FISHERIES RESEARCH INSTITUTE,MOA,TAIWAN

To understand the occurrence and abundance of the fish larvae and juveniles in the waters off northeastern Taiwan, larvae in the area of 24.5~27.0°N, 121~123.5°E were collected with a Bongo net, and environmental factors (temperature, salinity, and depth) were investigated with conductivity- temperature-depth instrument (CTD) casting during March~May 2005. In total, 4958 larvae representing 88 families and 187 species were collected from 93 nettings at 36 stations. Scomber japonicus, Auxis spp., S. australasicus, Trichiurus lepturus, Engraulis japonicus, Benthosema pterotum, and Trachurus japonicus were dominant, comprising 56.2% of the total catch in terms of numbers. Cluster analysis by the density of fish larvae (individuals (ind.)/1000 m³) and Bray-Curtis similarity indices, indicated the larval fish assemblages could be classified into 6 assemblage groups during March, April, and May. In March, S. japonicus (37.8%) was the most dominant, followed by T. japonicus and S. australasicus. In April, the fish assemblages were dominated by S. australasicus (19.55%), E. japonicus (14.03%), and T. japonicus (10.14%) distributed in the northwestern part of the study area, and T. lepturus (11.94%) and B. pterotum (10.07%) in the southeastern part. In May, Auxis spp. was the most dominant (25.33%). These results indicate that the study area in the spring is a spawning ground for mackerel (Scomber spp.) and scad (T. japonicus). The species composition and abundance of fish larvae changed drastically with month and location. The species succession and distribution were influenced by the spawning season of the fish and the meandering of the Kuroshio Current in the waters off northeastern Taiwan.