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juveniles indicate the razorbacks can swim through flows with an average velocity of 4 feet per second (fps) if the bottom velocities are 2 fps or less on a roughened surface. In video records of the flume tests the fish can be seen resting behind some of the larger boulders as they proceed upstream through the higher velocity sections (Mefford 2000b). Velocities in the Redlands fish passageway have been measured in the baffles and range from 2.3 to 3.5 fps. Since 1996, the Redlands fish passageway has been successfully negotiated by 49 endangered Colorado pikeminnow as well as over 42,000 other fish, of which 93% were the non-listed native species such as the flannelmouth sucker, bluehead sucker, and roundtail chub (Burdick 2000c). 3.3 Behavior Razorback suckers tend to follow the riverbanks, swimming along the channel bottom (Burdick 2000b). Because the rivers tend to be quite turbid during spring runoff and the visibility is poor, it is believed the fish rely almost exclusively on flow direction for orientation. Similarly, the Colorado pikeminnow is believed to orientate itself using flow direction, however, it is unknown whether or not the Colorado pikeminnow swim along the bottom of the channel or follow the riverbanks in a similar fashion to the razorback sucker. The fish passage entrance at the downstream end of the ladder is believed to be most easily accessible for the fish if the entrance is within 45 degrees of being parallel to the river flow (Mefford 2000a). Ideally, the ladder entrance is placed approximately 20 to 30 ft downstream of the whitewat~r from the diversion dam. Fish are drawn to the dam and then search for passage. Once the fish have reached the dam face they generally do not go back downstream to search for passage. Instead the fish continue to search at the most upstream accessible point. The ideal average velocity near the ladder entrance is approximately 4 fps. The target for attractive flow, plus flows in the fish ladder, is approximately 10 % of the river flow (SJRIP 2000). During spring runoff and higher flow events, 10 % can be impractical. 9 I I I I I I I I I I I I I I I I I I I