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

Utne, Kjell Rong; Skagseth, Øystein; Wennevik, Vidar; Broms, Cecilie; Melle, Webjørn; Thorstad, Eva B.

doi:10.3389/fmars.2022.824614

Cited by 12 publications

(5 citation statements)

References 43 publications

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“…While beyond the scope of this work, recent studies indicate that the here discussed contrasting periods in the Norwegian Basin have also affected fish (Eliasen et al, 2021;Kristiansen et al, 2022;Utne et al, 2022). The reduction of Arctic Water in the Norwegian Sea in the early 2000s resulted in reduced feeding of post-smolts of salmon (Utne et al, 2022), drop in marine growth of Norwegian salmon (Vollset et al, 2022), and in a marked shift of the herring feeding migration towards East Icelandic Current (Eliasen et al, 2021;Kristiansen et al, 2022). These results are in accordance with the results of this paper linking changes in the ocean climate to plankton production and species composition in the Norwegian Sea, and thereby changed productivity of the ecosystem.…”

Section: Discussionmentioning

confidence: 95%

Arctic and Atlantic Waters in the Norwegian Basin, Between Year Variability and Potential Ecosystem Implications

et al. 2022

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The ocean climate of the southern Norwegian Sea - the Norwegian Basin - is largely set by the relative amount of Atlantic Water in the eastern and Arctic Water in the western region. Here we utilized hydrographic data from repeated sections, together with annually gridded survey data of the upper 1000 m, to resolve the main hydrographic changes over the period 1995-2019. Based on integrated heat -and freshwater content, we divide into three periods. The first period 1995-2005, denoted Arctic, is characterized by relative fresh and cold Atlantic Water overlaying Arctic Intermediate Water that basically covers the whole Norwegian Basin. Differently, the conditions during the period 2006-2016, denoted Atlantic, are warmer and more saline, and the extent and thickness of Arctic Intermediate Water is greatly reduced. During the most recent period denoted Fresh, 2017-2019, there has been a major freshening of the Atlantic waters, the layer of Arctic Intermediate Water has not recovered, but instead a layer of warmer but relative fresh Arctic Water has expanded. We find that increased abundance of the Arctic zooplankton Calanus hyperboreus in the southern and eastern Norwegian Basin coincides with increased extent of Arctic Water. We also note that the overall mesozooplankton biomass in the Norwegian Basin is significantly higher during periods of relative high amount of Arctic Water. Furthermore, we show that both nitrate and silicate winter (pre-bloom) concentrations are significantly higher in the Arctic Water compared to Atlantic Water, and that there is a reduction in nutrients from the Arctic period compared subsequent Atlantic and Fresh periods. Since these nutrients can be interpreted as the potential for new production, changes in the influx of western Arctic waters are expected to have a bottom-up effect on the Norwegian Sea. Hence, this study indicates that the amount of Arctic waters and their concentration of nutrients and zooplankton are more important for the Norwegian Basin ecosystem functioning rather than the temperature of the Atlantic waters.

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Section: Discussionmentioning

confidence: 95%

Arctic and Atlantic Waters in the Norwegian Basin, Between Year Variability and Potential Ecosystem Implications

et al. 2022

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“…The early 1980s are also considered as the end of "The great salinity anomaly", which was a period with large inflow of cold and fresh Arctic water into the Norwegian Sea. The large proportion of Arctic water entering the Norwegian Sea is correlated to increased productivity (Skagseth et al, 2022), and to improved feeding conditions for post-smolts in the region (Utne et al, 2022). Therefore, salmon returning in 1983 and 1984 had probably been feeding in a very productive sea during the initial post-smolt phase, whereas salmon returning to rivers in 2013-2016 had been feeding in a warm and saline Norwegian Sea.…”

Section: Discussionmentioning

confidence: 99%

Overruled by nature: A plastic response to environmental change disconnects a gene and its trait

et al. 2023

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In Atlantic salmon, age at maturation is a life history trait governed by a sex‐specific trade‐off between reproductive success and survival. Following environmental changes across large areas of the Northeast Atlantic, many populations currently display smaller size at age and higher age at maturation. However, whether these changes reflect rapid evolution or plasticity is unknown. Approximately 1500 historical and contemporary salmon from the river Etne in Western Norway, genotyped at 50,000 SNPs, revealed three loci associated with age at maturation. These included vgll3 and six6 which collectively explained 36%–50% of the age at maturation variation in the 1983–1984 period. These two loci also displayed sex‐specific epistasis, as the effect of six6 was only detected in males bearing two copies of the late maturation allele for vgll3. Strikingly, despite allelic frequencies at vgll3 remaining unchanged, the combined influence of these genes was nearly absent in all samples from 2013 to 2016, and genome‐wide heritability strongly declined between the two time‐points. The difference in age at maturation between males and females was upheld in the population despite the loss of effect from the candidate loci, which strongly points towards additional causative mechanisms resolving the sexual conflict. Finally, because admixture with farmed escaped salmon was excluded as the origin of the observed disconnection between gene(s) and maturation age, we conclude that the environmental changes observed in the North Atlantic during the past decades have led to bypassing of the influence of vgll3 and six6 on maturation through growth‐driven plasticity.

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“…The large proportion of Arctic water entering the Norwegian Sea is correlated to increased productivity (Skagseth et al . 2022), and to improved feeding conditions for post-smolts in the region (Utne et al . 2022).…”

Section: Discussionmentioning

confidence: 99%

“…The early 1980's are also considered as the end of "The great salinity anomaly", which was a period with large inflow of cold and fresh Arctic water into the Norwegian Sea. The large proportion of Arctic water entering the Norwegian Sea is correlated to increased productivity 38 , and to improved feeding conditions for post-smolts in the region 39 . Therefore, salmon returning in 1983 and 1984 had probably been feeding in a very productive sea during the initial post-smolt phase, whereas salmon returning to rivers in 2013-2016 had been feeding in a warm and saline Norwegian Sea.…”

Section: The Absence Of Association Between Vgll3 and Age At Maturati...mentioning

confidence: 99%

Overruled by nature: A plastic response to an ecological regime shift disconnects a gene and its trait

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Skaala

Wennevik

et al. 2022

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In Atlantic salmon, age at maturation represents a life history trait with a sex-specific trade-off between reproductive success and survival, mediated by the vgll3 gene through sex-specific dominance. By genotyping ~1500 historical and contemporary samples of salmon from the river Etne with a 50k SNP-array, we identified three loci significantly associated with sea-age. These included vgll3 and six6, which collectively explained 50% and 36% of the age of maturation for males and females in the 1983-1984 period respectively. In the same period, we also observed sex-specific epistasis, where the six6 genotype only influenced age at maturation in males carrying the late-maturation vgll3 allele. Strikingly, the combined influence of these genes was nearly absent in all samples from 2013-2016, while allelic frequencies at vgll3 remained unchanged. Many salmon populations in the northeast Atlantic, including that from Etne, have been exposed to a major ecological regime shift in the marine environment in 2005. Because this is associated with consistently slower growth and higher age at maturation, we conclude that the regime shift has led to the sudden bypassing of the influence of vgll3 and six6 on maturation through growth-driven plasticity.

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

Cited by 12 publications

References 43 publications

Arctic and Atlantic Waters in the Norwegian Basin, Between Year Variability and Potential Ecosystem Implications

Arctic and Atlantic Waters in the Norwegian Basin, Between Year Variability and Potential Ecosystem Implications

Overruled by nature: A plastic response to environmental change disconnects a gene and its trait

Overruled by nature: A plastic response to an ecological regime shift disconnects a gene and its trait

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