Salinity mediates the competitive interactions between invasive mosquitofish and an endangered fish |
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Authors: | Carles Alcaraz Angelo Bisazza Emili García-Berthou |
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Institution: | (1) Institute of Aquatic Ecology, University of Girona, 17071 Girona, Spain;(2) Department of General Psychology, University of Padova, 35131 Padova, Italy |
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Abstract: | The interplay of abiotic factors and competition has a long history in ecology, although there are very few studies on the
interaction of salinity and competition in fish. Mosquitofish (Gambusia holbrooki) are among the most invasive fish worldwide, with well documented ecological impacts on several taxa such as amphibians and
small native fish. It has been previously hypothesized, based on field observations, that salinity limits the invasive success
of mosquitofish and provides a competitive refuge for Mediterranean cyprinodonts. We experimentally tested this hypothesis
by examining the agonistic behaviour and food competition between mosquitofish and an endangered native cyprinodont (Aphanius fasciatus) at three salinities (0, 15, 25‰). Intraspecific aggressive behaviour for both species was not significantly affected by
salinity. As salinity increased, mosquitofish decreased their aggressive behaviour towards cyprinodonts and captured less
prey. In contrast, the cyprinodonts did not change their behaviour with different salinity treatments, with the possible exception
of increased defensive acts in higher salinities, but captured more prey with increasing salinity because of the reduced efficiency
of mosquitofish. Our study confirms previous field observations that salinity limits the invasive success of mosquitofish
and provides one of the few experimental demonstrations that it may mediate behavioural and competitive interactions between
fish species. Condition-specific competition of mosquitofish might be expected with other species and ecosystems worldwide
and illustrates the importance of integrating biotic and abiotic factors in the study of interspecific interactions. |
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Keywords: | Condition-specific competition Agonistic behaviour Interference competition Gambusia holbrooki Aphanius fasciatus |
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