title: Attractiveness of food and avoidance from contamination as conflicting stimuli to habitat selection by fish.
abstract: Habitat selection by fish is the outcome of a choice between different stimuli. Typically, the presence of food tends to attract organisms, while contamination triggers an avoidance response to prevent toxic effects. Given that both food and contaminants are not homogeneously distributed in the environment and that food can be available in contaminated zones, a key question has been put forward in the present study: does a higher availability of food in contaminated areas interfere in the avoidance response to contaminants regardless of the contamination level? Tilapia fry (Oreochromis sp.; 2.5-3.0 cm and 0.5-0.8 g) were exposed to two different effluent samples, diluted along a free-choice, non-forced exposure system simulating a contamination gradient. Initially, avoidance to the effluents was checked during a one hour exposure. Afterwards, food was added to the system so that the availability of food increased with the increase in the level of contamination, and the avoidance response to contamination was checked during another hour. Results clearly showed a concentration-dependent avoidance response for both effluents during the first hour (i.e., with no food). However, in presence of the food, the avoidance pattern was altered: organisms were propelled to intermittently move towards contaminated areas where food availability was higher. The incursions were taken regardless of the potential risk linked to the toxic effects. In conclusion, even when the risk of toxicity was imminent, tilapia fry were more intensively stimulated by the attractiveness of the food than by repulsion to the contamination.
authors.affiliation: Centre for Functional Ecology (CFE), Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal; Central Department of Research (DCI), Ecuadorian Aquatic Ecotoxicology (ECUACTOX) Group, Universidad Laica Eloy Alfaro de Manabí (ULEAM), Ciudadela Universitaria, vía San Mateo, Manta, Ecuador. Electronic address: cristiano.araujo@icman.csic.es.
authors.forename: Cristiano V M
authors.initials: CVM
authors.lastname: Araújo
authors.affiliation: Central Department of Research (DCI), Ecuadorian Aquatic Ecotoxicology (ECUACTOX) Group, Universidad Laica Eloy Alfaro de Manabí (ULEAM), Ciudadela Universitaria, vía San Mateo, Manta, Ecuador.
authors.forename: Elizabeth N V
authors.initials: ENV
authors.lastname: Rodríguez
authors.affiliation: Central Department of Research (DCI), Ecuadorian Aquatic Ecotoxicology (ECUACTOX) Group, Universidad Laica Eloy Alfaro de Manabí (ULEAM), Ciudadela Universitaria, vía San Mateo, Manta, Ecuador.
authors.forename: David
authors.initials: D
authors.lastname: Salvatierra
authors.affiliation: Central Department of Research (DCI), Ecuadorian Aquatic Ecotoxicology (ECUACTOX) Group, Universidad Laica Eloy Alfaro de Manabí (ULEAM), Ciudadela Universitaria, vía San Mateo, Manta, Ecuador.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Cedeño-Macias
authors.affiliation: Central Department of Research (DCI), Ecuadorian Aquatic Ecotoxicology (ECUACTOX) Group, Universidad Laica Eloy Alfaro de Manabí (ULEAM), Ciudadela Universitaria, vía San Mateo, Manta, Ecuador.
authors.forename: Victoria C
authors.initials: VC
authors.lastname: Vera-Vera
authors.affiliation: Centre for Functional Ecology (CFE), Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
authors.forename: Matilde
authors.initials: M
authors.lastname: Moreira-Santos
authors.affiliation: Centre for Functional Ecology (CFE), Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Ribeiro
mesh_terms: D000818:Animals; D001362:Avoidance Learning; D017753:Ecosystem; D004781:Environmental Exposure; D005502:Food; D005506:Food Contamination / Q000032:analysis; D017210:Tilapia / Q000502:physiology*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical
keywords: Food availability; Habitat choice; Spatial distribution; Tilapia; Toxicity