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Climate Change Impacts North American Fish
For some time, researchers have been working to forecast the effects that climate change will have on North American fish. But recently they’ve been able to shift their approach because the impacts, far from just predictions, are already being felt.
Scientists with the U.S. Geological Survey have led a recent analysis of 31 studies that have been completed across the United States and Canada. Each documented some of the effects that climate change has already had on fish in the continent, with respect to individual fish species, populations, recreational fishermen and fisheries managers.
Thanks to the synthesis of all the studies, investigators say that they can see clear impacts of a changing climate, with real effects economically, socially and ecologically. With more knowledge and trends beginning to emerge, they are looking to tease out the stressors hurting inland fish and shift conservation resources and research as needed.
Smallmouth bass provide an example of how climate change presents fisheries managers both challenges and opportunities. Smallmouth bass, a popular recreational species, are expanding their range northward with climate change. This expansion can disrupt existing food webs but it also creates new prospects for recreational fishing.
Because many recreational fishers want to catch smallmouth bass, managers may need new techniques to accommodate increased fishing demand while still maintaining native coldwater fish communities. Consequently, management processes may likely be an exercise in managing stakeholder expectations for fisheries changing the most.
Among other findings of the analysis, scientists pinpointed that climate change may be altering abundance and growth of some North American inland fishes, particularly coldwater fish such as sockeye salmon, a species experiencing well-documented shifts in range, abundance, migration, growth and reproduction.
Climate change may also be causing earlier migrations and allowing species that never occurred together previously to hybridize. For example, native westslope cutthroat trout in the Rocky Mountains are now hybridizing with rainbow trout, a non-native species.
Shifts in species’ ranges are already changing the kinds of fish in a specific water body, resulting in new species interactions and altered predator-prey dynamics. For example, in Canada, smallmouth bass have expanded their range, altering existing food chains because the species compete against other top predators for habitat and prey fish.
Droughts are forecasted to increase in frequency and severity in many parts of North America, especially in arid rivers. Such droughts exacerbate the impacts of water flow regulation in ways that affect people, fish and aquatic systems.
These findings help to show how climate change is already impacting fish in North American lakes, rivers and streams. Knowing that is important for effectively addressing the changes in the future.
Funding for the analysis was provided by the National Climate Change and Wildlife Science Center. Studies considered in the work are published in the journal Fisheries.
Top image: Smallmouth bass following behind scuba divers in Sparkling Lake, Vilas County, Wisc. (Credit: Gretchen Hansen / Wisconsin Department of Natural Resources)