Fishery and population dynamics of Trichiurus lepturus (Linnaeus) off Veraval, north-west coast of India

Abstract

The fishery and population dynamics of Trichiurus lepturus (Linnaeus) from Veraval was studied for the period
2003-2006. The average annual catch was 18,813 t, forming 27.63% of the total trawl catches at Veraval. September
to December was the most productive period in terms of catch and catch rate. The length-weight relationship
showed that growth was allometric and there was no significant variation between the sexes. The growth parameters
L∞ and K were 134.1 cm and 0.29 respectively and the length attained at the end of 1, 2, 3, 4 and 5 years were
35.28, 60.16, 78.77, 92.70 and 103.12 cm respectively. The growth performance index (φ) was 3.717 and longevity
was 10.29 years. Recruitment pattern was trimodal with two major peaks during May - June and August -
October and one minor peak during January - March and the length at first capture was 14.11 cm. The natural
mortality, fishing mortality and total mortality were 0.51, 0.93 and 1.44 respectively and exploitation ratio was
0.64. The maximum sustainable yield was 14,565 t which was lower than the average annual catch indicating
over-exploitation of the species. The yield per recruit and biomass per recruit was 43.34 g and 46.6 g respectively
and increase in relative yield by 142.41% would be obtained by decreasing the present level of fishing by 60%.