An analysis of interannual variations of hairtail catches in East China Sea

Using annual hairtail catch and fishing effort data between 1951 and 1984, as well as time series of precipitation, wind speed, and sea surface temperature (SST), interannual trend and variation of hairtail catch in East China Sea (ECS) were analyzed and a regression catch model incorporating fishing effort and environmental variables were established. Hairtail catches showed a significant trend with fishing effort (R=0.89, P < 0.01), which can be well fitted by Gulland-Fox model. Catch increased with fishing effort between 1951 and 1974, but declined with further effort growth after 1974. After removing this trend with fishing effort, variation in catch can be significantly correlated to environmental variables. This includes annual precipitation in Yangtze River Valley and coastal East China, annual wind speed around Bohai, annual wind speed in Yangtze River estuary, February SST in ECS and Yellow Sea, annual average SST in central ECS, as well as winter monthly average SST in southern ECS. The regression catch model incorporating fishing effort and selected environmental variables has a correlation coefficient of 0.97 and a level of confidence of 99%. Regression model of catches between 1951 and 1984 was used to predict catch in 1985 and 1986 with less than 5% relative error. The analysis and modeling suggested that catch of hairtail in ECS was jointly influenced by fishing and environmental variations.