Researchers from University of Bristol have discovered that freshwater fish populations inhabiting polar regions are outperforming their equatorial relatives. Researchers have found that large-bodied migratory species, such as Atlantic salmon, thrive as rising temperatures create new habitats at the northern edges of their ranges.
The research analyzed a dataset comprising over 10,000 time series and included more than 600 species of fishes.
While climate change poses significant threats to biodiversity and is driving shifts in the distribution of various marine and terrestrial species as they seek suitable habitats, the effects of climate change on freshwater species have remained relatively unexplored.
“A common biological response to climatic warming in marine and terrestrial habitats is that populations are increasing at the poleward side of species ranges, as new environments are generated, and populations are declining at the equatorward side of species ranges, as conditions become too warm,” Co-author Professor Martin Genner explained.
The research team conducted a groundbreaking analysis by linking an extensive multicontinental database of riverine fish population abundance collected between 1958 and 2019 with temperature data from the same period. They discovered that water temperatures have risen by an alarming 0.21 °C per decade across various localities.
Their findings revealed that the observed trends in fish populations align closely with the expected impacts of climate change, particularly pronounced in time series that extend beyond 30 years.
The most striking species responses associated with climate change were seen in those with larger body sizes, higher trophic levels, migratory behaviors between rivers and seas, and broader geographical distributions. This includes notable species such as brown trout and popular coarse fish like European perch and northern pike, which are well-known to anglers.
Furthermore, the evidence suggests that positive changes in fish abundance due to warming are more likely to occur at higher altitudes, where cooler conditions prevail.
“These findings indicate that projected future warming will likely lead to widespread shifts in riverine community structure, including abundance declines at the trailing edge of species distributions,” said Professor Genner.
The team aims to understand the significance of climate change on freshwater fish populations compared to other stressors like pollution, habitat modification, and fishing activities.
“Our study has shown how warming waters are impacting freshwater river fishes, which are both rich in biodiversity and are traditionally important to cultures across the world,” he concluded. “We hope that shining a light on how climate change can affect freshwater fishes will lead to positive actions to enable their conservation and sustainable use. We need to learn more about how the impacts of climate change can be lessened through conservation strategies, such as habitat restoration.”
Journal reference:
Timothy M. Brown, Joseph O’Connor, and Martin J. Genner. Climate warming drives population trajectories of freshwater fish. PNAS, 2024; DOI: 10.1073/pnas.2410355121