A review of the likely effects of climate change on anadromous Atlantic salmonSalmo salarand brown troutSalmo trutta, with particular reference to water temperature and flow

Abstract

The present paper reviews the effects of water temperature and flow on migrations, embryonic development, hatching, emergence, growth and life-history traits in light of the ongoing climate change with emphasis on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta. The expected climate change in the Atlantic is for milder and wetter winters, with more precipitation falling as rain and less as snow, decrease in ice-covered periods and frequent periods with extreme weather. Overall, thermal limits for salmonids are species specific. Scope for activity and growth and optimal temperature for growth increase with temperature to an optimal point before constrain by the oxygen content of the water. The optimal temperature for growth decreases with increasing fish size and varies little among populations within species, whereas the growth efficiency may be locally adapted to the temperature conditions of the home stream during the growth season. Indirectly, temperature influences age and size at smolting through its effect on growth. Time of spawning, egg hatching and emergence of the larvae vary with temperature and selective effects on time of first feeding. Traits such as age at first maturity, longevity and fecundity decrease with increasing temperature whilst egg size increases with temperature. Water flow influences the accessibility of rivers for returning adults and speed of both upstream and downstream migration. Extremes in water flow and temperature can decrease recruitment and survival. There is reason to expect a northward movement of the thermal niche of anadromous salmonids with decreased production and population extinction in the southern part of the distribution areas, migrations earlier in the season, later spawning, younger age at smolting and sexual maturity and increased disease susceptibility and mortality. Future research challenges are summarized at the end of the paper.

Genomic tools for new insights to variation, adaptation, and evolution in the salmonid fishes: a perspective for charr

“…The switch to anadromy seems to be partly genetic and partly triggered by environmental conditions and smoltification involves a suite of changes including osmo-regulatory changes to survive in salt water, revised foraging behaviour, and developmental rate (Aas-Hansen et al, 2005;Jonsson & Jonsson, 2009;Dodson et al, 2013). This process is fundamentally similar across species in Oncorhynchus, Salmo and Salvelinus (Dodson et al, 2013).…”

“…It is also very important from a conservation perspective because it involves how organisms interact and can manage their changing environments including dams, habitat degradation, and pollution (Aas-Hansen et al, 2005;Jonsson & Jonsson, 2009;Dodson et al, 2013). Therefore, probably the most intensive area of ecological genomics research on salmonids to date has focused on the genetic basis of this trait.…”

Effects of climate change on fish reproduction and early life history stages

“…With the caveats noted above, the implication is that any changes in thermal regime occasioned by climate change will have major consequences for fish reproduction, and that these effects will be exercised across all stages of the reproductive process (Graham and Harrod 2009;Jonsson and Jonsson 2009;Pankhurst and King 2010). The extent of these effects will be determined by a range of factors including specific physiological tolerances, capacity for acclimation and adaptation, scope for behavioural avoidance, capacity to extend or shift ranges, and the timing of thermal challenges with respect to the reproductive cycle.…”

Effects of high ambient temperature on fish sperm plasma membrane integrity and mitochondrial activity — A flow cytometric study

“…Their reproductive success -and as a consequence, their fitness to reach brooder age -can be influenced by the extreme temperature affecting the gametes (eggs and sperm) either in the nature or during artificial propagation, gamete collection and storage [18,24].…”