Predation pressure of introduced mosquitofish (Gambusia holbrooki Girard), on the native zooplankton community. A case-study from representative habitats in the lower Mondego river Valley (Portugal)
2001; Volume: 20; Issue: 2 Linguagem: Inglês
10.23818/limn.20.26
ISSN2660-8537
Autores Tópico(s)Fish Biology and Ecology Studies
ResumoMosquitofish, Gambusia holbrooki, was introduced into the Iberian Peninsula in 192 1, becoming widely distributed in freshwater systems associated to rural and urban areas.However, the impact of its introduction on natural aquatic communities in such areas has never been properly assessed.In this paper, we evaluate the influence of G holbrooki on the zooplankton community of the river Mondego valley (Central Portugal).Spatial and temporal diet shifts were examined in two representative habitats of central Portugal, a typical rice field and a semi-natural protected wetland.Mosquitofish feed mainly on zooplankton (Copepoda, Cladocera, Rotifera and Ostracoda), although surface insects, such as aphids, collembolans, adult (imago) chironomids and other dipterans may constitute aditional food.Although Gambusia's ingestion rates are low, high population densities may cause a considerable predation pressure on zooplankton.Garnbusia was found to exert a stronger predation pressure on zooplankton in the rice field, where zooplankton presented scarcer populations, than in the semi-natural protected wetland.Consumption rates of Gambusia changed as a function of body size and reproductive period.Gambusia holbrooki exerted significant predation pressure on native zooplankton populations and certainly competed with other coexisting fish species.
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