Marine mortality in the river? Atlantic salmon smolts under high predation pressure in the last kilometres of a river monitored for stock assessment

Hugo de Moura Flávio*, Richard Kennedy, Dennis Ensing, Niels Jepsen, Kim Aarestrup

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The River Bush (Northern Ireland) is an index river for the estimation of Atlantic salmon, Salmo salar L., stock size, population dynamics and marine survival rates. Marine survival estimates are based on the number of smolts counted at a trap 3.5 km upstream of the river outlet. The survival from release to coastal inshore waters for acoustic‐tagged smolts released at the Bushmills trap varied between 32% and 68%, with both year and brightness during river exit playing a significant role in explaining the variations in survival. This constitutes an important survival bottleneck. Contrary to true marine mortality, this significant loss of smolts in the river and nearshore environments could be reduced by focused management actions. More studies on other rivers, where smolts are enumerated above the head of tide, could further partition smolt and post‐smolt mortality, help differentiate true marine survival and help understand fluctuations in adult returns.
Original languageEnglish
JournalFisheries Management and Ecology
Volume27
Issue number1
Pages (from-to)92-101
ISSN0969-997X
DOIs
Publication statusPublished - 2020

Keywords

  • Avian predation
  • Diel cycle
  • Management opportunity
  • Salmo salar
  • Seaward migration
  • Telemetry

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