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Migration pathways, speed and mortality of Atlantic salmon ( Salmo salar ) smolts in a Scottish river and the near‐shore coastal marine environment
Author(s) -
Lothian Angus J.,
Newton Matthew,
Barry James,
Walters Marcus,
Miller Richard C.,
Adams Colin E.
Publication year - 2018
Publication title -
ecology of freshwater fish
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 55
eISSN - 1600-0633
pISSN - 0906-6691
DOI - 10.1111/eff.12369
Subject(s) - salmo , fishery , shore , predation , population , geography , apex predator , ecology , flooding (psychology) , fish migration , oceanography , environmental science , biology , fish <actinopterygii> , geology , psychology , demography , sociology , psychotherapist
Long‐distance migration of Atlantic salmon ( Salmo salar ) is known to result in high levels of mortality. For a species experiencing global population decline, it is thus vital to better understand migration behaviour, both in the river and marine stages. Atlantic salmon smolts ( n = 50) were tracked using acoustic telemetry in the River Deveron, Scotland, and adjacent coastal area. Higher rates of mortality were observed in the river (0.77% per km) than the early marine stage of migration (0.0% per km). Mortality likely resulted from predation. Higher swim speeds were recorded in the early marine stage compared with the river (marine = 7.37 ± 28.20 km/day; river = 5.03 ± 1.73 km/day [mean ± SD ]), a potential predator avoidance behaviour. The majority of smolts leaving the river did so in darkness and on a flooding tide. Overall river and marine migration success were linked to nights of lower lunar brightness. Marine migration speed decreased with increasing environmental noise levels, a finding with implications for fisheries management. The migration pathway in the early marine environment did not follow obvious geographical features, such as the coastline. Thus, we suggest that early marine environment pathways are more influenced by complex water currents. These findings highlight factors that influence smolt migration survival and behaviour, areas on which future research should focus.