Gillnet Selectivity and Fishing Pressure on Sardinella gibbosa (Bleeker, 1849) off Southeast Coast of India

Abstract

A study was undertaken on the selectivity of small meshed gillnets and fishing pressure on Sardinella gibbosa along Thoothukudi, south east coast of India, with the view to understand the impact of various mesh sizes of gillnets on the fishery of Abstract A study was undertaken on the selectivity of small meshed gillnets and fishing pressure on Sardinella gibbosa along Thoothukudi, south east coast of India, with the view to understand the impact of various mesh sizes of gillnets on the fishery of S. gibbosa. The selectivity of gill nets was analysed as described by Sparre &Venema (1992) and the fishing pressure on various length groups was analysed using FiSAT. The study revealed a well-defined selectivity by gillnets with 26, 28 and 30 mm mesh sizes. The fishery was found un-affected by growth overfishing on recruitment overfishing as the commercially significant size group was found to be 110 to 160 mm which was higher than the estimated length at first maturity (100 mm). However, during the months from August to November notable landings of juveniles were reported, which was mainly due to the use of gillnets with 26 mm mesh size. The selectivity parameters such as length at first capture (lb), mean selection length (lc) and the escapement length (ld) for the selected gillnets were found to range from 90 to 107 mm, 115 to 135 mm and 145 to 165 mm respectively. The gillnet selection factor for S. gibbosa was estimated as 4.50. The study revealed the possibility for further increase in fishing effort for S. gibbosa along this coast based on the exploitation ratio (F/Z) of 0.39. The gillnet with 30 mm mesh size was found to be ideal for the commercial exploitation of S. gibbosa along this coast. The selectivity of gill nets was analysed as described by Sparre &Venema (1992) and the fishing pressure on various length groups was analysed using FiSAT. The study revealed a well-defined selectivity by gillnets with 26, 28 and 30 mm mesh sizes. The fishery was found un-affected by growth overfishing on recruitment overfishing as the commercially significant size group was found to be 110 to 160 mm which was higher than the estimated length at first maturity (100 mm). However, during the months from August to November notable landings of juveniles were reported, which was mainly due to the use of gillnets with 26 mm mesh size. The selectivity parameters such as length at first capture (lb), mean selection length (lc) and the escapement length (ld) for the selected gillnets were found to range from 90 to 107 mm, 115 to 135 mm and 145 to 165 mm respectively. The gillnet selection factor for S. gibbosa was estimated as 4.50. The study revealed the possibility for further increase in fishing effort for S. gibbosa along this coast based on the exploitation ratio (F/Z) of 0.39. The gillnet with 30 mm mesh size was found to be ideal for the commercial exploitation of S. gibbosa along this coast.