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Marine fish shows high heterogeneity in spatial aggregation. We analyzed the inter-deca-dal variations of stock density for Trichiurus japonicus in East China Sea (ECS) using geo-statistical approaches such as spatial autocorrelation and hotspot analysis, based on the data of T. japonicus from both bottom trawl fishery and research surveys in the open waters of ECS during 1971 to 2011, combined with the sea surface temperature (SST) and surface salinity data in the PN section in August. The global spatial autocorrelation statistics showed that Moran's I firstly decreased and then went up, indicating that the spatial aggregation patterns of T. japonicus was weakened in the beginning and then increased during 1971 to 2011. The surface salinity in the PN section displayed the opposite trend during the same period. The local spatial autocorrelation statistics showed that the population firstly moved to the southern ECS and then to the northern ECS except in 1971 in which the population concentrated in the middle of ECS because of the restriction of offshore fishing ground. The movement of hotspot areas of T. japonicus adaptively varied with the first EOF mode of SST in summer (sumEOF1), which indicated that the hotspot areas first moved southeastward with decreasing sumEOF1, and moved northeastward with increasing sumEOF1, but all of the hotspot areas were close to the northward branch of the Kuroshio Current.

Based on the catch amount data of Chinese squid jigger vessels from January to July 2006 and the sea current, sea surface temperature (SST) and chlorophyll-a (chl-a) data derived from satellites, the characteristics of Illex argentinus fishing grounds, their productivity, and environment factors in southwest Atlantic were analyzed. There were two main I. argentinus fishing grounds in southwest Atlantic, one in its south part (60 degrees 30' W, 45 degrees 30' S) and the other in the north part (58 degrees 00' W, 42 degrees 00' S). From January to July, the main fishing grounds migrated from south to north. The productivity fluctuated notably in different months, being higher from January to April and the highest in March. After May, the productivity decreased gradually. The locations of the fishing grounds had close relationships with Falkland cold current. North fishing ground located at the main axis of the current, with a current speed of about 28-60 cm x s(-1); and south fishing ground located at the west of the current, with a small scale anticyclone and a current speed of about 5-32 cm x s(-1). The favorable SST in the fishing grounds was 7 degrees C-15 degrees C, with a favorite SST of 12 degrees C, and the favorable chl-a concentration was 0.4-1.5 mg x m(-3), with a favorite chl-a concentration of 0.9-1.2 mg x m(-3). A significant positive relationship was observed between I. argentinus productivity and chl-a concentration (P < 0.05).