This paper reports the species diversity and spatial distribution patterns of icefishes (Salangidae) in both feeding and breeding seasons in Poyang Lake, eastern China. The data were collected by a series of comprehensive surveys in the summer of 2002 and the spring of 2003, with a specially designed icefish trawl. The survey focused on 40 sampling sites with a total area of 50 ha along shallow bays, where had been identified as suitable habitats for icefishes. Three species of icefishes, Neosalanx oligodontis, Neosalanx taihuensis and Hemisalanx brachyrostralis, were recorded from the survey, among which N. oligodontis, the smallest icefish, was the most predominant species with the highest relative abundance (Pi) of 71.5%, whereas, the largest icefish, H. brachyrostralis was the rarest species with the relative abundance of 2.9% only, and the intermediate sized icefish, N. taihuensis ranked as the second in predominance (Pi=25.6%), according to the summer data.
In summer, the distribution patterns of the three icefishes correlated with each other significantly, indicated similar habitat selection for feeding. Species richness index (R) and Shannon-Wiener diversity index (H′) was higher in the south than in the north part of the lake, which correlated well with the conservation status of the lake, e.g. the least disturbed area recorded with the highest species diversity of icefish assemblage.
In spring, however, the three species showed significant difference in spawning field selection. N. oligodontis occurred most diffusively in both northern and southern parts of the lake with the incidence of occurrence (IO) of 70.0%; N. taihuensis showed similar occurrence pattern but occurred in lower incidence (IO=55.0%), whereas H. brachyrostralis only laid eggs in the southern area and had the lowest incidence of occurrence (IO=30.0%). This result indicated that the habitats in southern area were highly qualified for all of the three species to spawn, but the northern habitats were just suitable for one (i.e. N. oligodontis) or in certain conditions for two (i.e. Neosalanx) species.
Hierarchical cluster analysis distinguished the 40 sampling sites into six habitat types, among which three types of habitats contributed significantly to the consistence of icefish assemblage. The southern habitats turned out to be the most important ones for the persistence and stability of icefish diversity in Poyang Lake.
Above all, this study indicated that the quality and distribution pattern of spawning field had shed high light on the icefish assemblage, and suggests paying more attention to the spawning field protection for the conservation and restoration of the wild icefishes in Poyang Lake.