Early rearing conditions of hotoke loach, Lefua echigonia

摘要

We have developed technology for producing seeding of the Hotoke loach, Lefua echigonia, designated as an endangered species by the Environment Agency and Kanagawa Prefecture. In selective of spawning bed experiment, Hotoke loaches were matured in a100 l PC tank with increased water temperature and long-day treatment, and natural spawning was induced using several types of aquatic plants. While the highest spawning was achieved with Uiromosu, fantinalis antipyreticus, spawning was also observed with Kinran, an artificial water plant. In experiments of mass egg-taking, designed to increase production, batches of 10 male/female parent fish were released into a 2tFRP tank with circulating filtration, and spawning was induced using Kinran. A total of2,179 hatched larvae were obtained from 1-year-old parents and 452 from 2-year-olds. We conducted rearing trials using the hatched larvae. Hatched larvae, breeding experiments under prefectual administration, we reared six groups of hatched larvae in 56l glass tanks with circulating filtration. Between 60 and 300 larvae were accommodated in each tank and were fed rotifer, Artemia, and particulate feed. The survival rate between 50 and 100 days was 12.3-77.0 percent, and seedlings with a body length of2-3cm were produced. In hatched larvae food experiment, we conducted a study trial on initial feeding in a 36 l glass tank. We found that the larvae could be reared with a combination si Artemia and particulate feed, excluding rotifers. In experiments of mass seed production, aimed at increased production, we reared hatched larvae via circulating filtration in three 2tFRP tanks. With a combination of Artemia and particulate feed, approximately 5,000 seedlings (3 cm size) were produced between 121 and 144 days.