title: Collective responses of a large mackerel school depend on the size and speed of a robotic fish but not on tail motion.
abstract: So far, actuated fish models have been used to study animal interactions in small-scale controlled experiments. This study, conducted in a semi-controlled setting, investigates robot5interactions with a large wild-caught marine fish school (∼3000 individuals) in their natural social environment. Two towed fish robots were used to decouple size, tail motion and speed in a series of sea-cage experiments. Using high-resolution imaging sonar and sonar-video blind scoring, we monitored and classified the school's collective reaction towards the fish robots as attraction or avoidance. We found that two key releasers-the size and the speed of the robotic fish-were responsible for triggering either evasive reactions or following responses. At the same time, we found fish reactions to the tail motion to be insignificant. The fish evaded a fast-moving robot even if it was small. However, mackerels following propensity was greater towards a slow small robot. When moving slowly, the larger robot triggered significantly more avoidance responses than a small robot. Our results suggest that the collective responses of a large school exposed to a robotic fish could be manipulated by tuning two principal releasers-size and speed. These results can help to design experimental methods for in situ observations of wild fish schools or to develop underwater robots for guiding and interacting with free-ranging aggregated aquatic organisms.
authors.affiliation: Centre for Biorobotics, Tallinn University of Technology, Akadeemia tee 15A, 12618 Tallinn, Estonia.
authors.forename: Maarja
authors.initials: M
authors.lastname: Kruusmaa
authors.forename: Guillaume
authors.initials: G
authors.lastname: Rieucau
authors.forename: José Carlos Castillo
authors.initials: JC
authors.lastname: Montoya
authors.forename: Riho
authors.initials: R
authors.lastname: Markna
authors.forename: Nils Olav
authors.initials: NO
authors.lastname: Handegard
mesh_terms: D000818:Animals; D040761:Biomimetic Materials; D008124:Locomotion / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D010473:Perciformes / Q000502:physiology*; D012371:Robotics; D013623:Tail / Q000502:physiology*; D000071442:Taxis Response