Effects of temporal and environmental factors on the fishing ground of Antarctic krill(Euphausia superba) in the northern Antarctic Peninsula based on generalized additive model

The present study analyzed the spatial-temporal distribution of fishing ground for Antarctic krill(Euphausia superba) in the subareas 48.1,48.2 and 48.3 from 1998 to 2009 using the generalized additive model(GAM) based on the data derived from Statistical Bulletin(Volume 23) of Commission for the Conservation of Antarctic Marine Living Resources(CCAMLR),and the relationship between standardized catch per unit fishing effort(CPUE) of Antarctic krill fishery and environmental factors [sea surface temperature(SST) and chlorophyll a concentration] were also analyzed.The results showed that the accumulation of deviance explained(%) of model to CPUE is 51.11,69.25 and 65.82 respectively and the variation that provides the maximum contribution is the month for 3 subareas.Standardized annual average CPUE was stable in the 3 subareas from 1998 to 2009.The inter-annual variation on average CPUE in the subarea 48.1 was smallest and that of subarea 48.3 was larger than subarea 48.2.Annual variation on average CPUE had no significant difference among 3 subareas,within the subarea 48.2 and the subarea 48.3,however,remarkable difference can be found on annual average CPUE in the subarea 48.1.The monthly average CPUE only presented the unimodal distribution in the 3 subareas,and the peak value of CPUE in the subareas 48.1,48.2 and 48.3 occurred in April,May and June respectively.The monthly average CPUE had no significant difference among 3 subareas,however,remarkable difference can be found on monthly average CPUE within 3 subareas.The suitable range of SST is-3 to 2℃ in the subarea 48.1,-2 to 2℃ in the subarea 48.2,0 to 5℃ in the subarea 48.3 respectively for forming Antarctic krill fishing ground and the dominant CPUE values ranged in the SST of-2 to 1℃ in the subarea 48.1,-1 to 0℃ in the subarea 48.2,0.8 to 2.4℃ in the subarea 48.3 respectively.The dominant proportions of CPUE values were in the range of 0 to 0.2 mg/m3 for chlorophyll a concentration in the subarea 48.1(53%),48.2(39%) and 48.3(51%).