Spatial variation in landlocked Atlantic Salmon smolt survival associated with dam passage, avian predation, and stocking location

Objective: Managers of Atlantic Salmon populations (Salmo salar) often stock smolts at downstream locations to minimize within-river mortality. However, downstream stocking may limit imprinting potential and homing ability of returning adults relative to stocking further upstream. We evaluated the survival differences between upstream and downstream stocking for landlocked Atlantic Salmon in a tributary to Lake Champlain.  
Methods: We radio tagged hatchery-reared smolts, monitored these for a 7-8 day holding period, then stocked them concurrently with 22,000 smolts at two release sites in two years. The downstream location (DS, river kilometer 16, no dam passage) was a historically used site in a dam tailrace, whereas the upstream site (US, river kilometer 27, two dams) was in a side-channel and stocked for the first time. We estimated survival, performed avian counts during stocking, and searched avian nesting colonies for transmitters.
Results: Within their respective stocking reache..., This radio-telemetry dataset was collected in 2021 and 2022 in the Winooski River Vermont.
Fish were radio tagged at Dwight D. Eisenhower National Fish hatchery and held for a period of 7-8 days before being stocked in the study area. A thorough description of the tagging process and pre-release holding period is provided in Heim et al. (2024) published in North American Journal of Fisheries Management. Heim, Kurt C., Jonah Withers, and Theodore Castro‐Santos. \"Tagger effects in aquatic telemetry: Short‐term and delayed effects of surgery in Atlantic Salmon smolts.\" North American Journal of Fisheries Management 44.2 (2024): 262-275.
Detections of fish were made at 9 fixed telemetry stations along the river., , # Spatial variation in landlocked Atlantic Salmon smolt survival associated with dam passage, avian predation, and stocking location

[https://doi.org/10.5061/dryad.vt4b8gv25](https://doi.org/10.5061/dryad.vt4b8gv25)

## Description of the data and file structure

## Tagging fish

Fish were tagged at Dwight D. Eisenhower National Fish Hatchery, observed for a period of 7-8 days, and those surviving the holding period were mixed with the full lot of hatchery smolts into trucks for stocking (Table 1, Heim et al. *in press*). Fish were tagged with the methods described in Liedtke et al. (2012) using transmitters (TX-PSC-I-27-D, 1.5 grams, 16.5 x 8.0 x 6.5 mm, Sigma Eight, Ontario CAN) transmitting on 164.340 and 164.480 MHz at a 4 second ping rate. Only fish weighing more than 30g were tagged to ensure a tag burden of less than 5%, and the realized tag burden averaged 3.2% (max = 4.9%, min = 1.6%, Heim et al. 2024).

## Mobile tracking fish

Fish were tracked in the lower Winooski River fr...