Yield isopleths of the halibut, hippoglossus hippoglossus, in northern Norway

Abstract

1. Data on age composition, growth, and mortality rates of the halibut, Hippoglossus hippoglossus, collected in Finmark, 1956-1960, supplemented with data on immature halibut from various localities in Northern Norway were examined. 2. A weight-length relationship was determined separately for males and females. 3. Total instantaneous mortality rate was determined for males and females based on age composition data. 2. Yield isopleths were calculated based on a knife-edged selection curve into the fishery and also on prolonged recruitment. In the latter case variable fishing effort was applied to the age groups to simulate the recruitment into the fishery and withdrawal away from the fishable stock of the large females. 5. A precise determination of maximum length or weight, natural and fishing mortality rate were not achieved. Hence the change in yield per recruit could only be suggested as a function of age at entry into the fishery and fishing mortality.