Marine Aquaculture Opportunities for Growth (1992) / Chapter Skim
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Environmental Issues
Environmental Issues
Pages 92-115
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From page 92... ...
. ENVIRONMENTAL IMPACTS OF MARINE AQUACULTURE Introduction Concerns about the environmental impacts of marine aquaculture include such diverse issues as waste from cages or ponds, introduction of nonindigenous species or disease, the presence of infrastructure associated with culture operations in public waters, and genetic alterations of wild stocks through escapement of cultivated animals or intentional releases for stock enhancement.
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From page 93... ...
Aquatic plant culture using traditional rafting techniques relies on available dissolved nutrients and sunlight. Cultivated aquatic plants remove nutrients and limit eutrophication of the coastal environment.
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From page 94... ...
disease-related threats to indigenous species; and (3) threats related to water quality degradation in the effluent receiving stream.
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From page 95... ...
Although no cases of aquaculture operations causing disease outbreaks in adjacent wild stocks have been documented, continued vigilance, escapement prevention, and shrimp disease research are essential if this industry is to continue to develop in the United States. For shrimp culture in the United States to be competitive in the worldwide shrimp marketplace, farms must use intensive production technology (Sandifer, 1988; Wyban and Sweeney, 19914.
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Water Quality Finfish or shrimp in ponds or tanks dramatically affect water quality primarily through excretions from feed inputs. Water quality differences between inlet and effluent waters are a function of the loading of fish, the water exchange rate (retention time)
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From page 97... ...
Pond effluent dissolved oxygen may be higher than that of the receiving body during the day due to photosynthetic activity. Cage systems are not artificially aerated and nave rapid water exchange.
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From page 98... ...
The composition of waste from cultured fish differs little from that contributed naturally by wild fish, but it differs significantly from that of warm-blooded animals. The effect of culture operations on coliform, and particularly fecal coliform bacteria, is a water quality concern.
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From page 99... ...
Settleable waste from culture operations may alter the ecosystem by changing the physical and chemical environment or by changing or reducing the numbers and species resident beneath net pens or downstream from effluents. Solid waste is estimated at between 0.5 and 0.7 g for each kilogram of fish produced (Paramatrix, 19901.
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From page 100... ...
"Concentrated aquatic animal production facilities" are defined as a hatchery, fish farm, or other facility that meets the criteria in appendix C of the Clean Water Act, or any such facility that the director determines is a significant contributor of pollution to waters. The criteria provided in appendix C generally include commercial-size marine aquaculture fish farms or other facilities that "contain, grow, or hold cold water aquatic animals in ponds, raceways, or other similar structures which discharge at least 30 days per year." Therefore, aquaculture production facilities that meet these criteria or are found to be significant contributors to water pollution are subject to NPDES permits under the Clean Water Act.
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From page 101... ...
Will the introduced species physically alter its surroundings? · Hybridization: Will inhibition of reproduction or, at the other end of the spectrum, interbreeding dilute or degrade native gene pools, reducing the potential for future benefits from wild gene stocks?
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From page 102... ...
argue against a purist opposition to mixing gene pools of Atlantic salmon for release. Genetic issues apply to all cultured species, but a recent controversy involves private salmon ocean ranching and public fisheries enhancement along the West Coast, where hundreds of millions of hatchery fish are released yearly (Waples et al., 1990~.
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From page 103... ...
farming is intensive and only remnant wild populations remain (NASCO, 1990~. The major risk from these hatchery programs is ecological interaction of hatchery and wild fish, resulting from overstocking natural waters or allowing wild stocks to become severely depleted (Sattaur, 1989~.
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From page 104... ...
Most cases of disease transfer from cultured to wild stocks occur in conjunction with introductions of nonindigenous species or populations. Weston's (1991)
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From page 105... ...
, and the states exercise varying degrees of control over the use and introductions of exotic nonindigenous species. Requirements include importation permits, an environmental risk report, inspection certifying the lack of disease, and in some cases, a disease history of the stock.
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From page 106... ...
Jacobsen (1989) reported OTC in the sediments beneath net pens in Norway, and drug resistance was transferred from a fish pathogen to a human pathogen in vitro and at temperatures as high as 36°C (Toranzo et al., 1984~.
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From page 107... ...
The process for obtaining formal approval of a drug is likely to involve a timeconsuming and expensive process. The FDA points out that current federal and state funding for drug development research is inadequate to meet the needs of the aquaculture industry, and suggests that congressional appropriations be allocated for this endeavor (Water Farming Journal, 1991~.
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This problem has resulted in the elimination of one-half or more potential culture sites in many regions, including the Chesapeake Bay and San Francisco Bay. Closures are also caused by nonpoint sources of pollution.
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From page 109... ...
RESOLVING ENVIRONMENTAL PROBLEMS In some cases, the mitigation of environmental problems associated with marine aquaculture may be possible through improved understanding of biological and ecological factors involved in culturing various marine species, and through engineering and technology solutions that allow new approaches to siting and to culture operations. These options are explored in
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From page 110... ...
Pp. 15-33 in Aquaculture Systems Engineering: Proceedings of the World Aquaculture Society and American Society of Agricultural Engineers Jointly Sponsored Session.
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From page 111... ...
Sandifer, ed. Baton, Rouge, La.: The World Aquaculture Society.
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World Aquaculture Society, World Aquaculture 90, Abstract T 17.2.
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Sandifer, ed. Baton Rouge, La.: World Aquaculture Society.
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Baton Rouge, La.: World Aquaculture Society. Weston, D.P., and R.J.
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From page 115... ...
1991. Intensive Shrimp Production Technology; the Oceanic Institute Shrimp Manual.
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