Research Document 1998/76

Size-at-age and condition of cod in Divisions 2J+3KL during 1978-1997

By G.R. Lilly

Abstract

The size-at-age and condition of cod in the offshore of Divisions 2J, 3K and 3L were monitored by sampling catches during research bottom-trawl surveys in the autumns of 1978-1997. Mean lengths-at-age and weights-at-age declined over time, with the decline most prominent in Division 2J. There has been some increase in recent years from a minimum in the early 1990s. Condition, as measured by somatic (gutted) weight relative to length cubed, declined dramatically in Division 2J in the early 1990s. There was a small decline in Division 3K and no decline in Division 3L. Condition has improved in Divisions 2J and 3K in recent years. Liver index, measured as liver weight relative to length cubed, declined considerably in Division 2J in the early 1990s and has since recovered somewhat, whereas it increased considerably in Division 3L in the early 1990s and has since declined somewhat. During previous assessments of this stock, weights-at-age at the beginning of the year (January 1) were estimated from the mean weights-at-age derived from sampling of commercial catches. Attention is drawn to several aspects of the commercial weight-at-age matrix, and the beginning of the year weights-at-age were updated for inclusion in the 1998 assessment.

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