Temporal-spatial Distribution Of Catch Composition And Its Impact Factors For Associate Schoolof Tuna Purse Seine In Western And Central Pacific Ocean

The tropical tuna have the habit of gathering around floating objects which was used by inventing fish aggregation device.Compared with free swimming school,this method is more efficient.Therefore,as an important term of gathering fish,it is widely used in tuna purse seine fisheries.Skipjack,yellowfin tuna and bigeye tuna are the target species in the fisheries of tuna purse seine in Western and Central Pacific Ocean.The large-scale use of FAD have been generally accepted as an effective mean to increase catches,but,to a certain extent,FAD changed the temporal and spatial distribution of tuna,behavior and germplasm health.A large part of the landed catch are juvenile yellowfin tuna and bigeye tuna.The production of tuna purse seine is closely related to the temporal and spatial distribution of tuna.There is a different in the aggregation effects of FAD school in different kinds of log and raft.The research cruises all took place in western Pacific from December 2014 to March 2016,aboards JINHUI NO.1.The FAD school catch yield,type and material data of log and raft,and marine environmental data were collected.The temporal and spatial distribution of three tuna species and the effects of environmental factors on the distribution of CPUE were analyzed under FAD school.The effects of different FAD were compared.In order to understand the aggregation effect of FAD on fish and achieve the purpose of resource assessment for FAD stocks,the spatial and temporal distribution of FAD school and its influencing factors were discussing.The main conclusion of this study as follows:(1)The study on the yield of three kinds of fishes and the CPUE temporal and spatial distribution shows that the CPUE and the average yield of both skipjack,yellowfin and bigeye tuna have a significant difference(P<0.05),which skipjack and yellowfin tuna show extremely significant difference(P<0.001).Both the highest yield and CPUE value of skipjack are in November,2015,and the production is 61 tons(SD=49.76t)and CPUE is 12.75 t/d.h(SD=8.53 t/d.h).The highest yield of yellowfin tuna and CPUE are in December(6t,SD=4.05t),October(1.67 t/d.h,SD=1.48 t/d.h),respectively.Both the highest yield and CPUE value of bigeye tuna are in August,2015(The production and CPUE value are 2.27 t and 0.59 t/d.h,respectively.And the SD are 4.61 t and 1.18 t/d.h,respectively).On the view of the latitude and longitude,high CPUE values range from 179° to 180° E and 1 ° to 2 ° S,which CPUE values are positively correlated with longitude(r=0.171),however,CPUE has negative correlation with latitude(r=-0.261).High CPUE values of yellowfin are from 175 ° to 176 °E,which is related to the latitude and longitude(R longitude =0.308 R latitude =0.104).High CPUE values of bigeye range from 175 ° to 176 °E,1 °to 2 °S.Both latitude and longitude are positive correlated with CPUE(r=0.192,r=0.099).(2)Production gravity moving: On the view of the yield gravity of skipjack,it is between 160°and 177 °E,moving to eastward and moving back and forth from 3 °18 ?S to 1°15?N.For yellowfin tuna,longitude gravity is moving from 159 °~ 177 ° E to eastward gradually and latitude gravity is moving back and forth from 3 °S to 2 ° N.The longitude yield gravity of the tuna is gradually moving from 169 ° ~174°E to eastward,and the latitude yield gravity moves back and forth between 0 °to 3 °.(3)Based on the total of ten factor of production data and ocean survey data,GAM model was used to analysis the correlation of each factor to skipjack CPUE.The results show that the optimal model's explanation was 15.5% to CPUE,the factor that provides the largest contribution is wind speed(6.44%).Based on the AIC,the optimal model: Ln(CPUE+mean)~s(Longitude)+s(Wind speed)+s(water speed 10m)+s(water speed 70m)+?.The optimal model's explanation was 18.7 % to yellowfin tuna CPUE,the factor that provides the largest contribution is day(8.28%).Based on the AIC,the optimal model: Ln(CPUE+mean)~ s(day)+s(month)+s(wind speed)+?.The optimal model's explanation was 3.29% to bigeye tuna CPUE.Based on the AIC,the optimal model: Ln(CPUE+mean)~ s(110m of water speed)+?.(4)Based on the R analysis found the fish collecting effects from different type of FAD.Log length has significant effects on skipjack CPUE(P=0.00767<0.05,R2 =0.478).Log length in the combination of log and raft have significant effects on the bigeye tuna CPUE(P=0.00317<0.05,R2=0.153).