| Based on the public domain catch and effort data of longline fishery fromWestern Central Pacific Fisheries Commission, the temporal and spatial changes ofAlbacore longline fishery in South Pacific were analyzed. And associated with the dataof Sea Surface Temperature(SST), vertical temperature, Sea Surface Height(SSH),salinity and vertical velocity, the relationship between these environmental factors andthe distribution of high CPUE(Catch Per Unit Effort) fishing grounds were discussedrespectively by superimposing them using GIS software Arcgis9.3. The results aresummarized as follows:(1) Temporal change of albacore longline fishery in South Pacific during2001to2010was analyzed. The results showed that, the monthly catches stayed at relativelylow level from January to March, and then began to increase since April and decreasesince September after reaching the maximum in June to August, and the catches ofOctober to December were close to January to March. The half year from April toSeptember had the peak production compared to the other half, and the catches fromJune to August were the maximum. The catches of same months fluctuated in these10years, and each month had a large increase in catches since2009. Most of the monthlycatches near2007were less than the other years, and the monthly catches near2002were more than the years nearby.The monthly change of the number of hooks was gentler compared to thechange of catches, and the trend was similar. The fishing effort of longline fisheries inSouth Pacific was significantly increased from2001to2010. And in addition to June toAugust, the peak months of the catches, the fishing efforts in September to December,the non-peak months, were also increased obviously.The CPUEs of the same month also fluctuated as the catches in these tenyears. Most of these were decrease first and then increase from2001to the vicinity of 2006, reaching a minimum in the vicinity of2003, then decrease again and then increase,reaching a minimum in the vicinity of2008. Most of the maximum of the monthlyCPUEs appeared in earlier years. But since the CPUEs had not reduced much overalland the number of hooks was increased, the resources of albacore is still thought to bestable.(2) Spatial distribution of albacore longline fishery in South Pacific during2001to2010was analyzed. The results showed that, the maximum of cumulativecatches distributed in the zones from10S to15S and15S to20S divided by latitudeand170E to175E and175E to180divided by longitude. And the zones from25S to30S and175W to170W also had the cumulative catches that stayed at a high level,while these from20S to25S and180to175W which were between the high catchzones were plummeted.The maximum of cumulative hooks distributed in the zones from0to5Sand5S to10S divided by latitude and170E to175E and175E to180divided bylongitude. The hooks of the zones which had plummeted cumulative catches weresignificantly less than the neighboring zones. And remove the influence of the fishingeffort of bigeye tuna and yellowfin tuna, the change of the number of hooks has asimilar trend with the cumulative catch.In addition to the three zones distributed in high latitude45S to50S and lowlatitude0to10S, the CPUEs in the zones divided by latitude were close, while theCPUEs in the zones divided by longitude were obvious fluctuated.(3) According to the public domain catch and effort data of longline fisheryfrom Western Central Pacific Fisheries Commission and the sea surface temperaturedata from NOAA, the distribution of albacore longline fishery grounds during2008to2010and its relationship with SST were analyzed quantitatively or qualitatively. Theresults showed that the fishing grounds in which albacore’s numbers accounted for over80%mainly located in the area of15N~40N and10S~45S, while high CPUE fishinggrounds were in25N~40N and10S~40S. In Northern Hemisphere summer thefishing grounds distributed mainly in South Pacific while in winter mainly in the North.The distributions in the three years were similar. The numbers of high CPUE fishinggrounds of North Pacific in2009and South Pacific in2010reduced substantiallycompared to the other two years respectively. The analysis of the relationship between CPUE and SST indicated that the favorite monthly SST of the albacore tuna longlinefishing grounds is16~22C in North Pacific and16~24C and around26C in SouthPacific.(4) According to the data of albacore CPUE in South Pacific in2008and thetemperature of five different depths, the range of vertical temperature correspond to C4and C3fishing grounds and the changes of the temperature itself were analyzed. Theresults showed that, C4fishing grounds distributed in two temperature ranges, herereferred as relatively high temperature region and relatively low temperature region. Atthe depth of15m, they were26C to30C and18C to22C; at the depth of46m, theywere26C to28C and18C to22C; at the depth of96m, they were22C to28C and18C to22C; at the depth of148m, they were20C to26C and16C to22C; at thedepth of197m, they were20C to22C and16C to18C. C3fishing groundsdistributed more complex, without two distinct temperature ranges, the minimum is12C and the maximum is30C. The changes of temperature in different depths in thesame month indicates the trend that the temperature drop gradient increases, as well asthe position of warm and cold water masses.(5) According to the data of albacore CPUE in South Pacific in2008and seasurface height data correspond, the relationship between them was analyzed, as well asthe distribution of sea surface height. The results showed that, the range of the seasurface height correspond to C4fishing grounds can be divided into two cases whichwere in the vicinity of0.4m and0.7m respectively, and the situation of C3fishinggrounds was similar that the ranges were in the vicinity of0.3m and0.7m respectively.The sea surface height was lower at high latitudes and higher at low latitudes in general.And the high values distributed mainly in the regions from5S to25S, which wouldcontract and expand and move in the north-south direction, while small-scale high-valuearea appeared in the region from25S to35S which has higher latitude.(6) According to the data of albacore CPUE in South Pacific in2008andsalinity data of15m depth correspond, the relationship between them was analyzed, aswell as the distribution of salinity. The results showed that, the range of salinitycorresponds to C4fishing grounds was34.5g/kg to36g/kg with little differencebetween months and without two interval parts. And the range corresponds to C3fishing grounds was34g/kg to36g/kg, slightly wider than C4fishing grounds. The area which has the salinity higher than36g/kg substantially distributes in the regionfrom150W to130W,10S to25S, and has a slight change of expansion andcontraction with the change of months. And the areas which have the salinity lower than34.5g/kg substantially distribute in three regions, including the area in the region from150E to170W,5S to20S which also has a change of expansion and contraction withthe change of months. And the months which have the minimum range of this area justcorrespond to the months which have the maximum of catches of albacore.(7) According to the data of albacore CPUE in South Pacific in2008and thevertical velocity of water flow of two depths, the relationship between them wereanalyzed. The results showed that, the area would be in the region where upwelling anddownwelling mixed apparently or had obvious upwelling or downwelling nearby whenit was C4fishing ground that month. |
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