Analysis of habitat distribution of Argentine shortfin squid(Illex argentinus) in the southwest Atlantic Ocean using maximum entropy model

The Argentine shortfin squid(Illex argentinus) in the southwest Atlantic Ocean is one of the most important economic cephalopod targets. Chinese traditional vessels had a very low yield in 2010 after a good harvest year in 2008. According to the catch data from the Chinese commercial squid jigging vessels and the oceanographic environmental data(Sea surface temperature, SST; Sea surface height, SSH and chlorophyll-a, chl.a) from 2008 to 2010, the potential habitat of I.argentinus in the main fishing season(from January to April) was analyzed, and these results were compared to the actual catch positions. The oceanographic environmental factors were combined to find the reasons of its distribution differences in these three years. Results showed that there was nearly same trend between the change of the potential distribution areas and actual catch positions. The habitat in north and south directions in 2008 and 2009 was large compared to the year of 2010, when the region was mainly south of 45°S. The Jackknife test indicated that the SST was the most important oceanographic environmental factor influencing the distribution of I.argentinus. The findings suggested that the SST isotherms can represent the change of ocean currents which can affect the distribution of the I.argentinus. The 12℃ SST isotherm may be a good indicator to search for the fishing ground. The different fishing stocks in 2010 may have impact on the model results. The SSH contour lines, representing the change of eddies can also affect the distribution of the I.argentinus, while the chl.a can only reflect it indirectly. Consequently we suggested that it's mainly needed to observe the changes of SST and SSH when doing the squid fishing ground searching.