High Temps, Low Water - Inland Fish Face an Uncertain Future
Warming waters are already affecting where inland fish across North America reproduce, grow, and where they live. For many anglers, and for local and state economies, these changes could spell trouble. Together, scientists from the USGS Missouri Cooperative Fish & Wildlife Research Unit (Missouri Unit) and the USGS National Climate Change and Wildlife Science Center (NCCWSC) are working hard to provide needed information to resource managers to help protect the country’s precious fish and their habitats.
A survey conducted by the U.S. Fish and Wildlife Service found that in 2011, 27.5 million U.S. residents went freshwater fishing. These anglers took about 369 million fishing trips and spent $25.7 billion on those trips. In the future, however, based on USGS-led studies of predicted effects of climate change on fish species distribution, anglers may have to fish for different species in their favorite fishing places, or travel to different areas to find the same fish.
To best manage fish populations and encourage fishing in a changing climate, resource and fisheries managers need a deep understanding of how both fish and anglers will respond to the effects of climate change. Providing scientific information to support this understanding is paramount – albeit challenging.
The good news is that research has started and is ongoing.
In 2015, for example, the Missouri Unit and NCCWSC brought together experts to begin to develop a broad understanding of the effects of climate change on fish and fisheries in North America. Results of the workshop discussions and related research were then published in 2016 in a set of four papers in a special issue of the journal Fisheries.
As part of this work, scientists conducted a review of 31 studies that document the impacts of climate change on individual fish species, populations, anglers, and fisheries managers across North America. One of the key takeaway messages from that work is that climate change effects on fish are rarely straightforward.
Fish that have the most documented risk, the researchers found, include those living in arid environments. As the frequency and severity of droughts is expected to increase in the future in many parts of North America, especially in arid rivers, water levels could decrease, affecting fish habitat and connectivity between streams.
Meanwhile, changing water temperatures can also cause suboptimal habitat for some fish; warmer water, for example, can stress coldwater fish. When stressed, fish tend to eat less and grow less, altering their ability to compete to survive. Sockeye salmon, for example, are a coldwater species experiencing well-documented shifts in range, abundance, migration, growth, and reproduction.
Climate change is also shifting the range and migration patterns of other species; in some cases, these changes are even creating more suitable habitat. It’s important to emphasize that these changes can result in new species interactions and alter predator-prey dynamics. For example, smallmouth bass have expanded their range and warmer waters have increased the availability of their prey fish, making the bass more competitive against other top predators, disrupting native food chains. In the Rocky Mountains, non-native rainbow trout are expanding into coldwater streams and mating with the native westslope cutthroat trout, creating hybrid fish.
To make matters even more complicated, the effects caused by climate are interacting with other human-related factors such as agricultural run-off and water use, making the direct cause of such changes especially difficult to determine and measure. The findings from this work, and other USGS-led projects across the country, help provide a more comprehensive picture of the impacts of climate change on our country’s treasured fish and freshwater habitats.
Participants in the 2015 workshop and development of the research products included Craig Paukert, and James Whitney, Missouri Unit; Colleen Caldwell, New Mexico Unit; Jeffrey Falk, Alaska Unit; Thomas Kwak, North Carolina Unit; David Fulton, Minnesota Unit; Brian Irwin, Georgia Unit; Abigail Lynch and Bonnie Myers, NCCWSC; and other partners from universities and organizations across the country. The workshop was funded by the Missouri Unit and NCCWSC.
This article was originally prepared for the Wildlife Management Institute's Outdoor News Bulletin. The story was adapted from a 2016 USGS feature story, In Hot Water: Climate Change is Affecting North American Fish.
Images on page:
Top: Smallmouth Bass, Gretchen Hansen
Bottom: Sockeye Salmon, Public Domain