Use of Inclined-Plane Traps to Study Movement and Survival of Atlantic Salmon Smolts in the Connecticut River

We determined the utility of inclined-plane traps for capturing smolts of Atlantic salmon Salmo salar and studied the timing of the downriver run and survival of smolts in the Connecticut River in 1985 and 1986. We captured 22 smolts with one trap in 1985, and 45 with three traps in 1986. Although these numbers were small, the results from both years were similar. Mean total lengths of smolts (ranges in parentheses) were 186 mm (152-206 mm) in 1985 and 178 mm (152-201 mm) in 1986. The migration period in both years extended from early April to mid-May. Mean river temperatures when smolts were captured were 10.5°C (4.5-16.0°C) in 1985 and 10.3°C (4.5-15.0°C) in 1986. Most smolts were captured several weeks after the period of peak spring flows that probably would have provided the safest passage past electricity generating stations. The recapture rates of tagged hatchery smolts stocked 8 km upstream from the trap were 1 of 4,400 (0.023%) in 1985 and 1 of 2,900 (0.034%) in 1986. These rates were significantly higher than the recapture rates of tagged hatchery smolts stocked in headwater tributaries. The seemingly poor survival of smolts from headwater tributaries was probably caused largely by the low river flows when smolts migrated and a lack of smolt protection or passage at electricity generating stations on the Connecticut River. Increasing the survival of smolts will require that downstream passage or protection be provided at all generating stations that are likely to kill or injure migrating smolts