Rising air and water temperatures caused by human-induced climate change can prove deadly for some species of fish. When temperatures get too high, past where many species can tolerate, the fish that cannot adjust to the warmer temperatures will die. High water temperatures means less available oxygen for fish to be able to breathe. Many fish species can temporarily adjust their lifestyles by reducing activity which allows them to consume less oxygen. However, this is only a short-term solution. Many species like the Atlantic Salmon have very active lifestyles and need to use a lot of energy to find food, mate and lay eggs. Higher temperatures can also reduce the chance of survival for fish eggs laid during spawning season. One of the questions I asked myself is “What can be done to help fish species that are sensitive to warmer temperatures?” Fish water-conditioning may be an answer!
Kathryn Smith and her colleagues from Dalhousie University in Halifax, Canada, pumped naturally cooled groundwater into the Wrights River in Nova Scotia in an attempt to provide reprieve from the warming waters to the native Atlantic Salmon. She said that they saw salmon in varying life stages congregating in the cold plumes this cooled water created.
Smith and her colleagues also tried a pump-less method by rerouting some of the water from the river to cool in a ground trench before returning to the river. This method they said only cooled the water a few degrees Celsius, however, fish were still seen throughout the summer sheltering in the colder water. Creating safe havens for these fish species to stay cool and literally breathe a sigh of relief is only a first step to helping fish survive in a climate warming world. Large areas, especially sensitive breeding areas, will need to be cooled to make the environments these fish are living in comfortable enough so that they can resume normal activity.
Image US Fish and Wildlife Service: Atlantic Salmon (Salmo salar)
Source: Ogasa N (2023) Pumping cold water into rivers could as as ‘air conditioning’ for fish. Science News. https://www.sciencenews.org/article/cold-water-river-salmon-fish-climate