The noise of passing boats may be more than a nuisance to Red-mouthed gobies (Gobius cruentatus), according to a study by Italian scientists that is to be published in a forthcoming issue of the journal Environmental Biology of Fishes.
The Red-mouthed goby is a species found living on the sea floor in the Mediterranean Sea and the western Atlantic Ocean, and is a territorial species that uses a variety of sounds to warn intruders away and during fighting.
Linda Sebastianutto and coauthors conducted a series of experiments to determine the effects of boat noise in masking acoustic communication in the Red-mouthed goby.
The authors used five wild-caught gobies (three females and two males), placing one in a tank that had been set up with a plastic shelter for a week and allowing it to become a resident. An intruder was then introduced in the tank and allowed to interact with the resident for 10 minutes, with the entire encounter being filmed with a video camera. The experiment was terminated as soon as the territorial contest was settled.
The authors ran a series of experiments in which low-frequency boat noise was played through an underwater speaker suspended at the opposite end of the tank during the encounters (conducted round-robin style) and another series in which the boat noise was not played back during the encounters.
The results of the experiments indicated that the resident fish were more submissive and less successful at repelling intruders in the presence of boat noise.
The authors surmise that the boat noise may be masking the acoustic communications between the fish, which they consider to be a key factor in determining the outcome of the territorial contests.
This may have negative effects on the gobies, since a diminished ability of the territorial fish to hold the territory has been proven to lead to an increase in aggressive contests, raise the levels of androgens in the resident fish to the detriment of courtship behaviour, reproductive activities and care of offspring.
For more information, see the paper: Sebastianutto, L, M Picciulin, M Costantini and EA Ferrero (2011) How boat noise affects an ecologically crucial behaviour: the case of territoriality in Gobius cruentatus (Gobiidae). Environmental Biology of Fishes, doi:10.1007/s10641-011-9834-y
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