Efficiency of the circle hook in comparison with J-hook in longline fishery

The efficiency of circle hook and J-hook in pelagic longline fishery were determined in 13 fishing stations in three designated areas. The research/training vessel, namely M.V. SEAFDEC, was employed for the fishing operations during 5 November to 4 December 2007. The survey area was mutually defined as area A: latitude 16 degrees N-19 degrees N and longitude 88 degrees E-91 degrees E (5 stations), area B: latitude 9 degrees N-14 degrees N and longitude 82 degrees E-85 degrees E (4 stations), area C: latitude 10 degrees N-12 degrees N and longitude 95 degrees E-97 degrees E (4 stations).

The main objective of this work was to evaluate the efficiency of 18/0 10 degrees offset circle hook in comparison with the J-hook using three different types of baits i.e., round scad (Decapterus sp.), milk fish (Chanos chanos) and Indian mackerel (Rastrelliger kanagurta). A total of 6,277 hooks were deployed during the survey program. The results appeared that, using circle hook, the percentage compositions of target fish (tuna and billfish) and bycatch fish were not much different, 46.67% and 53.33% respectively. In contrast, J-hook showed a higher difference between these 2 components, target fish 25.53% and bycatch fish 74.47%. Considering catch rates, in overall CPUE (individual/1,000 hooks) of circle hook was lower than that of J-hook (4.77 versus 7.48). When separated by fish group, for target fish the CPUE of circle hook was a little higher than J-hook (2.23 versus 1.91), but for bycatch fish the CPUE of J-hook was obviously higher (5.58 versus 2.55). Regarding to hooking position, the percentage of hooking position in mouth using circle hook was higher than that of J-hook (73.33% versus 53.19%) but the percentage in digestive system was lower (10% versus 38.3%).