mackerel (Scomber scombrus) stocks resulting from overfishing. These pelagic fishes are potential predators or competitors of the early life history stages of cod. We report a strong negative relationship between the biomass of these pelagic fishes and recruitment rate of southern Gulf cod. This is consistent with the recent suggestion that the success of large predatory fishes may depend on "cultivation" effects in which the adults crop down forage fishes that are predators or competitors of their young. Our results also point to the possibility of a triangular food web involving cod, seals, and pelagic fishes, making it difficult to predict the effect of a proposed cull of seals on the recovery of cod.
ISSN:0706-652X
1205-7533
DOI:10.1139/f00-104