Transcript Environmental and Conservation

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
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Total N applied with water (kg/ha)
• Add 8 kg/ha of nitrogen with pond water
Solutions to eutrophication
3
2.5
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Well
Pond
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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