Status of Nile Tilapia (Oreochromis niloticus) in Southern Mississippi

• What is the geographic distribution of Nile tilapia in southern Mississippi?
• How has this distribution changed over time (since introduction in the early 1990s)?
• What factors cause changes in distribution (e.g., shifts in environmental conditions; hurricanes)?
• What tools are available to either control or restrict expansion of the species?
• What effects does the species have on native fauna and habitats?

Goals:

• Monitor Nile tilapia populations
• Control Nile tilapia where possible (with assistance of State officials)
• Understand what environmental variables lead to changes in abundance and/or health
• Apply findings to other tilapia populations (where applicable)

From our field sampling, it appears that the hurricanes of 2005 (Katrina, Rita) did not disperse tilapia in southern Mississippi. This is a surprising finding, given that the storms flooded much of the coastal areas of southern Mississippi with a storm surge up to 30 feet.

Additionally, in 2006 we successfully controlled a population of Nile tilapia that was inhabiting an aquaculture facility that had been damaged by the hurricanes (and subsequently closed). This work stemmed the potential egress of these fish into the nearby natural marsh areas.

The salinity tolerance of Nile tilapia must be determined to help focus field sampling. Future sampling efforts will: 1) monitor the abundance and health of known populations, and 2) search for populations in areas where the species will likely expand its geographic range.

	Contact: Pamela J. Schofield, Ph.D. Florida Integrated Science Center, U.S. Geological Survey 7920 NW 71st Street Gainesville, FL 32653 pschofield@usgs.gov Website: http://fisc.er.usgs.gov/Nile_tilapia/nile_tilapia.html