Study of a fish way suitable for Hotoke loach (Lefua echigonia)
2008
Suguro, N.(Kanagawa-ken. Fisheries Technology Center, Miura (Japan)) | Suzuki, M. | Mizutani, S.
To study a fish way suitable for Hotoke loach (Lefua echigonia), testing was done using Cascade-M type and Chidori-X type. The fish ways were 30cm wide, their incline was 10deg, and the number of fish migrating upstream was counted at 2 hour intervals at flow rates of 250 and 500ml/s. The results have shown that both newborn fish and 1 year old fish migrated upstream at a higher rate in the Chidori-X type than in the Cascade-M type. And increasing the flow rate encouraged upstream migration. When testing using the Cascade-M type was performed narrowing its width from 30cm to 15cm and varying the flow rate between 125, 250, and 500ml/s, if the rise of the flow rate increased the depth inside the fish way, the one-year old fish migrated upstream at a higher rate. This suggests that if water depth equal to 90% or more of the body height of a fish species is ensured, it is possible for the fish to migrate using the Cascade- M type. To clarify the relationship between the upstream migration of Hotoke loach with time, the test was performed using Chidori-X type fish way. Four test periods were set: 12:00 noon, 6:00 p.m., midnight, and 6:00 a.m., and fish were allowed to migrate upstream for 6 hours each time. No differences were observed between the migration of the new born fish during the daytime and nighttime, but more one year old fish migrated upstream during the night. And at all time periods, many fish migrated upstream during the 2 hours immediately after the start of the test.
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