Growth and maturation of cod (Gadus morhua) of different year classes inthe Northwest Atlantic, NAFO subdivision 3Ps

摘要

Using data collected in fishery-independent bottom-trawl surveys of cod in NAFO subdivision 3Ps, we examine (1) the variations in growth and maturation of cod among year classes from 1969 to 1990 and (2) inter-relationships between growth and maturation of cod. To reduce impacts of outliers on data analyses, a robust maximum likelihood estimator is used to fit the von Bertalanffy growth function to size-at-age data. An overall indicator for pre-maturity growth of cod is developed using a robust principal component analysis. This study suggests that cod born during 1980s have smaller length-at-age values when compared with cod born in 1970s. The age at maturity declined steadily from the highest of 7 yr old for the 1981 year-class to 5 yr old for the 1990 year-class. Growth and maturation were significantly related to each other. A cohort of cod that had a higher growth rate in their young ages tended to mature earlier. The impacts of the findings in this study on the management of the fish stock are discussed. (C) 1999 Elsevier Science B.V. All rights reserved. [References: 62]