Research Document - 2000/096

Year-class strength of northern cod (2J3KL) and southern Grand Bank cod (3NO) estimated from the Pelagic Juvenile Fish Survey in 1999.

By E.L. Dalley, J.T. Anderson, and D.J. Davis

Abstract

The pelagic juvenile fish survey was carried out from August 23 to September 19, 1999 from southern Labrador to the southern Grand Bank, including the inshore areas of the northeast coast of Newfoundland (NAFO 2J3KLNO). Over the six years of the survey, abundance in 2J3KL declined from 1994 to 1996 and has increased since then. Abundance of pelagic juvenile Atlantic cod (Gadus morhua) was high in 1999, compared to surveys carried out 1994-1998, mostly as a result of high catches inshore. Similar to 1998, higher abundance in 1999 also resulted from relatively high abundance on the Grand Bank (3LNO). Higher abundance was observed on the Northern Grand Bank in 1999, in contrast to 1998, when higher abundance occurred in the southern portion. Abundance on the Northeast Newfoundland Shelf (2J3K) was low offshore while inshore it was the highest of any year. Catch rate inshore in 1999 was over 3x the previous high in 1994. Highest catch rates occurred in Conception Bay (3L) and Notre Dame Bay (3K) along the northeast coast of Newfoundland. Abundance in Trinity and Bonavista Bays was relatively low and almost no cod were found offshore in 2J3K. On the Grand Banks, juvenile cod were found throughout the surveyed area. As in 1998 juvenile cod on the Northern Grand Banks (3L) were larger than more northern areas (2J3K), although the difference in size in the two areas was not as great as in 1998. Cod in 3NO averaged 57.5 mm, while those in 3L (NGB) averaged 53.9 mm in length compared to mean lengths of 38.1 - 49.5 mm within the inshore bays. Condition factor was relatively high (1.73) in 1999, in contrast to 1998 when the lowest mean value (1.34) of any year was recorded. The relative condition factor was lower for 3NO than in 2J3KL. Mean growth rate was moderately high in relation to other years averaging 0.579 mm/day. Larval hatch dates ranged from early May which was relatively early compared to most years (except 1998) to early July. To the north, in 2J3KL, the production of young fish has increased in inshore areas and also on the Northern Grand Bank in 1999, but continues to be extremely low with no sign of recovery in the offshore areas. A relatively large year-class was measured on the southern Grand Bank for the second year in succession and appears to be a positive response by Atlantic cod to a warmer environment. There has been a general warming of oceanographic conditions throughout the period of the pelagic 0-group surveys.

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