Interpopulation variation in thermal physiology among seasonal runs of Chinook salmon

Abstract

Conservation of species facing environmental change requires an understanding of interpopulation physiological variation. However, physiological data is often scarce and therefore pooled across populations and species, erasing potentially important variability between populations. Interpopulation variation in thermal physiology has been observed within the Salmonidae family, although it has not been associated with seasonally distinct migratory phenotypes (i.e., seasonal runs). To resolve whether thermal physiology is associated with life-history strategy we acclimated four Sacramento River juvenile Chinook salmon populations (Coleman fall-run, Feather River fall- and spring-run and Sacramento River Winter-run) exhibiting different seasonal migratory phenotypes (fall-, spring- and winter-run), at 11, 16 and 20°C and assessed variation in growth rate, critical thermal maxima and temperature-dependent metabolic traits. We identified population differences in the physiological parameters measured and found compelling evidence that the critically endangered and endemic Sacramento River winter-run Chinook population exhibits thermal physiology associated with its early-migration life-history strategy. Acclimation to warm temperatures limited the growth and metabolic capacity of winter-run Chinook salmon, highlighting the risk of future environmental warming to this endemic population.

Local Thermal Adaptation occurs via Modulation of Mitochondrial Activity in Chinook Salmon

“…Notably, the thermal optima (T opt ) for AAS varied from 17.9°C in AK fish to as high as 24.6°C in the WA fish (Figure 1a). The WA population was particularly notable as the predicted T opt of 24.5°C is well above the T opt usually observed in this species (Poletto et al, 2017; Zillig, Lusardi, et al, 2023), which may reflect adaption to the thermally challenging stream in which this population spawns, where summer temperatures commonly exceed 26°C (Small et al, 2011) similar to the summer temperatures seen at the extreme southern end of this species range (Zillig, FitzGerald, et al, 2023).…”

“…These iconic fish are essential to the culture, food security and economy of the North Pacific, and are threatened across their range, with rising stream temperatures highlighted as a major contributor to this decline (Crozier et al, 2021). The vulnerability of Pacific salmon to high temperature stems from their anadromous life history, which promotes local adaption of reproductively isolated populations to historical streams conditions as a result of their return to natal streams to spawn (Eliason et al, 2011; Farrell et al, 2008; Zillig, FitzGerald, et al, 2023). As cold-water species, even modest increases in temperature can have severe consequences on population viability by reducing cardio-respiratory performance, which has been widely suggested to constrain thermal tolerance in salmonids (Clark et al, 2008) (Eliason et al, 2013), however the mechanistic basis of this vulnerability is an open question.…”

Fish Blood Response to Ash-Induced Environmental Alkalinization, and their Implications to Wildfire-Scarred Watersheds

“…To rapidly address the acute acid-base challenge, salmon appeared to have released glucose from glycogen stores and upregulated anaerobic respiration. However, the strategy appears to be temperature specific: salmon in the 20°C treatment have a lower aerobic scope than their 15°C counterparts (Zillig et al, 2023), so they may have 1) hastened their release of glucose from glycogen stores and 2) upregulated metabolic proton production (as evident by plasma lactate build-up (Robergs et al, 2004) to aid in rapid recovery of pHe. In contrast, salmon in the 15°C treatment did not significantly upregulate their glucose until 24 hours of exposure, and lactate levels were consistently about half those in fish at the warmer temperature.…”

Population variability in thermal performance of pre-spawning adult Chinook salmon

“…Our findings indicate that migration history (temperature and physical challenges) plays an important role in population thermal performance and physiological capacities. Intraspecific variability is not uncommon in other salmonids ( Lee et al, 2003b ; Eliason et al, 2011 ; Chen et al, 2013 , 2015 , 2018 ; Stitt et al, 2014 ; Verhille et al, 2016 ; Whitney et al, 2016 ; Poletto et al, 2017 ; Abe et al, 2019 ; Anttila et al, 2019 ; Zillig et al, 2021 ; Anlauf-Dunn et al, 2022 ; Zillig et al, 2022 ) and in other fish species such as killifish and Atlantic cod ( Fangue et al, 2006 ; Lucassen et al, 2006 ). Our findings complement previous work in adult sockeye salmon and egg/embryo Chinook salmon from coastal vs .…”