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 impoun..., , , # Smallmouth bass (*Micropterus dolomieu*) and chain pickerel (*Esox niger*) identified as Atlantic salmon (*Salmo salar*) smolt predators in a reservoir system

[https://doi.org/10.5061/dryad.qbzkh18v4](https://doi.org/10.5061/dryad.qbzkh18v4)

## Description of the data and file structure

We used Predation Event Recorders to characterize predation risk for Atlantic salmon (*Salmo salar*) smolts in the Penobscot River, Maine from April-May, 2022.

### Files and variables

#### File: per\_2022\_hobo\_20250224.csv

**Description:** Data from HOBO Pendant Temperature/Light Data Loggers attached to each Predation Event Recorder (PER).

##### Variables

* dep: a unique ID assigned to each PER deployment.
* start: the start of the deployment in local time.
* end: the end of the deployment in local time.
* pred: whether the smolt was predated (1) or not (0) during the deployment.
* top: the time of the predation event in local time. NA = no predation event. 
* per: the PER ID used in the de...,