Aquatic Nomads: The Life and Migrations of the Atlantic Salmon

Thorstad, Eva B.; Whoriskey, Fred; Rikardsen, Audun H.; Aarestrup, Kim

doi:10.1002/9781444327755.ch1

Cited by 113 publications

(173 citation statements)

References 129 publications

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“…Atlantic salmon (Salmo salar L.) is an anadromous species distributed across the North Atlantic Ocean, with both juveniles and post-spawned adults undertaking long-distance ocean feeding migrations [1]. Throughout their distribution range, many Atlantic salmon populations have experienced substantial declines [2,3].…”

Section: Introductionmentioning

confidence: 99%

Revealing the full ocean migration of individual Atlantic salmon

et al. 2018

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Background: Knowledge of the complete horizontal migration and vertical movements of Atlantic salmon (Salmo salar L.) during the marine phase is important for understanding the link between individual processes and population recruitment. We studied the detailed migration behaviour of six post-spawned adult Atlantic salmon from a North Norwegian river, during the entire ocean migration, by using high-resolution light-based geolocation archival tags. Results:The fish performed long-distance migrations and utilized Arctic areas from the eastern Barents Sea, to areas of Jan Mayen Island, and north to Svalbard. Four of six individuals exhibited a strong fidelity towards Jan Mayen Island, particularly during winter, which may suggest that the ecological conditions in these waters may be important for overwintering. One fish displayed exclusive utilization of the Barents Sea, indicating that growth and survival of some individuals are entirely dependent on these waters. The fish displayed a pelagic behaviour and all individuals spent more than 83% of the time in the uppermost 10 m of the water column. There was a strong seasonal trend in diving intensity, with the number of dives increasing with day length, independent of individuals' spatial distribution. Diving depth was positively correlated with the depth of the mixed layer. Conclusions:The Atlantic salmon displayed large individual variation in horizontal migrations, utilizing different ocean areas north of the Arctic Circle. This means that, despite the overall fidelity towards northern latitudes, individuals from the same population may experience highly different ecological conditions, potentially contributing to within-population variation in growth and survival. The seasonal correlation between diving intensity and day length, and spatial correlation between diving depth and depth of the mixed layer, indicate that the overall depth use of the Atlantic salmon depends on both spatially independent seasonal factors, and dynamic oceanographic conditions that facilitate food aggregations. This is the first study of Atlantic salmon to present detailed information about individuals' continuous horizontal migration and simultaneous vertical movements during the entire ocean migration, thus providing novel information on how habitat use change throughout the ocean residency.

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Section: Introductionmentioning

confidence: 99%

Revealing the full ocean migration of individual Atlantic salmon

et al. 2018

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“…Atlantic salmon feed in the open ocean and traverse coastal areas relatively quickly during the outward migration in the spring (Thorstad et al 2011). The rate of transit of returning adult salmon through coastal waters also is typically rapid (e.g.…”

Section: Salmon Lice Levels In Samples Of Wild Sea Troutmentioning

confidence: 99%

Effects of salmon lice Lepeophtheirus salmonis on wild sea trout Salmo trutta—a literature review

Thorstad¹,

Todd²,

Uglem³

et al. 2015

Aquacult. Environ. Interact.

121

142

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Salmon farming increases the abundance of salmon lice, which are ectoparasites of salmonids in the sea. Here we review the current knowledge on the effects of salmon lice on wild sea trout. Salmon lice feed on host mucus, skin and muscle, and infestation may induce osmoregulatory dysfunction, physiological stress, anaemia, reduced feeding and growth, increased susceptibility to secondary infections, reduced disease resistance and ultimately mortality of individual sea trout. Wild sea trout in farm-free areas generally show low lice levels. In farm-intensive areas, lice levels on wild sea trout are typically higher, and more variable than in farm-free areas. Lice on wild sea trout are found at elevated levels particularly within 30 km of the nearest farms but can also extend to further ranges. Salmon lice in intensively farmed areas have negatively impacted wild sea trout populations by reducing growth and increasing marine mortality. Quantification of these impacts remains a challenge, although population-level effects have been quantified in Atlantic salmon by comparing the survival of chemically protected fish with control groups, which are relevant also for sea trout. Mortality attributable to salmon lice can lead to an average of 12−29% fewer salmon spawners. Reduced growth and increased mortality will reduce the benefits of marine migration for sea trout, and may also result in selection against anadromy in areas with high lice levels. Salmon lice-induced effects on sea trout populations may also extend to altered genetic composition and reduced diversity, and possibly to the local loss of sea trout, and establishment of exclusively freshwater resident populations.

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“…Anadromous salmon from a single cohort can have variation of several years in both time spent in the river as juveniles and as adult in the ocean [9]. This means that for salmon tagged as juveniles, correction of survival estimates requires knowledge on temporal patterns in tag retention rates.…”

Section: Open Accessmentioning

confidence: 99%

Long-term PIT tag retention rates in Atlantic salmon (Salmo salar)

Foldvik

Kvingedal

2018

Anim Biotelemetry

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Background: Passive integrated transponder (PIT) tags are widely used in studies of various aspects of fish survival, movement and behaviour. Quality of such studies depends on the fish retaining the tags over the study period and that the tagging procedure or the tag does not influence behaviour or survival. Here we document PIT tag retention rates in hatchery-reared Atlantic salmon over a 533-day period from the late juvenile freshwater stage (pre-smolts) to young adults after 1 year in seawater. Fish were marked with 12-mm PIT tags, injected into their body cavity, as age 1+ pre-smolt and scanned for presence of PIT tags five times during the study.Results: Tag retention for the entire period was 91% and varied between periods (96.09-99.89%). For individual time steps, daily retention rate was lowest in the first period following tagging (days 0-49). After this period retention rate increased substantially, before again dropping close to initial levels at the two last periods (days 173-533). Length of fish was only significantly related to retention during the first period. No difference in retention rates was found between males and females. A subset of fish without detected tags was X-rayed to verify that lack of PIT detection was due to tag loss. Conclusion:The retention rates observed in this study clearly show that tag loss needs to be accounted for when analysing PIT tag data on Atlantic salmon. Further, the temporal changes in retention rate clearly challenge previous assertions that tag loss is something that primarily occurs shortly after tagging or during spawning.

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Aquatic Nomads: The Life and Migrations of the Atlantic Salmon

Cited by 113 publications

References 129 publications

Revealing the full ocean migration of individual Atlantic salmon

Revealing the full ocean migration of individual Atlantic salmon

Effects of salmon lice Lepeophtheirus salmonis on wild sea trout Salmo trutta—a literature review

Long-term PIT tag retention rates in Atlantic salmon (Salmo salar)

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