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Utilization of Transgenic Fish in Developing Countries: Potential Benefits and Risks

Utilization of Transgenic Fish in Developing Countries: Potential Benefits and Risks REX A. DUNHAM International Center for Living Aquatic Resources Management, MCPO Box 2631, 0718 Makati City, Philippines Abstract Recombinant DNA and gene transfer technology now allow the transfer, inheritance and expression of specific DNA or gene sequences into fish. Preliminary results on the performance of the resulting transgenic fish have been quite dramatic in some cases, especially when growth hormone genes are transferred. Utilization of high performance transgenic fish has the potential to greatly increase aquaculture production in developing countries and increase the income of poor farmers. Growth of some transgenic fish has been increased more than 10-fold in laboratory conditions. Response appears to be greatest in unimproved fish, which in most cases would benefit developing countries the most. The potential increase in production and production efficiency from successful transgenic fish application could relieve pressure on habitat destruction for food production, relieve pressure on overtished natural stocks and discourage introduction of exotic species. Application of transgenic fish in aquaculture has just begun and could expand within a few years. However, prior to commercialization of transgenic fish, public education, environmental risks and food safety issues should be addressed. Genetically improved fish generated by recombinant DNA technology probably do not pose any greater risk to the environment than fish genetically improved through traditional selective breeding, but environmental risk data is lacking to verify this hypothesis. Environmental risk data will be needed in a case-by-case basis until more is known concerning the aquaculture potential and ecological risk of transgenic fish. Research institutions need to address the lack of environmental risk data to help ensure that any future application of transgenic fish in developing (and developed) countries be done in an environmentally and socioeconomically sound manner. Socioeconomic study is lacking for detailed cost-benefit analysis, and policy research is needed for proper application or regulation of transgenic fish in these countries. Gene Transfer i Fish n Successful transfer of recombinant DNA into fish was first accomplished in 1985 (Zhu et al. 1985). Gene transfer in fish is now commonplace (Dunham 1990; Chen et al. 1995; Dunham 1996; Iyengar et al. 1996). Originally, DNA sequences from a variety of organisms, viruses, bacteria, animals, birds, fish and humans were transferred to fish. Although small DNA sequences from these organisms do not impart the general characteristics of these organisms to fish, most researchers have now chosen to focus on transfer of fish DNA constructs into fish to increase the likelihood of social acceptance of transgenic fish and because of the belief that fish-based constructs are more effective, although the latter has not been confirmed by research (Devlin et al. 1995). The initial transfer of fusion gene constructs into fish embryos results in mosaic individuals (Dunham 1990). In most cases, the effect of the transgene cannot be accurately measured in mosaic individuals. Fortunately, if the transgene is integrated in the gonadal tissue, the introduced DNA is usually inherited in a Mendelian fashion (Stuart et al. 1988, 1990; Zhang et al. 1990; Shears et al. 1991; Dunham et al. 1992; Chen et al. 1993) and the resulting progeny have the foreign DNA in every cell, allowing accurate evaluation of the expression and biological effects of the gene transfer. Foreign gene constructs can be readily expressed in transgenic fish. A variety of promoters from both fish and non-fish 0 Copyright by the World Aquaculture Society 1999 DUNHAM sources can drive the expression of the introduced genes (Iyengar et al. 1996). Although most genes transferred to fish have been expressed, the expression of the genes does not always alter performance (Dunham 1990), but many examples of altered performance of transgenic fish exists (Dunham and Devlin 1998). Transgenic technology has been controversial as it is a new and poorly understood technology. Lack of data on the potential ecological and socioeconomic impacts of transgenic fish has contributed to a growing debate (based on speculation rather than data) on the use of genetically engineered fish in society. The purpose of the following discussion is to review the status of transgenic fish technology, and present aspects of the potential benefits and risks of this technology in relation to developing countries to foster informed policy decisions regarding research and application of transgenic fish. Performance of Transgenic Fish The improvement of several economic traits of aquacultured fish through gene transfer could be desirable, including improvement of growth rate, feed conversion efficiency, disease resistance (Jiang 1993; Anderson et al. 1996), tolerance of poor water quality, temperature and salinity tolerance, body composition, carcass quality and flavor, dressout percentage (Chatakondi et al. 1994) and reproductive control. Of these traits, growth rate is the easiest to address and most research on transgenic fish with the potential for practical aquaculture application involves growth hormone gene transfer (Dunham 1996). A number of experiments have demonstrated that growth hormone gene transfer can increase growth rate from 11% to 30fold (Dunham 1990; Zhang et al. 1990; Dunham et al. 1992; Chen et al. 1993; Devlin et al. 1994; Chatakondi 1995; Devlin et al. 1995; Dunham 1996) including results from developing countries such as China and Cuba (Zhu et al. 1995; Chen et al. 1995; Martinez 1997). The most dramatic results have been obtained in laboratory environments that may or may not reflect performance in more realistic aquaculture environments (Du et d. 1992; Devlin et al. 1995). However, growth rate of transgenic channel catfish Zctalurus puncratus (Chitminat 1996) and common carp Cyprinus carpi0 (Chatakondi 1995) has been improved as much as 33% and 150%,respectively, in simulated commercial conditions in ponds, demonstrating real potential for aquaculture benefit. A gene or transgene can cause pleiotropic effects, a single gene affecting more than one trait. Pleiotropic effects can be positive or negative. All of the following examples are of transgenic fish containing extra growth hormone genes. Extremely rapid growing transgenic salmon (Devlin et al. 1994, 1995) and loach (10-30 fold increase in growth) possessing recombinant growth hormone genes can exhibit acromegaly, other deformities, fat deposits and early death. Transgenic salmon fry have altered coloration. The exogenous growth hormone affects expression of other growth related hormones such as IGE Preliminary results indicate fast growing transgenic channel catfish and common carp have improved feed conversion efficiency (Chatakondi 1995; Dunham 1996). Transgenic common carp have altered body shape and increased carcass yield. Transgenic common carp and channel catfish have increased protein levels and reduced fat in the carcass (Chatakondi et al. 1995a; Dunham 1996). Amino acid ratios and fatty acid ratios remain essentially unchanged between control and transgenic common carp. Preliminary results indicate disease resistance, survival and tolerance of low dissolved oxygen are improved in transgenic common carp possessing rainbow trout growth hormone DNA (Chatakondi 1995; Chatakondi et al. 1995b). Disease resistance will likely be improved directly, and is considered one of the traits that might be most impacted by TRANSGENIC FISH IN DEVELOPING COUNTRIES gene transfer (Jiang 1993). The results of Anderson at al. (1996) for genetically immunizing rainbow trout against infectious hematopoietic necrosis virus are promising. Reproductive performance of transgenic common carp and channel catfish containing growth hormone genes appears unaltered (Dunham et al. 1992; Chatakondi 1995; Dunham 1996). However, sperm production of GH transgenic Nile tilapia Oreochromis niloticus is reduced (Dunham and Devlin 1998). Current Commercial Application of Transgenic Organisms Transgenic bacteria and plants are widely utilized. Some transgenic animals are utilized as biological factories to produce pharmaceutical compounds (Murray et al., in press). Although technically not transgenic technology but recombinant DNA technology, human gene therapy has not met major opposition. In reality, these are somatic transgenic humans but germline transmission is not possible. In the case of fish, the first commercial application of transgenic fish has been initiated. Transgenic salmon are being grown in Scotland (Martinez 1997) and New Zealand. Applications have been filed in the United States to grow these fish. Socioeconomic Issues Several socioeconomic issues need to be addressed before any application of transgenic fish. These include public education, food safety, socioeconomic impact and environmental risk. The majority of the world’s population possibly has few reservations or opinions regarding production and consumption of transgenic fish and their ecological effects. Different societies vary in their concern or lack of concern regarding genetically engineered food (Custers and Sterrenberg 1992; Hallerman 1997). Bartley and Hallerman (1995) found that the majority of the world has great interest in exploring the possibility of application of transgenic fish in aqua- culture. More efficient food production through use of transgenic organisms may bring the price of food staples within the reach of more of the world’s poor. Initial surveys indicate that most US citizens have little understanding of biology or how their food is generated (Hoban and Kendall 1993). If asked if they had ever eaten a hybrid fruit or vegetable about 60% of rural and urban people in North Carolina responded that they had not, and about the same percentage indicated that it was unethical to eat a hybrid fruit or vegetable (Hoban and Kendall 1993). These answers illustrate that the general public does not have the knowledge to make informed judgements concerning genetically modified food, and likely base their opinions on popular media presentation rather than scientifically verified sources. Some environmental groups and scientists representing a small segment of society have concerns regarding transgenic fish (Hallerman 1997). Since transgenic fish are an unknown entity, concerns are valid and evaluation of transgenic fish should be thorough prior to utilization. Even if data from both environmental and production experiments are positive, philosophically some organizations will remain opposed to this technology considering it unnatural. Assuming positive results for aquaculture and environmental research, mechanisms should be established to educate the public and particularly legislative and regulatory organizations on the factual and beneficial aspects of transgenic food. Conversely, if risks outweigh benefits, dissemination of information to the public, farmers and government is also important. Data needs to be collected to assure that transgenic fish flesh is a nutritious and safe food. Research to date indicates body composition changes in transgenic fish are positive, as fat is reduced and protein levels in the edible meat increase (Chatakondi et al. 1995a). Berkowitz and Kryspin-Sorensen (1994) review food safety issues of transgenic fish including potential production of DUNHAM toxins. Their theoretical analysis shows that transgenic fish will likely be a safe food source. an exotic species since this would allow the expansion of a species outside its natural range. This type of transgenic research and application should be avoided. Antifreeze protein genes from winter flounder have been introduced into Atlantic salmon Salmo salar in an attempt to increase their cold tolerance (Shears et al. 1991). If this research were successful, a real possibility of environmental impact exists. Similarly, if tilapia were made more cold tolerant a strong possibility of detrimental environmental impact exists. Sterilization could reduce risk, but genetic means of sterilization such as triploidy decrease performance (Dunham 1996). Additionally, fertile brood stocks are necessary so risk is minimized but not eliminated. Most types of transgenic fish, including those that are growth hormone gene transformants, are more analogous to a selected line or domestic strain. The change in phenotype is similar to what would be observed or what would be the goal of strain selection, individual selection, intraspecific crossbreeding, interspecific hybridization, sex reversal or gynogenesis. If a fourfold increase in growth is possible through traditional breeding [and such gains are possible (Dunham 1996)], ecological impacts would be the same regardless of the mechanism of phenotypic alteration, traditional or biotechnological. Transgenic fish should be analogous to select lines and domestic strains in a second manner. Transgenic fish will likely be generated from select lines and domestic strains since these fish are generally more suited for aquaculture and already have increased performance in the aquaculture environment (Dunham 1996). Obviously the primary benefits of transgenic fish would be increased aquaculture production and profitability. However, other potential benefits exist in addition to those mentioned earlier. Escaped transgenic fish could add genetic diversity to populations. This would be artificially induced genetic diversity that Theoretical Comparison of Environmental Risk and Benefits Assuming there are environmental risks associated with transgenic fish, benefit-risk analysis is needed as well as development and implementation of policy mechanisms. Ecologically, the primary concerns regarding utilization of transgenic fish are loss of genetic diversity, loss of biodiversity, changes in relative abundance of species, expansion of habitat outside of native ranges, alteration of population dynamics and alteration of fitness upon release or escape followed by establishment of transgenic fish in the natural environment (Kapuscinski and Hallerman 1990; Hallerman and Kapuscinski 1995; Hallerman 1997). Conversely, utilization of transgenic fish in aquaculture could enhance genetic diversity and biodiversity by increasing food production and production efficiency, thus relieving pressure on commercial harvests of natural populations and decreasing pressure on land and water use for agriculture and aquaculture. The extent of phenotypic change from introduction of a fusion gene could be analogous to the development of an exotic species, a select line or domestic strain depending upon the magnitude of the phenotypic change. Transgenic fish could express phenotypes that are analogous to the formation of a new exotic species. Research on gene transfer that has a high probability of such a result should be avoided since it is well documented that exotic species can cause major changes in ecological and population balance and lead to the elimination of native species in the invaded environment. Approximately 11% of introductions actually become established and of these about 10% have negative ecological impacts (Welcomme 1988). Altering temperature or salinity tolerance would be analogous to the development of TRANSGENIC FISH IN DEVELOPING COUNTRIES some sectors of society would value and to which others would be opposed. The population genetics and fitness implications from such an event are not clear (Dunham 1996) and need further study. This artificial genetic diversity could actually increase fitness in some endangered populations or species and make such genetic units more viable. For example, natural and human induced factors (if we consider man an unnatural aspect of global ecology) have apparently reduced genetic variation in the cheetah to the point that reduced reproductive performance threaten their existence (O’brien et al. 1985, 1986). Gene transfer could be an option to restore reproductive performance, fitness and save this species and fish species in the future, and should be explored. Evidence exists that when humans began exploiting fish populations much more efficiently and intensively in the last 200 years, certain traits, such as size, have been genetically selected against (Ricker 1975, 1981). It is likely that we have permanently eliminated important growth genes and perhaps other genes from some fish species. Gene transfer might be an option to restore or partially restore phenotypes that have been “artificially” eliminated. Currently, it is common practice in Asia and other areas of the world to introduce exotic species to address perceived shortcomings in aquaculture performance of native species. Examples include the widespread introductions of Indian carps, Chinese carps and common carp (Gupta et al. 1997) throughout Asia and the introduction of tilapia throughout Asia and the South Pacific from Africa (Pullin 1988). Again, introduction of exotic species has the greatest potential to adversely affect biodiversity and, consequently, genetic diversity (Welcomme 1988). Utilization of transgenic fish derived from the indigenous aquaculture species is more likely to be an environmentally safe means of addressing the perceived aquaculture shortcomings of native species and is less likely to decrease loss of biodi- versity and genetic diversity compared to the continued practice of exotic species introduction. Since the risk of transgenic fish and other genetically modified aquatic organisms (Dunham 1996) are unknown, development and implementation of performance standards for research on transgenic fish in developing as well as developed countries would help ensure environmentally safe research (Bartley and Hallerman 1995; Hallerman and Kapuscinski 1995). The performance standards developed by the USDA (Agricultural Biotechnology Research Advisory Committee 1995) could serve as a model for development of such standards in developing countries. The current status of transgenic research, regulations and policy is found in Table 1. Prediction of Genetic Impact: Interaction of Wild and Domestic Fish The genetic impact of genetically improved, aquaculture fish could have neutral, positive or negative effects on wild populations short term or long term (Dunham 1996). Transgenic fish could escape and the transgene become part of the gene pool. This could add genetic diversity to the population, would lower or raise fitness or have no phenotypic or ecological effect. If there is a lowering of fitness, it could be temporary as the transgene should be selected against. Alternatively, if not completely selected against, it could impart a permanent genetic load upon the population with a long-term lowering of fitness (Farnsworth 1988). The mixing of the gene pools might enhance genetic resources, increase genetic variation or result in heterosis, all potentially positive results. The wild fish may outcompete and eliminate the domestic fish or the domestic fish may have no long term impact on the performance of the population, neutral or non-effects. Negative impacts could result from negative overdominance, which would theoretically be temporary, because of the elimination of domestic genotypes through competition. If DUNHAM TABLE Status of transgenic research and regulations for aquaculture species.' 1. Phenotypic enhancement Countr ykpecies Africa Australia Canada Salmon China Common carp Salmon Loach Europe Hungary Nile tilapia India Israel Common carp Japan New Zealand Salmon Norway Philippines Nile tilapia3 South Korea Loach Scotland Salmon United Kingdom Nile tilapia United States Common carp' Channel catfish Salmon Rainbow trout Trait Risk data Field testing growth anti-freeze growth growth growth + + + growth growth + + growth growth growth growth growth growth growth disease resistance growth disease resistance + + + + + + + + + + Yes I Information partially derived from Kapuscinski and Hallerman (1990). Bartley and Hallerman (1995). Hallennan and Kapuscinski (1995). Martinez (1997). 6 of 17 European countries polled had regulations (Bartley and Hallerman 1995). Research and fish terminated. large members of sterile transgenic fish escaped, they could decrease reproduction in natural populations by causing infertile matings. Triploid fish have demonstrated this potential in laboratory experiments (Dunham 1996). The escaped transgenic fish could replace the natural population. Depending upon the existence or absence of this genotype, genetic diversity would be lost. The long-term survival of that species or population at the location could be enhanced, decreased or unchanged. Environmental risk data to date, however, indicates that the above scenario is unlikely (Devlin et al. 1995; Dunham 1994; Dunham et al. 1995; Chitminat 1996; Farrell et al. 1997; Dunham and Devlin 1998). These experiments have thus far indicated that transgenic fish containing growth hormone genes have either the same TRANSGENIC FISH IN DEVELOPING COUNTRIES TABLE 1. Extended. Regulation Research performance standards Private support Commercialization requested Commercialization + + + + + +* + + + + + + + + + + + + + + or lowered reproductive capacity, increased vulnerability to predation, no improved growth when food is limiting and reduced swimming ability. Transgenic fish could become established, and hybridize with other species spreading the transgene to other species. This scenario is unlikely since reproductive isolating mechanisms usually, but does not always, restrict permanent gene flow between species (Argue and Dunham, in press). Most data indicate that wild fish are more competitive than domestic fish (Dunham 1996), resulting in the elimination of the domestic fish and their potential positive or negative impacts. However, recent evidence from salmonid research indicates that there are situations where domestic fish can have genetic impact on wild populations. When repeated large-scale escapes of domestic fish occur, genetic impact can occur just from the swamping effect of sheer force of numbers. Transgenic fish could make an impact in this scenario but again the consequences should not DUNHAM vary much from that of fish genetically altered by other means. Environmental Risk Data on Transgenic Fish Most ecological data on transgenic fish gathered to date indicate a low probability of environmental impact. Extremely fast growing salmon and loach have low fitness and die (Devlin et al. 1994, 1995). Fast growing transgenic tilapia have reduced sperm production. Transgenic channel catfish and common carp have similar reproduction and rate of sexual maturity compared to controls (Dunham et al. 1992; Chen et al. 1993; Chatakondi 1995). Genotype-environment interactions occur for growth of transgenic channel catfish (Dunham et al. 1995). When grown under natural conditions where food is limiting, the transgenic channel catfish has slightly lower survival than controls and grows at the same rate as non-transgenic controls. As in the case of most genetic improvement programs, genetically altered fish need adequate food to express their potential. Predator avoidance of transgenic channel catfish and controls were equal (Chitminat 1996). All transgenic fish evaluated to date have fitness traits that are either the same or weaker compared to controls (Dunham and Devlin 1998). sound ecological reasons as well as protects future resources for exploitation, except in situations where genetic impact on the natural population is desirable. Conclusion and Recommendations Production of transgenic fish is a promising approach to enhance global food security and efficiency by developing high performance fish. This genetic improvement strategy should be examined for fish in developing countries. Transgenic fish may actually provide better protection of natural genetic resources by relieving pressure on natural exploitation and decreasing the need for destruction of habitat for increased food production. Early evidence indicates that high performance transgenic fish may actually have low fitness, decreasing the likelihood of their establishment in the wild and of associated potential impacts. Simultaneously, efforts should be organized to evaluate the potential environmental risk of transgenic fish. The reproductive performance, foraging ability and predator avoidance are the key factors determining fitness of transgenic fish, and should be a standard measurement prior to commercial application. Transgenic research on carps and tilapia should be initiated. The benefits of increased aquaculture production, genetic restoration and diversity, and potential protection of natural populations of fish and aquatic habitat by more efficiently using land and water resources and protection of biodiversity and genetic diversity and the risks of environmental, ecological or genetic damage need to be more thoroughly studied for these fish. Currently, transgenic fish research is conducted in China, Cuba, India, Korea, Philippines and Thailand, and other developing countries will follow. Transgenic fish development is inevitable in developing countries, and in fact, has already begun. The first transgenic fish ever produced were developed in China (Zhu et al. 1985). Orga- Common Goals of Aquaculture and Genetic Conservation The preservation of genetic diversity should be a common goal for both aquaculture breeders and managers of natural populations. Wild populations and their genes represent a living gene bank that is needed for future resources for genetic improvement for utilization in aquaculture. Additionally, large breeding programs which maintain diverse genotypes could also function as living gene banks. Therefore, transgenic fish research as well as aquaculture genetics research should be conducted in a manner that minimizes genetic impact on natural populations for TRANSGENIC FISH IN DEVELOPING COUNTRIES Hayat, N. Chatakondi, A. C. Ramboux, P. L. Duncan, and R. A. Dunham. 1993. Expression and inheritance of RSVLTR-rtGH1 complementary DNA in the transgenic common carp, Cyprinus carpio. Molecular Marine Biology and BioLiterature Cited technology 2938-95. Agricultural Biotechnology Research Advisory Chen, T. T., J. K. Lu, M. J. Shamblott, C. M. Cheng, C. M. Lin, J. C. Burns, R. ReimschuesCommittee. 1995. Performance standards for sel, N. Chatakondi, and R. A. 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Government and non-government organizations need to take an active role in con- Chatakondi, N. G. 1995. Evaluation of transgenic common carp, Cyprinus carpio, containing rainducting the appropriate research to ascertain bow trout growth hormone in ponds. Doctoral disthe benefits and risks of transgenic fish. Sosertation, Auburn University, Auburn, Alabama, cioeconomics, policy and impact assessUSA. ment research is also needed to ensure that Chatakondi, N., R. Lovell, P. Duncan, M. Hayat, T. Chen, D. Powers, T. Weete, K. Cummins, and farmers and poor consumers benefit from R. A. Dunham. 1995a. Body composition of development or implementation of transtransgenic common carp, Cvprinus carpio, congenic fish in aquaculture. This type of retaining rainbow trout growth hormone gene. search and development of effective disAquaculture 138( 1-4):99-109. semination strategies is important for ob- Chatakondi, N., A. Nichols, T. T. Chen, D. A. Powers, and R. A. Dunham. 1995b. 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Utilization of Transgenic Fish in Developing Countries: Potential Benefits and Risks

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Wiley
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Copyright © 1999 Wiley Subscription Services, Inc., A Wiley Company
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0893-8849
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1749-7345
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10.1111/j.1749-7345.1999.tb00312.x
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Abstract

REX A. DUNHAM International Center for Living Aquatic Resources Management, MCPO Box 2631, 0718 Makati City, Philippines Abstract Recombinant DNA and gene transfer technology now allow the transfer, inheritance and expression of specific DNA or gene sequences into fish. Preliminary results on the performance of the resulting transgenic fish have been quite dramatic in some cases, especially when growth hormone genes are transferred. Utilization of high performance transgenic fish has the potential to greatly increase aquaculture production in developing countries and increase the income of poor farmers. Growth of some transgenic fish has been increased more than 10-fold in laboratory conditions. Response appears to be greatest in unimproved fish, which in most cases would benefit developing countries the most. The potential increase in production and production efficiency from successful transgenic fish application could relieve pressure on habitat destruction for food production, relieve pressure on overtished natural stocks and discourage introduction of exotic species. Application of transgenic fish in aquaculture has just begun and could expand within a few years. However, prior to commercialization of transgenic fish, public education, environmental risks and food safety issues should be addressed. Genetically improved fish generated by recombinant DNA technology probably do not pose any greater risk to the environment than fish genetically improved through traditional selective breeding, but environmental risk data is lacking to verify this hypothesis. Environmental risk data will be needed in a case-by-case basis until more is known concerning the aquaculture potential and ecological risk of transgenic fish. Research institutions need to address the lack of environmental risk data to help ensure that any future application of transgenic fish in developing (and developed) countries be done in an environmentally and socioeconomically sound manner. Socioeconomic study is lacking for detailed cost-benefit analysis, and policy research is needed for proper application or regulation of transgenic fish in these countries. Gene Transfer i Fish n Successful transfer of recombinant DNA into fish was first accomplished in 1985 (Zhu et al. 1985). Gene transfer in fish is now commonplace (Dunham 1990; Chen et al. 1995; Dunham 1996; Iyengar et al. 1996). Originally, DNA sequences from a variety of organisms, viruses, bacteria, animals, birds, fish and humans were transferred to fish. Although small DNA sequences from these organisms do not impart the general characteristics of these organisms to fish, most researchers have now chosen to focus on transfer of fish DNA constructs into fish to increase the likelihood of social acceptance of transgenic fish and because of the belief that fish-based constructs are more effective, although the latter has not been confirmed by research (Devlin et al. 1995). The initial transfer of fusion gene constructs into fish embryos results in mosaic individuals (Dunham 1990). In most cases, the effect of the transgene cannot be accurately measured in mosaic individuals. Fortunately, if the transgene is integrated in the gonadal tissue, the introduced DNA is usually inherited in a Mendelian fashion (Stuart et al. 1988, 1990; Zhang et al. 1990; Shears et al. 1991; Dunham et al. 1992; Chen et al. 1993) and the resulting progeny have the foreign DNA in every cell, allowing accurate evaluation of the expression and biological effects of the gene transfer. Foreign gene constructs can be readily expressed in transgenic fish. A variety of promoters from both fish and non-fish 0 Copyright by the World Aquaculture Society 1999 DUNHAM sources can drive the expression of the introduced genes (Iyengar et al. 1996). Although most genes transferred to fish have been expressed, the expression of the genes does not always alter performance (Dunham 1990), but many examples of altered performance of transgenic fish exists (Dunham and Devlin 1998). Transgenic technology has been controversial as it is a new and poorly understood technology. Lack of data on the potential ecological and socioeconomic impacts of transgenic fish has contributed to a growing debate (based on speculation rather than data) on the use of genetically engineered fish in society. The purpose of the following discussion is to review the status of transgenic fish technology, and present aspects of the potential benefits and risks of this technology in relation to developing countries to foster informed policy decisions regarding research and application of transgenic fish. Performance of Transgenic Fish The improvement of several economic traits of aquacultured fish through gene transfer could be desirable, including improvement of growth rate, feed conversion efficiency, disease resistance (Jiang 1993; Anderson et al. 1996), tolerance of poor water quality, temperature and salinity tolerance, body composition, carcass quality and flavor, dressout percentage (Chatakondi et al. 1994) and reproductive control. Of these traits, growth rate is the easiest to address and most research on transgenic fish with the potential for practical aquaculture application involves growth hormone gene transfer (Dunham 1996). A number of experiments have demonstrated that growth hormone gene transfer can increase growth rate from 11% to 30fold (Dunham 1990; Zhang et al. 1990; Dunham et al. 1992; Chen et al. 1993; Devlin et al. 1994; Chatakondi 1995; Devlin et al. 1995; Dunham 1996) including results from developing countries such as China and Cuba (Zhu et al. 1995; Chen et al. 1995; Martinez 1997). The most dramatic results have been obtained in laboratory environments that may or may not reflect performance in more realistic aquaculture environments (Du et d. 1992; Devlin et al. 1995). However, growth rate of transgenic channel catfish Zctalurus puncratus (Chitminat 1996) and common carp Cyprinus carpi0 (Chatakondi 1995) has been improved as much as 33% and 150%,respectively, in simulated commercial conditions in ponds, demonstrating real potential for aquaculture benefit. A gene or transgene can cause pleiotropic effects, a single gene affecting more than one trait. Pleiotropic effects can be positive or negative. All of the following examples are of transgenic fish containing extra growth hormone genes. Extremely rapid growing transgenic salmon (Devlin et al. 1994, 1995) and loach (10-30 fold increase in growth) possessing recombinant growth hormone genes can exhibit acromegaly, other deformities, fat deposits and early death. Transgenic salmon fry have altered coloration. The exogenous growth hormone affects expression of other growth related hormones such as IGE Preliminary results indicate fast growing transgenic channel catfish and common carp have improved feed conversion efficiency (Chatakondi 1995; Dunham 1996). Transgenic common carp have altered body shape and increased carcass yield. Transgenic common carp and channel catfish have increased protein levels and reduced fat in the carcass (Chatakondi et al. 1995a; Dunham 1996). Amino acid ratios and fatty acid ratios remain essentially unchanged between control and transgenic common carp. Preliminary results indicate disease resistance, survival and tolerance of low dissolved oxygen are improved in transgenic common carp possessing rainbow trout growth hormone DNA (Chatakondi 1995; Chatakondi et al. 1995b). Disease resistance will likely be improved directly, and is considered one of the traits that might be most impacted by TRANSGENIC FISH IN DEVELOPING COUNTRIES gene transfer (Jiang 1993). The results of Anderson at al. (1996) for genetically immunizing rainbow trout against infectious hematopoietic necrosis virus are promising. Reproductive performance of transgenic common carp and channel catfish containing growth hormone genes appears unaltered (Dunham et al. 1992; Chatakondi 1995; Dunham 1996). However, sperm production of GH transgenic Nile tilapia Oreochromis niloticus is reduced (Dunham and Devlin 1998). Current Commercial Application of Transgenic Organisms Transgenic bacteria and plants are widely utilized. Some transgenic animals are utilized as biological factories to produce pharmaceutical compounds (Murray et al., in press). Although technically not transgenic technology but recombinant DNA technology, human gene therapy has not met major opposition. In reality, these are somatic transgenic humans but germline transmission is not possible. In the case of fish, the first commercial application of transgenic fish has been initiated. Transgenic salmon are being grown in Scotland (Martinez 1997) and New Zealand. Applications have been filed in the United States to grow these fish. Socioeconomic Issues Several socioeconomic issues need to be addressed before any application of transgenic fish. These include public education, food safety, socioeconomic impact and environmental risk. The majority of the world’s population possibly has few reservations or opinions regarding production and consumption of transgenic fish and their ecological effects. Different societies vary in their concern or lack of concern regarding genetically engineered food (Custers and Sterrenberg 1992; Hallerman 1997). Bartley and Hallerman (1995) found that the majority of the world has great interest in exploring the possibility of application of transgenic fish in aqua- culture. More efficient food production through use of transgenic organisms may bring the price of food staples within the reach of more of the world’s poor. Initial surveys indicate that most US citizens have little understanding of biology or how their food is generated (Hoban and Kendall 1993). If asked if they had ever eaten a hybrid fruit or vegetable about 60% of rural and urban people in North Carolina responded that they had not, and about the same percentage indicated that it was unethical to eat a hybrid fruit or vegetable (Hoban and Kendall 1993). These answers illustrate that the general public does not have the knowledge to make informed judgements concerning genetically modified food, and likely base their opinions on popular media presentation rather than scientifically verified sources. Some environmental groups and scientists representing a small segment of society have concerns regarding transgenic fish (Hallerman 1997). Since transgenic fish are an unknown entity, concerns are valid and evaluation of transgenic fish should be thorough prior to utilization. Even if data from both environmental and production experiments are positive, philosophically some organizations will remain opposed to this technology considering it unnatural. Assuming positive results for aquaculture and environmental research, mechanisms should be established to educate the public and particularly legislative and regulatory organizations on the factual and beneficial aspects of transgenic food. Conversely, if risks outweigh benefits, dissemination of information to the public, farmers and government is also important. Data needs to be collected to assure that transgenic fish flesh is a nutritious and safe food. Research to date indicates body composition changes in transgenic fish are positive, as fat is reduced and protein levels in the edible meat increase (Chatakondi et al. 1995a). Berkowitz and Kryspin-Sorensen (1994) review food safety issues of transgenic fish including potential production of DUNHAM toxins. Their theoretical analysis shows that transgenic fish will likely be a safe food source. an exotic species since this would allow the expansion of a species outside its natural range. This type of transgenic research and application should be avoided. Antifreeze protein genes from winter flounder have been introduced into Atlantic salmon Salmo salar in an attempt to increase their cold tolerance (Shears et al. 1991). If this research were successful, a real possibility of environmental impact exists. Similarly, if tilapia were made more cold tolerant a strong possibility of detrimental environmental impact exists. Sterilization could reduce risk, but genetic means of sterilization such as triploidy decrease performance (Dunham 1996). Additionally, fertile brood stocks are necessary so risk is minimized but not eliminated. Most types of transgenic fish, including those that are growth hormone gene transformants, are more analogous to a selected line or domestic strain. The change in phenotype is similar to what would be observed or what would be the goal of strain selection, individual selection, intraspecific crossbreeding, interspecific hybridization, sex reversal or gynogenesis. If a fourfold increase in growth is possible through traditional breeding [and such gains are possible (Dunham 1996)], ecological impacts would be the same regardless of the mechanism of phenotypic alteration, traditional or biotechnological. Transgenic fish should be analogous to select lines and domestic strains in a second manner. Transgenic fish will likely be generated from select lines and domestic strains since these fish are generally more suited for aquaculture and already have increased performance in the aquaculture environment (Dunham 1996). Obviously the primary benefits of transgenic fish would be increased aquaculture production and profitability. However, other potential benefits exist in addition to those mentioned earlier. Escaped transgenic fish could add genetic diversity to populations. This would be artificially induced genetic diversity that Theoretical Comparison of Environmental Risk and Benefits Assuming there are environmental risks associated with transgenic fish, benefit-risk analysis is needed as well as development and implementation of policy mechanisms. Ecologically, the primary concerns regarding utilization of transgenic fish are loss of genetic diversity, loss of biodiversity, changes in relative abundance of species, expansion of habitat outside of native ranges, alteration of population dynamics and alteration of fitness upon release or escape followed by establishment of transgenic fish in the natural environment (Kapuscinski and Hallerman 1990; Hallerman and Kapuscinski 1995; Hallerman 1997). Conversely, utilization of transgenic fish in aquaculture could enhance genetic diversity and biodiversity by increasing food production and production efficiency, thus relieving pressure on commercial harvests of natural populations and decreasing pressure on land and water use for agriculture and aquaculture. The extent of phenotypic change from introduction of a fusion gene could be analogous to the development of an exotic species, a select line or domestic strain depending upon the magnitude of the phenotypic change. Transgenic fish could express phenotypes that are analogous to the formation of a new exotic species. Research on gene transfer that has a high probability of such a result should be avoided since it is well documented that exotic species can cause major changes in ecological and population balance and lead to the elimination of native species in the invaded environment. Approximately 11% of introductions actually become established and of these about 10% have negative ecological impacts (Welcomme 1988). Altering temperature or salinity tolerance would be analogous to the development of TRANSGENIC FISH IN DEVELOPING COUNTRIES some sectors of society would value and to which others would be opposed. The population genetics and fitness implications from such an event are not clear (Dunham 1996) and need further study. This artificial genetic diversity could actually increase fitness in some endangered populations or species and make such genetic units more viable. For example, natural and human induced factors (if we consider man an unnatural aspect of global ecology) have apparently reduced genetic variation in the cheetah to the point that reduced reproductive performance threaten their existence (O’brien et al. 1985, 1986). Gene transfer could be an option to restore reproductive performance, fitness and save this species and fish species in the future, and should be explored. Evidence exists that when humans began exploiting fish populations much more efficiently and intensively in the last 200 years, certain traits, such as size, have been genetically selected against (Ricker 1975, 1981). It is likely that we have permanently eliminated important growth genes and perhaps other genes from some fish species. Gene transfer might be an option to restore or partially restore phenotypes that have been “artificially” eliminated. Currently, it is common practice in Asia and other areas of the world to introduce exotic species to address perceived shortcomings in aquaculture performance of native species. Examples include the widespread introductions of Indian carps, Chinese carps and common carp (Gupta et al. 1997) throughout Asia and the introduction of tilapia throughout Asia and the South Pacific from Africa (Pullin 1988). Again, introduction of exotic species has the greatest potential to adversely affect biodiversity and, consequently, genetic diversity (Welcomme 1988). Utilization of transgenic fish derived from the indigenous aquaculture species is more likely to be an environmentally safe means of addressing the perceived aquaculture shortcomings of native species and is less likely to decrease loss of biodi- versity and genetic diversity compared to the continued practice of exotic species introduction. Since the risk of transgenic fish and other genetically modified aquatic organisms (Dunham 1996) are unknown, development and implementation of performance standards for research on transgenic fish in developing as well as developed countries would help ensure environmentally safe research (Bartley and Hallerman 1995; Hallerman and Kapuscinski 1995). The performance standards developed by the USDA (Agricultural Biotechnology Research Advisory Committee 1995) could serve as a model for development of such standards in developing countries. The current status of transgenic research, regulations and policy is found in Table 1. Prediction of Genetic Impact: Interaction of Wild and Domestic Fish The genetic impact of genetically improved, aquaculture fish could have neutral, positive or negative effects on wild populations short term or long term (Dunham 1996). Transgenic fish could escape and the transgene become part of the gene pool. This could add genetic diversity to the population, would lower or raise fitness or have no phenotypic or ecological effect. If there is a lowering of fitness, it could be temporary as the transgene should be selected against. Alternatively, if not completely selected against, it could impart a permanent genetic load upon the population with a long-term lowering of fitness (Farnsworth 1988). The mixing of the gene pools might enhance genetic resources, increase genetic variation or result in heterosis, all potentially positive results. The wild fish may outcompete and eliminate the domestic fish or the domestic fish may have no long term impact on the performance of the population, neutral or non-effects. Negative impacts could result from negative overdominance, which would theoretically be temporary, because of the elimination of domestic genotypes through competition. If DUNHAM TABLE Status of transgenic research and regulations for aquaculture species.' 1. Phenotypic enhancement Countr ykpecies Africa Australia Canada Salmon China Common carp Salmon Loach Europe Hungary Nile tilapia India Israel Common carp Japan New Zealand Salmon Norway Philippines Nile tilapia3 South Korea Loach Scotland Salmon United Kingdom Nile tilapia United States Common carp' Channel catfish Salmon Rainbow trout Trait Risk data Field testing growth anti-freeze growth growth growth + + + growth growth + + growth growth growth growth growth growth growth disease resistance growth disease resistance + + + + + + + + + + Yes I Information partially derived from Kapuscinski and Hallerman (1990). Bartley and Hallerman (1995). Hallennan and Kapuscinski (1995). Martinez (1997). 6 of 17 European countries polled had regulations (Bartley and Hallerman 1995). Research and fish terminated. large members of sterile transgenic fish escaped, they could decrease reproduction in natural populations by causing infertile matings. Triploid fish have demonstrated this potential in laboratory experiments (Dunham 1996). The escaped transgenic fish could replace the natural population. Depending upon the existence or absence of this genotype, genetic diversity would be lost. The long-term survival of that species or population at the location could be enhanced, decreased or unchanged. Environmental risk data to date, however, indicates that the above scenario is unlikely (Devlin et al. 1995; Dunham 1994; Dunham et al. 1995; Chitminat 1996; Farrell et al. 1997; Dunham and Devlin 1998). These experiments have thus far indicated that transgenic fish containing growth hormone genes have either the same TRANSGENIC FISH IN DEVELOPING COUNTRIES TABLE 1. Extended. Regulation Research performance standards Private support Commercialization requested Commercialization + + + + + +* + + + + + + + + + + + + + + or lowered reproductive capacity, increased vulnerability to predation, no improved growth when food is limiting and reduced swimming ability. Transgenic fish could become established, and hybridize with other species spreading the transgene to other species. This scenario is unlikely since reproductive isolating mechanisms usually, but does not always, restrict permanent gene flow between species (Argue and Dunham, in press). Most data indicate that wild fish are more competitive than domestic fish (Dunham 1996), resulting in the elimination of the domestic fish and their potential positive or negative impacts. However, recent evidence from salmonid research indicates that there are situations where domestic fish can have genetic impact on wild populations. When repeated large-scale escapes of domestic fish occur, genetic impact can occur just from the swamping effect of sheer force of numbers. Transgenic fish could make an impact in this scenario but again the consequences should not DUNHAM vary much from that of fish genetically altered by other means. Environmental Risk Data on Transgenic Fish Most ecological data on transgenic fish gathered to date indicate a low probability of environmental impact. Extremely fast growing salmon and loach have low fitness and die (Devlin et al. 1994, 1995). Fast growing transgenic tilapia have reduced sperm production. Transgenic channel catfish and common carp have similar reproduction and rate of sexual maturity compared to controls (Dunham et al. 1992; Chen et al. 1993; Chatakondi 1995). Genotype-environment interactions occur for growth of transgenic channel catfish (Dunham et al. 1995). When grown under natural conditions where food is limiting, the transgenic channel catfish has slightly lower survival than controls and grows at the same rate as non-transgenic controls. As in the case of most genetic improvement programs, genetically altered fish need adequate food to express their potential. Predator avoidance of transgenic channel catfish and controls were equal (Chitminat 1996). All transgenic fish evaluated to date have fitness traits that are either the same or weaker compared to controls (Dunham and Devlin 1998). sound ecological reasons as well as protects future resources for exploitation, except in situations where genetic impact on the natural population is desirable. Conclusion and Recommendations Production of transgenic fish is a promising approach to enhance global food security and efficiency by developing high performance fish. This genetic improvement strategy should be examined for fish in developing countries. Transgenic fish may actually provide better protection of natural genetic resources by relieving pressure on natural exploitation and decreasing the need for destruction of habitat for increased food production. Early evidence indicates that high performance transgenic fish may actually have low fitness, decreasing the likelihood of their establishment in the wild and of associated potential impacts. Simultaneously, efforts should be organized to evaluate the potential environmental risk of transgenic fish. The reproductive performance, foraging ability and predator avoidance are the key factors determining fitness of transgenic fish, and should be a standard measurement prior to commercial application. Transgenic research on carps and tilapia should be initiated. The benefits of increased aquaculture production, genetic restoration and diversity, and potential protection of natural populations of fish and aquatic habitat by more efficiently using land and water resources and protection of biodiversity and genetic diversity and the risks of environmental, ecological or genetic damage need to be more thoroughly studied for these fish. Currently, transgenic fish research is conducted in China, Cuba, India, Korea, Philippines and Thailand, and other developing countries will follow. Transgenic fish development is inevitable in developing countries, and in fact, has already begun. The first transgenic fish ever produced were developed in China (Zhu et al. 1985). Orga- Common Goals of Aquaculture and Genetic Conservation The preservation of genetic diversity should be a common goal for both aquaculture breeders and managers of natural populations. 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Journal of the World Aquaculture SocietyWiley

Published: Mar 1, 1999

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