Science and Technology

The highly specialised sensory system in freshwater fish

A group of CERIS researchers were part of an interdisciplinary study of sensory system in freshwater fish and mechanisms to respond to rapid changes of water flow downstream in hydroelectric power plants.

A team of researchers found that fish detect changes in water velocity, depth and that, through swimming behaviour, fish are able to reduce the energy expenditure associated with locomotion. This interdisciplinary study was carried out by teams from CERIS and Centre for Biorobotics – Tallinn University of Technology, and was funded by the EU Framework Programme for Research and Innovation Horizon 2020 (FIThydro Project).

The results of this study, recently published in PLoS ONE magazine, suggest that the presence of obstacles and the consequent alteration of hydraulic conditions can be favourable for fish. According to Maria João Costa, researcher at CERIS and author of the study, “the effects of altered flows on fish behaviour are unknown. The rapid growth of hydroelectric power and the uncertainty of climate change require that we study the variation of turbine flow in hydroelectric power plants and its effects from a ‘fish perspective’”.

Fish process information from the surrounding environment through a highly specialised sensory system, the lateral line. This system consists of a set of hair cells sensitive to small mouvements in the water, which are located in tubular channels or in the body surface. This is the first study that includes individual and group fish observing and a new biomimetic technology.

Barb fish are essential to the structure of fish communities and to the ecological integrity of river ecosystems. “We found that the Iberian barb fish reacts to water flow variation in very different ways, both individually and in groups. It is important to know if their natural ability to perceive the hydraulic conditions allows them to adapt to the stress imposed by these water flow variations”, said Isabel Boavida, researcher at CERIS and also co-author of the study.

“It was very interesting to see how the Iberian barb fish behaviour is affected by the pressure variations. This was a unique opportunity to combine sensor technology research with the observation of biological responses, which is rarely studied”, said Jeffrey Tuhtan, one of the principal investigators at the Centre of Biorobotics and also co-author of the study.

This type of solution, based on fundamental principles of nature, has gained relevance and will boost the resilience of biological communities to deal with the effects of climate change. “It’s natural that we look at these organisms and their adaptive characteristics. They evolved to survive and persist”, said Juan Francisco Fuentes-Pérez, researcher at the Centre for Biorobotics and co-author of the study.

António Pinheiro, Técnico professor and co-author of the study, highlights that there is still “a long way to go in what concerns fish sensory system. These highly specialised systems allowed these fish to adapt and to survive for Ages, and it’s not easy to understand how these systems work and the consequent fish behaviours”.

Knowing the fish sensory system and mechanisms to respond to rapid changes in water flow can help the scientific community to develop new biomimetic solutions, in order to ensure the resilience of these organisms. The evolution of fish began about 500 million years ago so it is quite probable that they have learned some tricks to adapt to the surrounding environment and to persist until the present day with great success.