FEMALES OF A STREAM GOBY CHOOSE MATES THAT COURT IN FAST WATER CURRENTS

Males of the stream goby Rhinogobius sp. DA with exclusive paternal care court females in fast water currents. Female choice of this goby was observed in the field. A fast current itself does not seem to be advantageous to females for mating. Neither large male size nor long male dorsal fin, both being sexually dimorphic traits, was related to female selectivity. Females favored males that courted on points at which the water current was relatively fast. Water velocity at male courtship points was positively correlated with a condition factor for males, indicating that males of poor physical condition do not court in fast water currents. Hence, this mate choice pattern enables females to mate with males of good physical condition. Male condition factor itself, however, was not related to selectivity by females. Circumstantial evidence suggest that this female choice pattern will result in mating with males having sufficient energy reserves, i.e. high parental quality.