Fishery, mortality rates and yield per recruit ofRibbonfish Trichiurus lepturus Linnaeus

The months of abundance for Trichiurus lepturus, forming 61.2 to 95.3% of the ribbonfish catches, are October to December with minor peaks in April-May and July-August. Majority of the fish caught belonged to the 'O' age group and fish older than 3 years are scarce in the commercial catches. Based on the data for 1967-71, the instantaneous total mortality coefficient, Z, was estimated at 1.2 from the average catch curve with boatseine as standard gear. Instantaneous coefficient of natural mortality, M, was estimated as 0.9. The yieW-in-weight-per-recruit values werie computed at various levels of fishing mortality rates and ages of exploitation by tiie simple Beverton and Holt model, as modified by Jones, at three different levels of natural mortality rates, M = 0.7, 0.9 and 1.1. This study clearly showed that even at the young age of exploitation (Tpl = 0.3 years) the ribbonfish population is underfished and there is considerable scope to increase the yield by stepping up the fishing effort.