Radio Telemetric Investigation of Downstream Passage of Atlantic Salmon Smolts at Bellows Falls Station
Atlantic salmon, Bellows Falls, bypass, canal, Connecticut River, downstream fish passage, fish bypass, fish ladder, hatchery, hydroelectric, log sluice, migration, New England Power, radio tags, radio telemetry, salmon, smolt, turbines
Atlantic salmon smolts typically migrate downstream in the Connecticut River during the months of April and May when water temperatures exceed 48-50F (9-10C). At this time of the year, river flows usually exceed the 11,000 cfs required for full-capacity operation of the Bellows Falls hydroelectric station. At such times downstream migrating smolts are expected to utilize overflow at the dam to bypass the generating station. When river flows of less than 11,000 cfs occur during the smolt migration period, a 'worst case' situation applies in which all river flow and, consequently, all migrating smolts, are diverted to the power canal. To investigate the use of various exits from the power canal by downstream migrating smolts, 119 smolts from the White River National Fish Hatchery were radio-tagged and released into the power canal at Bellows Falls Station during a series of five experiments. Two factors, flow through the log and ice sluice (the expected principal route for smolts bypassing the turbines) and time of release (afternoon vs. evening), were manipulated during the experiments. Of the 119 smolts released into the canal, 111 were observed to utilize one of the canal exits (log and ice sluice, fish bypass pipe, fish ladder, turbines), six were unaccounted for and were assumed to have passed through the turbines, and two smolts (or their transmitters) remained in the canal after termination of the experiments. For all experiments combined, 69% of the smolts passed through the turbines with 19, 8, and 4% of the smolts passing downstream through the log and ice sluice, fish bypass pipe, and fish ladder, respectively. The greatest proportion of smolts bypassing the turbines was 47% (9 of 19 fish) under conditions of high flow (255 cfs) through the ice and log sluice following an evening release of the fish. Of the two log and ice sluice flows tested (111 cfs, 255 cfs), the flow of 255 cfs appeared to be more successful at promoting fish bypass around the turbines.