The occurrence of non-indigenous Nile tilapia, Oreochromis niloticus (linnaeus) in coastal Mississippi, USA: Ties to aquaculture and thermal effluent

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We studied the distribution and abundance of Nile tilapia, Oreochromis niloticus near two aquaculture facilities for two years in coastal wetlands in southeastern Mississippi, USA. In 280 collections, we represented 29 families, 65 taxa, and 86,415 fishes with a variety of gear types. Oreochromis niloticus ranked sixth in abundance overall and ranked second among those stations sampled in the Pascagoula River watershed and sixteenth among Coastal River stations. Water temperature downstream from the facility effluents was always warmer than ambient, and at the Pascagoula River facility, it never dropped below 15.1°C over the three years examined. Thus, normal environmental conditions, the presence of the downstream thermal refuge, and the generally low salinity of the bayous of our region all combine to provide a quality environment for continued survival of released fish. Furthermore, O. niloticus seem to spawn year-round, and fish as small as 79.9 mm TL were found to carry mature eggs, suggesting that, if they are born early in the season, they could reproduce during their first summer of life. Further spread of O. niloticus and introduction of new species are expected as aquaculture expands. The philosophy that allows the escape or release of non-indigenous taxa into our present landscape, justified by the belief that species will not survive or become established, is fallible.