1Graduate School of Science and Technology, 2Faculty of Fisheries, Nagasaki University, Nagasaki, Nagasaki 852-8521, Japan
The actual conditions of the catch and discards of by-catch from a small-scale trawl fishery in the Ariake Sea have not yet been clarified. Therefore, 14 small-scale trawl fishing sessions in the Ariake Sea were carried out to investigate this quantitatively. The length and weight of catch were measured and the number and weight of discards were calculated. The results showed that the total amount of catch was much greater in the summer than in the winter. The discard percentage based on the total catch in weight ranged from 36-67% with an average of 53%. An average of 93% of the total discards in weight was bony fish and cartilaginous fish. The main discarded species in unmarketable fishes were thornback ray Platyrhina sinensis and genko sole Cynoglossus interruptus. The main discarded species in marketable fishes was frog flounder Pleuronichthys cornutus, which is the target fish of small-scale trawl fishery in the Ariake Sea.