Changes in Greenland Halibut Growth, Condition and Fecundity in the Northwest Atlantic (Flemish Pass, Flemish Cap and Southern Grand Bank)

Abstract

The Greenland halibut fishable stock has been declining substantially since late-1980s, according to both surveys and commercial fishery indices, particularly among the ages 10+, which corresponds to the females age at 50% maturity. In this paper the effect of this apparent reduction in the stock abundance on growth and reproductive parameters is examined. Among growth parameters, the analysis of the first year growth is undertaken both by cohort and by geographic areas, assuming that density dependence might be the most severe at younger age classes. This is made using records of the respective first annual ring otolith diameters. Other growth related index such as the condition factor is also analysed. Neither significant differences in the first year growth have been observed between areas analysed, nor between cohorts, during the period 1988 to 1996. Mean condition factor-at-age for ages 1 to 13 were stable during this same period. About the reproductive parameters, two aspects are considered: the interannual variations in length-at-maturity and in the potential fecundity. Female length at maturity varied between 64.5 and 69.5 cm. Female potential annual fecundity ranged between 15 000 and 158 000. It increases with female age, but the mean fecundity-at-age variations were not significant either between years of sampling or between cohorts. A common feature observed is the relative stability of those characteristic through the period analysed, which could support a certain resiliency of the life history traits in this species.