November 1, 2023
By Ali Groulx, Park Interpreter
Temperatures can create many different obstacles for living things. Humans must account for temperature when dressing themselves for the day. Some animals must adjust their hair growth for thicker coats in the winter. Specialized animals like amphibians must be able to freeze themselves to survive the cold temperatures, and reptiles like turtles need to adjust their body chemistry to survive long periods of time underwater. As the lakes freeze over, life under the ice gets a little slower, too. Fish who prefer temperate waters can rest or lightly bury themselves in the muck, using the sediment as a blanket to protect against the colder waters. The colder water does not slow down all fish, though. In Michigan, fish who prefer colder water emerge from the deep, dark depths and show themselves in full force. Historically, winter is a time of food scarcity for humans. For thousands of years, the Anishinaabe have continued to utilize ice fishing to feed communities during these times of scarcity. The shifting climate has made ice fishing increasingly difficult; recently our fresh waters have not frozen over until late in the winter season, which has impacted modern-day anglers whether they fish for sport or to sustain their families. For the Michiganders on land and the fish who thrive in the cold waters, this is not ideal. Monitoring fish behaviors and underwater ecosystems as we move forward is an important window into the affects of climate change within our fresh waters.
How do fish survive in the water during the winter, especially if it is frozen over? There are plenty of ways! Cold-blooded species’ internal temperatures are directly influenced by the temperature of their environments. Most fish gather in schools, or large groups, slowing down their metabolisms and sinking to deeper waters to rest. The lower depths provide waters that are denser, warmer, and more oxygenated, and the ice cover and snowpack above provides some insulation against the frigid wind. Alternatively, winter is the time for cold-water fish to shine. These fish have evolved mechanisms to account for the conditions in which they live. By utilizing biochemical adaptations, fish who prefer cold water can adjust certain processes in their bodies by using different enzyme configurations. Cold-water fish and arctic fish can survive and thrive in cold waters by allowing their bodies to use enzymes in different ways to trigger the same body processes as a warmer-water fish would.
When the water dips to a frigid 40°F, fish like the lake trout can move around more than they would in warmer periods. Lake trout show signs of discomfort in waters over 60°F. These fish are lightning-fast predators, trapping their prey by pinning them to the bottom of the lake, or utilizing the ice cover to do the same. Once winter sets in, the typical summer hangout spots of pike, walleye, and
panfish are used by the cold-resilient lake trout. Underwater geographical features help lake trout conceal themselves, waiting to attack the fish who forage in the open as cold fronts arrive. As the climate becomes increasingly warmer, in turn, our waters are becoming warmer. This indicates trouble for the cold-water fish who call our lakes and streams home, making them more vulnerable to predators like the sea lamprey who thrives in warmer waters. Salmon, walleye, cisco, and trout will have an increasingly hard time finding areas that suit their needs, because sub-60°F temperatures in our waters will be increasingly hard to come by. This affects their breeding behaviors, feeding behaviors, and everything in between. Even though some Michigan lakes are stocked by humans with fish, those practices are changing in areas where the water has become an unsuitable habitat for cold-water fish.
As waters warm, mitigation must take place. Natural flora that is returned to the banks of streams and rivers can make up for some of the human-caused impact on vulnerable waters, but eventually, difficult choices will need to be made when assessing the future of historically colder waters. Fish have an impact on traditional culture within the lives of all Michiganders. The whitefish, a species of trout, is a culturally significant cold-water fish in Michigan. Known as adikameg in Ojibwemowin, the language of the Ojibwe, the whitefish has sustained communities for centuries. Early European explorers were introduced to this fish and exalted them as a fantastic source of food. During the lumbering era and the early 1900s, the impact of colonial-led activities caused the whitefish to experience damages to their early winter spawning habitats upriver. Their population began to decline rapidly, as new generations of fish were not created. Habitat restoration has taken place in the last century, and regulations along with mindful management and monitoring have shown that the whitefish have returned to some parts of their historic breeding grounds. With the climate warming, however, the actions taken to protect the whitefish are becoming more and more crucial to the biodiversity and the sustainability of the Great Lakes. Warmer waters leave few areas for the whitefish to inhabit during the summer months. If not for human consumption value, the removal of whitefish within the Great Lakes food web would also cause destruction amongst other species. Along with their important ecological niche, the whitefish’s cultural significance and reliability as a high-quality source of food for the communities they live near lends to their importance within the Great Lakes Basin.
For the residents of Michigan past and present, ice fishing has been a staple in providing sustenance for families and communities in times of dormancy for many plants and animals. Michigan’s historical 4-season climate has been shifting year after year, seeing warmer winters and water level fluctuations that are far enough from the ‘norm’ to have a measurable impact on the residents of Michigan, whether they be the humans on land or the fish residing in our greatest asset, our fresh waters. As we move forward, our cold-water fish will experience warmer temperatures and changes in habitats they were once familiar with. Sustainable fishing practices and mitigation through native plantings and land-use changes are tools we can use in conjunction with scientific studies and citizen-scientist observations throughout the changing seasons. With enough eyes on the waters, armed with knowledge, culture, and science, the cold-water fish in Michigan have a fighting chance despite the warming waters. The success and rebound of many climate-affected plants and animals is largely dependent on actions that we take going forward in our warming world.
Sources and Further Reading:
Winter: An Ecological Handbook by James C. Halfpenny and Roy Douglas Ozanne
Fish of Michigan Field Guide by Dave Bosanko