Effects of Gear Characteristics on the Presence of Bigeye Tuna (thunnus Obesus) in the Catches of the Purse-seine Fishery of the Eastern Pacific
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چکیده
Effects of gear characteristics on the presence of bigeye tuna (Thunnus obesus) in the catches of the purse-seine fishery of the eastern Pacific Overfishing of bigeye tuna in the eastern Pacific Ocean has motivated a search for pratical means of reducing bigeye catch. We develop a classification algorithm for the presence/absence of bigeye in purse-seine sets on floating objects, the dominant mode of purse-seining for bigeye, using the tree-based method random forests to explore the effects of gear characteristics. Although the location of the set was the strongest determinant of the presence of bigeye catch with these data, in some areas, bigyeye were more likely to be caught on floating objects with greater underwater depths and with deeper purse-seine nets. Misclassified sets were found to be concentrated within certain vessels, suggesting that the existence of additional 'vessel effects' on the presence of bigeye which may be amenable to further study. Results indicate that fishermen can avoid catching bigeye in some areas by changing the depth of the material hanging from the floating object and the actual fishing depth of the net, or by moving to other fishing areas. However, we believe that the complex nature of gear and environmental interactions, and the impact of gear restrictions on the catches of tuna species other than bigeye, argue 1 against the feasibility of fishery-wide gear restrictions.
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...
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متن کامل
Shifting from marine reserves to maritime zoning for conservation of Pacific bigeye tuna (Thunnus obesus).
Over 50% of the total bigeye tuna (BET) landed in the Western Central Pacific Ocean is caught incidentally in the purse seine fishery and sold for canning at prices less than US$2/kg. The remainder is landed in longline fisheries directed at BET and sold as fresh or frozen tuna at prices greater than US$10/kg. The combined fishing mortality by all gears will soon reduce the BET biomass in the P...
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The main target species of Japanese purse seine operated in the tropical waters of the Pacific Ocean is skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) consisted of nearly 98 % to their total catch weight and the remaining is bigeye tuna (Thunnus obesus) according to logbook. The recent study of the vertical distribution of the three species around drifting FADs (fish ...
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تاریخ انتشار 2007