Abstract
Long-term macrobenthic faunal change was investigated in the Shigetomi-higata tidal flats of northern Kagoshima Bay by means of surveys conducted in spring and autumn of 1994 and 2005. Density and biomass of all species of macrobenthic animals and sediment characteristics were surveyed along four transect lines covering the entire intertidal area of the flats. In total, 37 and 38 species were collected from this area in 1994 and 2005 respectively. Density and biomass of the various benthic animals have changed differently among the transects, but gastropods remarkably increased in both density and biomass during this period along most of the transects. Especially, Batillaria multiformis dominated the flats in 2005 but were not found in 1994. In contrast, the density, biomass, and species number of bivalves decreased, and decrease of Ruditapes philippinarum in both density and size of individuals was remarkable. The dominant polychaete changed from Notomastus sp. with a larger body size to Armandia lanceolata with a smaller body size. In general, epibenthic and smaller species increased whereas endobenthic and larger species and larger individuals decreased during this period. We could not identify the environmental factors responsible for causing these faunal changes, but topographic changes in the tidal flats may have played a role in the biomass change of R. philippinarum.
