Effects of El Nino/La Nina on distribution of fishing ground ofDosidicus gigasoff Peru waters

Jumbo flying squid,Dosidicus gigas,which is distributed in the waters off Peru,and is an important economic squid,has been caugth by many countries in the world.The study on large-scale environmental change on distribution of D.gigas is important for scientifically fishing and mastering the changing regularity.In this study,the fishing data from Chinese squid jigging fleets,sea surface temperature(SST) and the water temperatures data from 0 to 200 m(sea temperature at 15 meters layer,T15;sea temperature at 50 meters layer,T50;sea temperature at 100 meters layer,T100;sea temperature at 200 meters layer,T200) are used to analyze the large-scale environmental changes on distribution of D.gigas under the different conditions of El Nio and La Nia.The result indicated that under El Nio,the fishing ground was around 79° 84°W and 10° 17°S with the optimal SST range of 19 22 ℃ during October to December in 2006 and 2009,while under La Nia during October to December in 2007,the fishing ground was located around 81° 85°W and 10° 14°S with the optimal SST range of 17 20 ℃.The main fishing ground in the year of La Nia moved to further northward for 1 2° latitude and its average SST decreased 2 ℃ compared with that in the years of El Nio.The distribution of water layers temperature indicated that T15 and T50 in 2007 was significantly higher than that in 2006 with the maximum temperature difference of 6~9 ℃,and but T100 and T200 in 2007 was little higher than that in 2006 with the maximum temperature difference of 1 ℃.The vertical temperature structure indicated that the upwelling is not formed in fishing ground from October to December in 2006,and the fishing ground was distributed at the mixed region between oceanic water and coastal water.But the strong upwelling is formed in coastal waters from October to December in 2007,and the fishing ground was distributed at the intensive isotherm around the upwelling area.Moreover,the strong upwelling will lead to producing more nutrients in the squid habitat layer,which will be useful for squid to feed and make change of the distribution of D.gigas.It is concluded that El Nio/La Nia events are closely related to the change of distribution of fishing ground of D.gigas.