Assessment of the age and growth of three fin fish species from a tropical estuary (Cochin, west coast of India)

Abstract

Data on three fin fish species were collected from the Cochin estuary (part of the Vembanad–Kol wetland system, India) from January 2018 to December 2019. The present study presents the first comprehensive results on fisheries demographics within this estuary, based on length-frequency data, to calculate vital demographic dynamic factors and estimate the stock of the commercially important three fin fish species. A variety of evaluations were conducted using the FiSAT II program. Caranx heberi had an asymptotic length (L) of 304.5 mm and a growth constant (K) of 1.1 year-1, while Etroplus suratensis had an asymptotic length (L) of 158.55 mm as well as a growth constant (K) of 1.1 year-1. For all the species studied, the age at zero-length (t0) had been calculated and varied from −0.04 to −0.14. Oreochromis mossambicus had longevity (tmax) of 4.76 yr and a growth performance index (ɸ) of 4.51, whereas E. suratensis had 2.72 and 4.44. E. suratensis had overall mortality (Z), natural mortality (M), and fishing mortality (F) of 2.93, 1.2 and 1.73 year-1, respectively, while C. heberi had 1.42, 1, and 0.42 year-1. The present exploitation level is greater than the optimum exploitation rate, according to the relative yield per recruit (Y/R) study, indicating over-exploitation of two examined finfish species and moderate exploitation for one species. Management measures such as mesh size limitations, restricted fishing efforts, and the proclamation of restricted seasons are required to save these species from extinction.