Catch of experimental longline, purse seine and handline in the South China Sea, Area III: Western Philippines

Abstract

This paper presents the tuna longline fishing operation conducted in western Philippine waters as well as the port sampling conducted in Zambales. The longline fishing operation was not successful in catching tuna but caught the deep swimming species such as sharks, lancet fish and opah. The undefined and shallow thermocline might have contributed to the unsuccessful fishing operations. Another reason might be the spatial distribution of tunas brought about by the El Ni–o event, which causes the spreading of the warm water mass from the western Pacific Ocean to the eastern Pacific Ocean allowing the yellowfin tunas to have a wider space to move. Yellowfin tuna stock in the western Philippine waters belongs to the juvenile and subadult population while the skipjack tunas belong to the adult population as most of the catch observed during port sampling were mature. The juvenile and sub-adult stages of yellowfin tunas were not the proper size for the longline fishery, which may explain in part why no tuna was caught during the research cruise. These sizes are available principally to the purse seine fishery as observed in the port sampling survey.