Habitat Use of the Grazing Goby (<i>Sicyopterus japonicus</i>) in Response to Spatial Heterogeneity in Riparian Shade

Abstract

ABSTRACT The local density of the grazing goby (Sicyopterus japonicus) and benthic algal production were investigated in a 720 m reach of the Sate River in the northern part of Okinawa Island, Japan. The reach was spatially heterogenous in riparian shade and was divided into three segments (open-canopy, shaded and patchy segment) based on vegetation cover. In the reach, the goby was more abundant in the open-canopy segment and open-canopy patches than in the adjacent shaded segment and shaded patches. Between the open-canopy and shaded segments there was no significant difference in the algal biomass; however, the algal growth rate was greater in the open-canopy segment than in the shaded segment. These results indicate that the spatial heterogeneity in riparian shade controls the habitat use of the goby, with open-canopy areas with high algal renewal rates being preferred.