MOVEMENT OF FISH LARVAE WITH TIDAL FLUX IN THE TANSHUI RIVER ESTUARY,NORTHERN TAIWAN

Movement of fish larvae in relation to tidal flux in the Tanshui River estuary was studied for 4 seasons during 1989 and 1990. The dominant species were Engraulis japonicus in spring, Sardinella spp. in summer, Encrasicholina punctifer in autumn, and Arius thalassinus in winter. The estuary had 2 flood tides daily, but the larvae were abundant only at 1 of the 2 flood tides. The timing of occurrence of peak abundance was independent of the diel period of light and dark. Size and stage compositions were not significantly different between surface and bott om water layers (p > 0.05), but were significantly different between 2 successive flood tides (p < 0.01), indicating that larvae in the estu ary are evenly distributed in the water column, and that the larvae in the 2 successive flood tides were perhaps from different shoals.