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5.1.1 Introduction

Biotechnology in fisheries and aquaculture represents a range of technologies that present opportunities to increase growth rate in farmed species, improve nutrition of feeds for aquaculture, improve fish health, help restore and protect environments, extend the range of aquatic species and improve management and conservation of wild stocks. In this e-mail conference, the focus is on genetic biotechnologies, with a brief treatment of related reproductive and gene banking technologies, and the appropriateness of their application in the fishery sector in developing countries. It is important to note that developing countries produce more fishery products from aquaculture, inland capture fisheries and marine capture fisheries than developed countries. The coverage of the biotechnologies here is not comprehensive, but should be enough to stimulate discussion in the conference.

The vast majority of aquatic genetic resources are found in wild populations of fishes, invertebrates and aquatic plants. Fishstat, the FAO database on fishery statistics, lists 1 235 taxa of common aquatic species that are harvested by humans in major fisheries; thousands more species are taken by small-scale fishers. It also contains information on 440 species that are farmed, but just 20 of these taxa account for approximately 80 percent of world aquaculture production. Domestication of aquatic species has not proceeded to the same level as it has in the crop and livestock sectors. Genetic biotechnologies must be used both to assist in the further domestication of aquatic species and to help manage and conserve the genetic resources found in wild populations.

5.1.2 Genetic biotechnologies in the fishery sector

This Background Document provides a summary of recently developed biotechnologies that could be used or more widely used, in the fishery sector in developing countries. Genetic biotechnologies that can be used in fisheries and in aquaculture include those that help to manage genetic resources and those for genetic improvement.

For management of genetic resources, markers can be used in the identification of management units and of endangered species to assist fishery management and they can also help broodstock management in stocking programmes. These markers may be genes, proteins (i.e. the products of genes) sequences of DNA or the phenotypic expression of genes (different colours, shapes, etc.). In the 1960’s, analysis of proteins revealed a wealth of genetic diversity in wild populations. Protein analysis is now relatively fast and inexpensive, but it requires tissue samples to be stored and transported frozen. DNA analysis is becoming the method of choice because of the small amount of tissue needed, the fact that the tissue can be stored dried or in alcohol and because DNA analysis reveals much more genetic variation than protein analysis.

Several kinds of DNA markers exist, such as RFLPs, AFLPs, RAPDs and microsatellites. These, as well as other kinds of markers, can be used to analyse gene frequencies and genetic variation in and between different groups of fish. Studies carried out using these technologies in fish populations have revealed high levels of genetic variation distributed throughout the fish genome.

Genetic improvement technologies cover a range of techniques requiring different levels of expertise and resources. Chromosome-set manipulation (i.e. polyploidy induction) is an established technique to increase the number of chromosome sets (ploidy number) in an organism. Temperature, chemical and pressure shocks applied to fish eggs can be used to produce triploid (three chromosome sets) individuals that have desirable culture traits. Sex-reversal and the production of single-sex groups of fish is also a simple technology that combines hormone treatment and chromosome-set manipulation.

Hybridization, i.e. the mating of genetically different groups from the same species (intra-specific hybridization) or from different species (inter-specific hybridization), is a simple technique that is now easy to accomplish due to our increased knowledge of reproductive biology. It can be used to combine good traits from two different species into one group of fish or to transfer a characteristic of one group to another. A problem is that breeding hybrids with hybrids results in a non-uniform and unpredictable group of fish that is generally not well suited for culture. Therefore, for hybrid production, the parent-lines must be maintained pure. The above genetic improvement techniques are considered short-term strategies, where the gains are seen in one or two generations.

Selective breeding is a longer-term strategy where gains are accumulated at each generation of selection. Molecular markers may now increase the efficiency of selective breeding by facilitating the identification of quantitative trait loci, i.e. genes that control complex characters such as growth rate and environmental tolerance and secondly, by making it possible to use molecular markers linked to QTLs to identify desirable individuals or families.

Genetic engineering and the production of transgenic organisms is an active area of research and development in aquaculture. This is a medium-long-term strategy in that development and testing of stable transgenic lines requires time. The large size and hardy nature of many fish eggs allows them to be manipulated rather easily and facilitates gene transfer by direct injection of a foreign gene or by electroporation, where an electric field assists gene transfer.

In the next three sections, currently available biotechnologies are briefly discussed in the context of fishery management, aquaculture and conservation respectively.

5.1.3 Biotechnologies in fishery management

The role that the application of genetic principles can play in the sustainable use and conservation of living aquatic resources is being increasingly appreciated by resource managers, policy-makers and the international community. Fishery management requires information on the fishery resources in order to be effective. Primary information needs include:

Genetic analysis of the resources can address these information needs. Gene and genotype frequencies of different markers can provide information on, inter alia, species identification, population stock structure, hybridization and gene flow. Often, data from other sources, e.g. studies of tagged fish or of external characters of fish, cannot provide such information or are extremely difficult to collect in certain areas such as large river systems, floodplains or marine areas.

The use of protein and DNA data in fishery management requires collection of baseline (or background) genetic information. Genetic data were used to determine how sub-groups of Pacific salmon differed from each other in the Pacific Northwest. This required the analysis of hundreds of stocks of salmon but, once completed, endangered stocks were identified, levels of migration were estimated and the contribution of different stocks to a mixed stock ocean fishery was estimated.

Protein and DNA information has been used to identify endangered species that are either inadvertently captured in wild fisheries or are purposefully taken illegally. DNA analysis of legally sold whale meat revealed that many samples came from protected species of whale and dolphin. Species of shark are often difficult to identify because it is only the fins or flesh that are for sale; DNA analysis can be used to identify the species that provided the tissue and has the added advantage that dried tissue or less-than-fresh samples from markets can be studied.

5.1.4 Biotechnologies in aquaculture

Genetic biotechnologies in aquaculture focus primarily on increasing growth rate, but also include disease resistance and increased environmental tolerance. There are several biotechnologies that can be applied to farmed aquatic species.

Selective breeding, i.e. traditional animal breeding, started with the common carp several thousand years ago. However, it has only recently been applied to a handful of other species of food fish such as catfish, trout and tilapia. Therefore, many farmed aquatic species are very similar to their wild relatives. Selective breeding programmes have yielded significant and consistent gains of 5-20 percent per generation in species of, inter alia, Atlantic salmon, catfish and tilapia.

Hybridization is a simple genetic technology that has become easier with the development of artificial breeding techniques, such as the use of pituitary gland extract and other hormones to initiate gamete development and induce spawning (i.e. the depositing of eggs), and an increased understanding of environmental cues that influence reproduction, such as day length, temperature or water current. Many of the natural reproductive isolating mechanisms that species develop in the wild can now be overcome by fish farmers.

These improvements in reproductive technologies have also assisted aquaculturists greatly in their efforts to domesticate aquatic species. In addition, by making it possible to remove the natural constraints and timing of breeding, farmers are able to mate many more species at the times that are most beneficial and thus help to ensure a steady and consistent supply of fish to the market.

Chromosome-set manipulation can be used to produce triploid organisms that generally do not channel energy into reproduction because of problems associated with development of reproductive organs. Initially it was thought that this energy saving would result in increased growth rate, but this seems not to be the case. The real advantage of triploids seems to be in their functional sterility. For example, triploid oysters do not produce gonads (i.e. reproductive glands) and are therefore marketable at times of the year when mature oysters have an off-taste because of production of gametes (i.e. sex cells - the ovum, or egg (female), and sperm (male)).

In aquaculture, one sex is often more desirable than the other. For example, female sturgeon produce caviar, male tilapia grow faster than females whereas it is the female trout and salmon that generally grow faster than the males. The production of single-sex groups of fish takes advantage of these differences between the sexes and can be accomplished by manipulation of the developing gametes and embryo. The manipulation can be in the form of denaturing (i.e. destroying) the DNA in gametes followed by chromosome-set manipulation or by hormonal sex-reversal and subsequent breeding. The phenotypic sex of many aquatic species can be changed by administering appropriate hormones. For example, genetically male tilapia can be turned into females through estrogen treatments. These genetic males when mated with normal males produce a group of all-male tilapia that grow faster and have less unwanted matings (that lead to overcrowding and stunting) than a group of mixed-sex tilapia. Some of the all-male offspring would have two male chromosomes and these could be used as broodstock for subsequent generations, thus avoiding the use of hormones in the broodstock. Hybridization can also be used to produce single-sex groups of fish, when the sex-determining mechanisms in the parental lines are different (for example, hybridization of Nile tilapia and the blue tilapia).

Genetic engineering is a vague term that has come to be nearly synonymous with gene transfer, i.e. the production of transgenic fish or GMOs. This technology is progressing rapidly and it is now possible to move genes between distantly related species. Gene transfer in fish has usually involved genes that produce growth hormone and has been shown to dramatically increase growth rate in carp, catfish, salmon, tilapia, mudloach and trout. A gene from the winter flounder that produces an anti-freeze protein was put into salmon in the hope of extending the farming range of the fish. The gene did not produce enough of the protein to extend the salmon’s range into colder waters, but it did allow the salmon to continue growing during cold months when non-transgenic salmon would not grow. Transgenic technology is currently in the research and development stage. To our knowledge there are no transgenic aquatic plants or animals available to the consumer. Cryopreservation

The development of cryopreservation or low-temperature technology allows the short- and long-term storage of gametes. Currently, these low-temperature techniques can only be used on male gametes; eggs and embryos can generally not be stored in this way. Freezing gametes can increase the flexibility of a fish breeder, especially when breeding species where the sexes mature or migrate at different times, when the breeding season is very short, when the breeders are far apart or when one sex is exceptionally rare. Fish health

Genetic biotechnologies are being used to improve fish health through conventional selection for disease resistance and through the use of molecular investigation of pathogens for characterization and diagnosis. DNA-based technologies are being used now to characterize different species and strains of pathogens. Genetic characterization of the pathogen may also reveal information about its origin, e.g. DNA analysis revealed two strains of crayfish plague fungus in Sweden: one from the local species and one originating in Turkey. Once the pathogen is characterized, DNA probes can be developed to screen for specific pathogens in tissue, whole animals and even in water and soil samples. These techniques are being used to detect viral diseases of marine shrimp throughout the world and for bacterial and fungal pathogens in fishes in many areas.

Genetically engineered vaccines are also being developed to protect fish against pathogens. Genetic immunization of rainbow trout with a glycoprotein gene from the virus causing viral haemorrhagic septicaemia has recently been shown to induce high levels of protection against the virus. Work is also underway on immunizing carp, salmon and other fishes with genetically engineered vaccines for other diseases.

The new molecular techniques are extremely sensitive and can identify pathogens in fish long before there are any clinical signs of the disease. This has implications for quarantine and the trade of aquatic species, which is currently governed by the World Trade Organization and the Office International des Epizooties. Trade can be restricted based on the disease status of a product or a region; identification of minute quantities of a pathogen or of a new strain of an existing pathogen could change or influence existing trade patterns. Farming system

Farming systems for aquatic species are diverse and include industrial-scale farms, family ponds and culture based fisheries (stocking), in both developed and developing countries. Often, there is a division of the production process where fingerlings (i.e. small fish, especially up to one year of age) or eggs are produced by the seed-supplier, but the grow-out to market size is done elsewhere. In the case of sea going salmon, there is often a seed supplier operating a hatchery near a river, a fingerling producer in a freshwater lake, and another group that grows the fish to market size in the sea. Marine shrimp hatcheries in Asia are usually small family-owned ventures, whereas in Latin America they are more industrial in scale. Appropriateness of genetic biotechnologies must take these different systems into consideration.

5.1.5 Biotechnologies in conservation

Genetic biotechnologies can be used to reduce the impacts of farmed fish on wild populations, to identify and manage endangered species and to manage captive populations in aquaria or in species recovery programmes. In several areas, farmed fish must be made triploid, i.e. sterile, in order to reduce their impact on wild populations should they escape from the fish farm. Generally, the planned use of transgenic fish also includes the provision that they are sterile, to reduce the chance of mixing with other fishes. Genetic manipulation and polyploidization can be combined to regenerate endangered species. This can be done from frozen sperm by denaturing the DNA in an egg of a related species, fertilizing with frozen sperm from the endangered species and then duplicating the chromosome set of the fertilized egg.

5.1.6 Certain factors that should be considered in the discussion

The key question in this e-mail conference is how appropriate the different biotechnologies may be for the fishery and aquaculture sectors in developing countries today.

The question of appropriateness should consider the following elements:


In the Background Document prepared for this conference, a brief coverage of some main biotechnologies was provided. These included the use of protein or DNA markers, triploidization, sex-reversal, hybridization, selective breeding, freezing of male gametes, genetic modification of fish and finally, DNA-based technologies to diagnose and characterize fish pathogens and to develop vaccines. They were discussed in the context of three main areas: fishery management, aquaculture and conservation.

However, participants in the conference focused to a large degree on a single biotechnology, the use of genetic modification, in a single main area, aquaculture. Of the 26 messages posted during the conference, 19 dealt only with this theme. Apart from genetic modification, the technology of triploidization was also much discussed, but only in the context of its application to GM fish.

A range of factors (such as the impact on human health, the status with respect to intellectual property rights, the costs or capacity-building required) that might influence the appropriateness of the different biotechnologies were also mentioned in the Background Document. But again, one factor dominated the discussions: the potential ecological risk or environmental impact of GM fish.

Section 5.2.1 of this document attempts to summarize the main elements of the discussions. Specific references to messages posted, giving the participant’s surname and the date posted (day/month of the year 2000), are included. The messages can be viewed at Section 5.2.2 gives the name and country of the people that sent referenced messages. No messages came from some of the developing countries (Brazil, China and Cuba) that have active programmes in fisheries biotechnology.

5.2.1 Topics discussed in the conference The nature of GM fish

There was some basic disagreement about how different GM fish were from non-GM fish. Muir (1/9) maintained that GM fish were very different as they could retain all the benefits of the wild species, while the transferred gene (the transgene) could potentially confer major advantages on the individual fish, such as being able to spawn at different times or invade new habitats. Conversely, the transgene could also make individuals less fit than wild types by affecting traits such as juvenile survival (Muir, 30/8). Moav (4/9 and 28/9) maintained that GM fish lines were similar to the domesticated parental lines which created them and that their genetic superiority for traits such as growth rate or disease resistance would be similar to that achievable through many years of conventional selective breeding. Production of GM fish in developing countries

Currently, there is no commercial growth of GM fish, either in the developed or developing world. Norris (23/8), however, predicted that within the next five years or so, production of GM fish for human consumption would be a reality. She argued that there were two reasons why it might happen in a developing country such as Chile. The first is that Chile is an important producer of farmed fish, thus representing a major potential market for the technology. Secondly, consumer opposition to GMOs in general is far tamer than in developed countries, a point also made by Mair (15/9). Halos (12/9) emphasized that in densely populated developing countries with rising population numbers the priority is providing people with food as “poor people do not care to save for tomorrow since they fear tomorrow may not come for them, anyway”. Mair (15/9) concluded that concerns about human health and environmental aspects of GM fish would inevitably be weighted lower when food security was a major issue, which could result in GM fish in aquaculture being adopted first in developing rather than developed countries. Potential environmental impact of GM fish

As mentioned earlier, this was the major topic taken up by the participants during the conference. Discussions touched on four main areas:

a) Growing GM fish where wild relatives exist

Muir (30/8) pointed out that, unlike the situation of domesticated animals, domesticated GM fish might escape into an ecosystem where the wild non-GM members of the same species are found (e.g. a hypothetical case might be production of transgenic Atlantic salmon in the Atlantic Ocean). He argued that this was a major concern because a) the wild relatives are likely to be an integral part of the ecosystem and disruption of the species could affect the entire ecosystem; and b) the escaped individuals can establish themselves by interbreeding with the wild relatives.

For this situation, Muir (30/8 and 1/9) summarized results from a paper he co-authored in 1999 which, using a theoretical model, considered the potential consequences of a small number of GM fish escaping and mating with their wild relatives. His results showed that if the transgene increased mating success but reduced the viability of transgenic offspring, then the local fish population could be driven to extinction. Halos (31/8) pointed out that the introduction of a new fish strain or of a superior conventionally bred strain might have the same consequences on a wild fish population and that this phenomenon was thus not unique to GM fish. She reported that this had already happened with the native catfish strain in the Philippines.

Regarding fish escapes, Halos (12/9) and Mair (15/9) both described the problems, especially due to large environmental extremes, of enforcing risk management strategies in developing countries. Mair (15/9) concluded, based on his practical experiences, “I would never like to guarantee that any domesticated fish cannot escape from an aquaculture facility”.

Halos (31/8) argued that if GM fish mated with wild relatives, this might increase genetic diversity in the wild population. Muir (1/9), however, refuted this, concluding that GM fish (or exotic non-GM fish species) might in the short-term add diversity but, in the long-term, they decrease it because they eliminate competitors.

b) Growing GM fish where wild relatives do not exist

Moav (4/9) pointed out that in his country, Israel, carp had been imported from Europe and that the transgenic carp (with increased growth rates) that they had developed in Israel would not present such potential problems as there was no native carp population. Muir (5/9) suggested that the issue of the production of GM fish in regions where the wild species does not exist was of great importance and that there was a range of other potential examples, such as the production of transgenic tilapia in Cuba or transgenic Atlantic salmon in the Pacific. He had two major concerns about such potential initiatives:

c) Triploidization

With such concerns expressed about the potential ecological risk of GM fish mating with non-GM wild relatives, the potential application of triploidization to GM fish to ensure their sterility was raised (Ibarra, 6/9). Benfey (6/9) pointed out that reliable technologies for making GM fish triploid exist for salmonids and that this was a simple way to ensure they would not breed if they escaped into the wild. He also suggested that companies producing transgenic fish might want to only sell sterile fish, in order to protect their investment.

In theory, each individual GM fish could be tested to ensure it was triploid before being released, a procedure already established in some situations with the grass carp in the United States (Benfey, 7/9; Kapuscinski, 22/9). Chevassus (11/9), however, pointed out that it is possible to test for triploidy but not for sterility and that in some species, although not in salmonids, a few or large number of triploid individuals may in fact be fertile. Muir (6/9) also argued that it is actually hard to quantify how successful a sterilization technique such as triploidization may be if the true probability of failure is very low (e.g. one in a million), because, to reliably quantify it, an extremely large number of fish, more than normally tested, may be required.

Muir (11/9) also pointed out that even though triploid males might be sterile they may still mate with fertile females of the wild species, thus interfering with reproduction and breeding of the wild population. To avoid this potential problem, he thus proposed that GM fish, in addition to being made triploid, should also be sex-reversed so that only females be grown. Mork (11/9) reported that a Working Group on the Application of Genetics in Fisheries and Mariculture, belonging to the Mariculture Committee of the International Council for the Exploration of the Sea, had considered the issue of triploidization at various times throughout the 1990s. An impetus for this work was the finding that some previously triploid Pacific oysters (Crassostrea gigas) introduced to the east coast of the United States reverted back to the diploid state. Their conclusion in a 1995 report was that “no current mass triploidization/sterilization technique is guaranteed 100 percent effective”.

Mair (15/9) pointed out that there was an additional reservation about the application of triploidization in aquaculture of GM fish in developing countries, i.e. that “the application of triploidy in commercial stocks (mainly salmonids and grass carp) has been limited to species that are habitually bred using artificial fertilization and incubation. For most of the important species in developing country aquaculture (namely tilapias and carp) artificial fertilization is rarely used and therefore application of triploidy on a commercial scale would be very unlikely to be viable”.

d) Biosafety

Such discussions on the potential impact of GM fish escaping into the wild and the use of technologies such as triploidization to minimize potential risks, brought up the main issue of biosafety which, broadly defined in relation to GMOs, involves assessing and monitoring the effects of possible gene flow, competitiveness and the effects on other organisms, as well as possible deleterious effects of the products on health of animals and humans. Ibarra (6/9) noted that in developing countries there was a substantial lack of human resources in the fishery sector trained in genetics and that this could lead to the situation where “potentially high-risk biotechnologies will become implemented without a careful evaluation”. Norris (23/8) also expressed the fear that GM fish might be introduced in developing countries “without even considering risk assessment for such introductions”. Ashton (25/9) insisted that, prior to release of any fish, GM or not, in developing countries, there was a need for adequate biosafety protocols, legal instruments, liability procedures and a clear thread of responsibility for any damage that might be caused to the countries by their release. Del Valle Pignataro (27/9) lamented the fact that, in relation to introducing non-native species (GM or not) to developing countries, it was not possible in most cases to establish strict regulatory/monitoring systems, due to factors such as low economic priority or the lack of qualified human resources.

Gjoen (5/9) argued that it was difficult to foresee all the risks involved with GM fish and that the precautionary principle should be given priority, a view that was shared by Ashton (25/9). The need for carrying out risk assessment in a scientifically sound manner was emphasized in a few messages (Moav, 4/9; Muir, 5/9; Gjoen, 5/9; Moav, 28/9). Use of genetic modification versus other alternatives

Genetic modification dominated discussions in the conference. Nevertheless, some participants did consider other biotechnologies and other aspects of aquaculture in developing countries. Doering’s (25/9) perspective was that, with few exceptions, the fish species cultured today are wild and that enormous gains for traits such as productivity, growth rate or survival can be achieved by selective breeding, assisted by molecular methods. He argued that, apart from concerns about the potential environmental impact, “transgenic aquatic animals are not sensible or cost-effective in the genetic background of a wild animal and the enormous productivity gains to be made by intensive selective breeding”. Norris (23/8) also emphasized that many developing countries were “in need of practical help and advice in developing good aquaculture breeding and husbandry practices which would benefit their programmes greatly”.

Ibarra (6/9) suggested that most of the currently available genetic biotechnologies are very appropriate for developing countries and that the main reason for their under-use was the “lack of human resources within the fishery and aquaculture sector trained in the adequate use of those genetic biotechnologies”.

Doering (25/9) emphasized that many of the current problems in aquaculture in developing countries have low-technology solutions and that “the species appropriate for culture in developing countries generally do not have the production economics to justify many high cost inputs such as vaccines and artificial larval feeds”. He argued that policy-makers and scientists can become over-enthusiastic for molecular techniques, ignoring the large capacity-building needs that these technologies require. His conclusion was that “investments in developing countries on farmer education, reducing culture stress and improving water quality as well as domestication will yield higher returns than investments in high technologies”.

Ashton (25/9) argued for the prioritization of local solutions in developing countries and that management systems which secure the protection, husbandry and sustainability of native species should first be put in place before any fish, GM or not, are introduced. Del Valle Pignataro (27/9) supported this viewpoint. She suggested that prioritization should be given to domestication, culture and (eventual) genetic improvement of native fish species that are already exploited and that have good consumer acceptance in developing countries. She gave a summary of their ongoing marine fish efforts in this direction in Mexico, which will eventually involve the use of selective breeding with medium-level biotechnologies

5.2.2 Name and country of participants with referenced messages

Ashton, Glenn. South Africa
Benfey, Tillmann. Canada
Chevassus, Bernard. France
Del Valle Pignataro, Gabriela. Mexico.
Doering, Don. United States
Gjoen, Hans Magnus. Norway
Halos, Saturnina. The Philippines
Ibarra, Ana. Mexico
Kapuscinski, Anne. United States
Mair, Graham. Thailand
Moav, Boaz. Israel
Mork, Jarle. Norway
Muir, Bill. United States
Norris, Ashie. Ireland

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