We are seeing many species struggle with rising global temperatures amidst climate change. However, multiple studies have shown that the rainbow trout (Oncorhynchus mykiss) has an impressive ability to acclimate to these changes. The rainbow trout is a cool-water species native to the northern Pacific and its tributaries (National Park Service 2015).

Photo courtesy of the Ohio Department of Natural Resources.

A study by Adams et al. (2022) used a population of 3,000 hatchery trout to assess their thermal acclimation potential. The fish were separated into tanks and tested at a range of temperatures from 15-25 degrees Celsius. Despite being a cool-water species that prefers waters below 20 degrees Celsius, the results found that the fish were able to consistently acclimate to temperatures above 20 degrees.

Li et al. (2024) conducted a similar study by testing the mitochondria and livers of rainbow trout after acclimating them to warmer temperatures. They found that acclimation can greatly reduce liver damage and improve mitochondrial function when the trout are exposed to increased temperatures.

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Despite only being native to the Pacific, rainbow trout are stocked throughout the US and other countries as a valuable sport fish. Their ability to acclimate to a warming climate will be a useful tool for managing fish species in the future.

Sources:

Adams OA, Zhang Y, Gilbert MH, Lawrence CS, Snow M, Farrell AP (2022) An unusually high upper thermal acclimation potential for rainbow trout. Conservation Physiology 10(1).

Li H, Yu H, Zhang X, Huang W, Zhang C, Wang C, Gao Q, Dong S (2024) Temperature acclimation improves high temperature tolerance of rainbow trout (Oncorhynchus mykiss) by improving mitochondrial quality and inhibiting apoptosis in liver. Science of Total Environment 912.

Rainbow Trout. National Park Service. https://www.nps.gov/shen/learn/nature/rainbow-trout.htm

Rainbow Trout. Ohio Department of Natural Resources. https://ohiodnr.gov/discover-and-learn/animals/fish/rainbow-trout

The Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) is a fully-aquatic salamander species. They live in cool, fast, and highly-oxygenated streams in the Appalachian Mountains. Sadly, this species has been on the decline since the 1970’s, and climate change continues to pose threats against them (Virginia Department of Wildlife Resources).

A study by Terrell et al. (2021) analyzed the potential physiological affects of climate change on hellbenders. In a laboratory setting, growth rates and immune system functions were studied at a variety of temperatures to test Eastern Hellbenders ability to cope with climate change. It was found that both growth rate and immune function suffered at higher temperatures. Hellbender immune systems were found to be most susceptible at high and low temperatures. While global average temperatures are rising, it is also predicted that we will have lower minimum temperatures. Exposure to both higher and lower temperatures could cause problems for hellbender immune health. The salamanders experienced slower growth rates during warmer summer temperatures following the breeding season. This lack of growth after an energy-demanding reproduction phase, may lead to population struggles with warming temperatures.

Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis). Photo courtesy of the Virginia Department of Wildlife Resources.

Eastern Hellbenders are already threatened or endangered in many of the states they inhabit (Virginia Department of Wildlife Resources). With a changing climate, these animals will continue to struggle. Much effort and continued research is necessary if we wish to save the beloved hellbender.

References:

Eastern Hellender. Virginia Department of Wildlife Resources. https://dwr.virginia.gov/wildlife/information/eastern-hellbender/

Terrell KA, Quintero RP, Galicia VA, Bronikowski E, Evans M, Kleopfer JD, Murray S, Murphy JB, Nissen BD, Gratwicke B (2021) Physiological impacts of temperature variability and climate warming in hellbenders (Cryptobranchus alleganiensis). Conservation Physiology 9 (1). doi:10.1093/conphys/coab079