Difference in habitat use between the two related goby species of Gymnogobius opperiens and Gymnogobius urotaenia: a case study in the Shubuto River System, Hokkaido, Japan

Abstract

The longitudinal and cross-sectional differences in habitat use between Gymnogobius oppeiens and Gymnogobius urotaenia (sister species) were investigated from June to July 2011 in the Shubuto River System, southwestern Hokkaido, Japan. Generalized linear model revealed that watercourse distance from the sea had a significant influence on the abundances of both G. opperiens and G. urotaenia but in different ways. That is, G. opperiens had a distributional peak at the middle reaches, but the abundance of G. urotaenia gradually decreased with increasing distance from the sea. In addition, the lateral distribution patterns of G. opperiens and G. urotaenia, and all the local environmental variables were significantly different between the fringe and the mid-channel habitats. Both G. opperiens and G. urotaenia were most abundant along the margins of the river. However, the former species was frequently collected from the mid-channel, whereas the latter species was never collected in the habitat. These results coincide with previous observations asserting habitat segregation of the two goby species. The differential habitat use between the two species may be related to the differences in their population sizes and morphologies.