Spatial-temporal Distribution Of CPUE And Relations To Marine Environment For The Albacore(Thunnus Alalunga) In South Pacific Ocean

Albacore(Thunnus alalung) was one of the main catch fisheries for longline fishery in South Pacific Ocean. It had an positive significance on the development of tuna longline fishery for China, that the spatial-temporal distribution and relations to marine environment for albacore(Thunnus alalunga) in South Pacific Ocean were analyzed. Based on the data on the catch of albacore longline fishery in South Pacific Ocean and Sea Surface Temperature(SST), Chlorophyll a concentration(Chl-a) and Sea Surface Height Anomaly(SSHA) by remote sensing, we analyzed the spatial-temporal distribution of Catch Per Unit Effort(CPUE) of albacore and their relationss by using ArcGIS and mathematical statistic methods. Meanwhile this present study analyzed rate of contribution on the spatio-temporal and environmental factors to the fishing grounds distribution of albacore(Thunnus alalunga) using Generalized Additive Model(GAM).The results are summarized as follows:1) Temporal change of albacore longline fishery in South Pacific Ocean was analyzed. The results showed that, the fishery mainly distributed in the sea near 4 oS ~28 oS, 158 oE~176 oE. As time had gone on, the catch of albacore in South Pacific Ocean were caught through the year and the CPUE values in summer and autumn were higher than them in spring and winter. The rich catch of albacore in South Pacific Ocean appeared from later March to September and the highest catch appeared during the m onth of 5-7. Comparing CPUE from 2009 to 2010, CPUE were obviously superior than it in 2011 and 2012Analyzed the trend of the catch gravity central of South Pacific Ocean albacore in the full series from 2009 to 2012, we could see: the trend of the catch gravity central of albacore appeared from south to north by latitude and moved to northwest by longitude. The catch gravity central in 2009 and 2012 migrated to north and other to south.2) The results showed that the optimum SST of albacore fishing center ranged fro m 27.0 to 30.5 ℃ and the second optimum SST of albacore fishery ranged from 20 to 24℃.The fishing grounds were widely distributed in higher temperature(>24℃) and few fishing grounds were in low temperature(<24℃). There were significant differences of theoptimum SST during different periods: From January to March, the optimum SST was 27~30℃; During April to later September, the optimum SST was among 27~30℃ and 20~23℃, while there were also a small amount of the fishing grounds owning the higher CPUE values in low temperature; During the last period, the optimum SST of albacore fishing center ranged from 25 to 28℃.Compared with SST during the earlier periods, the scope was declined.3) The results indicated that the optimum Chl-a ranges of this fishery were 0.02~0.05mg/m3. From January to March, the suitable rangs were 0.01~0.06mg/m3. During April to eariler September, the suitable ranges of Chl-a variables were 0.02~0.07mg/m3. From later September to December, the optimum rangs were 0.01~0.08mg/m3. The relatively high CPUE was corresponded with the higher Chl-a.4) The results indicated that the SSHA mainly ranges of this fishery was 0~26cm. The SSHA was lower at high latitudes. The SSHA was in the negative extremum and appeared reunion distribution, the higher SSHA at low latitudes was in the positive pole zone(5oS ~15 oS).This area would contract and expand from south to north.5) Selected the week, the latitude, the longitude, the SST, the Chl-a and the SSHA, we analysed the relations between CPUE and the six factors. The results of stepwise GAM showed that the SST was the most significant influence to the CPUE in the environmental factors, then the SSHA was the second. The results showed that the Chl-a had few impacts to the CPUE; the week was the most significant influence to the CPUE in the other factors, the latitude was the second, and then was the longitude.