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The First Genetically Engineered Fish
In the early 1980's, a cover story in Science captured the attention of many scientists with the first report of dramatic growth enhancement in an animal through genetic engineering. A few years later, scientists in the People's Republic of China produced the first genetically engineered fish (Zhu et al. 1985, Zhu et al. 1986). They inserted novel growth hormone genes into goldfish, hoping to increase the growth rates of farmed fish. Notably, faster growing genetically engineered fish could become the first animal GEOs approved for human consumption. Genetic engineering has become a tool for altering traits in aquatic organisms beyond what was possible through traditional breeding.

Growth-enhanced genetically engineered female mouse (59 g.), to the right of unmodified sister (28 g.). Both mice are approximately 24 weeks old. Photo (R.L. Brinster and R. E. Hammer, School of Veterinary Medicine, University of Pennsylvania) appears with permission from Science, Vol. 222, No. 4625, November 18, 1983. ©American Association for the Advancement of Science.

Marine Genetically Engineered Organisms (GEOs)
Early achievements prompted laboratories around the world to genetically modify a variety of marine genetically engineered organisms (marine GEOs). Researchers initially focused on modifying growth in fish that are farmed for human food. Some of these genetically engineered fish showed dramatically faster growth, reaching market size in one-quarter to half the normal time (Cook et al. 2000, Nam et al. 2001). These faster growing fish also converted food to energy more efficiently--they need less food per unit of growth (Nam et al. 2001, Nam et al. 2001a, Rahman et al. 2001). Efforts then expanded to insert a greater variety of fish genes in fish, shellfish, and algae. Table 1 summarizes representative examples of marine GEOs that are being engineered for aquaculture to produce human food; as bio-factories to produce pharmaceuticals, industrial chemicals or dietary supplements; in bio-remediation to remove contaminants from water; and as water quality monitors to detect contaminants that damage genes of living organisms.

Five growth-enhanced genetically engineered loach (largest is approximately 31 cm., 291 g.), pictured above their unmodified sibling (approximately 9.4 cm., 9 g.). The fish shown are six months old. Photo (from Nam et al. 2001) appears with permission from Journal of the World Aquaculture Society, Vol. 32, No. 4, December, 2001. ©World Aquaculture Society.

Five growth-enhanced genetically engineered coho salmon, to the right of their unmodified siblings. The fish shown are 14 months old; the largest transgenic fish is 41.8 cm. Photo appears with permission from Robert H. Devlin.

Marine GEOs Gain Ground
Research and development of marine GEOs took off rapidly for two primary reasons--ease and economics. Genetic manipulations are easier and often cheaper in fish and shellfish species than in terrestrial livestock such as chickens or pigs. The relative ease of regenerating adult algae from pieces of tissue or primitive cells makes these aquatic plants prime candidates for genetic modification. Aquaculture, the intended end use of many marine GEOs, is one of the fastest growing food-producing sectors; global production has grown at an annual rate of almost 10 percent since 1984 compared with 3 percent for livestock meat and 1.6 percent for capture fisheries (Inland Water Resources and Aquaculture Service 1997), amounting to 39.4 million tons of aquatic animal and plant production valued at U.S. $52 billion in 1998 (FAO Fisheries Department 2002). Aquaculture is also the fastest growing sector of US agriculture, with the total value of products sold increasing from $45 million in 1974 to over $978 million in 1998 (Anonymous 1997, National Agricultural Statistics Service 2000).

Advantages and Disadvantages of Marine GEOs: A Preview
Different people and different environments could experience different benefits or harms if businesses widely adopted some of the marine GEOs presented in Table 1. How would this affect different kinds of producers, consumers, and ecosystems? The outcome will depend on characteristics of the GEO and the environments into which it might escape. The outcome will also depend on how the GEO is produced, patterns of consumer acceptance, and other key social and economic factors.

Environmental risks of marine GEOs escaping from aquaculture systems vary depending on the facility, the GEO and accessible environments but are noteworthy enough to raise science-based concerns (Kapuscinski and Hallerman 1991, NRC 2002). The difficulty of preventing large-scale escapes from some facilities, such as floating cages, adds to these concerns. For example, thousands to hundreds of thousands of farmed salmon have escaped from fish cages damaged by storms, predators, and wear and tear (Carr et al. 1997, Youngson et al. 1997, Gross 1998, Fisk and Lund 1999, Noakes et al. 2000, Volpe 2000, Volpe et al. 2000). In a landmark settlement of a Clean Water Act lawsuit against one cage-farming business, Heritage Salmon, Inc., the parties agreed to a ban on the company's growing genetically engineered salmon strains in Maine (Environmental Law Center 2002; US District Court, District of Maine 2002). Marine GEOs raised on land in secure and properly managed recirculating aquaculture systems pose little or no hazard of escaping into natural waters. (A future issue of Marine Biotechnology Briefs will address assessment and management of environmental risks posed by escapes of marine GEOs.)

The environmental effects of widespread adoption of marine GEOs would also depend on how farmers choose to produce a GEO. Consider, for example, farming of growth-enhanced fish that reach market size in one-quarter to half the normal time and need less food. If a farm adopting such fish maintains its current annual level of production, the local environment would benefit from a significant reduction in uneaten food and feces discharged from the farm and the potential to fallow the grow-out site during part of the year. Alternatively, the faster growth to market size might stimulate farmers to run 2-4 production cycles in the time formerly needed for 1 cycle. The same grow-out site would therefore generate up to 2-4 times more feces and uneaten feed, which could substantially degrade water quality and the health and survival of aquatic organisms in the affected waters. Water quality risks would be greatest if the fish were grown in open floating cages, where the waste moves directly into the surrounding waters. The wastewater produced by fish raised in on-land facilities, from which the effluent comes out of a single pipe, can be more easily treated before being discharged into the environment. Fish raised on land in secure, recirculating aquaculture systems pose almost no water quality risks.

Better food conversion of growth-enhanced fish offers an environmental benefit by reducing fish farming's dependence on feed ingredients derived from wild-caught fish, of which many species are over-fished. Salmon, trout and some other farmed fish require fish meal or fish oil in their diet; better food conversion would reduce the amount of these ingredients needed for each gram or pound of weight gain. If future widespread adoption of faster growing genetically engineered fish stimulates an industry-wide increase in total production of farmed fish, then the total amount of wild-fish ingredients used by the industry would increase rather than decrease.

Other research may lead to commercialization of genetically engineered marine plants or microorganisms as biological factories to produce nutritional, pharmaceutical or industrial compounds. One example is the engineering of diatoms--microscopic light-dependent organisms--to thrive on simple sugar nutrients and no longer need light to grow. Future commercial developments based on this line of research could encourage a shift from producing diatoms and small algae in large outdoor lagoons or ponds to more easily controlled indoor fermentation tanks. This shift could reduce conversion of natural habitats into constructed lagoons or ponds and greatly reduce escape of the GEOs into natural waters. Commercial development would also raise questions about accidentally producing a new aquatic nuisance species because the engineered trait--thriving without light--could give these GEOs a competitive advantage over their wild counterparts in some cases. It would be important to assess the adequacy of containment in commercial facilities using indoor fermentation tanks and to conduct scientifically reliable tests of the ecological safety of the genetically engineered diatoms.

Safe Enough?
Blanket assertions claiming that marine GEOs are generally beneficial or generally risky are not realistic. Only with scientifically reliable and publicly credible safety assessments, verification and monitoring of different marine GEOs will policy makers have the adequate capability to decide if proposed uses of a marine GEO are safe enough (ISEES 2002). Forthcoming issues of Marine Biotechnology Briefs will examine an approach and the basis for making scientifically and publicly credible decisions about the risks and benefits of different marine GEOs.

Return to text of Marine GMO Brief-Issue 1

Finfish

Mullosks

Marine Plants

Marine Microorganisms

Crustaceans

Species	Target Modified Traits	Proposed Application	Status of Development
Finfish
Mud Loach	Increased growth rates, improved feed conversion and likely sterility after insertion of mud loach growth hormone driven by mud loach ß-actin regulatory region (Nam et al. 2001, Nam et al. 2001a)	Aquaculture for human food	Research
Channel Catfish	Enhanced bacterial resistance after insertion of moth peptide antibiotic, cecropin B gene (Dunham et al. 2002)	Aquaculture for human food	Research
Medaka	Faciliation of better detection of mutations (presumably caused by environmental pollutant factors) after insertion of a bacteriophage vector (serves as a mutational target). After exposure to mutagenic agent, vector DNA is removed, inserted into indicator bacteria--where mutant genes can be easily measured (Winn et al. 1995, Winn et al. 2000, Winn 2001, Winn 2001a, Winn et al. 2001)	Industrial uses; Environmental uses	Research; method has been patented
Atlantic salmon	Increased growth rate and food conversion efficiency by inserting Chinook salmon growth hormone gene that is switched on year-round, thereby fostering growth to occur year-round, rather than mainly in the summer (Cook et al. 2000, Hew and Fletcher 1996)	Aquaculture for human food	Method has been patented; FDA is reviewing application for commercial use
Red Sea Bream	Increased growth rates after insertion of an "all fish" growth hormone - ocean pout antifreeze protein gene promoter and Chinook salmon growth hormone (Zhang et al. 1998)	Aquaculture for human food	Research
Rainbow Trout	Improved carbohydrate metabolism after insertion of human glucose transporter type I and rat hexokinase type II, cloned with viral (CMV) and piscine (sockeye salmon metallothionein-B and histone 3) promoters. Potentially allows giving fish feed that contains plant materials. (Pitkanen et al. 1999)	Aquaculture for human food; Industrial uses	Research
Trout	Increased growth rate and food conversion efficiency via insertion of sockeye salmon growth hormone gene (Devlin et al. 2001)	Aquaculture for human food	Being used as a model for other research
Zebrafish	Production of male-only offspring by injecting into fish eggs an altered gene that prevents the fish's aromatase enzyme from transforming reproductive hormone androgen into estrogen; lack of estrogen prevents development of female fish (Woody 2002)	Biological control of aquatic nuisance species, such as carp	Research; being used as a model for other research
Carp	Improved disease resistance by inserting a human interferon gene (Zhu 2001)	Aquaculture for human food	Research
Goldfish	Increased cold tolerance after insertion of ocean pout antifreeze protein gene (Wang et al. 1995)	Aquaculture for human food	Research
Tilapia	Increased growth rate and food conversion efficiency after insertion of tilapia growth hormone gene (Martinez et al. 2000)	Aquaculture for human food	Seeking regulatory approval
Tilapia	Production of clotting factor after insertion of human gene for clotting factor VII, for medicinal applications (Aquagene 2001)	Pharmaceutical Production	Research
Tilapia	Increased growth rate, food conversion efficiency, and utilization of protein after insertion of chinook salmon growth hormone with ocean pout antifreeze promoter (Rahman et al. 2001)	Aquaculture for human food	Research
Mollusks
	Potential improved disease resistance and growth acceleration in mollusks by harnessing altered genetic material from a virus to introduce foreign DNA (Burns and Chen 1999).	Aquaculture for human food	Research; method has been patented
Oysters	Improved disease resistance by introduction of retroviral vectors. Researchers are determining most effective method of insertion (Lu et al. 1996, Burns and Friedman 2002)	Aquaculture for human food	Research
Marine Plants
Seaweed	Enhanced production of carrageenan or agar (both are valuable to the food, pharmaceutical, and cosmetic industries) after introduction of foreign DNA (Cheney and Duke 1995)	Industrial uses	Research; method has been patented
Algae (Spirulina)	Potential improved nutritional and medicinal value of commonly consumed Spirulina. Method to achieve such trait changes recently confirmed via successful integration and expression of a genetically engineered marker gene (Zhang et al. 2001)	Aquaculture for human food	Research
Algae	Enhanced ability to bind heavy metals after successful expression of a foreign class-II metallothionein (chicken MT-II cDNA) (Cai et al. 1999)	Bioremedial application	Research
Marine Microorganisms
Diatoms	Reduced dependence on light for growth after insertion of human gene for biochemical involved in metabolism of sugar (Zaxlavskaia et al. 2001)	Industrial uses	Research
Crustaceans
Crayfish	Production of transgenic offspring (in crayfish and live-bearing fish) after injection, in parents' gonads, of replication-defective pantropic retroviral vector. Successful transgenic individuals expressed neomycin phosphotransferase gene (neoR) (Sarmasik et al. 2001)	Aquaculture for human food	Research; being used as a model for other research
Kuruma Prawns	Potential improved growth rate through gene insertion. Researchers are currently inserting marker genes to confirm most appropriate GE method (Preston et al. 2000)	Aquaculture for human food	Research

References

Return to text of Marine Biotechnology Brief-Issue 1

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