Within FIThydro, scientists study how fish adapt to rapid changes in their surrounding freshwater environment. Understanding how a fish’s advanced sensing system helps them react to rapid changes in the flow environment, will help scientists develop new designs for nature-based solutions to improve climate change resilience.

The interdisciplinary research group includes scientists from the research center CERIS – Civil Engineering Research and Innovation for Sustainability at University of Lisbon, where the experiments took place and from the TalTech Centre for Biorobotics, which has developed a bioinspired artificial lateral line sensor. For their study, the researchers 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 as well as in groups.

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, one of the main research objects, 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’,” Maria Joao Costa, a PhD research biologist with the University of Lisbon and first author, explains.

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.

How fish sense and react to their surroundings

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 lateral line sensing technology.

“We 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,” says Isabela Boavida, a senior researcher at the University of Lisbon.

Jeffrey Tuhtan, a principle investigator from TalTech states: “It was exciting to compare the results of the artificial lateral line with actual observations of fish behavior. This was a very unique opportunity to combine sensor research with real-world biological observations, something which is rarely done.”

Improving climate change resilience

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

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. “A fish’s sensing abilities are incredibly advanced compared to what we engineers have available, and this is likely part of the reason they have survived for hundreds of millions of years” explains Prof. Antonio Pinheiro, co-author from the University of Lisbon. “When we develop nature-based solutions for improving resilience to climate change, it makes sense to look to fish and other ancient organisms which are designed for survival,” says Juan Francisco Fuentes-Perez, a PhD candidate at TalTech and co-author.

The results of the study are published in the article “Fish under pressure: Examining behavioral responses of Iberian barbell under simulated hydropeaking with instream structures” in PLOSOne.

Jeffrey Tuhtan (TUT)
Picture rights: Jeffrey Tuhtan, Tallinn University of Technology, Centre for Biorobotics