Data from: Smallmouth bass (Micropterus dolomieu) and chain pickerel (Esox niger) identified as Atlantic salmon (Salmo salar) smolt predators in a reservoir system

Reservoir predation has been identified as a leading mortality source for
smolts migrating through impounded river systems. We investigated smolt
predation risk for an endangered Atlantic salmon (Salmo salar) population
in the Weldon Dam reservoir in the Penobscot River, Maine, USA. In spring
2022, we characterized the fates of 390 tethered smolts. Smolts were
exclusively predated by two predator species not native to the study area:
chain pickerel (Esox niger, n=43) and smallmouth bass (Micropterus
dolomieu, n=42). Using Cox-proportional hazard analysis, we estimated that
23% (95% CI = 15–29%) of tethered smolts were expected to be predated
within a one-hour deployment. Water temperature was the primary driver of
predation risk as predation probability increased from 10% to 33% when
temperature increased from 5°C to 15°C. Smolts also incurred above-average
predation risk when they were within 40 m of shore. We demonstrate that
non-native fish predation may drive patterns of high impoundment mortality
and that risk is spatially and temporally heterogeneous within these
systems. Collectively, this study offers direct evidence of
species-specific predation on Atlantic salmon smolts and illuminates
potential strategies to mitigate predation risk during reservoir
migration.