COMPOSITION AND DISTRIBUTION OF FISH LARVAE SURROUNDING THE UPWELLING ZONE IN THE WATERS OF NORTHEASTERN TAIWAN IN SUMMER

Abstract

We investigated the species composition and distribution of fish larvae surrounding the upwelling zone in the waters of northeastern Taiwan in July 2011. The surface water had higher temperatures (25.7 degrees C-28.3 degrees C) and lower salinity (33.67-34.05 psu) than did lower water columns. A divergent trend was observed between temperature and salinity in the waters above 80 m. Moreover, we identified a cold-core eddy at the upwelling of the Kuroshio subsurface at waters approximately 60 m beneath the surface. In total, 1834 fish larvae were collected from eight stations; 85 taxa contributing to 60 families were identified. The abundance of fish larvae varied among stations. The five predominant larval taxa, which constituted 50% of the total fish larvae, were Auxis spp. (30.14%), Sciaenidae spp. (6.73%), Decapterus spp. (6.29%), Champsodon spp. (5.52%), and Gobiidae spp. (4.83%). Higher diversity and lower evenness index values were recorded in areas of high temperature and low salinity. Two larval fish assemblages, Mixed Coastal Group and Upwelling Group, were identified from a cluster analysis. Mixed Coastal Group exhibited higher density, higher temperature, and lower salinity than Upwelling Group did. Thus, in general, the density, spatial distribution, composition, and diversity of fish larvae differed, and the salinity at the 20-m layer exerted a more substantial effect on larval distribution in this study.