The effects of nutritional state, sex and body size on the marine migration behaviour of sea trout

Eldøy, Sindre Håvarstein; Bordeleau, Xavier; Lawrence, Michael; Thorstad, Eva B.; Finstad, Anders G.; Whoriskey, Fred; Crossin, Glenn T.; Cooke, Steven J.; Aarestrup, Kim; Rønning, Lars; Sjursen, Aslak Darre; Davidsen, Jan Grimsrud

doi:10.3354/meps13670

Cited by 20 publications

(17 citation statements)

References 66 publications

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“…In general, the tagged individuals remained close to their presumed home river during the marine feeding migration. The restricted migratory distances observed here (< 7 km) were much smaller than observed in other tracking studies of brown trout (typically 15–30 km) in marine fjord habitats 24 , 25 , 27 , 28 . Brown trout generally remain in near-coastal areas during their seaward migrations, close to their river of origin (< 80 km), and on the Patagonian Continental Shelf, brown trout have never been reported in the catch record further than 50 km from their rivers of origin 65 .…”

Section: Discussioncontrasting

confidence: 73%

“…While marine migrations are risky, energetic demands driven by the costs of reproduction and growth may determine whether or not a fish moves to sea. It has been shown that individual brown trout, particularly females with low somatic energy stores in spring-time, will migrate further away from the home watercourse to search for prey and facilitate nutritional and somatic re-conditioning 27 , 28 , 74 . Therefore, it might be predicted that these far-ranging individuals are more likely to encounter and explore new freshwater habitats.…”

Section: Discussionmentioning

confidence: 99%

“…Based on previous studies, it has been shown that brown trout are variable in their use of estuaries. Some brown trout remain in the estuary 24 , 28 , 81 , 82 throughout the feeding season, while others move more quickly through the transition zone and into marine waters 24 , 28 , 79 .…”

Section: Discussionmentioning

confidence: 99%

“…As an anadromous, iteroparous species, the ability of brown trout to make more than one sea feeding migration may be condition-dependent 25 , 28 . Factors such as individual body length, sex, and nutritional state are known to influence the spatiotemporal aspects of marine habitat use 27 .…”

Section: Introductionmentioning

confidence: 99%

“…For example, in Norwegian populations, larger, nutritionally depleted individuals, especially females, tend to migrate furthest from their home watercourses. This is probably because more distant pelagic areas offer individuals greater foraging opportunities, which can offset the costs of reproduction to somatic body condition and increase future growth, fecundity, and fitness 25 , 27 , 28 .…”

Section: Introductionmentioning

confidence: 99%

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Marine habitat use and feeding ecology of introduced anadromous brown trout at the colonization front of the sub-Antarctic Kerguelen archipelago

Davidsen

Bordeleau

Eldøy

et al. 2021

Sci Rep

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In 1954, brown trout were introduced to the Kerguelen archipelago (49°S, 70°E), a pristine, sub-Antarctic environment previously devoid of native freshwater fishes. Trout began spreading rapidly via coastal waters to colonize adjacent watersheds, however, recent and unexpectedly the spread has slowed. To better understand the ecology of the brown trout here, and why their expansion has slowed, we documented the marine habitat use, foraging ecology, and environmental conditions experienced over one year by 50 acoustically tagged individuals at the colonization front. Trout mainly utilized the marine habitat proximate to their tagging site, ranging no further than 7 km and not entering any uncolonized watersheds. Nutritional indicators showed that trout were in good condition at the time of tagging. Stomach contents and isotope signatures in muscle of additional trout revealed a diet of amphipods (68%), fish (23%), isopods (6%), and zooplankton (6%). The small migration distances observed, presence of suitable habitat, and rich local foraging opportunities suggest that trout can achieve their resource needs close to their home rivers. This may explain why the expansion of brown trout at Kerguelen has slowed.

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Section: Discussioncontrasting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Marine habitat use and feeding ecology of introduced anadromous brown trout at the colonization front of the sub-Antarctic Kerguelen archipelago

Davidsen

Bordeleau

Eldøy

et al. 2021

Sci Rep

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Genomic dynamics of brown trout populations released to a novel environment

Kurland

Rafati

Ryman

et al. 2022

Ecology and Evolution

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Population translocations occur for a variety of reasons, from displacement due to climate change to human-induced transfers. Such actions have adverse effects on genetic variation and understanding their microevolutionary consequences requires monitoring. Here, we return to an experimental release of brown trout (Salmo trutta) in order to monitor the genomic effects of population translocations. In 1979, fish from each of two genetically (F ST = 0.16) and ecologically separate populations were simultaneously released, at one point in time, to a lake system previously void of brown trout. Here, whole-genome sequencing of pooled DNA (Pool-seq) is used to characterize diversity within and divergence between the introduced populations and fish inhabiting two lakes downstream of the release sites, sampled 30 years later (c. 5 generations). Present results suggest that while extensive hybridization has occurred, the two introduced populations are unequally represented in the lakes downstream of the release sites. One population, which is ecologically resident in its original habitat, mainly contributes to the lake closest to the release site. The other population, migratory in its natal habitat, is genetically more represented in the lake further downstream. Genomic regions putatively under directional selection in the new habitat are identified, where allele frequencies in both established populations are more similar to the introduced population stemming from a resident population than the migratory one. Results suggest that the microevolutionary consequences of population translocations, for example, hybridization and adaptation, can be rapid and that Pool-seq can be used as an initial tool to monitor genome-wide effects.

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Individual patterns of anadromy determine the cost of salmon lice exposure in brown trout

Hawley,

Urke,

Kristensen

et al. 2024

Ecosphere

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Facultative anadromous salmonids may alter migratory behavior to mitigate against detrimental infections of aquaculture‐derived salmon lice (Lepeophtheirus salmonis); however, this likely incurs negative growth and fitness consequences. This flexibility in migratory behavior also creates analytical challenges in estimating lice infestation levels and the consequences of exposure. We utilized simulated individual migration trajectories of facultatively anadromous brown trout (Salmo trutta) (N = 8049), generated from spatial‐temporal fjord‐use models fitted to empirical tracking data (N = 517). These trajectories were superimposed with open‐access spatial‐temporal modeled lice densities. Individual accumulated lice exposure and infestation were simulated over a 6‐month period for smolts and annually for veteran migrant life‐stages. The degree of lice‐induced mortality was estimated according to year (2013–2015), population (N = 5), and life‐stage of brown trout, within a semi‐enclosed fjord system (Sognefjorden, Norway). A gradient of lice was spatially distributed throughout the fjord. Highest densities were modeled in the outer‐fjord at a closer vicinity to aquaculture facilities. Accordingly, estimates of accumulated lice infestation were higher for individuals that underwent long‐distance migrations, residing for longer in the outer‐fjord, with limited differences observed between years. As most brown trout remained in the inner‐fjord, an area protected from aquaculture, individual accumulated levels of lice exposure and infestation were low, resulting in infestation estimates largely below critical‐mortality thresholds. The fraction of total mortality attributed to lice during sea‐sojourn was greater for long‐distance migrants (smolts: 25.3%; veteran migrants: 14.8%) versus those remaining within the inner‐fjord (smolts: 14.7%; veteran migrants: 1.7%). This resulted in an unequal contribution of lice to total mortality among populations (range: 3.3%–34.3%). Despite an equal distribution of lice exposure for all populations within the fjord, diverse mortality consequences among populations were estimated, largely resulting from individual selection of migration trajectory. Therefore, generic models of lice effects on facultative anadromous salmonids should be used with caution. Instead, the application of simulated migration trajectories to incorporate flexible behavior at the individual level is suggested. The findings indicate that Sognefjorden brown trout may have reduced their seaward migration extent to avoid direct mortality from salmon lice. This emphasizes the importance of monitoring and management actions to preserve selection for anadromy.

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The effects of nutritional state, sex and body size on the marine migration behaviour of sea trout

Cited by 20 publications

References 66 publications

Marine habitat use and feeding ecology of introduced anadromous brown trout at the colonization front of the sub-Antarctic Kerguelen archipelago

Marine habitat use and feeding ecology of introduced anadromous brown trout at the colonization front of the sub-Antarctic Kerguelen archipelago

Genomic dynamics of brown trout populations released to a novel environment

Individual patterns of anadromy determine the cost of salmon lice exposure in brown trout

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