The early marine distribution of Atlantic salmon in the North‐east Atlantic: A genetically informed stock‐specific synthesis

Gilbey, John; Utne, Kjell Rong; Wennevik, Vidar; Beck, Alexander; Kausrud, Kyrre; Hindar, Kjetil; Leániz, Carlos García de; Cherbonnel, Corrine; Coughlan, Jamie; Cross, Tom F.; Dillane, Eileen; Ensing, Dennis; García‐Vázquez, Eva; Hole, Lars Robert; Holm, Marianne; Holst, Jens Christian; Jacobsen, Jan Arge; Jensen, Arne Johan; Karlsson, Sten; Maoiléidigh, Niall Ó; Mork, Kjell Arne; Nielsen, Einar Eg; Nøttestad, Leif; Primmer, Craig R.; Prodöhl, Paulo A.; Prusov, Sergey; Stevens, Jamie R.; Thomas, Katie; Whelan, Ken; McGinnity, Philip; Verspoor, Eric

doi:10.1111/faf.12587

Cited by 37 publications

(56 citation statements)

References 194 publications

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“…Up until recently, this work has been hampered by a lack of certainty about where the various populations of Atlantic salmon reside during their marine migration. Thanks to technological advances and collaborative efforts, some progress has been made on this very recently (Almodóvar et al, 2020;Gilbey et al, 2021;Rikardsen et al, 2021), allowing targeted hypotheses to now be generated on salmon migration and distribution patterns in the sea. Data such as those described in this paper are crucial in providing definitive answers as to why marine survival of Atlantic salmon continues to decline.…”

Section: Discussionmentioning

confidence: 99%

Decadal Trends in the Migration Phenology of Diadromous Fishes Native to the Burrishoole Catchment, Ireland

et al. 2022

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Migration is an important ecological trait that allows animals to exploit resources in different habitats, obtaining extra energy for growth and reproduction. The phenology (or timing) of migration is a highly heritable trait, but is also controlled by environmental factors. Numerous studies have reported the advancement of species life-events with climate change, but the rate and significance of such advancement is likely to be species specific, spatially variable and dependent on interactions with population and ecosystem changes. This is particularly true for diadromous fishes which are sentinels of change in both freshwater and marine domains, and are subject to considerable multiple stressors including overfishing and habitat degradation. Here, we describe trends in the migration phenology of three native Irish migratory fishes over half a century, Atlantic salmon (Salmo salar), brown trout (Salmo trutta) and European eel (Anguilla anguilla). The trends were derived from daily counts of 745,263 fish moving upstream and downstream through the fish traps of the Burrishoole catchment, an internationally important monitoring infrastructure allowing a full census of migrating fish. We found that the start of the seaward migration of eel has advanced by one month since 1970. The commencement of the salmon smolt migration has advanced by one week, although the rest of the migration, and the entirety of the trout smolt run has remained stable. The beginning of the upstream migration of trout to freshwater has advanced by 20 days, while the end of the run is more than one month later than in the 1970’s. The greatest phenological shift has been in the upstream migration of adult salmon, with at least half of migrating fish returning between one and two months earlier from the marine environment compared to the 1970’s. The earlier return of these salmon is coincident with reduced marine survival and decreasing body size, indicating considerable oceanic challenges for this species. Our results demonstrate that the impacts of climate change on the phenology of diadromous fish are context-dependent and may interact with other factors. The mobilization of long-term datasets are crucial to parse the ecological impacts of climate change from other anthropogenic stresses.

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Section: Discussionmentioning

confidence: 99%

Decadal Trends in the Migration Phenology of Diadromous Fishes Native to the Burrishoole Catchment, Ireland

et al. 2022

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“…More information about surveys objectives, trawling and biological sampling is given by Utne et al (2021a). Salmon larger than 35 cm before August and larger than 40 cm in August (Gilbey et al, 2021) were excluded from further analyses to ensure that the dataset only included post-smolts.…”

Section: Biological Samplingmentioning

confidence: 99%

“…To understand spatial and temporal variation in the postsmolt diet, the data sampled along the post-smolt migration routes in the northeast Atlantic region, as identified by Gilbey et al (2021), were divided into five regions. The diet of postsmolts sampled in each region is presented on an annual basis.…”

Section: Regional and Temporal Variation In Dietmentioning

confidence: 99%

“…Despite being one of the world's most studied fish species, detailed knowledge of the ocean distribution of Atlantic salmon has been limited. Recent studies based on advances in genetic and electronic tagging methods have shown how Atlantic salmon post-smolts (the life stage when they have entered the marine environment for the first time and until the end of the first winter in the sea) and adults use large areas of the North Atlantic Ocean, and how salmon from different regions vary in their migration patterns and distribution (Strøm et al, 2017;Bradbury et al, 2021;Gilbey et al, 2021;Rikardsen et al, 2021). The increased knowledge on the oceanic distribution of Atlantic salmon has provided new opportunities to analyze and understand the causality underlying the variation in marine growth and survival.…”

Section: Introductionmentioning

confidence: 99%

“…The increased knowledge on the oceanic distribution of Atlantic salmon has provided new opportunities to analyze and understand the causality underlying the variation in marine growth and survival. The distribution of post-smolts from different European regions in the northeast-Atlantic Ocean was recently mapped (Gilbey et al, 2021). The area west of Ireland and Scotland and further north into the Norwegian Sea is an important migratory pathway for post-smolts in the Northeast Atlantic.…”

Section: Introductionmentioning

confidence: 99%

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Impacts of a Changing Ecosystem on the Feeding and Feeding Conditions for Atlantic Salmon During the First Months at Sea

et al. 2022

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During the last decades, many wild Atlantic salmon populations have declined dramatically. One hypothesis for an observed reduction in salmon marine growth and survival is reduced abundance of prey. However, the effect of spatial and temporal variation in marine prey abundance on post-smolt feeding conditions is poorly understood. Here we use stomach content data from 2572 salmon post-smolts sampled during 25 years in the Northeast Atlantic Ocean to examine spatial and temporal changes in diet and stomach fullness. Sandeel larvae west of Scotland and Ireland and in the northern North Sea, herring larvae in the eastern part of the Norwegian Sea, and amphipods in the western part of the Norwegian Sea were particularly important prey species. There was a reduction of fish larvae in the post-smolt stomachs over a large geographic area when comparing the period 1995–2004 to 2008–2019. This may be result of a bottom-up driven process, as increasing extent of Arctic Water masses and zooplankton abundance were positively correlated with post-smolt stomach fullness in the Norwegian Sea. Furthermore, the interspecific competition for fish larvae between post-smolts and mackerel may have increased with a larger mackerel stock expanding the feeding migrations northwards since 2007.

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Temporal shifts in the marine feeding of individual Atlantic salmon inferred from scale isotope ratios

Power,

Thorstad,

Forseth

et al. 2023

Ecology and Evolution

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Given the limited information on prey use during the marine residency period for Atlantic salmon, scales were collected from salmon at return to the River Namsen (Norway) for spawning after 1 year at sea, and scale material from the first and second summer marine feeding periods was analysed using stable isotope methods to understand dynamics of their trophic ecology. As the salmon increased in size from the first to second summer, they reduced their feeding niche and specialised more (narrowed the δ13C range) and increased their dependency on higher tropic level (δ15N) prey, likely fish. Changes in δ13C indicated a consistent pattern of movement towards the north and west between summer feeding periods. Hence, salmon during their first year at sea may have a migration route roughly resembling that of previous spawners, as inferred from earlier tagging studies. Feeding conditions and nutrient composition during the last summer at sea, i.e. in the months before returning to the river for spawning, impacted final body size and within‐season timing of return. Fish undergoing the largest trophic niche shift (δ13C and δ15N combined) between summer feeding periods, returned earliest. The earliest returning fish had the fastest specific growth rates at sea. Hence, salmon encountering abundant high‐quality fish food during the marine migration, particularly during the last months, may reach a size and energetic state whereby it is better to return early to a safer environment in freshwater than risk being eaten by a big predator at sea. Both trophic status (δ15N), resource use (δ13C) and growth rates were significantly correlated between feeding periods. Nutrient composition during the first summer at sea did not impact the fish body length after the following winter, but growth conditions during the first summer evidenced carry‐over effects from the first to the second summer of feeding.

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The early marine distribution of Atlantic salmon in the North‐east Atlantic: A genetically informed stock‐specific synthesis

Abstract: This is an open access article under the terms of the Creat ive Commo ns Attri butio n-NonCo mmerc ial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Cited by 37 publications

References 194 publications

Decadal Trends in the Migration Phenology of Diadromous Fishes Native to the Burrishoole Catchment, Ireland

Decadal Trends in the Migration Phenology of Diadromous Fishes Native to the Burrishoole Catchment, Ireland

Impacts of a Changing Ecosystem on the Feeding and Feeding Conditions for Atlantic Salmon During the First Months at Sea

Temporal shifts in the marine feeding of individual Atlantic salmon inferred from scale isotope ratios

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