The Operational Characteristics And Setting Area Arrangement For Free Swimming School By Chinese Tuna Purse Seine Fleets In The Western And Central Pacific Ocean

The Western and Central Pacific is the main area for tuna purse seine,Katsuwonus pelamis and Thunnus albacores,which can gather and form a large school(called free swimming school)under certain environment conditions,they are the important targeting species for the tropical tuna purse seine fishery,Katsuwonus pelamis is the main economic fish species with the largest single species catch in the Western and Central Pacific Ocean.There is an irreplaceable fishing economy in the Pacific island countries.Since 2007,Parties to the Nauru Agreement(PNA)implement a "Vessel Day Scheme"(VDS)of "charging by the Day" for purse seine fisheries in the EEZ of the Pacific island countries.That is to limit the operating days of purse seine fishing vessels in the PNA waters.Purchase fishing days of island area scientifically,or after purchased fishing days,reduce the time when stay resource countries' exclusive economic zones but nonoperating,including looking for fish,sailing and stay time,increase the effective operating time,improve the fisheries economic efficiency,is the challenge for each of the tuna purse Seine fishery enterprise.Therefore,it is particularly important to accurately determine the position of the fishing ground and improve the operating efficiency of the fishing vessels.Accurately grasp the impact mechanism of environmental change on fish migration and accurately locate the location of fishing grounds,which will provide support for fishing operations.Based on data of fishing positon,fishing date and catch of set on free swimming school from the logbooks of Chinese tuna purse seine fishing fleet operating on the Western and Central Pacific Ocean between 2013 and 2017,analyzed the operational characteristics of Chinese tuna purse seine fleets setting on free swimming school in the Western and Central Pacific Ocean,which include average number of nets per month,the fishing success rate,the net catch per unit effort during FADs closure and non-FADs closure,The relationship between monthly and yearly variation of free swimming school fishing grounds gravity and the South Oscillation Index(SOI)obtained from the US Climate Analysis Center during the period accordingly,based on the change of the center of gravity of the fishing ground in the Exclusive Economic Zone caused by anomaly climatic phenomena,optimized the fishing operation strategy of the fleet..This study will be helpful for understanding the change of fishing ground in tuna purse seine fishery in the Western and Central Pacific Ocean and providing reference for Chinese tuna purse seine fishery enterprises to purchase the operating days of the Exclusive Economic Zone of Pacific islands states.The main conclusions of this study are as follows:(1)There was an extremely significant difference in the average monthly number of nets per vessel in Chinese tuna purse seine fleets(P<0.01)between FADs closure and non-FADs closure;(2)There was no significant difference in the nominal CPUE(Catch Per Unit Effort)in Chinese tuna purse seine fleets between FADs closure and non-FADs closure;(3)There was an extremely significant difference in the fishing success rate(P<0.05)in Chinese tuna purse seine fleets between FADs closure and non-FADs closure;(4)Chinese tuna purse seine fleets fishing areas with high catches located where sea surface temperature(SST)was above 29.5?;fishing ground gravity was mainly distributed between 160°E and 175°W;the center of free swimming fishing ground gravity had a tendency to move eastward from 2013 to 2015,there was no evident monthly variation for the center of fishing ground gravity;when SOI was positive,the “warm pool” of the Western and Central Pacific Ocean moves toward the west,and the center of free swimming fishing ground gravity also shifted westward;in comparison,the center of free swimming fishing ground gravity shifted eastward when SOI is negative for a period of time.Correlation analysis showed that there was a significant negative correlation between SOI and the fishing ground gravity(r was-0.27,p<0.05).(5)Under the background of abnormal climate phenomenon,Chinese tuna purse seine fishery enterprises to purchase the operating days of the Exclusive Economic Zone(EEZ)of Pacific islands states can refer to the following Suggestions.(1)When there is a high probability of La Ni?a,the purchase of Papua New Guinea and Nauru's exclusive economic zone operating days can be considered in particular.Consideration should also be given to the number of operating days purchased from the exclusive economic zones of Papua New Guinea and nauru to the north and south of Micronesia and the Solomon islands;(2)If it is in a normal year,the purchase of Nauru and Kiribati EEZ operation days should be considered,and Tuvalu should be considered.(3)When there is a high probability of El Ni?o,fleets purchase of Kiribati exclusive economic zone operating days should be considered,and arrange the operation plan in the high seas with only 26 days.(4)When a transition from one stage to another occurs in the same year,it may be necessary to arrange the working days in a wider area in the longitude direction.