Co-evolution of movement behaviors by tropical pelagic predatory fishes in response to prey environment: A simulation model

Tropical oceanic fishes, such as tunas, billfishes, and sharks, live together in the same environment – the pelagic open ocean. In situ experiments have been developed to observe horizontal and vertical movements of individuals of different pelagic species, but the fact that these species share the same environment has not been studied yet. In this paper we propose a minimal model in which the movement behavior of oceanic predator fishes is driven entirely by their biotic environment, without consideration of physiological constraints. Such idea is explored with computer simulations based on the Latent Energy Environments model (Menczer and Belew 1996a). The behaviors of an evolving population of artificial fishes adapt in a three-dimensional environment where spatial distributions and temporal dynamics of prey are based on data from acoustic observations of the open ocean in French Polynesia. Interactions among individuals are modeled through their shared prey resources. Simulations provide adapted individuals for which movement patterns are analyzed, in order to: (i) compare artificial individuals to real fishes (three species of tunas, three species of billfish, and one species of shark) observed by acoustic telemetry, and (ii) examine how the artificial fishes exploit their environment. Beyond our expectations, most of the artificial individuals evolve vertical patterns virtually identical to those exhibited by fishes in the wild. The agreement between our simple computational model and ethological data validates minimal assumption models for the study of behaviors in multi-species ecosystems.