Nutritional correlates of the overwintering and seaward migratory decisions and long-term survival of post-spawning Atlantic salmon

Abstract Despite the importance of iteroparity (i.e. repeated spawning) for the viability of Atlantic salmon populations, little is known about the factors influencing the migratory behaviour and survival prospect of post-spawned individuals (kelts). To test the hypothesis that post-spawning nutritional condition underlies differences in spatiotemporal aspects of the habitat use and survival of migrating Atlantic salmon kelts, we physiologically sampled and acoustically tagged 25 individuals from the Middle River, Nova Scotia in autumn 2015. Kelts were subsequently tracked within their natal river during the winter months, and as far as 650 km away along known migration pathways towards the Labrador Sea and Greenland. Some kelts were detected nearly 2 years later, upon their return to the natal river for repeat spawning. Overall, kelts in poor or depleted post-spawning nutritional state (i.e. low body condition index or plasma triglyceride level): (i) initiated down-river migration earlier than higher condition kelts; (ii) experienced higher overwinter mortality in the natal river; (iii) tended to spend greater time in the estuary before moving to sea and (iv) did not progress as far in the marine environment, with a reduced probability of future, repeat spawning. Our findings suggest that initial differences in post-spawning condition are carried through subsequent migratory stages, which can ultimately affect repeat-spawning potential. These results point to the importance of lipid storage and mobilisation in Atlantic salmon kelts for mediating post-spawning migratory behaviour and survival.

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Minor shifts towards more natural conditions in captivity improve long-term survival among reintroduced Atlantic salmon

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2019-0201 ◽

2020 ◽

Vol 77 (5) ◽

pp. 931-942

Author(s):

Andrew B. Harbicht ◽

Dylan J. Fraser ◽

William R. Ardren

Keyword(s):

Atlantic Salmon ◽

Life Histories ◽

Thermal Conditions ◽

Cost Effective ◽

Growth Conditions ◽

Adult Survival ◽

Term Survival ◽

Long Term Survival ◽

Release Times

Elevating winter water temperatures is a common practice when rearing salmonids for supplementation or reintroduction. Doing so elevates developmental rates, producing larger juveniles with greater smolt-to-adult survival, but does not guarantee improved adult returns to stocked tributaries. To test whether more natural developmental conditions improve adult returns to stocked tributaries, three consecutive cohorts of yearling (age 1+) landlocked Atlantic salmon (Salmo salar) were released into two tributaries of Lake Champlain. Cohorts were reared under two winter thermal conditions (seasonal surface water and above-seasonal groundwater) and (or) two release times (early and normal). Relative to standard hatchery practices, modelled returns to experimental tributaries increased over replicate cohorts by 286% on average following exposure to seasonal rearing temperatures, but decreased by 89% on average when release dates were advanced. By utilizing cost-effective shifts towards hatchery rearing techniques that more closely resemble natural growth conditions, we demonstrate how hatchery programs may improve long-term survival and returns for fish species with complex life histories involved in supplementation and reintroduction programs.

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Ontogenetic Change in Behavioral Responses to Structural Enrichment From Fry to Parr in Juvenile Atlantic Salmon (Salmo salar L.)

Frontiers in Veterinary Science ◽

10.3389/fvets.2021.638888 ◽

2021 ◽

Vol 8 ◽

Author(s):

Ingeborg Bjerkvik Alnes ◽

Knut Helge Jensen ◽

Arne Skorping ◽

Anne Gro Vea Salvanes

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Animal Behavior ◽

Environmental Enrichment ◽

Control Treatment ◽

Term Survival ◽

Juvenile Atlantic Salmon ◽

In Captivity ◽

Positive Effect

Enrichment is widely used as a tool for studying how changes in environment affect animal behavior. Here, we report an experimental study investigating if behaviors shaped by stimuli from environmental enrichment depending on the stage animals are exposed to enrichment. We used juvenile Atlantic salmon (Salmo salar) in their first autumn. This is a species commonly reared for conservation purposes. Previous work has shown that environmental enrichment had no effect on long-term survival when the fry stage (smaller than 70 mm) was released, but that if late parr stages (larger than 70 mm) are released, enrichment is reported to have a positive effect on smolt migration survival. Here, we explored the effect of enrichment at two different stages of development. Both stages were reared and treated for 7 weeks (fry at 11–18 weeks and parr at 24–31 weeks after hatching) before tested for behavior. Responses known to be associated with exploratory behavior, activity, and stress coping were quantified by testing 18-week-old fry and 31-week-old parr in a six-chamber maze on 7 successive days after rearing in structurally enriched (plastic plants and tubes) or plain impoverished rearing environments. The data show that Atlantic salmon are sensitive to stimuli from structural enrichment when they are parr, but not when in the fry stage. Parr deprived of enrichment (control treatment) were reluctant to start exploring the maze, and when they did, they spent a longer time frozen than enriched parr, suggesting that deprivation of enrichment at this life can be stressful. Our data suggest that structural enrichment could have the potential to improve welfare for salmonids in captivity and for survival of released juvenile salmon if structural enrichment is provided at the parr stage and the fish reared for conservation are released at the parr stage.

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Caspases and apoptosis

Essays in Biochemistry ◽

10.1042/bse0380009 ◽

2002 ◽

Vol 38 ◽

pp. 9-19 ◽

Cited By ~ 121

Author(s):

Guy S Salvesen

Keyword(s):

Cysteine Proteases ◽

Signalling Pathways ◽

Term Survival ◽

Mature Adult ◽

Intracellular Signalling Pathways ◽

Adult Cell ◽

Caspase Family ◽

Cell Fragments ◽

Pro Inflammatory Cytokines

The ability of metazoan cells to undergo programmed cell death is vital to both the precise development and long-term survival of the mature adult. Cell deaths that result from engagement of this programme end in apoptosis, the ordered dismantling of the cell that results in its 'silent' demise, in which packaged cell fragments are removed by phagocytosis. This co-ordinated demise is mediated by members of a family of cysteine proteases known as caspases, whose activation follows characteristic apoptotic stimuli, and whose substrates include many proteins, the limited cleavage of which causes the characteristic morphology of apoptosis. In vertebrates, a subset of caspases has evolved to participate in the activation of pro-inflammatory cytokines, and thus members of the caspase family participate in one of two very distinct intracellular signalling pathways.

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