Population parameters and stock status of skipjack tuna Katsuwonus pelamis (Linnaeus, 1758) from Indian waters

Fishery and population and stock characteristics of Katsuwonus pelamis from the seas of the Indian mainland were studied from 2012 to 2017. The average annual landing was 9,843 t, with annual variations from 5,780 to 16,232 t. Major contributions were from the maritime states of Tamil Nadu (3,671 t), Andhra Pradesh (3,173 t) and Kerala (1,790 t). Gillnetters contributed 71.45% to the landings with a catch rate of 1.72 kg/unit. von Bertalanffy's growth equation was Lt = 85.0 [1 - e(-0.50 (t + 0.03618))] for the western Bay of Bengal (wBoB) and Lt = 95.5 [1 - e(-0.54 (t + 0.03184))] for eastern Arabian Sea (eAS), with natural mortality and fishing mortality being 0.85 and 1.37 and 0.86 and 1.13 for these regions respectively. Recruitment was continuous and unimodal along wBoB and bimodal along eAS. The exploitation ratio and maximum sustainable yields were 0.62 and 5,761 t for the former region and 0.57 and 2,406 t for the latter region. With present exploitation and yield close to that maximum permissible, stocks are optimally exploited. The maximum relative yield was obtained at the current level of fishing; hence, no further increase in effort is possible. Stock indicative population parameters were identical for both regions, suggesting a unit stock in the Indian mainland waters.