Advances in biotechnology over the past several decades have provided the tools necessary for artificial manipulation of genes and chromosomes in living organisms. The creation of transgenic fish and shellfish is a topic of great interest in aquaculture research due to the potential improvements in production that this technology can offer (Zbikowska 2003; Dunham 2004). Major areas of transgenic research in fish include use of growth hormones (GHs) to increase growth and feed conversion efficiency; use of antifreeze proteins (AFPs) for enhanced cold tolerance and freeze resistance; use of antimicrobial peptides for increased disease resistance; use of metabolic genes to promote low-cost, land-based diets; and genetic methods for inducing sterility. Although transgenic work in fish is well established, research with marine invertebrates is only in the initial stages due to complications with introduction and expression of foreign genes. Early research with marine invertebrates has led to the development of successful gene transfer methods, with studies focused on improving disease resistance. In addition to transgenic research, advances in chromosome manipulation (polyploidy) also show potential for improving production in the aquaculture industry, particularly in the case of shellfish. Use of polyploidy in aquaculture can result in sterility, along with enhanced growth and survival rates and increased quality of final products. 

The aquaculture industry is the fastest growing of the animal food-producing sectors, increasing at an average rate of 8.9% per year since 1970 (FAO 2004). Although landings from capture marine fisheries increased about 5-fold in the period from 1950 to 1990, annual growth has become slow to stagnant over the past 15 years (FAO 2000, 2006). As a result of factors such as population growth, urbanization, and rising per capita incomes, world fish consumption more than tripled over the period of 1961 to 2001, increasing from 28 to 96.3 million metric tons (FAO 2004). The global demand for fish and fishery products is predicted to continue to increase in the years to come—from 133 million tons in 1999 to 2001 to 183 million metric tons by the year 2015. Taking into account indications that capture fisheries are close to or have already reached their potential, the world is looking toward aquaculture and its technologies to fulfill the expanding food demands: by 2020, aquaculture is expected to supply 41% of the global food fish production (compared to 3.9% in 1970 and 29.9% in 2002) (Delgado and others 2002; FAO 2004). 

Despite predictions of a growing aquaculture industry, stagnant world capture fisheries and increased populations are projected to lead to a global shortage of fish and fish products in the years to come (Delgado and others 2002). As a result, prices are expected to rise: it has been predicted that by 2015, fish prices will increase by about 3.2%1 (FAO 2004), and by 2020, prices for mollusks, finfish, and crustaceans are expected to increase by 4% to 16%2 (Delgado and others 2002). Use of biotechnology in aquaculture has the potential to alleviate these predicted fish shortages and price increases by enhancing production efficiency, minimizing costs, and reducing disease. However, the incorporation of transgenic organisms into the food chain has been met with massive criticism from both the environmental and human health sectors. This review paper will cover current advances in the manipulation of genes and chromosomes for use in aquaculture along with a discussion of the controversy surrounding transgenic technology in aquaculture. 

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