Offshore tuna longline fishery, which mainly targets bluefin tuna,
yellowfin tuna, bigeye tuna and albacore and other bycatch species such
as sharks, is one of the important offshore fisheries in Taiwan.
Analyzable results from the catches of tuna fishery and biological data
are the important basis for assessment and management of tuna resource,
including fluctuations of the catch and length-weight of tuna catching by
the offshore longline fishery and the recruitment of larva fish. The
temporal-spatial variations and the biology of these four tunas and shark
bycatch are researched in this study for being the basis of management of
tuna longline fishery.