FISHERIES RESEARCH INSTITUTE,MOA,TAIWAN

In order to understand the distribution and abundance of tuna larvae in the surrounding waters of Taiwan, samples from five cruises were examined, which included 62 stations in 2005, 2007 and 2009. A total of 131 larval tuna were collected using an ORI net, including samples of T. alalunga (28), T. albacares (48), T. obesus (28) and T. orientalis (27). T. albacares larvae were most abundant in spring and summer. In spring, the ambient sea surface temperatures for T. alalunga, T. albacares, T. obesus and T. orientalis were 27.1, 27.1, 27.2 and 27.5 ℃, respectively. In summer, the ambient temperatures for T. alalunga, T. albacares, T. obesus and T. orientalis were 30.3, 30.1, 29.9 and 30.2 ℃, respectively. The results showed that tuna larvae were found primarily in the Kuroshio Current and the Kuroshio Branch Current mixed with South China Sea Surface Water. More tuna larvae were found in the oceanic area than in the coastal area. The distribution patterns and abundances measured differently in different years, which might relate to the fluctuation of water temperature, salinity or prey abundances. Further studies should be designed to locate the spawning grounds and to collect the information regarding the ambient environment of the tuna larvae in order to figure out the causes of annual differences.