Environmental Impacts of Aquaculture Effluents Josh Vinson

Aquaculture Industry Increase in seafood demand due to: 1. Increased per capita consumption 2. Increased global population Wild food fish populations currently being over fished Wild caught fish production has remained steady at 60-70 mT /yr since early 1980’s Wild caught fish production can’t be increased Increased seafood demand must be met with increase in cultured seafood -rapid industry growth = environmental concern?

Aquaculture Effluent Effluents: refers to either a continuous or intermittent discharge of a liquid from an aquaculture facility Effluent composition Dissolved compounds 1. Phosphorus 2. Nitrogen Sludge Fecal material and uneaten feed

Dissolved Compounds Phosphorus and Nitrogen Organic matter Cause eutrophication Algal blooms Kills fish and other benthic organism alterations in food chains removal of oxygen Organic matter Increased BOD Decreases DO in water column and sediments Alters benthic food chains and ecology Can kill higher life

Sludge Sludge: refers to the solid particulate portion of aquaculture effluents. Composed primarily of fecal material and uneaten feed. Volume directly related to feeding rates. Nutrients (P, N), and organic matter leaches out or is broken down and ultimately becomes dissolved compounds. Impacts are the same as those for dissolved compounds, but management and treatment differs. End product of sludge treatment is typically used as agricultural fertilizer.

Aquaculture Methods And Associated Degree of Environmental Impact 3 Broad categories of aquaculture Extensive Deals primarily with shellfish slow, low-volume, dilute continuous waste Semi-intensive Cages High stocking densities large volume of continuous, untreated waste released Raceways large volume of continuous, treated waste. Ponds Intermittent release of, treated waste. Intensive Closed – recirculating systems (CRSs)

Aquaculture Methods

Management Strategies Goal: Reduce environmental impact of aquaculture without decreasing production Funding for research Improve feed conversion ratios (FCR) –ratio of gain in wet body weight to the amount of feed fed Improve organism-specific feeds to increase nutrient retention. Improve waste treatment methods Educate Farmers on: Method benefits and drawbacks Integrated aquaculture techniques Ex Waste-water-fed mollusk farming can be used to recover excess nutrients Best Management Practices (BMP) plans Encourage communication between researchers and commercial facilities via conferences and meetings