How fish adapt to climate change

Scientists have studied how fish adapt to rapid changes in the surrounding freshwater environment to understand how marine life may respond to climate change.

Freshwater biodiversity is rapidly declining worldwide, and nature-based solutions which increase the resilience of ecological communities are becoming increasingly important in helping communities prepare for the unavoidable effects of climate change.

Researchers from Tallinn University of Technology in Estonia and Universidade de Lisboa in Portugal varied the water current and depth in a simulated river with obstacles, and found that fish were able to rapidly adapt to the changes when alone and also when in groups.

"The findings suggest that cues initiated by obstacles in the flow can be detected by fish to find energetically-beneficial places in the flow even under extreme and rapid environmental change," said Jeffrey Tuhtan, a researcher at Tallinn University of Technology.

The concept of observing fish in simulated rivers as individuals or in groups is not unusual, but the effects of rapid environmental variations, such as quickly changing water depths due to hydropower plant operations or a flash flood remain largely unknown.

Barbel are a common fish species in many European rivers, and are usually found in rocky-bottomed and slow flowing rivers with plenty of dissolved oxygen.

"These fish are an important indicator of ecosystem health in the Iberian peninsula and in many other European rivers. Hydropower operations and the uncertainty caused by climate change mean we need to begin to look at the compound effects of rapid changes, from 'the fish's perspective'," said Maria Joao Costa, a research biologist at the University of Lisbon.

Fish sense their surroundings using the biological lateral line, which consists of canals and tiny hair-like structures which are sensitive to minute changes in the water motion and pressure near the fish's body.

This study was the first to combine biological observations of individuals and groups of fish with a new bioinspired sensing technology.

The researchers observed that both individual fish and groups of fish reacted to the changing flow conditions in very clear ways and wondered if their natural flow sensing abilities were guiding their ability to cope with the stressors.

"It was exciting to compare the results of the artificial lateral line with actual observations of fish behaviour. This was a very unique opportunity to combine sensor research with real-world biological observations, something which is rarely done," said Juan Francisco Fuentes-Perez, a PhD candidate at Tallinn University of Technology.

"A fish's sensing abilities have developed over millions of years and are incredibly advanced compared to what engineers have available. This is likely part of the reason they have survived for hundreds of millions of years," said Isabela Boavida, a senior researcher at the University of Lisbon.

"Understanding how a fish's advanced sensing system help them react to rapid changes in the flow environment will help scientists develop new designs for nature-based solutions to improve climate change resilience," Boavida said.

"With more than 500 million years of real-world experience, fish are likely to have learned a few tricks for quickly adapting to challenging conditions" said Antonio Pinheiro, from the University of Lisbon.