SCIENTIFIC COMMITTEE FOURTH REGULAR SESSION 11-22 August 2008 Port Moresby, Papua New Guinea EFFECTS OF DEPTH OF UNDERWATER STRUCTURES OF FADS ON CATCH OF BIGEYE TUNA (THUNNUS OBESUS) IN THE TROPICAL WATERS OF THE WESTERN PACIFIC OCEAN WCPFC-SC4-2008/FT-WP-1
نویسندگان
چکیده
The main target species of Japanese purse seine operating in the tropical waters of the western Pacific Ocean is skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares), which account for nearly 98 % of their total catch in weight and the remaining is bigeye tuna (Thunnus obesus) according to the catch based on logbook data. The recent study of the vertical distribution of the three species around drifting FADs (fish aggregating devices) indicates that the skipjack tuna distribute relatively shallower depth layer compared to other two species. A typical FAD consists of floating foundation and underwater structures, which is used-up fishing net. Therefore shortening the length of the underwater structure of FADs (depth of FADs) might be effective to reduce the bigeye tuna catch. Relationship of the species composition of purse seine catch and the depth of FADs was investigated by port samplings and by logbook, of 77 sets and 556 sets, respectively from April 2007 to March 2008. We conducted three analyses for each dataset which assessed effects for presence/absence of bigeye catch, effects for catch ratio of bigeye to total catch per set and effects for catch amount of bigeye per set. Although significant effects of depth of FADs are found in some scenario, the expected effect that bigeye is more likely to be caught FADs with deeper depth is not detected. 2 National Research Institute of Far Seas Fisheries, Fisheries Research Agency, 5-7-1 Orido, Shimizu-ku, Shizuoka-city, Shizuoka 424-8633, Japan 3 Email: [email protected]
منابع مشابه
SCIENTIFIC COMMITTEE FOURTH REGULAR SESSION 11-22 August 2008 Port Moresby, Papua New Guinea EFFECTS OF GEAR CHARACTERISTICS ON THE PRESENCE OF BIGEYE TUNA (Thunnus obesus) IN THE CATCHES OF THE PURSE-SEINE FISHERY OF THE EASTERN PACIFIC OCEAN WCPFC-SC4-2008/FT-IP-1
Effects of gear characteristics on the presence of bigeye tuna (Thunnus obesus) in the catches of the purse-seine fishery of the eastern Pacific Ocean Overfishing of bigeye tuna in the eastern Pacific Ocean has motivated a search for a practical means of reducing the catch of bigeye tuna in mixed species aggregations. To explore the effects of gear characteristics on the catch of bigeye tuna, a...
متن کاملSCIENTIFIC COMMITTEE FOURTH REGULAR SESSION 11-22 August 2008 Port Moresby, Papua New Guinea ACOUSTIC IMAGING, VISUAL OBSERVATIONS, AND OTHER INFORMATION USED FOR CLASSIFICATION OF TUNA AGGREGATIONS ASSOCIATED WITH FLOATING OBJECTS IN THE PACIFIC OCEAN WCPFC-SC4-2008/FT-IP-2
Purse seiners operating in the Pacific Ocean catch large quantities, in various proportions, of skipjack, yellowfin, and bigeye tunas associated with floating objects, in particular fish-aggregating devices (FADs). There is concern about the high fishing mortality rates on small bigeye and yellowfin tunas associated with floating objects from purse-seine fisheries, and the negative impact on su...
متن کاملSCIENTIFIC COMMITTEE FOURTH REGULAR SESSION 11-22 August 2008 Port Moresby, Papua New Guinea NOTE ON THE STOCK STRUCTURE OF PACIFIC BIGEYE TUNA TO BE USED IN STOCK ASSESSMENTS
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SCIENTIFIC COMMITTEE FOURTH REGULAR SESSION 11–22 August 2008 Port Moresby, Papua New Guinea A PRELIMINARY STOCK ASSESSMENT OF BIGEYE TUNA IN THE WESTERN AND CENTRAL PACIFIC OCEAN USING STOCK SYNTHESIS; A COMPARISON WITH MULTIFAN-CL WCPFC-SC4-2008/SA-WP-2
A parallel assessment of the current WCPO bigeye assessment, conducted using MULTIFAN-CL (MFCL), was undertaken using Stock Synthesis (SS) software. The two models incorporated the equivalent data sets (catch, effort, size composition, and tag data) and, where possible, the MFCL assumptions were mimicked in the SS model. Differences in the underlying model structure were noted, where relevant. ...
متن کاملSCIENTIFIC COMMITTEE FOURTH REGULAR SESSION 11-22 August 2008 Port Moresby, Papua New Guinea ORIGIN OF YELLOWFIN TUNA (Thunnus albacares) IN THE HAWAIIAN ISLANDS: PRELIMINARY ASSESSMENT OF NATAL SIGNATURES IN OTOLITHS WCPFC-SC4-2008/BI-WP-2
The purpose of this project is to examine the potential of using tuna hard parts as natural markers to refine our understanding of population structure of tropical tuna. Yellowfin tuna (Thunnus albacares) were selected for study as tagging data and recent studies suggest that the movement patterns of yellowfin may be highly variable and more restricted than other tunas. Hawaiian yellowfin provi...
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