Gillnet selectivity of the Indian oil sardine Sardinella longiceps fished in the Sea of Oman

Abstract

The size selectivity of drift gill-nets for Sardinella longiceps was investigated in the Sea of Oman using a range of nets between 3.3 and 5.7 cm stretched mesh size. All nets had a hanging ratio of 0.5. A total of 1 211 Indian oil sardines were caught in 5 experimental nets, the majority of which were retained by the 3.3, 3.8 and 4.5 cm mesh nets. Peak selectivity was reached at 14.9 cm FL for the 3.3 cm mesh size increasing to 16.9 cm for the 3.8 cm mesh size. The estimated and observed length frequency distributions were unimodal. A log-normal selection function indicated that the highest selectivity was obtained when the length class to mesh size (l:m ) ratio was 4.4. Sardinella longiceps's relative abundance was estimated to be the highest at 16.4 cm FL, with numbers decreasing beyond this peak. This would indicate that selectivity by gilling is optimal with a mesh size of 3.8 cm with nets having a hanging ratio of 0.5. This mesh size appears to satisfy two criteria: high catch efficiency and protection of juveniles.

Keywords

• sardine
• gill net
• selectivity
• mesh-size
• arabian sea