Changes in Abundance and Certain Biological Characteristics of Grand Bank American Plaice, Hippoglossoides platessoides

Abstract

Commercial exploitation of American plaice on the Grand Bank increased from the early 1950s reaching a peak of about 90,000 tons in the mid-1960s. Catches have subsequently declined to about 45,000–50,000 tons annually. The increased exploitation of plaice was reflected in declines in catch per hour and stock abundance of fully vulnerable age-groups and an increase in the rate of instantaneous fishing mortality (F). The documentation of these was particularly strong in ICNAF Division 3L, but appeared to be somewhat erratic in 3N, probably because of incomplete sampling of the stock prior to the mid-1960s.Average size at age increased gradually from the early 1950s to the 1970s apparently because of increased growth rate in the initial 2 or 3 yr of life. Coupled with the increased size at age were significant declines in the age at sexual maturity.Significant correlations were found between stock abundance and asymptotic length (L_∞), and size at age 5 and 10 in Division 3L and while positive trends could be demonstrated between some of these and mean bottom temperature, the correlations were not significant.