Environmental and Conservation Issues Kevin Fitzsimmons, Ph.D. Professor - University of Arizona Sec. / Tres. - American Tilapia Association President - US. Aquaculture Soc. Chapter of WAS May 30, 2001

Environmental Impacts Impacts of feral tilapia on native fishes Effluents Eutrophication - effluents contributing to nutrient enrichment Drug residues Processing plant wastes

Feral Tilapia Impacts of feral tilapia on native fishes Tilapia are “pioneer “ species, they thrive in disturbed habitats Often introduced into areas that have severe environmental damage where natives are already at risk

Feral Tilapia Tilapia have been introduced into 90 countries Many imported for weed or insect control Tilapia populations have escaped and fish have thrived in the wild Compete for food, nesting spots and other resources

Feral Tilapia Colorado River case Dams, diversion of water, remove flood danger Natives were adapted to survive during flood events, flows changed algae and invertebrate communities Tilapia constitute 90% of the river’s biomass

Solutions - Use all male tilapia All males, less likely to breed and become established Can be hormonally switched, genetically male, or triploids

Use red skin varieties of tilapia Red tilapia are easier to find if escaped Survival is low in the wild Predation is high from birds, fish, humans

Effluents Tilapia wastes rich in nitrogen, phosphorus, dissolved organic matter Increases Biological Oxygen Demand Increases dissolved carbon dioxide Nutrient enrichment and increased BOD contributes to eutrophication

Effluents Pond effluents can pollute receiving streams Raceway and tank systems have concentrated wastes from filters Cages contribute waste load to lake Salt water culture can impact reefs or other marine ecosystems

Solutions to eutrophication Use wastewater to irrigate field crops Good source of nitrogen, phosphorus and organic matter

Solutions to eutrophication Add 8 kg/ha of nitrogen with pond water

Solutions to eutrophication Add 2.5 kg/ha of phosphorus with pond water

Solutions to eutrophication - Integrate with shrimp culture Polyculture benefits Shrimp will graze on tilapia wastes

Integrate with shrimp culture Polyculture benefits Production in low salinity, low impact

Photo of mangrove in Peru

Mangrove farm in Peru Effluent from salt water tilapia can be used to irrigate and fertilize mangrove restoration Rich community is not good habitat for tilapia

Conservation of genetic variability Breeding to native tilapias Inbreeding of farm stocks

Conservation projects GIFT, and other breeding projects Domestication - Vests