Understanding the population parameters for unicorn leatherjacket, Aluterus monoceros (Linnaeus, 1758) exploited along the Western Bay of Bengal

Abstract

Information on age and growth for monocanthid species globally is limited. Aluterus monoceros forms an important fishery in the northern Indian Ocean; however, information on its population dynamics is sparse, as the species has not been explicitly studied. This study elucidates the population parameters from 1031 individuals landed in the multi-day trawl fishery along the western Bay of Bengal from January 2017 to December 2019. Total length ranged from 21.5 to 64.4 cm with a mean of 47.54 cm. Von Bertalanffy growth equation was L_t = 67.67 [1 – e ^{–0.32 (t + 0.0592)}]. The fishery was dominated by 3 and 4-year-old age classes and the estimated lifespan was 9.32 years. Recruitment was observed throughout the year and was bimodal, with the major pulse from October – February and the minor pulse from April – June producing 52.44 % and 36.24 %, respectively of the annual recruits. Natural mortality, fishing mortality and total mortality per year were 0.66, 0.55 and 1.21, respectively. Exploitation ratio was 0.45 and exploitation rate was 0.32. Though the species is currently underexploited, considering their lower capture sizes and their occurrence as by-catch in the trawl fishery, precautionary approach is suggested with management measures targeted at protecting their early life history stages.