Abstract:

Based on the data from four oceanographic censuses taken by trawlboat in the Minjiang Estuary and Xinghua Bay in April (spring) and September (summer) of 2008, the species composition, similarity (Ochilai coefficient) and ecological adaptation of fish assembles in these areas were studied. The results indicated that in Xinghua Bay, a total of 108 species of fish was identified, among which 48 species occurred in spring and 81 species in summer respectively. Trachurus japonicus was one of the keystone species in spring of Xinghua Bay, The other species, including Chaeturichthys stigmatiaswere common species. In summer, Polynemus sextarius became keystone species and the other species, including Dasyatis akajei, were common ones. In the Minjiang Estuary, 77 species were identified, among which 36 species occurred in spring and 57 species in summer. Both Coilia mystus and Harpodon nehereuswere dominant species during spring. In the studied areas, species number of warm water species was highest of all, the proportions of which were as high as 76.62% in total number of species in the Minjiang Estuary and 75.00% in Xinghua Bay. In view of salinity adaptation, the coastal species and the nearshore species were most diversified, with a proportion of 91.67% in total species number of the Xinghua Bay and 87.01% of the Minjiang Estuary. And there were more estuarine species in the Minjiang Estuary comparing with Xinghua Bay. The similarity values between the species compositions of the two waters were higher than the similarities between different seasons respectively in each area. Thus, in studied areas, the species variations of the fishes were mainly determined by seasonal change, while the salinity variation was a minor one.

Key words: Minjiang Estuary, Xinghua Bay, species composition, fish fauna, ecological group, similarity