Exotic Species

The hypersaline environments and salterns present in the western Mediterranean region (including Italy, southern France, the Iberian Peninsula and Morocco) contain autochthonous forms of the brine shrimp Artemia, with parthenogenetic diploid and tetraploid strains coexisting with the bisexual species A. salina. Introduced populations of the American brine shrimp A. franciscana have also been recorded in these Mediterranean environments since the 1980s. Based on brine shrimp cyst samples collected in these countries from 1980 until 2002, we were able to establish the present distribution of autochthonous brine shrimps and of A. franciscana, which is shown to be an expanding invasive species. The results obtained show that A. franciscana is now the dominant Artemia species in Portuguese salterns, along the French Mediterranean coast and in Cadiz bay (Spain). Co-occurrence of autochthonous (parthenogenetic) and American brine shrimp populations was observed in Morocco (Mar Chica) and France (Aigues Mortes), whereas A. franciscana was not found in Italian cyst samples. The results suggest these exotic A. franciscana populations originate as intentional or non-intentional inoculations through aquacultural (hatchery effluents) or pet market activities, and suggest that the native species can be rapidly replaced by the exotic species.

For some time, the rate of non-native fish introductions has been increasing in South America. There are many reasons for introductions: reservoir stocking programs, aquaculture, sport fishing, control of disease vectors, and the pet trade. Accidental
escapes also contribute significantly. In Brazil, despite federal and state regulations, there are misunderstandings about such concepts as native, exotic, allochthonous, or autochthonous fishes and introductions, translocations, reintroductions, and transfers of fishes. Known impacts of exotic fishes include native species extinction, changes in competition and predation rates, limnological perturbations, introduction of diseases and parasites, hybridization with native species, and changes in fisheries composition. The few recorded benefits of non-native species introductions are restricted to the improvement of fish production and sport fisheries. InMinas Gerais, Brazil, records of exotic species have increased over the past seven years. In some of the most important river basins of that state, alien fish species might represent up to 40% of the fish fauna. Congeneric species, such as Hyphessobrycon bifasciatus and the exotic H. eques, can be captured from the same water body and the non-native species can be much more abundant than the native species. The recent introduction of Leporinus macrocephalus from the Pantanal may cause the same impact to the native
L. copelandii. The widespread introduction of the peacock bass and other piscivorous species is the cause of local extinctions in the central lake of Lagoa Santa and in the Rio Doce valley lakes. Genetic problems can also be foreseen with the release of
hybrids of Pseudoplatystoma corruscans and P. fasciatum in areas where only the first species naturally occurs. Tilapine species, the most widely distributed exotics within
the state, have had negative impacts on fisheries and on fish species compositions in reservoirs. Solution to these problems must involve the following: (1) better enforcement of legislation governing the sale and transport of live organisms, (2) development of native-species aquaculture, and (3) public awareness programs on the adverse impacts of exotic species to the native fish fauna.