Fish assemblages in the mangrove creeks of northern and southern Taiwan

A bimonthly study of the spatial variations in fish assemblages in the six mangrove creeks along the western coast of Taiwan was conducted from Februa ry 1996 to February 1997. Fyke nets were used to collect fishes in each of three creeks in the north (subtropical) and south (tropical) regions. A tot al of 79 fish species belonging to 33 families were collected and, of these , the Gobiidae, Mugilidae, Leiognathidae, and Cichlidae were the most diver se families. The fish assemblages in each creek were dominated by a small n umber of small fishes, most of which are the young of commercially importan t species. Their life cycles occurred to some extent in estuarine environme nts. Analyses by classification and ordination separated the assemblages in to a northern group and a southern group and showed that the assemblages we re far more temporally varied in the southern creeks than in the northern c reeks. Fifty fish species were recorded in the northern creeks and 49 fish species in the southern creeks, with 20 species present in both regions. No significant difference in number of species per netting was detected betwe en the regions. The number of individuals and biomass per netting were grea ter in the northern creeks than in the southern creeks. Rainfall and organi c content of sediments may be responsible for the difference in fish abunda nce between the regions. In the northern creeks the assemblages were domina ted by Liza macrolepis and Lira affinis in winter and spring, but the assem blages were more diverse in summer and fall. In the southern creeks, the as semblages were always characterized by several species and their dominance varied from month to month. The differences in the assemblage structure in northern and southern mangrove creeks are likely due to the oceanic current patterns around Taiwan.