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

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.