An experiment of tuna longline conducted by light falling-net fishing vessel

An experiment of tuna longline were conducted by light falling-net fishing vessel YUE DIAN YU NO. 42212in the north waters of the Nansha Islands from March to April in 2015 on the premise that the experiment has no effect on the falling-net fishing. During the trip, the falling-net operated 297 times within 40 d with total catch of 129. 6 t and average catch rate of 336.4 kgh-1. Sthenoteuthis oualaniensis was the dominant species, accounting for 85.31% of the total catch, and Thunnus albacares occpuied 0.21% of the total. Longline operated 2 700 hooks within 7 fishing times. The total catch was 1 281.6 kg. Xiphias gladius and T. albacares were the main species, accounting for 72.88% and 11.16% of the catch, respectively. The average hooking rate and catch per unit effort (CPUE) were 25.74 ind( 1 000 hook)-1 and 427.48 kg(1 000 hook)-1 , respectively. The hooking rate and CPUE for T. albacares were 1.90 ind(1 000 hook)-1 and 52.74 kg(1000 hook)-1, and were 3.76 ind( 1 000 hook)-1 and 291.86 kg(1 000 hook)-1 for X. gladius. The experiment proves that tuna longline and light falling-net have exactly the same fishing ground and operation time without conflict. Compared with professional longline vessels, tuna longline fishing conducted by falling-net vessels has less investment and lower production cost. It is suggested to extend the offshore fishing season and solve the problem of tuna preservation.