Fishery of flatfishes with observations on the biology and stock assessment of the Malabar sole, Cynoglossus macrostomus Norman, 1928 exploited off Kerala coast

Abstract

The flatfishes form one of the important demersal fishery resources exploited along Kerala coast. Annual average production of flatfishes was 16938 t during 1985-2012, of this Cynoglossus macrostomus formed 85.4%. Peak landings were recorded from September onwards after south-west monsoon. The von Bertlanffy’s growth parameters estimated for C. macrostomus were L∞ = 186 mm and K = 0.70 y-1. The fish attained 94, 141,169, 175 and 183 mm at the end of 1, 2, 3, 4 and 5 years. The age determination based on the length frequency data showed that life span was five years. Total mortality observed was 2.34 y-1, and natural mortality 1.10 y-1. The length-weight relationship showed no significant variation between sexes. The spawning is prolonged with two peaks. The size at first maturity is estimated as 102 mm for females and 95 mm for males. Females dominated the fishery. The resource at present is being exploited at the optimum level in Kerala. The total and standing stock of this species along the Kerala coast is 20,400 t and 9,052 t respectively. The exploitation rate (E) was estimated as 0.63. The relative yield per recruit and biomass per recruit analysis also showed that the stock of C. macrostomus in Kerala is exploited optimally.