Journal Article

Capelin are good for cod: can the northern stock rebuild without them?

G. A. Rose and R. L. O'Driscoll

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 59, issue 5, pages 1018-1026
Published in print January 2002 | ISSN: 1054-3139
Published online January 2002 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1006/jmsc.2002.1252
Capelin are good for cod: can the northern stock rebuild without them?

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The stock of northern cod (Gadus morhua) off Newfoundland and Labrador is at its lowest level in recorded history, with no rebuilding of northern spawning aggregations since the fishing moratorium in 1992. Cod diet was historically dominated by capelin (Mallotus villosus), which have been scarce in the northern areas since 1990. Using the study areas Hawke Channel and Trinity Bay within the historical northern cod range, and Placentia Bay (south coast), we examine growth, condition, and reproductive potential with respect to capelin diet in 18 000 cod sampled primarily in January and June of the years 1996–2000. Overall diet weights differed among areas and seasons (Placentia=Hawke>Trinity in January; Placentia>Trinity=Hawke in June). However, just 7 of 3383 cod stomachs (0.2%) from Hawke contained capelin (PFI=0). In contrast, 10% of cod of ages 3–7 in Placentia and Trinity Bays preyed on capelin and overall capelin partial fullness indices (PFI) were 0.2–0.4. Capelin PFIs were correlated with an index of availability (potential contact of capelin within 40 km of cod) calculated from acoustic surveys. Seasonally adjusted cod liver condition was strongly associated with capelin availability (p<0.05), and the liver index was highly correlated with gonad size in mature females (especially 4–6-year-olds). The links between capelin availability and cod diet, growth, condition, and reproductive potential suggest that cod rebuilding requires capelin and tends to mirror capelin distribution (Placentia>Trinity≫Hawke).

Keywords: acoustic survey; Atlantic cod; capelin; cod reproductive potential; liver index; PFI

Journal Article.  0 words. 

Subjects: Environmental Science ; Marine and Estuarine Biology

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