51 



Ecological and genetic effects of cultured stocks on wild stocks. DifTerent types of 

 marine aquaculture operations ofTer difFerent degrees of confinement for cultured 

 fishes. Few individuals escap>e from on-shore tank culture systems. Large numbers 

 of fish escape from sea cage aquaculture operations (citations in Hallerman and 

 Kapuscinski 1992). Sea ranching operations involve deliberate release of entire 

 aquaculture stocks. Because very large numbers of individuals may be cultured, 

 even a small percentage of escapees may be large relative to native populations. 

 Hence, a large proportion of the fish in a given ecosystem may have originated from 

 aquaculture operations. For example, 15-20 percent of the salmon examined from 

 54 Norwegian rivers in 1987 were escapees from culture operations, ranging up to 

 80 percent in one particular river (Egidius et al. 1991). 



The importance of ecological impacts of cultured fish on native stocks is a matter 

 of controversy. In freshwater ecosystems, the ecological impacts of cultured 

 salmonids on wild stocks through competition and behavioral interaction (e.g., Vin- 

 cent 1974, Bachman 1984) have become well recognized. In estuarine and marine 

 systems, understanding of ecological interactions among cultured and wild stocks is 

 quite limited. Concerns center on competition for food resources in the estuarine 



?ortion of the life cycle, especially for out-migrating salmonids (Himsworth 1981). 

 he potential for competition among fish of aquaculture and wild origins in the open 

 ocean is debated, witn little quantitative information available. Potential ecological 

 effects of cultured aquatic organisms poses particular concern when threatened or 

 endangered sp)ecies and strains are in the ecosystem at issue. Authorization might 

 be provided in legislation for the research needed in these areas. 



The genetic implications of non-indigenous cultured stocks on wild stocks has be- 

 come a contentious issue, especially in the Pacific Northwest (Hilbom 1992, 

 Stickney 1994). Cultured stocks of a species differ genetically from wild stocks, 

 whether through deliberately practiced selective breeding or passively occuring 

 founder effects, genetic drift, and adaptation to culture conditions. Influx of fish 

 from mariculture operations poses a threat to native gene pools (Waples 1991, 

 Hindar et al. 1991). The array of gene frequencies for fitness-related traits con- 

 stitutes the native population's adaptation to its ecosystem, and frequently includes 

 combinations of genes which must oe expressed together for maximal fitness to be 

 realized. Mixing with an exotic gene pool can shift gene frequencies and disrupt im- 

 portant gene combinations, reducing the fitness of the native population. Major 

 shifts in allele frequencies can happen quickly — assuming that 30 percent of the in- 

 dividuals in a river originate from cultured stocks, over half of the genetic stock 

 structure of the species can be lost in one generation (Mork 1991), i.e., native gene 

 pools can be threatened with extinction. One of the most important factors leading 

 to the decline of over 200 salmon stocks in the Pacific Northwest is interaction with 

 cultured fish (Nehlson et al. 1991). 



The development of genetically modified aquatic organisms through gene transfer, 

 chromosome set manipulation, and interspecific hybridization, and their potential 

 use in aquaculture adds further complexity to the issue of ecological and genetic ef- 

 fects of cultured stocks on wild stocks (Kapuscinski and Hallerman 1990a, 

 Hallerman and Kapuscinski 1992). For example, dramatic growth rate increases 

 have been reported for Atlantic salmon expressing an introduced growth hormone 

 gene (Du et al. 1992), yet we have little sense of wnat impacts such fish might pose 

 were they to escape from a net-pen mariculture operation (Kapuscinski and 

 Hallerman 1990a, Hallerman and Kapuscinski 1992). Programs encouraging risk as- 

 sessment while promoting development of aquatic GMOs will be critical in address- 

 ing this gap in knowledge (Hallerman and Kapuscinski 1993). Suitable language 

 could be incorporated in the bill for the Marine Biotechnology Investment Act, if re- 

 introduced. 



Presence of infrastructure associated with aquaculture associated with culture op- 

 erations in public waters. Many people choose to live near the ocean or its bays in 

 order to enjoy amenities such as natural beauty. Aquaculture facilities, notably 

 floating net-pen operations, are widely held to be unsightly. Conflicts have ensued 

 between landowners and aquaculturists, which sometimes have been taken to the 

 courts. Lawsuits, or threat of lawsuits, have constrained the development or 

 mariculture in the United States, particularly in F*uget Sound. Targeted develop- 

 ment of submerged aquaculture systems should address aesthetic objections to 

 mariculature facilities in sensitive areas. 



A second infrastructure-related problem is posed by solid and liquid waste dis- 

 posal from processing and packing plants on the coast. Improved waste reduction, 

 use, and disposal methods are needed, which could be approached by authorization 

 of targeted research. 



Alteration of natural ecosystems. Siting of aquaculture operations sometimes has 

 had major impacts on natural ecosystems. For example, snrimp farms often have 



