Ecological regime shift in the Northeast Atlantic Ocean revealed from the unprecedented reduction in marine growth of Atlantic salmon

Vollset, Knut Wiik; Urdal, Kurt; Utne, Kjell Rong; Thorstad, Eva B.; Sægrov, Harald; Raunsgard, Astrid; Skagseth, Øystein; Lennox, Robert J.; Østborg, Gunnel Marie; Ugedal, Ola; Jensen, Arne J.; Bolstad, Geir H.; Fiske, Peder

doi:10.1126/sciadv.abk2542

Cited by 57 publications

(119 citation statements)

References 55 publications

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“…Further, some males never leave their home river and instead mature at a small size at the parr life stage, and so, mature individuals returning from the sea can be several thousand times larger than their mature river-bound counterparts. In recent decades, wild Atlantic salmon stocks have been in decline, with factors suggested to have contributed to this decline including climate change, aquaculture, illegal fishing, hydropower dams and harvesting of prey species (Chaput, 2012;Czorlich et al, 2022;Dadswell et al, 2021;Harvey et al, 2022;ICES, 2019;Vollset et al, 2022). Some of these factors have also been associated with life-history changes in the wild stocks, with some populations experiencing a decrease in the number or proportion of early-maturing individuals (Vollset et al, 2022), while others are reporting a decrease in large, late-maturing, individuals (Czorlich et al, 2018(Czorlich et al, , 2022Olmos et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Strong effects of temperature, population and age-at-maturity genotype on maturation probability for Atlantic salmon in a common garden setting

Åsheim

Debes

House

et al. 2022

Preprint

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Age at maturity is a key life history trait and involves a trade-off between survival risk and reproductive investment, has close connections to fitness, and is an important factor for population structures. Temperature can have a dramatic influence on life history in ectotherms, but this influence may differ between populations. While an increasing number of studies have examined population-dependent reactions with temperature, few have investigated this in the context of maturation timing. Atlantic salmon is a highly relevant study species for improving understanding of this topic as it displays considerable variation in life-history strategies, including maturation timing. Additionally, a large amount of this variation in maturation timing has been associated with a genomic region including the strong candidate gene vgll3, but the effect of this gene in the context of different environments and populations has not been studied. Using a large-scale common-garden experiment, we find strong effects of temperature, population, and vgll3 genotype on maturation in 2-year-old male Atlantic salmon. Observed maturation probability was 4.8 times higher in individuals reared at a mean temperature of 8.6°C compared to 6.9°C. This temperature effect was population-specific and was higher in the southern population compared to the northern population, potentially due to a higher intrinsic growth in the southern population as well as growth-temperature interaction. The early-maturation vgll3*E associated with a significantly higher maturation probability, but there was no vgll3-interaction with temperature or population. Both body condition and body mass associated strongly with maturation; the body-condition association was stronger in fish carrying the vgll3*E allele, and the body mass association was only present in the warm treatment. Our findings demonstrate that the relative effect of vgll3 on maturation timing is similar for two populations and two thermal environments and gives new perspectives on the relative effect of vgll3 compared to such influences. Additionally, we show that populations can vary in their response to temperature change in terms of maturation timing, and that high intrinsic growth could potentially be associated with higher thermal sensitivity for life history variation.

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Section: Introductionmentioning

confidence: 99%

Strong effects of temperature, population and age-at-maturity genotype on maturation probability for Atlantic salmon in a common garden setting

Åsheim

Debes

House

et al. 2022

Preprint

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“…These changes in the ecosystem most likely affected the abundance of prey important for salmon through bottom-up processes, as shown in the present study. The findings are furthermore supported by a drop in marine growth for Norwegian salmon occurring simultaneously as the Norwegian Sea ecosystem changed (Vollset et al, 2022). Analogous ecosystem changes have been shown to impact feeding conditions in the Northwest Atlantic Ocean, where capelin is an important prey species for Atlantic salmon.…”

Section: Discussionmentioning

confidence: 59%

“…The drop in condition factor was associated with reduced stomach fullness, indicating poorer prey availability and feeding opportunities during this period (Utne et al, 2021a). A reduced growth of Atlantic salmon from several populations based on scale analyses has also been shown during this period (Jensen et al, 2012;Trehin et al, 2021;Vollset et al, 2022). The observed reduction in stomach fullness, condition factor and individual growth may explain the reduced marine survival after 2004.…”

Section: Introductionmentioning

confidence: 80%

“…The vast ocean areas used by Atlantic salmon as marine feeding grounds, and the lack of annual ocean surveys targeting Atlantic salmon, have limited the possibilities of detailed studies addressing the different hypotheses on why marine growth and survival have declined. There is large regional and temporal variation in marine growth and survival of Atlantic salmon (ICES, 2021a;Vollset et al, 2022), further complicating such studies.…”

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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“…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. The earlier return migration, coupled with smaller body size, point to several fruitful lines of investigation including: physiological challenges associated with growth rates (Tréhin et al, 2021;Vollset et al, 2022), changing ocean currents (Caesar et al, 2021), decreased feeding opportunities (Peyronnet et al, 2008;Utne et al, 2021) and trophic mismatches (e.g., Burthe et al, 2012). All of these potential causative agents are consistent with the impacts of anthropogenic climate change on the ocean, and are likely to interact in synergistic and antagonistic ways with Atlantic salmon stocks.…”

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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Ecological regime shift in the Northeast Atlantic Ocean revealed from the unprecedented reduction in marine growth of Atlantic salmon

Cited by 57 publications

References 55 publications

Strong effects of temperature, population and age-at-maturity genotype on maturation probability for Atlantic salmon in a common garden setting

Strong effects of temperature, population and age-at-maturity genotype on maturation probability for Atlantic salmon in a common garden setting

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

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

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