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

Predatory fishes, such as tunas, billfishes, and sharks, coexist in pelagic regions of the tropical oceans. In situ experiments have revealed horizont al and vertical movement patterns for different pelagic species, but the in fluence of the biotic environment on movement behaviour has not been studie d. In this paper, we propose a simple model in which the movement behaviour of these fishes is driven entirely by the biotic environment, without impl ementing physiological constraints. We explore this concept via computer si mulations based on the Latent Energy Environments model [Menczer, F., Belew , R.K., 1996a. From complex environments to complex behaviors. Adapt. Behav . 4(3/4), 317-63]. In our model, multiple behaviours for artificial fishes evolve in a three-dimensional environment where spatial and temporal distri butions of prey are patterned after hydroacoustic data taken during ultraso nic telemetry experiments on tunas in the open ocean in French Polynesia. I nteractions among individuals are modeled through their shared grey resourc es. Movement patterns of the adapted individuals are analyzed to: (i) compa re artificial individuals with real fishes (three species of tuna, three sp ecies of billfishes, and one species of shark) observed by ultrasonic telem etry; and (ii) examine how the artificial fishes exploit their environment. Most of the individuals evolved vertical patterns virtually identical to t hose exhibited by fishes in the wild. The agreement between our simple mode l and the ethological data validates the use of computational models for st udies of the characteristics of multiple species inhabiting a common ecosys tem. (C) 2000 Elsevier Science B.V. All rights reserved.