Final Report Summary - INVASIVE FISH (The effects of invasive fish on native species)
Invasive introduced species are a leading cause of biodiversity loss and global change. Understanding the ecological impacts of introduced species and how abiotic factors mediate their invasive success is of enormous conceptual and applied importance. The mosquitofish (Gambusia holbrooki) is among the 100 worst invasive species and has been shown to displace a number of native amphibian and fish species. The overall aim of this project was to investigate interactions between invasive mosquitofish and native Iberian species using a range of theoretical (modelling, biostatistics, information capture), experimental (field and aquarium studies) and ecological (surveys, environmental measurements) techniques. Specific objectives were to: i) experimentally test the competition between G. holbrooki and an endemic, threatened cyprinid (Aphanius iberus); ii) test whether intrinsic and extrinsic factors mediate this competition; and iii) assess wider ecological effects of interactions between these two species.
From the perspective of the impacts of the invasive species medium size individuals and males are likely to have a greater effect. Moreover, the effects of male mosquitofish are not limited to aggression as their harassment of native female fish is likely to disrupt normal social interactions of, and potentially causing physical damage to, A. iberus. Any of these effects are likely to be more severe at higher temperatures when mosquitofish are more active. Conversely, for the native species we showed that medium sized and female fish are more vulnerable, but at lower temperature any harmful interactions will be less severe. In addition to furthering scientific knowledge these results can contribute to conservation efforts by highlighting which individuals of the invasive species to target in management and eradication programs and which endemic species individuals are in greater need of protection. This also adds to the growing body of information available to policy makers concerned with the effects of climate change.
In terms of environmental pollutants we showed that the behaviour of the invasive species is affected by arsenic exposure. As G. holbrooki has been introduced worldwide, and arsenic pollution is a wide-reaching problem, this is a potentially globally important finding. Moreover, the algae which were thought to ameliorate the harmful effects of arsenic by absorbing these chemicals may actually increase the problem. As eutrophication may be caused by increased aquatic ammonia and ammonia is a byproduct of fish metabolism, the differing potential for eutrophication by native and invasive fish species and possible chemical interactions between these two species may also be important. This will shed light on the wider environmental effects of this invasive species thus again providing information to aid policy makers in conservation efforts.
From the perspective of the impacts of the invasive species medium size individuals and males are likely to have a greater effect. Moreover, the effects of male mosquitofish are not limited to aggression as their harassment of native female fish is likely to disrupt normal social interactions of, and potentially causing physical damage to, A. iberus. Any of these effects are likely to be more severe at higher temperatures when mosquitofish are more active. Conversely, for the native species we showed that medium sized and female fish are more vulnerable, but at lower temperature any harmful interactions will be less severe. In addition to furthering scientific knowledge these results can contribute to conservation efforts by highlighting which individuals of the invasive species to target in management and eradication programs and which endemic species individuals are in greater need of protection. This also adds to the growing body of information available to policy makers concerned with the effects of climate change.
In terms of environmental pollutants we showed that the behaviour of the invasive species is affected by arsenic exposure. As G. holbrooki has been introduced worldwide, and arsenic pollution is a wide-reaching problem, this is a potentially globally important finding. Moreover, the algae which were thought to ameliorate the harmful effects of arsenic by absorbing these chemicals may actually increase the problem. As eutrophication may be caused by increased aquatic ammonia and ammonia is a byproduct of fish metabolism, the differing potential for eutrophication by native and invasive fish species and possible chemical interactions between these two species may also be important. This will shed light on the wider environmental effects of this invasive species thus again providing information to aid policy makers in conservation efforts.