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Marine Ecology Progress Series

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MEPS 363:227-240 (2008)  -  DOI:

Atlantic cod and snow crab predator–prey size relationship in the Gulf of St. Lawrence, Canada

Denis Chabot1,*, Bernard Sainte-Marie1, Karine Briand1,2,4, John Mark Hanson3

1Direction des sciences halieutiques et de l’aquaculture, Institut Maurice-Lamontagne, Pêches et Océans Canada, C.P. 1000, Mont-Joli, Quebec G5H 3Z4, Canada
2ISMER, Université du Québec à Rimouski, 300 allée des Ursulines, Rimouski, Quebec G5L 3A1, Canada
3Gulf Fisheries Centre, Fisheries and Oceans Canada, P.O. Box 5030, Moncton, New Brunswick E1C 9B6, Canada
4Present address: SPC Headquarters, BP D5, 98848 Noumea Cedex, 95 Promenade Roger Laroque, Anse Vata, New Caledonia

ABSTRACT: Atlantic cod Gadus morhua stomach contents (n = 30 973, including 28 377 non-empty stomachs) and morphometric measurements on live snow crab Chionoecetes opilio and cod were examined to assess the predator–prey relationship between these 2 species. The most common snow crab instars found in cod stomachs were III and V (~6 to 8 and ~12 to 16 mm carapace width [CW], respectively) in the northern Gulf of St. Lawrence (GSL) and VI and VII (~17 to 23 and ~23 to 31 mm CW, respectively) in the southern GSL. A significant positive relationship was found between cod length and the largest and smallest CW of snow crab ingested by cod. Positive relationships were also found between gape width and body length in cod and between 3 measures of size (maximum span, width at rest, length at rest) and CW in snow crab. Snow crab length at rest was closely related to cod gape width, suggesting that the largest snow crab ingested by cod must be attacked from the side. There appears to be a plateau at 65.1 mm in the relationship between maximum snow crab CW and cod length, caused by the absence of large (adolescent and adult) male snow crab in cod stomachs. Other studies have found recently moulted, soft-shell snow crabs in cod stomachs, but this appears to be rare. Thus, snow crabs are susceptible to predation by cod mostly for the first 4 yr of post-settlement in the GSL. Any effect of cod predation on the snowcrab fishery would be felt 6 to 11 yr later, given growth models established for the GSL.

KEY WORDS: Chionoecetes opilio · Gadus morhua · Gape width · Prey selection

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Cite this article as: Chabot D, Sainte-Marie B, Briand K, Hanson JM (2008) Atlantic cod and snow crab predator–prey size relationship in the Gulf of St. Lawrence, Canada. Mar Ecol Prog Ser 363:227-240.

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