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Less anxious salmon smolt become easy prey during downstream migration
Jonatan Klaminder1, Micael Jonsson1, Johan Leander1
1Department of Ecology and Environmental Science, Umeå University, 90187 Umeå, Sweden.
The Science of the Total Environment
|June 19, 2019
Summary
Oxazepam, an anxiolytic drug, did not improve hatchery salmon smolt migration and increased predation risk. This pharmaceutical is unsuitable for enhancing salmon stocking success in natural river systems.
Area of Science:
- Fisheries Science
- Ecotoxicology
- Behavioral Ecology
Background:
- Hatchery-raised salmon smolts often exhibit suboptimal migration behavior, hindering stocking effectiveness.
- An anxiolytic drug, oxazepam, has been proposed to enhance salmon smolt migration based on mesocosm studies.
Purpose of the Study:
- To evaluate the efficacy of oxazepam treatment in improving the migration performance and survival of hatchery-reared Atlantic salmon smolts in a natural river environment.
Main Methods:
- Acoustic telemetry was used to monitor migration rate and survival of Atlantic salmon (Salmo salar) smolts exposed to oxazepam (200 μg/L) versus a control group.
- Migration performance was assessed over a 21-km river-to-sea route in a boreal river in Northern Sweden.
Main Results:
- Oxazepam-exposed smolts exhibited delayed migration initiation compared to control fish.
- No significant difference in downstream migration speed was observed between groups.
- Exposed smolts faced a considerably higher predation probability, attributed to increased risk-taking and reduced predator vigilance.
Conclusions:
- Oxazepam exposure is an unsuitable management strategy for priming salmon smolt migration in natural systems.
- Behavioral modifications induced by oxazepam, such as increased activity and risk-taking, negatively impact survival.
- Findings highlight ecological concerns regarding pharmaceutical pollution and its effects on wildlife behavior and survival.
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