In the Great Lakes region of the United States (but not limited to that region), native trout
populations have been on the decline due to human stimulated environmental activities. These delicate fish require cold, oxygen full, clean water to survive and reproduce. However, with an increase in deforestation, mining operations, agriculture, and other climate changes, the needed cool water habitat for trout is slowly warming and becoming unlivable for the fish. Adding to the already stressed native fish, the introduction of invasive species that choke out and prey on the native trout add another danger to the already dangerous life as a native trout. In this essay I will explain how an increase in water temperature caused by human activity and the introduction of invasive fish species have caused the native trout population of the Great Lakes region to decline significantly. Despite the damage done, there is hope for native fish. Efforts from non-profit organizations and environmental groups have made good progress in reversing the harm done to these fish from past decades. Although human activities have been stained by insouciance, we also hold the power to reverse the trends of past decades of not fully putting the natural environment first.
Before getting into the challenges that trout face, it is important to know the habitat that is required for their survival. As touched on above, trout thrive in cold water, generally below 60℉ that is also rich in oxygen. That is why streams, rivers, and creeks are where you’ll most likely find trout. Although they aren’t strictly limited to moving water, trout also thrive in deep cold northern lakes like the great lakes. Trout need gravel beds to be able to spawn. Shaded cover by rocks or plants give trout a place to hide from predators and the sun’s heat. When any of these characteristics are disturbed, trout are more prone to become stressed which can cause disease to spread quickly. Trout are a keystone species in ecosystems, if the trout aren’t healthy, that is a clear indication that something is wrong in the ecosystem.
With trout being such a delicate fish species, big disruptions to their habitat, like clear
cutting a forest, can be a major blow to their population. According to Jason McLachlan at
Counter Punch, “The Forests of the Midwest Lost Midwest 8,000 Years of Stored Carbon in Just 150 Years”, Jason continues “forests in the upper Midwest gained almost a billion tons of carbon over the last 8,000 years”. This shocking statistic not only indicates the release of carbon dioxide into the atmosphere, but that also means the shade that those trees provided is also gone. Without shade covering a stream or river the temperature rises. Circling back to the carbon being released, this causes warmer air temperatures as well, which leads to two things: Midwest snow melting sooner and warming the water on top of the less shade due to no plant cover.
Snow melting sooner in the spring can lead to flooding. These high water levels wash
out nests killing the laid eggs and smaller fish. A study from the Michigan DNR in 2020 on the famous Au Sable river revealed that during “the Fall 2017 to Spring 2018 time period, saw heavy precipitation in the form of spring and fall rain events, as well as heavy snow over winter.” it continues to say “ High flows were likely the most important contributor to the trout population decline.” High water levels can be devastating to trout populations and can take years to become stable again. Nature is going to do what it’s going to do regardless, humans add to the mess.
Something that is however 100% human doing is the dumping of mining waste into
streams and rivers. Currently, the biggest mining threat isnt happening in the midwest, but rather all the way across the US in Alaska, the Pebble Mine. The Pebble Mine located on the Bristol Bay in Alaska “Bristol Bay is one of the last places on Earth with such bountiful and sustainable harvests of wild salmon” (EarthJustice). While salmon aren’t trout, they are the close cousins, both fish are in the Salmonids family, along with char, whitefish, and grayling. To build the Pebble Mine the project would involve “mining a pit over a mile long, a mile wide and 200 meters deep, destroying nearly 3,500 acres of wetlands, lakes, and ponds and 81 miles of salmon streams” (EarthJustice). Those lakes, ponds, and streams are essential for the sockeye salmon spawning and for the thousands of people that rely on the salmon for jobs and food. Although the Pebble Mines is thousands of miles away from the Great Lakes, there are still thousands of active and inactive mines located in the Great Lakes region. Spills are bound to happen, and without large environmental activists fighting for better management, they can soon infect the Great Lakes and the rivers that run to them.
While mining operations do pose a big threat on native fish populations, it isn’t the only
man made hazard. Agriculture poses just as big a risk for trout populations as mining. Bruce Ingram from Outdoor America did a study on brook trout populations in Maryland. “However, as agricultural, forestry, and development activities have increased over the past century, brook trout habitat has declined. These land-use changes have contributed to stream warming, increased erosion, and the loss of riparian cover—all factors that degrade brook trout habitat” (Outdoor America). Ingram also ties in deforestation as mentioned earlier. Agriculture not only causes erosion which causes runoffs, but it also involves chemicals. Chemicals like fertilizers and pesticides wash into streams, lakes, and rivers where trout live. These chemicals cause an imbalance in the pH, oxygen, and acidity levels which is harmful to trout. The unfortunate thing about this is that it is nearly impossible to stop this. With farming comes rain and erosion which washes the chemicals away leading them to water. Lowering the oxygen levels directly harms the fish with spawning and health. With the need for more farms due to increasing human population, the battle with agriculture and trout health will always be a thing.
Environmental issues aren’t the only dangers native trout need to face, invasive species
have played a massive role in decreasing the population as well, especially in the Great Lakes area. In Wisconsin, brook trout were once plentiful in the streams, however, in the 1800’s brown trout were introduced from European settlers (Olson 2024). These brown trout today have thrived in streams all across North America. They have successfully been able to reproduce without human assistance. Brown trout also live better in water that is a few degrees warmer than brook trout. As temperature rises, brown trout have started to take over the small streams and rivers that cover the Midwest choking out the brook trout, pushing the brook trout out of feeding and spawning grounds. Brook trout are one of two native char (salmonid) to the greats lakes region. While brown trout are equally as fun to catch recreationally, humans need to also think about the brook trout as well.
The second native char to the Great Lakes region is the Lake Trout. Lake trout thrive in the Great Lakes cold deep water. However, highly invasive species like the sea lamprey and zebra mussels have taken over the lakes. These two invasive species thrive in warmer water
and with temperatures rising, the Great Lakes have become a utopia for them. Zebra mussels cover the lake’s bottom making it very hard for lake trout to spawn, and the sea lamprey eats them alive. Lamprey don’t only target lake trout, they also target anything that swims. While efforts have been made to suppress these vampires for decades, we are just starting to see improvements in lake trout populations. “In November, The Great Lakes Fishery Commission’s (GLFC) Lake Superior Committee announced that lake trout, a popular fish nearly exterminated by sea lampreys and overfishing in the mid-1900s, has fully rebounded” (James Proffitt 2025). The battle on invasive species is far from over, zebra mussels and lamprey are still infecting the Great Lakes but with help of environmental groups and scientists, their numbers are growing smaller and native species are multiplying.
While humans are the ones that started the mess of invasive species and other
environmental problems like deforestation and water contamination, we are also the ones
cleaning it up. Environmental groups, communities, tribes, and the government are all trying their best to fight for the native fish of the Great Lakes region. There’s still a lot of work to be done, “Projections indicate that brook and brown trout are expected to lose 68% and 32% of their current suitable habitat across Wisconsin, respectively, by the mid-21st century” (Maitland 2022). Volunteering for your local Trout Unlimited chapter or donating money to fight the Pebble Mine are all great ways to help. Going out on your own and picking up trash on the side of rivers is a great way to help and get some exercise and nature time. The trout can’t fight for themselves so we must do it for them. It’s not just for the trout, it’s for the ecosystem in general.
To bring it all together, humans are the ultimate reason trout populations are decreasing.
With increasing deforestation, mining, and farming the environment that native trout live in is being ruined. Water temperatures are rising due to shade being cut away, chemicals from farms and mines are being washed or poured into rivers lowering oxygen levels and killing fish. Spawning beds are being washed out by early flooding. Invasive species are also doing a lot of damage, zebra mussels are covering the lake bottoms preventing spawning, lamprey are eating the fish alive, and other non-native trout are choking the native ones out. But, it’s not too late, recent studies have shown recovery for some species. The native trout of the Great Lakes region and the ecosystem that relies on them need a helping hand.
flyfluence.com 
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