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Using nonlethal tissue biopsies, we investigated somatic energy, lipid composition, and condition in post-spawned Atlantic salmon (Salmo salar) (kelts, n = 69) returning to sea in the spring and explored contrasts as a function of previous migration and spawning history, length and sex. Using mark–recapture analysis, we also explored linkages between spawning history and probability of future repeat spawning. Lipid density was significantly higher in previously spawned individuals compared to first-time spawned fish and in females compared to males. Fatty acid composition differed significantly among spawning histories. Return rates to consecutive spawning the following year were consistent with spawning history-dependent differences in lipid density, as first-time spawned kelts had lower return rates compared to consecutive repeat spawned kelts. We suggest that spawning history related contrasts in nutritional state in post-spawned Atlantic salmon may be a carry-over effect of differences in the feeding habitat as affected by spawning-history-dependent migration strategies. Alternatively, it may represent an adaptive response to increased survival and recovery potential with age. [ABSTRACT FROM AUTHOR]

Atlantic salmon are facing population declines and loss of productivity within populations due to anthropogenic impact factors and reduced survival at sea. Biobanking is an increasingly used tool to conserve the genetic integrity and diversity of populations threatened by extirpation. The aim of the current article is to discuss the opportunities and challenges that increased use of cryopreservation brings to biobanking activities, using the Norwegian Gene Bank (NGB) for Atlantic salmon as a model system. The NGB was established in 1985 and involves a traditional living gene bank, as well as "frozen gene bank" where paternal germplasm is stored as cryopreserved sperm. Cryopreservation is a method where cells or tissues are frozen in liquid nitrogen to temperatures where all biological processes are paused, thus allowing the cells to remain viable after later warming/thawing to temperatures above 0°C. Cryopreservation is therefore used in long‐term preservation of genetic diversity and characteristics of wild populations. Until recently, implementation of large scale use of cryopreserved sperm in the live gene bank has been limited by a lack of protocols/capacity to preserve larger portions of sperms. More recent developments in cryopreservation methodologies, now enables preservation of samples sufficient for mass fertilization. Mass fertilization by cryopreserved sperm opens new opportunities to gene bank operations, including increased capacity to restore lost populations, mitigation of genetic changes in broodstock fish, as well as increased capacity at live gene bank facilities through the replacement of older males with frozen sperm. Knowledge demands regarding potential genetic damage to cryopreserved milt and potential epigenetic effects caused by the cryopreservation procedure should, however, be addressed. [ABSTRACT FROM AUTHOR]

Migratory behaviour may vary according to the life history and demographic attributes of fish and lead to the spatial segregation of distinct population segments during the non-breeding season. In adult Atlantic salmon, spawning history differences are associated with intra-population variation in marine movements, but the degree of connectivity in spatial resource use among and within maiden and repeat spawning salmon is not well understood. We analysed muscle fatty acids (FAs), δ13C and δ15N of Atlantic salmon returning to spawn, and found significant differences among spawning histories. Maiden and alternate repeat spawning Atlantic salmon were differentiated from consecutive repeat spawners by fatty acid biomarkers associated with distinct biogeographic regions of the Labrador Sea, consistent with differential migration and divergent feeding locations. The presence and pattern of feeding contrasts among spawning history groups were further supported by dorsal muscle δ15N, which covaried with FA compositional values and distinguished consecutive repeat spawners from the two other groups. Because the degree of connectivity among population segments affects the ecological factors faced by such groups, an improved understanding of differential migration is necessary to better predict potential population responses to environmental change. [ABSTRACT FROM AUTHOR]

Increasing conservation and animal-welfare concerns have driven the development of non-lethal sampling of fish populations, with the use of muscle tissue biopsies now being routinely applied as a sampling method in the wild. Crucial to the success of non-lethal sampling, however, is an evaluation of the short- and long-term consequences of the treatment and ultimately the determination of how these may affect organism mortality and other fitness-related traits. The current study evaluated the use of a dorsal muscle biopsies on post-spawned Atlantic salmon emigrating to sea and undertaking a 2-month long-feeding migration before returning to spawn. Using mark-recapture, return rates and growth were compared between fish that were biopsied and externally tagged, and a control group tagged only with external tags. The biopsy treatment showed no lasting effects on fish as estimated from the two key fitness-related parameters. Results, therefore, suggest the technique can be more widely applied to gather information on marine migrating Atlantic salmon and other anadromous fishes that can be intercepted as they descend and ascend rivers during seasonal migrations. Coupled with modern tagging technologies, the use of biopsies may facilitate an improved understanding of movement and its consequences in terms of feeding patterns and growth. [ABSTRACT FROM AUTHOR]

Owing to the iteroparous nature of Atlantic salmon (Salmo salar), a seaward migrating cohort may consist of juveniles and adults that differ in size, maturity, experience, and in the motivation and consequences of migratory movements. Few studies have investigated the role of ontogeny in shaping intrapopulation variability in movement patterns among Atlantic salmon monitored under the same environmental conditions. This study contrasted the movements of smolts and kelts in two Canadian (Newfoundland) populations from marine entry through coastal embayments and quantified the influence of local water temperatures on movement patterns. Significant differences in migration routes, migration speed, and diel movements between smolts and kelts were present. Kelts generally displayed faster, more directed, and less nocturnal movements compared with smolts. Temperature influenced seaward movement positively, as well as the degree of diurnal movement. Prolonged nearshore residency by smolts and kelts in the two embayments was accompanied by a considerable improvement in ocean thermal conditions, hypothesized to promote open ocean entry during conditions favorable to migration performance. [ABSTRACT FROM AUTHOR]

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