http://digital.csic.es/bitstream/10261/44729/1/Taranger%20et%20al_%2c%20GCE.pdf

Control of puberty in farmed fish

Polyploid fish and shellfish: Production, biology and applications to aquaculture for performance improvement and genetic containment

Here we critically review the scale and extent of adaptive genetic variation in Atlantic salmon (Salmo salar L.), an important model system in evolutionary and conservation biology that provides fundamental insights into population persistence, adaptive response and the effects of anthropogenic change. We consider the process of adaptation as the end product of natural selection, one that can best be viewed as the degree of matching between phenotype and environment. We recognise three potential sources of adaptive variation: heritable variation in phenotypic traits related to fitness, variation at the molecular level in genes influenced by selection, and variation in the way genes interact with the environment to produce phenotypes of varying plasticity. Of all phenotypic traits examined, variation in body size (or in correlated characters such as growth rates, age of seaward migration or age at sexual maturity) generally shows the highest heritability, as well as a strong effect on fitness. Thus, body size in Atlantic salmon tends to be positively correlated with freshwater and marine survival, as well as with fecundity, egg size, reproductive success, and offspring survival. By contrast, the fitness implications of variation in behavioural traits such as aggression, sheltering behaviour, or timing of migration are largely unknown. The adaptive significance of molecular variation in salmonids is also scant and largely circumstantial, despite extensive molecular screening on these species. Adaptive variation can result in local adaptations (LA) when, among other necessary conditions, populations live in patchy environments, exchange few or no migrants, and are subjected to differential selective pressures. Evidence for LA in Atlantic salmon is indirect and comes mostly from ecological correlates in fitness-related traits, the failure of many translocations, the poor performance of domesticated stocks, results of a few common-garden experiments (where different populations were raised in a common environment in an attempt to dissociate heritable from environmentally induced phenotypic variation), and the pattern of inherited resistance to some parasites and diseases. Genotype x environment interactions occurr for many fitness traits, suggesting that LA might be important. However, the scale and extent of adaptive variation remains poorly understood and probably varies, depending on habitat heterogeneity, environmental stability and the relative roles of selection and drift. As maladaptation often results from phenotype-environment mismatch, we argue that acting as if populations are not locally adapted carries a much greater risk of mismanagement than acting under the assumption for local adaptations when there are none. As such, an evolutionary approach to salmon conservation is required, aimed at maintaining the conditions necessary for natural selection to operate most efficiently and unhindered. This may require minimising alterations to native genotypes and habitats to which populations have likely become adapted, but also allowing for population size to reach or extend beyond carrying capacity to encourage competition and other sources of natural mortality.

A critical review of adaptive genetic variation in Atlantic salmon: implications for conservation

Induced triploidy is widely accepted as the most effective method for producing sterile fish for aquaculture and fisheries management. Artificially produced triploids generally differ from conspecific diploids in three fundamental ways: they are more heterozygous, they have larger but fewer cells in most tissues and organs, and their gonadal development is disrupted to some extent. Despite these basic biological differences, triploids are similar in most respects to diploids when examined at the whole animal level. The only clear differences relate to the effects of impaired gametogenesis on the reproductive physiology and behavior of triploids, especially in females. Other apparent differences include reduced aggressiveness, occasional specific morphological abnormalities, and inferior performance when reared under suboptimal conditions. The causes of these latter two problems are poorly understood but must be addressed if triploids are to be used more extensively.

The Physiology and Behavior of Triploid Fishes

Today, over 94% of all adult Atlantic salmon (Salmo salar) are in the aquaculture niche and wild numbers continue to decline while aquaculture numbers increase. The developmental and evolutionary forces in the aquaculture or "domestic" niche are so unlike those in the wild niche that two distinct biologies are being created from the original Atlantic salmon species. We may now need to recognize a new biological entity — Salmo domesticus — and treat it as an "exotic" when it escapes into the wild. Escapement therefore raises important concerns about ecological and genetic impacts, both within and outside the native range of Salmo salar. This paper explains why escaped domestic Atlantic salmon have had an impact on wild Atlantic salmon populations and now threaten Pacific salmonids as well. A polarization of views between aquaculturists and environmentalists will not resolve the problems. The three interest groups in fisheries — aquaculture, biodiversity, and capture — must begin to work together if we are to take up the challenge of preserving biodiversity and if aquaculturists, who hold the future of Atlantic salmon in their hands, can be expected to willingly prevent further impacts from their industry. Resume : Aujourd'hui, 94 % des saumons de l'Atlantique (Salmo salar) adultes sont issus de l'aquaculture, et les effectifs de saumons sauvages continuent de decroitre tandis que les effectifs provenant de l'aquaculture augmentent. Les forces agissant sur le developpement et l'evolution des saumons d'aquaculture, ou des saumons « domestiques », sont si differentes de celles agissant sur les saumons sauvages que deux biologies distinctes se sont formees a partir du saumon atlantique d'origine. Nous pouvons aujourd'hui considerer une nouvelle entite biologique — Salmo domesticus — et la traiter comme une entite exotique quand elle s'echappe dans le milieu naturel. Le fait que des saumons d'aquaculture s'echappent dans le milieu naturel souleve des inquietudes importantes au chapitre des impacts ecologiques et genetiques tant a l'interieur qu'a l'exterieur de l'aire de repartition naturelle de Salmo salar. Le present article explique pourquoi les saumons atlantiques domestiques evades ont eu un impact sur les populations sauvages de l'espece et menacent maintenant aussi les salmonides du Pacifique. Les problemes ne trouveront pas de solution dans une polarisation des positions des aquaculteurs et des environnementalistes. Les trois groupes d'interets du secteur des peches — les aquaculteurs, les personnes qui se preoccupent de la biodiversite, et les pecheurs — doivent commencer a collaborer si nous voulons reussir a preserver la biodiversite et si nous voulons faire en sorte que les aquaculteurs, qui ont l'avenir du saumon atlantique en leur pouvoir, en arrivent a freiner volontairement les impacts de leur industrie. (Traduit par la Redaction) Gross 144

G.W. Friars

Papers

Freshwater performance of triploid Atlantic salmon (Salmo salar) in New Brunswick aquaculture

Effects of winter temperature and feeding regime on the rate of early maturation in Atlantic salmon (Salmo salar) male parr

Applications of selection for multiple traits in cage-reared Atlantic salmon (Salmo salar)

Correlated responses to selection for grilse length in Atlantic salmon