Fish Fleeing Climate Change Face Declining Numbers, Researchers Warn

Jerusalem, 18 March, 2024 (TPS) -- An extensive international study has revealed a concerning trend: species of fish fleeing toward the poles to avoid rising sea temperatures are experiencing a marked decline in abundance. Contrary to previous assumptions, the findings paint a worrisome picture of the impact of climate change on marine ecosystems.

The study, led by PhD student Shahar Chaikin and Prof. Jonathan Belmaker of Tel Aviv University correlated two global databases tracking fish population sizes over time and range shift velocities among marine fishes. The findings were recently and published in the peer-reviewed Nature Ecology & Evolution journal.

“The faster fish shift toward the poles, the faster their abundance declines. Apparently, it is difficult for these populations to adapt to their new surroundings,” said Belmaker. This challenges the conventional wisdom that rapid range shifts might ensure the survival of species, suggesting instead that such movements might indicate heightened vulnerability to climate change.

“Species shifting their geographical range more rapidly towards the poles are, in fact, more likely to lose their abundance,” Chaikin added. The study also found that fish populations closer to the cooler polar margins of their range experienced more rapid declines in abundance compared to equatorial populations of the same species.

Examining over 2,500 fish populations encompassing 146 species predominantly from the Atlantic and Pacific Oceans in the Northern Hemisphere, the researchers found a stark correlation between rapid poleward shifts and declining population abundance. On average, a poleward shift of 17 kilometers per year was associated with a staggering 50% decline in population abundance.

The implications of these findings are profound, with significant ramifications for conservation efforts and environmental policymaking, the researchers said. The study advocated for a reevaluation of the conservation status of various species and populations, emphasizing the need for closer monitoring and careful management of populations exhibiting rapid poleward range shifts.

“The common belief is that rapid range shifts safeguard a species against local population decline. But in this study, we found that the opposite is true,” Belmaker said.

The study built on previous research by the same team, which highlighted similar patterns among local fish species along Israel’s coastline. Moving forward, the researchers intend to delve deeper into the causal relationship between rapid range shifts and declining abundance in additional marine species beyond fish.