Spatio-temporal dynamics in the location of the fishing grounds and catch per unit effort (CPUE) for Chilean jack mackerel (Trachurus murphyi Nichols, 1920) from Chinese trawl fleets on the high seas of the Southeast Pacific Ocean, 2001-2010

The decadal spatio-temporal distribution of the fishing effort and catch per unit effort (CPUE) for Chilean jack mackerel, Trachurus murphyi, stock are poorly understood. Data from the Chinese jack mackerel fleet was used to describe the location of the fishing effort and the relationship between standardized CPUE and sea surface temperatures (SST) during the period 2001-2010. A significant change in the spatio-temporal distribution of fishing effort and standardized CPUE was observed for jack mackerel during the study period. From January to March, the average CPUE was generally <15 tonnes (t) per net, except for 2007-2009. CPUE increased significantly during the autumn-winter (April to August), then gradually decreased in the spring and early summer (September to December). Average standardized CPUE in 2001-2005 was 23.3t per net, but decreased to 19.7t per net in 2006-2010. The change in the gravity center location of CPUE between months was similar during the primary fishing period (autumn to winter) in 2001-2006. After 2006, the pattern began to differ in July-October, which resulted in fishers spending more time to search for aggregations. A seasonal change was observed in the range of SSTs associated with high CPUE. Generally, the optimal SST range was from 13.0-15.0 degrees C in autumn, 12.0-14.0 degrees C in winter, 13-16 degrees C in spring, and 15-19 degrees C before 2006. However, a 1-2 degrees C decrease in the optimal range in recent years was associated with a shift in the fishing grounds location to the southern area. In 2009, the optimal SST range was lower than in all other years. Taken together, the results suggest that a more thorough understanding of the seasonal or decadal relationship between SST and location of the fishing grounds is critical to improving the efficiency of the fishery and its management.