Abstract
We examined the gastrointestinal contents of the Hotoke loach (Lefua echigonia) sampled throughout the four seasons at two sites in valley-bottom paddy fields in Aichi Prefecture, Japan. The highest number of individuals belonged to family Chironomidae, followed by class Copepoda and family Lepidostomatidae. Wet weight was highest in Chironomidae, followed by the families Erpobdellidae and Tipulidae. At both sites, the percent index of relative importance (%IRI) of Chironomidae samples was highest in Hotoke loach of standard length < 50 mm and lower in those with greater lengths (50-60 mm) that foraged primar-ily on heavier aquatic prey such as Erpobdellidae, Lepidostomatidae and Tipulidae. We detected a weak positive correlation be-tween loach standard length and maximum wet weight of prey. At both sites, Chironomidae had the highest %IRI among prey taxa in all seasons, except for June at Site B, and the %IRI of Chironomidae was higher in winter than in all other seasons. Although we did not investigate the abundance of benthic invertebrates or other Hotoke loach prey organisms at the sites, our results imply that the loach utilises chironomids year round, and especially in winter, such that it is highly dependent on this family. The findings of this study highlight the importance of conserving environments that are rich in chironomids, the main food resource of the Hotoke loach during the juvenile stage and in winter, and which provide a habitat for a variety of benthic organisms, including large aquatic invertebrates such as Erpobdellidae and Tipulidae.
