Fishways for warmwater species: Utilization patterns, attraction efficiency, passage efficiency, and relative physical output

Upstream migration and fishway use by anadromous species are fairly well documented and understood. Very little information exists about similar behaviour among riverine warmwater species. Because many of these species use fishways, a better understanding of fishway effectiveness can be used to offset dam and weir blockage effects, by providing improved upstream passage. Several fishways on the Grand River, Ontario were monitored for five years (1995–1999) and utilization patterns were documented for 30 warmwater fish species relative to seasonal, thermal and hydraulic dynamics. There were seasonal species shifts, with some overlap, from percids, to catostomids, to cyprinids, to ictalurids, back to percids and then centrarchids as water temperatures increased from 4°C to 25°C in the Grand River. Maximum fishway use by several species occurred during periods of decreased water clarity during or after storms. More proximately, water velocity and species-specific swimming/position holding abilities affected fishway use. Using digital radiotelemetry, movement patterns of 109 radiotagged fish (smallmouth bass Micropterus dolomieu, white suckers Catostomus commersoni and walleye Stizostedion vitreum), as well as attraction and passage efficiency of three Denil fishways were collectively examined. Attraction efficiency for white suckers was between 50 and 59%, and passage efficiency was between 38% and 55%. Attraction efficiency for smallmouth bass was 55–82% and passage efficiency was 33–36%. For walleye, attraction efficiency was 21%, and passage efficiency was between 0 and 4.2%. Variability among species-specific efficiencies was related to fishway design, water velocity, turbulence, swimming ability and swimming strategy. There was an exponential decline in the numbers of smallmouth bass and white suckers that used each fishway relative to water velocity. The maximum water velocities used by white suckers and smallmouth bass were 0.96 m/s and 0.99 m/s, respectively. Distracting flows upstream from the fishway entrances appeared to affect attraction, particularly for smallmouth bass. To address this problem, the entrances to two of the fishways were modified. An experiment was then designed to illustrate the effect of the modifications on attraction rates of pumpkinseed Lepomis gibbosus. Overall attraction rates increased by a factor of three after entrance modifications. Median relative attraction rates also increased significantly from 0% to 2% after fishway entrances were modified. Further experiments were then conducted with electromyographic (EMG) telemetry and smallmouth bass to attempt to evaluate physical output associated with passage through both of the modified fishways. EMG levels from areas near the fishway exits were significantly greater than maximum EMG levels recorded during critical swimming speed trials. Smallmouth bass appeared to exceed their aerobic scope of activity during ascent of both fishways. EMG data reflected combinations of burst and prolonged swimming activity and indicated the relative differences in muscular activity and physical output required to use each fishway type. Finally, positive biological effects of dams were investigated, after evidence suggested that some fish spawn in habitat immediately downstream. Radiotagged walleye occupied areas with suitable spawning substrate downstream from the Dunnville dam. At the Mannheim weir, creation and maintenance of microhabitats that supported large numbers of greenside darters Etheostoma blennioides and stonecats Noturus flavus, occurred downstream. These unique riffle habitats, with unembedded substrate, were maintained by pulsed river discharges associated with precipitation, upstream reservoir regulation, freshets, and ice scour.