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Recent research has uncovered a noteworthy trend in the populations of freshwater fish, revealing that species residing in colder, polar regions are exhibiting greater success compared to those near the equator.
Notably, larger migratory species, including Atlantic salmon, are experiencing a surge as climate change causes temperatures to rise, thereby expanding their habitat options closer to their northern range limits.
This study, published in PNAS, draws on a comprehensive dataset consisting of over 10,000 time series from more than 600 different fish species.
Although climate change poses a significant threat to biodiversity and has led to extensive shifts in species distribution in both marine and terrestrial environments, its effects on freshwater species remain underexplored.
Co-author Professor Martin Genner remarked, “A typical biological reaction to climate warming observed in marine and terrestrial environments is the increase in populations at the polar side of species ranges due to the emergence of new habitats, contrasted with declines at the equatorial side where temperatures become too extreme.”
The research team utilized a vast database of riverine fish population abundance recorded from 1958 to 2019, correlating this data with temperature records over the same period. The findings indicated a warming trend in sampled waters averaging 0.21 °C per decade.
Results indicated that the population trends aligned with expectations stemming from climate change, with a more significant impact noted in data spanning over three decades.
Species exhibiting these climate-responsive trends were primarily those with larger body sizes, higher trophic levels, migratory behaviors between rivers and seas, and broader distributions. Prominent examples include brown trout and various coarse fish such as European perch and northern pike, which are widely recognized by anglers. Additionally, populations showed a stronger positive response to warming in cooler, elevated regions.
According to Professor Genner, “The results suggest that as climate change progresses, significant alterations in riverine community structures are likely, including declines in population numbers at the trailing edge of species distributions.”
The research team is now focusing on further dissecting the impact of climate change on freshwater fish populations compared to other environmental stressors, including pollution, habitat loss, and fishing pressures.
He concluded, “Our investigation sheds light on how increasing water temperatures are affecting freshwater fish, a group that is both biodiversity-rich and culturally significant worldwide. We aim to raise awareness of these impacts in hopes of prompting actions that promote their conservation and responsible management.”
“There is a critical need to explore effective conservation strategies, such as habitat restoration, to mitigate the adverse effects of climate change.”
Source
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