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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 25 20 15 Well Pond 10 5 em be r Se pt Au gu st Ju ly Ju ne M ay 0 Ap ril Total N applied with water (kg/ha) • Add 8 kg/ha of nitrogen with pond water Solutions to eutrophication 3 2.5 2 Well Pond 1.5 1 0.5 em be r Se pt Au gu st Ju ly Ju ne M ay 0 Ap ril Total P applied with water (kg/ha) • 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
