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On July 4th, the first Independence Day fireworks will shoot into the sky reflecting off the nearby lake or river, making that familiar pop! pop! sound throughout the night. 

Curious smallmouth bass following behind scuba divers in Sparkling Lake, Vilas County, Wis. Photographer: Gretchen Hansen, Wisconsin Department of Natural Resources

On July 4th, the first Independence Day fireworks will shoot into the sky reflecting off the nearby lake or river, making that familiar pop! pop! sound throughout the night. With all the exciting pyrotechnics, it’s easy to overlook the fish living just under the water’s surface.

Freshwater fish may seem impervious to the outside world under their protective layer of water, but climate change is already having major impacts on fish both around the world and right here in our backyards and communities.

With 2014 being Earth’s warmest year on record since 1880, climate change is an ever-present threat to freshwater environments. Changes in temperatures and precipitation levels are already having major impacts on fish populations. Fish are not only important because of their cultural, recreational and commercial value for humans but they also serve as a central piece of the food web for other fish and animals like birds, otters and bears. Understanding the effects of climate change on this important resource is paramount.

Research is Key and Underway

The effects of climate change on fish are rarely straightforward. Climate change affects how fish reproduce, grow and where they can live, and it impacts warmwater and coldwater fish differently. These varying and complex interactions create a challenge for scientists to determine and predict the exact consequences of climate change on different fish species and highlight the need for fisheries and climate change research.

The good news is that research has already started. United States Geological Survey scientists have already conducted studies on species at risk from climate change, including the Chinook salmon, westslope cutthroat trout and native bull trout.

Researchers take a break to snap a quick photo in Bozeman, Mont., during a workshop on climate change impacts on fish in the United States and Canada.

And earlier this month, researchers from USGS and other federal and state agencies and academia gathered in Bozeman, Mont., with the goal of synthesizing the most up-to-date and real-world examples of climate change impacts on fish across North America and understanding how these changes will inevitably affect fisheries management and the public.

Winners and Losers: Non-Native Smallmouth Bass vs. Native Lake Trout

In Ontario, Canada, non-native smallmouth bass, a warmwater fish, are expanding into northern lakes once dominated by native lake trout, a coldwater fish. With rising lake water temperatures, habitat often becomes more unsuitable for native coldwater fish and more favorable for warmwater fish to invade. To make matters worse for the native lake trout, the non-native smallmouth bass eat the trout’s top food choice, minnows, reducing food available to the native inhabitants. Less minnows to eat and hotter temperatures means lake trout will decrease. As scientist James Whitney from the Missouri Cooperative Fish and Wildlife Research Unit explained, “Climate change will add to and perhaps multiply the effects of other stressors, like non-native species introductions, that are currently impacting fish physiology.”

Sometimes There Are No Clear Winners or Losers

Take pink salmon for example. Salmon are born in fresh water but spend most of their life in the ocean until they migrate back to streams or rivers to reproduce. Salmon migrate when environmental conditions, such as temperature, are the best for successful breeding. In Auke Creek, Alaska, pink salmon, on average, are migrating from the ocean to rivers to lay eggs two weeks earlier than they were 40 years ago to avoid warmer temperatures. The earlier migration is due to small-scale evolution (microevolution) or changes in genes that favor early migration in response to a changing climate.

Black bear surveys sockeye salmon as they migrate up river to reproduce in Auke Bay, Alaska in 2011. Photographer: Evan Barrientos

Changes in when and where salmon are located will have “major consequences for other organisms that depend on salmon like bears, gulls, mink, and even humans,” said Ryan Kovach, the lead scientist on this study and a USGS research fisheries biologist.

The Human Side of Things

“One of our challenges is understanding what managers and decision makers can do to adapt to climate change,” says Craig Paukert with the USGS Missouri Cooperative Fish and Wildlife Research Unit. “We must help decision makers find ways to protect, restore and enhance fisheries under a changing climate.”

Fish of all species are affected in some way by climate change and this in turn impacts other species and ecosystems, but there is also a whole other side to the story that Paukert is referring to: managing fisheries for human use and consumption.

According to the U.S. Fish and Wildlife Service, 33.1 million people fished in 2011 and spent 41.8 billion dollars in the United States alone. Depending on an anglers’ fish of choice, climate change may force them to fish for a different kind (bass instead of trout for example), choose a different stream to fish in or stop fishing altogether. These changes can significantly affect local economies and livelihoods. To best manage fish populations and encourage fishing in a changing climate, managers need a deep understanding of how both fish and anglers will respond to the effects of climate change.

Angler catches a fish during a Panfish Fishing Tournament on June 6, 2015 on Brownlee Reservoir in Oregon. Fish serve as an important recreational, commercial, and cultural resource in the United States and Canada. Credit: Baker County Tourism

Looking to the Future

“The current state of the science shows that climate change is impacting fish in lakes, rivers and streams, but knowing that is just the first step in being able to address the changes to these important natural resources and the communities which depend upon them,” said Abigail Lynch, a fisheries biologist with the USGS National Climate Change and Wildlife Science Center. “USGS and partners are working to provide a fuller and more comprehensive picture of climate change impacts on North American fish for managers, scientists and the public, alike.”

So as those fireworks zing across the sky during the upcoming holiday, take a moment to ponder the importance of freshwater fish for our society and the critical need to understand how climate change is and will continue to impact fish throughout North America and the world.

Want to know more? Stay tuned for a synthesis publication on the documented effects of climate change on inland fish in a special 2016 issue in the journal Fisheries.

Check out the publications on the smallmouth bass and lake trout study and pink salmon migration study.

Other Links:

Climate Change Threatens Native Trout Diversity

Climate Change Accelerates Hybridization between Native and Invasive Species of Trout

Climate Change Threatens Native Trout Diversity (Bull Trout)

Predicting Climate Change Impacts on Aquatic Ecosystems across the Pacific Northwest (Webinar)

Fish Habitat and Climate Change: Implications for the Desert Southwest, Midwestern Smallmouth Bass, and Eastern Brook Trout (Webinar)

Predicted Climate Change Effects on Fisheries Habitat and Production in the Great Lakes (Webinar)




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