Strong effects of temperature, population and age-at-maturity genotype on maturation probability for Atlantic salmon in a common garden setting

Abstract

Age at maturity is a key life history trait and involves a trade-off between survival risk and reproductive investment, has close connections to fitness, and is an important factor for population structures. Temperature can have a dramatic influence on life history in ectotherms, but this influence may differ between populations. While an increasing number of studies have examined population-dependent reactions with temperature, few have investigated this in the context of maturation timing. Atlantic salmon is a highly relevant study species for improving understanding of this topic as it displays considerable variation in life-history strategies, including maturation timing. Additionally, a large amount of this variation in maturation timing has been associated with a genomic region including the strong candidate gene vgll3, but the effect of this gene in the context of different environments and populations has not been studied. Using a large-scale common-garden experiment, we find strong effects of temperature, population, and vgll3 genotype on maturation in 2-year-old male Atlantic salmon. Observed maturation probability was 4.8 times higher in individuals reared at a mean temperature of 8.6°C compared to 6.9°C. This temperature effect was population-specific and was higher in the southern population compared to the northern population, potentially due to a higher intrinsic growth in the southern population as well as growth-temperature interaction. The early-maturation vgll3*E associated with a significantly higher maturation probability, but there was no vgll3-interaction with temperature or population. Both body condition and body mass associated strongly with maturation; the body-condition association was stronger in fish carrying the vgll3*E allele, and the body mass association was only present in the warm treatment. Our findings demonstrate that the relative effect of vgll3 on maturation timing is similar for two populations and two thermal environments and gives new perspectives on the relative effect of vgll3 compared to such influences. Additionally, we show that populations can vary in their response to temperature change in terms of maturation timing, and that high intrinsic growth could potentially be associated with higher thermal sensitivity for life history variation.

Adipose tissue mitochondrial respiration in Atlantic salmon: implications for sex-dependent life-history variation

“…In our study, neither genotype nor mitochondrial respiration was associated with body condition of fish (analogous to BMI). A lack of vgll3 genotype effect on body condition in salmon was also found in the same cohort as our study fish earlier (29). However, these results do not contradict our hypothesis since body condition effects may be manifested at a different time or life-stage (20), or alternatively, was not observed due to low statistical power.…”

“…Samples of adipose tissue were collected from fish reared as part of another study during August-September 2020 and were approximately 2 years 8 months post hatch (average mass 1kg (Table 2)). Details of fish rearing, feeding, and temperatures are shown in (29) until Feb 2020 (in Feb-Aug 2020, conditions largely followed those in 2019). We collected samples from Neva population individuals from the high temperature treatment.…”

Temperature and dietary energy content influence female maturation age and egg nutritional content in Atlantic salmon

“…The two populations exhibited different rates of maturation with the females of the Neva population showing higher rates of maturation compared to the Oulu females. These population differences could, in part, be due to lower growth rate and smaller body size of the Oulu fish as has been observed for the males in this study population (Åsheim et al ., 2022). Although the body size of the Oulu fish overall was smaller compared to the Neva population, we did not find significant differences between the populations in the size of the females that matured.…”

“…In this study, these two populations will be referred to as the Neva and Oulu populations, respectively. Details of the populations, crossing design, and rearing are explained in Åsheim et al . (2022).…”

“…Each individual was marked with a 12 mm Passive Integrated Transponder (PIT) tag to allow for individual identification and a fin clip was taken for parentage and population assignment as done in Åsheim et al . (2022).…”