Fishway Attraction Enhancement

Two Denil fishways on the Grand River, Ontario, have been monitored for activity by several dozen fish species annually since 1994. Fishway use was related to water temperature, water velocity, season, and the ease with which fishway entrances were located. Simple modifications to the entrances of two Denil fishways resulted in increased attraction efficiency for pumpkinseed Lepomis gibbosus. Entrances were enlarged and repositioned approximately 2 m closer to the weir face, in areas where radiotagged fish congregated. After modifications, overall relative rates of recapture were 39 % (95 % C.I. = 32 – 46 %), representing a 2.6 – 3 fold increase in fishway use relative to pre-modification conditions. Median instantaneous recapture rates also increased significantly from 0 % at both fishways to approximately 2 %, after fishway entrances were modified. Fishway entrances should be located as close to a dam or weir face as possible, but velocity barriers from spillway or tailrace discharge must not compromise access. Similar modifications may be made to other fishways to improve attraction efficiency for warmwater species.