Lizardfish fishery of Kerala with some aspects of the stock characteristics of the greater lizardfish Saurida tumbil (Bloch, 1795)

Abstract

The fishery of lizardfishes and population dynamics of the dominant species Saurida tumbil landed in Kerala by mechanised trawlers were studied for the period 2007-2011. Annual landings of lizardfishes in Kerala during the period ranged between 6,715 to 10,600 t with an average annual landing of 8,992 t, which formed 5.2% of the total landings of the state. The seasonal peak in catch was recorded during August – October. Three species contributed to the lizardfish fishery of Kerala, of which, S. tumbil formed 59%. The overall sex ratio of S. tumbil was 1:1.2 with mature females encountered in most months with a peak during September – November. The von Bertalanffy growth parameters (VBGF) estimated using ELEFAN were L∞ = 517.0 mm, K = 0.40 year-1 and t0 = -0.1879. The length attained at the end of 1, 2, 3, 4 and 5 years were 195.5, 301.5, 372.6, 420.2 and 452.1 mm, respectively. Recruitment was round the year with peaks during May-June and October-November accounting for 55% of the total recruitment. The average instantaneous rate of total, natural and fishing mortalities were 1.34, 0.44 and 0.90 respectively. The length at first capture was 285 mm at which the age works out to be 1.6 years. The optimum length for exploitation (Lopt) was 378 mm at the age (topt) of 3.1 years. Mean size in the catch was lower than optimum size for exploitation; which necessitates caution to increase the minimum mesh size from the present level. The resource is being exploited at a level (E = 0.67) almost equal to the maximum exploitation (Emax = 0.69), indicating overexploitation of the resource. As the annual average yield is 33% higher than the MSY estimated, there is a need for reducing the fishing effort to sustain the fishery.