DOCUMENT SARM-10-14b VERTICAL DISTRIBUTION OF 17 PELAGIC FISH SPECEIS IN THE LONGLINE FISHERIES IN THE EASTERN PACIFIC OCEAN

S Pelagic deep longline was widely used in targeting tunas of high economic values with other fish species caught incidentally as bycatch. Identifying characteristics of vertical distribution of fish species that interact with longline can provide critical information needed for the development of effective measures to mitigate bycatch species and is essential for ecosystem conservation. Much work has been done to investigate the vertical distribution of pelagic species; however, most of the work was focused on single species. The objective of this study is to estimate depth distribution of species captured in the China’s tuna longline fishery and to evaluate the difference in depth distribution among species. We estimated depth distribution for 17 frequently captured species based on a Chinese longline fishing trip targeting bigeye tuna in the eastern Pacific Ocean during February-November 2006. The mean depth and depth distribution of 13 bycatch species were significantly different from that of the targeted bigeye tuna. Mean depth and depth distribution were found to be not different significantly between the females and males for 7 species. An analysis using generalized linear model suggests that species, latitude, longitude and month had significant influences on depth of hook at which a fish was captured. The information derived from such a study can play an important role in avoiding/reducing bycatch in pelagic fisheries.