Time series covering up to four decades reveals major changes and drivers of marine growth and proportion of repeat spawners in an Atlantic salmon population
Abstract Wild Atlantic salmon populations have declined in many regions and are affected by diverse natural and anthropogenic factors. To facilitate management guidelines, precise knowledge of mechanisms driving population changes in demographics and life history traits is needed. Our analyses were...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2022-04-01
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| Series: | Ecology and Evolution |
| Subjects: | |
| Online Access: | https://doi.org/10.1002/ece3.8780 |
| _version_ | 1828032343902781440 |
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| author | Alison Harvey Øystein Skaala Reidar Borgstrøm Per Tommy Fjeldheim Kaja Christine Andersen Kjell Rong Utne Ingrid Askeland Johnsen Peder Fiske Synne Winterthun Sofie Knutar Harald Sægrov Kurt Urdal Kevin Alan Glover |
| author_facet | Alison Harvey Øystein Skaala Reidar Borgstrøm Per Tommy Fjeldheim Kaja Christine Andersen Kjell Rong Utne Ingrid Askeland Johnsen Peder Fiske Synne Winterthun Sofie Knutar Harald Sægrov Kurt Urdal Kevin Alan Glover |
| author_sort | Alison Harvey |
| collection | DOAJ |
| description | Abstract Wild Atlantic salmon populations have declined in many regions and are affected by diverse natural and anthropogenic factors. To facilitate management guidelines, precise knowledge of mechanisms driving population changes in demographics and life history traits is needed. Our analyses were conducted on (a) age and growth data from scales of salmon caught by angling in the river Etneelva, Norway, covering smolt year classes from 1980 to 2018, (b) extensive sampling of the whole spawning run in the fish trap from 2013 onwards, and (c) time series of sea surface temperature, zooplankton biomass, and salmon lice infestation intensity. Marine growth during the first year at sea displayed a distinct stepwise decline across the four decades. Simultaneously, the population shifted from predominantly 1SW to 2SW salmon, and the proportion of repeat spawners increased from 3 to 7%. The latter observation is most evident in females and likely due to decreased marine exploitation. Female repeat spawners tended to be less catchable than males by anglers. Depending on the time period analyzed, marine growth rate during the first year at sea was both positively and negatively associated with sea surface temperature. Zooplankton biomass was positively associated with growth, while salmon lice infestation intensity was negatively associated with growth. Collectively, these results are likely to be linked with both changes in oceanic conditions and harvest regimes. Our conflicting results regarding the influence of sea surface temperature on marine growth are likely to be caused by long‐term increases in temperature, which may have triggered (or coincided with) ecosystem shifts creating generally poorer growth conditions over time, but within shorter datasets warmer years gave generally higher growth. We encourage management authorities to expand the use of permanently monitored reference rivers with complete trapping facilities, like the river Etneelva, generating valuable long‐term data for future analyses. |
| first_indexed | 2024-04-10T15:03:19Z |
| format | Article |
| id | doaj.art-a2a2be9479b041f7b763fb073a370b4b |
| institution | Directory Open Access Journal |
| issn | 2045-7758 |
| language | English |
| last_indexed | 2024-04-10T15:03:19Z |
| publishDate | 2022-04-01 |
| publisher | Wiley |
| record_format | Article |
| series | Ecology and Evolution |
| spelling | doaj.art-a2a2be9479b041f7b763fb073a370b4b2023-02-15T09:01:28ZengWileyEcology and Evolution2045-77582022-04-01124n/an/a10.1002/ece3.8780Time series covering up to four decades reveals major changes and drivers of marine growth and proportion of repeat spawners in an Atlantic salmon populationAlison Harvey0Øystein Skaala1Reidar Borgstrøm2Per Tommy Fjeldheim3Kaja Christine Andersen4Kjell Rong Utne5Ingrid Askeland Johnsen6Peder Fiske7Synne Winterthun8Sofie Knutar9Harald Sægrov10Kurt Urdal11Kevin Alan Glover12Institute of Marine Research Bergen NorwayInstitute of Marine Research Bergen NorwayFaculty of Environmental Sciences and Natural Resource Management Ås NorwayInstitute of Marine Research Bergen NorwayInstitute of Marine Research Bergen NorwayInstitute of Marine Research Bergen NorwayInstitute of Marine Research Bergen NorwayNorwegian Institute for Nature Research Trondheim NorwayInstitute of Marine Research Bergen NorwayInstitute of Marine Research Bergen NorwayRådgivende Biologer Bergen NorwayRådgivende Biologer Bergen NorwayInstitute of Marine Research Bergen NorwayAbstract Wild Atlantic salmon populations have declined in many regions and are affected by diverse natural and anthropogenic factors. To facilitate management guidelines, precise knowledge of mechanisms driving population changes in demographics and life history traits is needed. Our analyses were conducted on (a) age and growth data from scales of salmon caught by angling in the river Etneelva, Norway, covering smolt year classes from 1980 to 2018, (b) extensive sampling of the whole spawning run in the fish trap from 2013 onwards, and (c) time series of sea surface temperature, zooplankton biomass, and salmon lice infestation intensity. Marine growth during the first year at sea displayed a distinct stepwise decline across the four decades. Simultaneously, the population shifted from predominantly 1SW to 2SW salmon, and the proportion of repeat spawners increased from 3 to 7%. The latter observation is most evident in females and likely due to decreased marine exploitation. Female repeat spawners tended to be less catchable than males by anglers. Depending on the time period analyzed, marine growth rate during the first year at sea was both positively and negatively associated with sea surface temperature. Zooplankton biomass was positively associated with growth, while salmon lice infestation intensity was negatively associated with growth. Collectively, these results are likely to be linked with both changes in oceanic conditions and harvest regimes. Our conflicting results regarding the influence of sea surface temperature on marine growth are likely to be caused by long‐term increases in temperature, which may have triggered (or coincided with) ecosystem shifts creating generally poorer growth conditions over time, but within shorter datasets warmer years gave generally higher growth. We encourage management authorities to expand the use of permanently monitored reference rivers with complete trapping facilities, like the river Etneelva, generating valuable long‐term data for future analyses.https://doi.org/10.1002/ece3.8780Atlantic salmonmarine growthsalmon licesea temperatureveteran spawnerszooplankton |
| spellingShingle | Alison Harvey Øystein Skaala Reidar Borgstrøm Per Tommy Fjeldheim Kaja Christine Andersen Kjell Rong Utne Ingrid Askeland Johnsen Peder Fiske Synne Winterthun Sofie Knutar Harald Sægrov Kurt Urdal Kevin Alan Glover Time series covering up to four decades reveals major changes and drivers of marine growth and proportion of repeat spawners in an Atlantic salmon population Ecology and Evolution Atlantic salmon marine growth salmon lice sea temperature veteran spawners zooplankton |
| title | Time series covering up to four decades reveals major changes and drivers of marine growth and proportion of repeat spawners in an Atlantic salmon population |
| title_full | Time series covering up to four decades reveals major changes and drivers of marine growth and proportion of repeat spawners in an Atlantic salmon population |
| title_fullStr | Time series covering up to four decades reveals major changes and drivers of marine growth and proportion of repeat spawners in an Atlantic salmon population |
| title_full_unstemmed | Time series covering up to four decades reveals major changes and drivers of marine growth and proportion of repeat spawners in an Atlantic salmon population |
| title_short | Time series covering up to four decades reveals major changes and drivers of marine growth and proportion of repeat spawners in an Atlantic salmon population |
| title_sort | time series covering up to four decades reveals major changes and drivers of marine growth and proportion of repeat spawners in an atlantic salmon population |
| topic | Atlantic salmon marine growth salmon lice sea temperature veteran spawners zooplankton |
| url | https://doi.org/10.1002/ece3.8780 |
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