To update the consensus on the effectiveness of fish passage mitigation structures or “fishways,” I conducted a meta‐analysis on the fish passage literature and synthesized attraction and passage efficiency estimates from 60 peer‐reviewed articles. One hundred unique species were studied at 75 unique fishways of various designs and sizes yielding 210 and 252 estimates of attraction and passage efficiency, respectively. Following Bunt et al. (River Research and Applications, 28, 2012, 457), the fishways were grouped into five types: nature‐like, denil, pool‐and‐weir, vertical slot or locks and lifts that were operated automatically. Generalized linear mixed effects models showed that fishway type was not a significant predictor of passage efficiency, although nature‐like fishways had significantly lower attraction efficiency than other types. Neither fishway slope, nor elevation change was significant predictors of attraction or passage efficiency. Models comparing efficiency between ecological guilds of fishes (pelagic or benthic and rheophilic or limnophilic) showed that attraction and passage efficiency were highest for pelagic rheophiles and lowest for limnophiles. Models comparing migratory guilds of fishes (diadromous, potamodromous, facultative or non‐migratory) showed that diadromous species outperformed other guilds, as expected. Fish that were captured inside or above fishways had significantly higher passage performance than fish that were naive to the fishway. Inconsistency in fishway evaluation methods was pervasive in the surveyed literature and made this meta‐analysis challenging. When designing studies of fishway evaluations, researchers should conform to best practices so that their results are more generalizable and their conclusions of wider scope.

Impacts of low-head, run-of-the-river dams on migratory fish movements depend on the structure of the dam, river hydrology, and the ability of fish to navigate the tailrace environment. Here, we present results from a 3-year movement study in which telemetered Paddlefish Polyodon spathula and Smallmouth Buffalo Ictiobus bubalus were tracked as they approached and sometimes migrated past Claiborne Lock and Dam (CLD), a low-use low-head lock-and-dam structure on the Alabama River. A spillway portion of the dam is periodically inundated during early spring, dependent on precipitation and releases from the next upstream dam. Our goals were to (1) quantify dam passage rates for both species, (2) assess the importance of factors affecting passage success, and (3) quantify space use patterns in the tailrace. Both species exhibited annual upstream migrations during the study period. Correlation of daily average river position versus the CLD hydrograph showed that movements by both species appeared to be related to flow variation. Passage efficiency (range = 10.7-30.2%) varied between species and among years, with tailrace gauge height being the most important factor affecting passage success for both species. Using an acoustic positioning system in the tailrace, we quantified space use by individuals of both species. Time spent in the tailrace (mean = 3.9 continuous days; range = 0-94 continuous days) did not differ between individuals that passed and those that did not pass. Fine-scale position estimates showed that space use differed between species, across gauge heights, and between individuals that passed and those that did not pass. Differential space use may be due to the species' habitat preferences or swimming abilities. Our findings provide information to inform potential design of mitigation structures, and they also identify the need for additional work required to more fully understand the mechanisms of passage success versus failure for these and other native potamodromous species.

Coastal rivers and estuaries provide habitat and migratory corridors for freshwater estuarine-opportunists. We evaluated movement patterns of 61 blue catfish Ictalurus furcatus in the tidal York and Rappahannock rivers in Virginia, USA with acoustic telemetry from July 2015 to June 2016. To evaluate river-specific movements, we utilized a multistate Cormack-Jolly-Seber (CJS) model within a Bayesian framework to estimate probabilities of detection and transition (movement) among established salinity zones (i.e., tidal-fresh [0-0.5 ‰], oligohaline [>0.5-5 ‰], mesohaline [>5-18 ‰]). We considered flow as an environmental covariate. Despite high site fidelity in tidal-fresh zones, some individuals displayed movements into oligohaline and mesohaline habitats indicative of partial migration. Once downstream movement occurred, the probability of staying in the new salinity zone was higher than the probability of movements to other salinity zones. In the Rappahannock River only, movement upstream from mesohaline habitats was associated with below average flow. As flow increased, the probability of remaining in oligohaline and mesohaline zones increased. Our study shows blue catfish can move into downstream areas of tidal rivers with elevated salinities and that increased freshwater flow may allow them to remain in these habitats for extended durations.