Body shape and fin size in juvenile Atlantic salmon (Salmo salar): effects of temperature during embryogenesis

Abstract

Temperature during egg incubation and early development influences later life stages of fishes, potentially influencing survival. Throughout its distribution, Atlantic salmon (Salmo salar Linnaeus, 1758) have experienced population declines, and in view of ongoing global warming, we tested if temperature during the earliest developmental stages modified body shape and fin size when temperatures averaged 2.6 vs. 5.6 °C. This temperature difference simulates increases predicted in climate change scenarios. Based on previous studies, we hypothesized that salmon originating from eggs subjected to cold incubation temperatures would have slimmer bodies and larger pectoral and dorsal fins than salmon from eggs that experienced warmer temperatures. After hatching, the juveniles were raised for 1 year under identical temperatures, after which we measured their body shape and fin areas. We found no support for our hypothesis regarding body shape. Indeed, we found the opposite, with cold-incubated salmon having deeper bodies than warm-incubated salmon. For fin size, the pectoral fins of cold-incubated salmon were larger than for warm-incubated salmon as predicted, but there was no difference in dorsal fin size. These results suggest that global warming may lead to altered body shape and fin size, possibly affecting swimming performance, and thus raise questions about the ecological consequences of the changes.

Egg incubation temperature influences the population‐specific outmigration rate of juvenile brown troutSalmo trutta

“…But this may not only result from differences in growth. Greenberg et al (2021) observed that 1-year-old juveniles of S. salar incubated as eggs in heated water had a slimmer, more smolt-like body shape than similar-sized S. salar offspring that were produced from colder eggs.…”

“…Greenberg et al . (2021) observed that 1‐year‐old juveniles of S. salar incubated as eggs in heated water had a slimmer, more smolt‐like body shape than similar‐sized S. salar offspring that were produced from colder eggs. This may suggest that the warm offspring were ready for migration younger and smaller than those incubated in colder water.…”

Differences in growth between offspring of anadromous and freshwater brown trout Salmo trutta

“…(2017) reported that the populations of R. temporaria from temporary pools had a higher degree of developmental plasticity than tadpoles of the same species from permanent pools. In contrast, juvenile S. salar incubated as eggs in warm water (7°C) were slimmer than conspecifics incubated in cold water (3°C) (Greenberg et al ., 2021), showing another difference between S. trutta and S. salar .…”

Identifying and conserving sympatric diversity in trout of the genus Salmo, with particular reference to Lough Melvin, Ireland

“…Morphometric and meristic characters can be substantially influenced by the environment resulting in phenotypic differences that don't reflect genetic differences (Etheridge et al, 2012). Morphometric characteristics such as body and fin shape, as well as meristic characters, including gill rakers, can be affected by the age of the individual as well as temperature and population density during early development (Campbell et al, 2021; Greenberg et al, 2021; Lindsey, 1981, 1988; Ross et al, 2006). Eurasian trout raised in an enriched hatchery environment differ in their colouration and spotting patterns from siblings reared in a conventional hatchery set up (Yaripour et al, 2020).…”