Estimates of growth, mortality and stock of the Indian squid Loligo duvauceli orbigny, exploited off Mangalore Southwest coast of India

Abstract

Both male and female Loligo duvauceli exploited off Mangalore exhibited allometric growth. The growth rate and asymptotic length (males = 41.5 cm: females = 24.5 cm) showed distinct differences between sexes. Females grew at a faster rate (K = 1.15 + 0.086 yr-'; P < 0.05). while males grew slower (K = 0.92 2 0.078 yr '; P < 0.05) but reached a larger ultimate size and age. The life-span is estimated to be 3.2 years for males and 2.6 years for females. The total average annual stock was estimated as 1088 tons and the average exploitation ratio for the period was above 0.7 for both sexes. but showed a declining trend. The maximum sustainable yield (MSY) was estimated as 877.3 tons and this could be achieved by a 358 decrease in fishing effort. Studies revealed the need for regulation of the fishery by raising the age at first capture (from 0.3 to 0.8 yr for males and from 0.5 to 0.6 yr for females) by increasing the cod-end mesh size of the trawl net by 80%