Spawning environments and seasonal change in the appearance of the fluvial catfish, Silurus tomodai

Abstract

The spawning environment and seasonal changes in appearance of the Japanese silurid catfish Silurus tomodai were investigated in an upstream reach of a river in northern Mie Prefecture, central Japan. Eggs and larvae of the species were primarily found in highly localized areas around plant roots or in shallow accumulated litter at the water’s edge. Silurus tomodai was apparent from April to November, its activity increasing in the breeding season (from May to July). Laboratory feeding experiments indicated that juvenile proportions of lower jaw length to snout length, snout length to head length (HL), and interorbital width to HL may show greater variation than their mature counterparts.