An Attempt to Create Depths for Fish Wintering in an Agricultural Canal during a Non-irrigation Period

The following 3 types of depths were created to investigate the effects on wintering fish in an agricultural canal: (1) a 30-cm-deep dammed section of the canal; (2) a 60-cm -deep hand-dug section of the canal that was covered; and (3) a 60-cm-deep hand-dug section of the canal that was left uncovered. The number of fish species, fish density and the diversity index were compared at each sampling station during the same months the previous year. The 3 above-mentioned parameters showed increased values after the depths were created. Fish density in the covered 60-cm-deep section was higher than that in the 60-cm-deep section with no cover. Moreover, the fish marked previously in the mark and recapture method either remained at the same depth or moved from a depth with no cover to a covered depth. Therefore, the depth with a cover could be especially effective for fish wintering. Consequently, bank trees, overhead banks, and submerged plants should be conserved as a cover for wintering fish.