49 



for NOAA's mariculture programs, and it is in this context that I offer my comments 

 today. The committee chairman has asked me to discuss the environmental effects 

 associated with marine aquaculture, and to briefly address the role of science and 

 technology in promoting environmentally sound marine aquaculture. 



ENVIRONMENTAL EFFECTS ASSOCIATED WITH MARINE AQUACULTURE 



Aquaculture, like all agriculture, causes environmental impacts. The environ- 

 mental impacts of aquaculture have received particular scrutiny because 

 mariculture is fairly new in the United States and because it frequently is con- 

 ducted in public waters (National Research Council 1992). As we consider reauthor- 

 ization in light of national ocean policies, we must design programs which promote 

 marine aquaculture while protecting the environment. NOAA programs should pro- 

 mote aquaculture development which not only is economically viable, but also 

 enviromentally sustainable. Environmental concerns associated with marine aqua- 

 culture are diverse, ranging from introduction of exotic species to impacts of aqua- 

 culture effluents to ecological and genetic impacts of escaped aquaculture stocks on 

 wild stocks. I will provide a brief overview of the major concerns posed by aqua- 

 culture, providing references to more thorough reviews. 



Introduction of exotic species. With the growth of mariculture, the frequency of 

 new species introductions has grown, especially over the past 25 years. The rise of 

 mariculture has led to broad distribution of finfisn, especially salmonids 

 (Sindermann 1986), shrimps, and molluscs (Chew 1990). In addition to the desired, 

 positive impacts of species introductions for mariculture, a growing body of evidence 

 indicates negative ecological and socioeconomic effects. These impacts include: 



• Introductions of pathogens and parasites. Two cases leading to major economic 

 impacts are: (1) the introduction of the protozoan parasite Bonamia ostreae to Eu- 

 rope with the softshell clam Mya arenaria (Chew 1990), which led directly to the 

 loss of the softshell clam fishery in Europe, and (2) the wide spread of infectious 

 hypodermal and hematopoietic necrosis virus (IHHNV) with the distribution of 

 shrimp from Central and South America (Sindermann 1986). 



• Habitat alteration. Through their growth or activities, introduced species can 

 alter the physical habitat characteristics of the receiving ecosystem, negativelv im- 

 pacting indigenous species and human activities. For example, introduced witn Pa- 

 cific oysters, the seaweed Sargassum muticum has become a nuisance to boaters 

 and fishermen on the coasts of Vancouver Island (Bourne 1979). 



• Heightened competition or predation. For example, prodigious settlements of ju- 

 venile Pacific oyster Crassostrea gigas resulted in its colonization of all sites for- 

 merly occupied by C. anguiata in France (Maurin and LeDantec 1979), destroying 

 the fishery for the latter. 



• (}ene pool deterioration. The possibility that an introduced species can hybrid- 

 ize with an indigenous species poses the danger of compromising the fitness or even 

 the genetic integrity of the indigenous species. For example, poor management of 

 tilapia stocks (Oreochromis sp.) nas allowed unwanted hybridization of previously 

 pure species by escapes into the wild and vice versa (McAndrew and Maiumdar 

 1983). Interspecific hybridization of tilapia stocks is so widespread that it has be- 

 come difficult to find pure-species stocks and the performance of many stocks has 

 been compromised (Pullin 1983) 



• Unwanted socioeconomic effects. For example, introduction of the exotic Pacific 

 oyster Crassostrea gigas in Australia for mariculture purposes led to decline of the 

 Sydney rock oyster Saccostrea commercial is, which was the object of a commercial 

 fishery (Chew 1990). 



Environmental issues posed by exotic aquatic species are treated in depth by the 

 American Fisheries Society (1986), Courtenay and Stauffer (1989), Pollard (1989), 

 DeVoe (1992), Rosenfield and Mann (1992), Sindermann et al. (1992), and the Office 

 of Technology Assessment (1993). A number of protocols for reaching decisions on 

 proposed introductions of non-indigenous species exist (Sindermann 1986, Kohler 

 and Courtenay 1986), and federal policies are being formulated consequent to adop- 

 tion of the Non-indigenous Aquatic Nuisance Prevention and Control Act of 1990. 



Introduction and spread of parasites and diseases. Movements of cultured species 

 consequent to mariculture activity often has caused the simultaneous introduction 

 of parasites and pathogens even in cases where the host was an indigenous species. 

 The most dramatic example may be the monogenean fluke Gyrodactylus salaris, 

 which is believed to have been introduced into Norwegian waters with the import 

 of Atlantic salmon smolts for mariculture in the 1970s. It has now spread to 32 Nor- 

 wegian river stocks (Egidius et al. 1990), where it has become one of the primary 

 causes of mortality (Johnson and Jensen 1988). Adoption of a protocol for quar- 

 antine of newly-imported aquaculture stocks, such as that outlined by Sindermann 



