Fyke net fishery and population parameters of shrimps in the Columbuththurai landing site of Jaffna lagoon, Sri Lanka.

Abstract

This study evaluates the fyke net fishery and population parameters of shrimps inhabiting in the Jaffna lagoon. Catch effort and shrimp morphometric data were collected at Columbuththurai landing site from 2018 August to 2019 April by making biweekly field visits. FiSAT was used to estimate the population parameters of shrimps. The fyke net fishing is carried out throughout the year in the Jaffna lagoon by 90 % of the Columbuththurai fishers by using traditional fishing crafts. About 15 % of the gear's total harvest was immediately discarded into the sea, and the remaining were landed. Uneconomical value organisms such as seaweeds, small shellfish, small-sized starfish, and smalls crabs were major components of discard organisms. The shrimp harvest's weight accounted for 60 % of the landed biomass, including biomass of Penaeus semisulcatus, Penaeus indicus, Penaeus monodon, Penaeus latisulcatus, Metapenaeus dobsoni, and Penaeus japonicus. Of which, Penaeus semisulcatus, Penaeus latisulcatus, and Metapenaeus dobsoni were dominant in the catch composition. CPUE of shrimps ranged from 1.42±1.14 kg per fyke net per fishing day in August 2018 to 3.25±2.14 kg per fyke net per fishing day in December 2018. Asymptotic length and condition factor of Penaeus semisulcatus, Penaeus latisulcatus, and Metapenaeus dobsoni were estimated as 15.36 cm, 2.20 yr-1; 20.0 cm, 0.70 yr-1 and 9.59 cm, 1.70 yr-1 respectively. The estimated natural mortality (M) and fishing mortality (F) in Penaeus semisulcatus, Penaeus latisulcatus and Metapenaeus dobsoni were 3.61 yr-1 and 2.59 yr-1; 1.58 yr-1 and 4.00 yr-1 and 3.47 yr-1 and 3.26 yr-1, respectively. The recruitment period for shrimps was predicted. Penaeus latisulcatus stock in the Jaffna lagoon seems to be overexploited (E>0.05). This study's findings will be important to manage and sustainably utilize shrimp resources in the Jaffna lagoon.