Estimation of River Herring Fishway Passage and Juvenile Productivity in a System with Restored Habitat Access

Anadromous Alewife and Blueback herring, collectively known as river herring, are important forage fish species in the northwest Atlantic experiencing declines from historical abundances. Throughout the eastern seaboard, much of their historical spawning grounds are inaccessible due to dam construction.  Recently, fishways have been installed to increase access to native habitat. To evaluate this restoration method, river herring passage and juvenile productivity were assessed in the Carman’s River, NY. From 2012-2014, river herring were both PIT and acoustically tagged to determine passage success. Video monitoring was implemented to determine total fish passage counts. Tagging studies showed 30% (n=74) of tagged river herring attempted passage, and only 15% (n=37) were successful. Generalized linear model analysis indicated a significant correlation between length and probability of successful passage. Seven tagged fish successfully passed through the fishway multiple times in one spawning season, indicating that traditional counting methods may overestimate abundance. To determine productivity, juvenile river herring were sampled in both tidal and restored habitat to estimate growth rates and species relative abundance. Total juvenile river herring abundance, blueback herring abundances and hybridization rates increased each year. Juveniles caught in the restored habitat were smaller in mean length and emigrated later in the season.