1	Aquaculture and Invasive Species Amy J. Benson U.S. Geological Survey
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3	Nonindigenous species have been ranked second only to habitat loss as the greatest threat to biodiversity.
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5	Aquaculture in the U.S. Catfish Oysters Crawfish Trout Clams Baitfish Tilapia Hybrid striped bass Shrimp Mussels Sturgeon
6	Statutes Governing the Introduction of Exotic Species
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8	Fish Introductions Internationally
9	Number of foreign fish species introduced to each country
10	List of Species and Number of Countries into Which They Have Been Introduced Xiphophorus helleri 11 Procambarus clarkii 11 Oreochromis aureus 17 Poecilia reticulata 24 Salmo trutta 29 Hypophthalmichthys molitrix 38 Ctenopharyngodon idella 49 Micropterus salmoides 49 Cyprinus carpio 59 Oreochromis mossambicus 66 Oncorhynchus mykiss 82
11	Number of foreign fish species introduced to each continent
12	Salmonid Introductions Worldwide
13	Centrarchid Introductions Worldwide
14	Tilapia Introductions Worldwide
15	Asian Carp Species Introductions Worldwide
16	Crustacean Introductions Worldwide
17	Other Groups (not salmonids, centrarchids, tilapia, carps or crustaceans)
18	Reasons for which species have been introduced Aquaculture Sport Ornamental Improvement of wild stocks New food fisheries Fill a vacant niche Forage for predators Restoration of fisheries Establish a wild stock Accidental Escape or release from aquaria and bait bucket Diffusion through waterway Introduced with other species Live transportation for consumption Ballast water of ships Shipping water (zooplankton) Packing material (seaweed) Control of unwanted species Aquatic vegetation Mosquitoes Snails Blooms of phytoplankton Other fish (usually exotic)
19	Numbers of Nonindigenous Aquatic Species in the US by Pathway of Introduction Aquarium pet releases 161 Sportfishing 114 Bait bucket releases 94 Forage 48 Human food 22 Conservation 21 Biocontrol 20 Ornamental 19 Aquaculture farms 6 Unknown 4
20	Numbers of Nonindigenous Aquatic Species Introduced into the US Foreign to US Native to US Amphibians 13 24 Crustaceans 15 15 Fishes 176 331 Mollusks 29 7 Reptiles 21 33
21	Percentages of All Aquatic Species in the US Introduced from Other Continents South America 22 Asia 20 Eurasia 16 Europe 13 Africa 12 Central America 6 Australia 2 South Pacific 1 Oceans 1 Unknown 4
22	Attributes for Successful Colonization Broad physiological tolerances for: Temperature extremes Low oxygen levels Fluctuations in salinity Turbidity and pollution Drought Feeding habits and diet: Diet composition Feeding schedules Vulnerability to predation Reproductive behavior: Rapid growth and maturation Extended or continuous breeding Multiple clutches Advanced parental care
23	Risks from Introductions Degradation of host environment: Changes in vegetation Changes in water quality turbidity, DO, pH, temp., siltation, eutrophication Disruption of host community: Competition Predation Stunting Genetic degradation of host stock: Hybridization Introduction of diseases and parasites Spatial alterations Aggression Overcrowding
24	Risks from Aquaculture Nutrient pollution Organic matter, nitrogen, phosphorus Algae and phytoplankton blooms Oxygen depletion Bacterial pollution Water conflicts (depletion of water supplies) Hatchery predators Chemical pollution (herbicides, antibiotics)
25	Documentation of the Impacts of Introduced Species Horwitz 1982 Philip 1983 Murphy and Terre 1984 Barel et al. 1985 Hocutt et al. 1986 Deacon 1988 Echelle and Connor 1989 Waples et al. 1990 Minckley and Deacon 1991 Moyle and Leidy 1992 Courtenay 1993 Tyler et al. 1999
26	Ways to prevent or minimize impacts Diking ponds (questionable) Sand and gravel filtration of all effluent Keep out of flood prone areas Assure triploidy Sterilization
27	Benefits from Aquaculture Supply of healthy fish and shellfish for human consumption (protein source) Recreational fishing opportunities Supports local (and global) economies Bait & tackle stores, marinas, motels & restaurants Aquarium animals for hobbyists Jobs
28	Plants closely associated with aquarium trade known to be invasive Hydrilla verticillata (Hydrilla) Egeria densa (Brazilian waterweed) Hygrophila polysperma (Indian hygrophila) Limnophila sessiliflora (Asian marshweed) Myriophyllum aquatium (parrot’s feather) Najas minor (brittle naiad) Spirodela punctata (dotted duckweed)
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31	Aquarium fishes
32	Gene Emond
33	Bighead carp
34	Silver carp (Hypophthalmichthys molitrix)
35	Silver carp
36	Grass carp (Ctenopharyngodon idella) Imported for rooted aquatic weed control Have been introduced into 45 states Impacts include: Competition for food with invertebrates Changes in macrophyte, phytoplankton, and invertebrate communities Interference with reproduction of other fishes Reproducing in the wild (KY, TN, IL, MS, AR, TX, MO, LA)
37	Grass carp
38	Black carp (Mylopharyngodon piceus)
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40	Armored catfish (Pterygoplichthys multiradiatus)
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46	Daphnia lumholtzi
47	African clawed frog (Xenopus laevis)
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51	Summary Aquaculture can have little impact on our natural resources if taken into consideration Aquaculturists must take some responsibility All releases or escapes have an impact however minute it may be The movement of biological material for the purpose of aquaculture does not have to stop, but procedures should be adopted to minimize the risk of introductions into the wild
52	Recommended Reading Nonindigenous Freshwater Organisms by Claudi and Leach (eds.), 2000 Nonindigenous Fishes by Fuller, Nico, & Williams, 1999 Harmful Non-Indigenous Species in the United States by U.S. Congress, 1993 Dispersal of Living Organisms into Aquatic Ecosystems by Rosenfield and Mann (eds.), 1992. Introductions and Transfers of Marine Species by DeVoe (ed.), 1992 Biological Pollution by McKnight (ed.), 1993 International Introductions of Inland Aquatic Species by Welcomme, 1988, FAO Tech. Pap. 294 Distribution, Biology, and Management of Exotic Fishes by Courtenay and Stauffer (eds.), 1984 Murky Waters: Environmental Effects of Aquaculture in the US by Goldburg and Triplett, 1997 (Report by the Environmental Defense Fund)