Maturation in Atlantic salmon (Salmo salar, Salmonidae): a synthesis of ecological, genetic, and molecular processes

Abstract

Over the past decades, Atlantic salmon (Salmo salar, Salmonidae) has emerged as a model system for sexual maturation research, owing to the high diversity of life history strategies, knowledge of trait genetic architecture, and their high economic value. The aim of this synthesis is to summarize the current state of knowledge concerning maturation in Atlantic salmon, outline knowledge gaps, and provide a roadmap for future work. We summarize the current state of knowledge: 1) maturation in Atlantic salmon takes place over the entire life cycle, starting as early as embryo development, 2) variation in the timing of maturation promotes diversity in life history strategies, 3) ecological and genetic factors influence maturation, 4) maturation processes are sex-specific and may have fitness consequences for each sex, 5) genomic studies have identified large-effect loci that influence maturation, 6) the brain-pituitary–gonadal axis regulates molecular and physiological processes of maturation, 7) maturation is a key component of fisheries, aquaculture, conservation, and management, and 8) climate change, fishing pressure, and other anthropogenic stressors likely have major effects on salmon maturation. In the future, maturation research should focus on a broader diversity of life history stages, including early embryonic development, the marine phase and return migration. We recommend studies combining ecological and genetic approaches will help disentangle the relative contributions of effects in different life history stages to maturation. Functional validation of large-effect loci should reveal how these genes influence maturation. Finally, continued research in maturation will improve our predictions concerning how salmon may adapt to fisheries, climate change, and other future challenges.

Strong regulatory effects of vgll3 genotype on reproductive axis gene expression in immature male Atlantic salmon

“…The age at which an individual reproduces, its age at maturity, is a critical time-point in an organism's life history as it affects fitness traits including survival, and reproductive success (Mobley et al, 2021). There is considerable variation in maturation age both within and among species, and maturation timing thus contributes to the remarkable variation observed in the life history strategies of organisms (Healy et al, 2019).…”

“…The age at which an individual reproduces, its age at maturity, is a critical time-point in an organism's life history as it affects fitness traits including survival, and reproductive success (Mobley et al, 2021). There is considerable variation in maturation age both within and among .…”

“…The copyright holder for this preprint this version posted August 8, 2021. ; https://doi.org/10.1101/2021.08.08.455548 doi: bioRxiv preprint species, and maturation timing thus contributes to the remarkable variation observed in the life history strategies of organisms (Healy et al, 2019). The process of maturation is influenced by both genetics and the environment, and includes changes in levels of sex hormones and behaviour (Varlinskaya et al, 2013), but the specific factors leading to variation in maturation timing are not well understood (Mobley et al, 2021).…”

Refining the genomic location of SNP variation affecting Atlantic salmon maturation timing at a key large-effect locus

“…Furthermore some (mostly) male individuals, known as mature parr, reach maturation in the freshwater environment without having migrated to sea. This age at maturity can vary both within and among populations, and contributes markedly to the diversity of life-history strategies of this species (Mobley et al 2021;Erkinaro et al 2019). Late maturation is associated with larger size, and therefore increased fecundity in females and greater reproductive success in males.…”

Environmental Factors and Genetic Diversity as Drivers of Early Gonadal Maturation: A Gonadosomatic Index Based Investigation on Indian Shad, Tenualosa ilisha Population of Bangladesh

“…However, interpretation on whether these variations are caused by different migratory patterns or is the cause of reciprocal migration is not yet understood. The genetic architecture of vertebrates, including fish, is a ubiquitous and potent caliber that shapes ovarian maturation, leading to defining the next generation (Barson et al, 2015;Mobley et al, 2021). It is well established that the gonadal maturation of migratory Atlantic Salmon is strongly influenced by genetic factors affecting the span of different life stages (Healy et al, 2019).…”