Distribution, diet and potential ecological impacts of the introduced Mozambique mouthbrooder Oreochromis mossambicus Peters (Pisces: Cichlidae)in Western Australia

摘要

Oreochromis mossambicus is a highly successful invader of aquatic ecosystems due to its adaptable life history, trophic flexibility, ability to tolerate extreme and often unfavourable environmental conditions and maternal care of offspring. Upon introduction to areas outside of its natural range, these characteristics often give O. mossambicus a competitive advantage over indigenous fishes. Accordingly, O. mossambicus may have deleterious impacts on aquatic communities. Since nonindigenous O. mossambicus populations were first observed in Western Australia in the Gascoyne/Lyons River system (ca 25°S) in 1981, the species has spread north to the Lyndon and Minilya Rivers (ca 23°S), and south to the Chapman River (ca 28°S). There is a high probability of further range expansions of this cichlid in Western Australia due to natural dispersal and human-mediated translocation. Adult and juvenile O. mossambicus consumed primarily detritus and vegetal matter, though juveniles collected from the Gascoyne River were carnivorous. There was no demonstrable dietary overlap between O. mossambicus and the carnivorous and omnivorous sympatric species in the Chapman and Gascoyne Rivers. However, a statistically significant dietary overlap was noted between O. mossambicus and the native species Craterocephalus cuneiceps and Hypseleotris aurea in the Lyons River. Anecdotal observations of agonistic behaviour by breeding male O. mossambicus indicated that such behaviour was mainly directed towards other breeding males. The semi-arid climate of the Indian Ocean (Pilbara) Drainage Division results in the reduction of riverine habitats to small isolated pools during extended dry periods. Thus, in these restricted environments resource competition may occur between O. mossambicus and indigenous species.