Permalink : http://hdl.handle.net/2115/82359

JaLCDOI : 10.14943/bull.fish.71.1.1

KEYWORDS : Mollusk;Assemblage;Intertidal zone;Hakodate Bay

This study described quantitative data on the current molluscan assemblage on the intertidal platform around Kattoshi, Hakodate Bay, southern Hokkaido, Japan. A total of 25 gastropod species and ten bivalve species were recorded from four-season sampling. Cluster analysis and subsequent indicator value (IndVal) calculation showed that the platform has three groups of sites with different assemblages. Group-1 accounted for 78-88% of the sites and was characterized by two gastropods Barleeia angustata and Reticunassa fratercula, which were also the top two species in the annual abundance. The indicator species of Group-2 (6-13% of the sites) included three gastropods, Cantharidus japonicus, Lirularia iridescens and Homalopoma sangarense. Group-3 was the least abundant (3-8% of the sites) and Batillaria cumingii and Ruditapes philippinarum were significant indicators. Overall, the current molluscan assemblage of the platform was characterized by two extremely dominant gastropod species, B. angustata and R. fratercula, while a previous study found H. sangarense to be dominant from December 1996 to August 1997. These results indicate the molluscan assemblage has changed over the past quarter-century.