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
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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 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 classification algorithm for the presence/absence of bigeye tuna catch in purse-seine sets on floating objects is developed, using the tree-based method, random forests. Although the location of the set was the strongest determinant of bigeye tuna catch with these data, bigeye tuna in some areas were more likely to be caught on floating objects with greater underwater depths and with deeper purse-seines. Misclassified sets that caught bigeye tuna were concentrated within certain vessels, suggesting the existence of additional vessel effects. Results indicate that fishers may avoid catching bigeye tuna in some areas by changing the depth of the material hanging from the floating object and the actual fishing depth of the purse-seine, or by moving to other fishing areas. Nonetheless, given the complexity of configuring a purse-seine, and the difficulties associated with monitoring compliance with gear regulations, fishery-wide gear restrictions would be problematic.
منابع مشابه
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
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...
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 کاملEffects of Gear Characteristics on the Presence of Bigeye Tuna (thunnus Obesus) in the Catches of the Purse-seine Fishery of the Eastern Pacific
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 m...
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