Survival Improvements Measured at Fish Guidance Systems Designed to Improve Safe Downstream Passage of Diadromous Fish

Many diadromous fish species, such as Pacific and Atlantic salmon (Onchorhynchus spp., Salmo salar), the shads and river herring (Alosa spp.), and American eel (Anguilla rostrata), are in danger of extinction throughout some or all of their range.  Impacts to these populations include entrainment at hydroelectric dams and other water conveyance facilities.  State and federal laws now mandate protection of these and other fish populations.  Facility operators must often implement physical or operational modifications to reduce fish entrainment.  This presentation will document the improved fish passage survival results at several Fish Guidance System (FGS) installations in North America.  The FGS has been demonstrated to successfully guide downstream migrating fish to safer bypass routes, thereby reducing entrainment and improving survival.  Most fish species migrate downstream in the thalweg, taking advantage of higher water velocities.  The FGS is designed to exploit this migratory behavior and guide fish to a safer point of egress.  The FGS is composed of a series of floating panels anchored across the river channel.  The design and configuration of the FGS varies at each site according to hydraulic conditions and species present.  Acoustic telemetry and hydroacoustic studies conducted on various FGS installations indicate that from 53% to upwards of 92% of downstream migrating juvenile Pacific and Atlantic salmon were successfully guided to a safer bypass route in a variety of facility configurations and hydraulic conditions.  Further research is needed, but the FGS should also provide significant survival benefits to other downstream migrating fish species that demonstrate similar migration behavior, including juvenile shad and herring (Alosa spp.), adult eels (A. rostrata) and kelts (O. mykiss, S. salar).