How appropriate are currently available biotechnologies for the fishery sector in developing countries ?
Biotechnology in fisheries and aquaculture represents a range of
technologies that present opportunities to increase growth rate in farmed
species, to improve nutrition of feeds for aquaculture, to improve fish
health, to help restore and protect environments, to extend the range of
aquatic species and to improve management and conservation of wild stocks.
In this e-mail conference, the focus will be 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% 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.
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 (3 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
Hybridisation, i.e. the mating of genetically different groups from the same
species (intra-specific hybridisation) or from different species
(inter-specific hybridisation), 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 (QTLs), 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
In the next three sections, we will briefly discuss currently available
biotechnologies in the context of fishery management, aquaculture and
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
- an identification of the resource;
- the breeding or stock structure of the resource;
- an estimate of the size of the resource; and
- the identification of key habitat that the resource requires.
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,
hybridisation 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 that 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.
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
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% per generation in species of, inter alia,
Atlantic salmon, catfish and tilapia.
Hybridisation 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
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.
Hybridisation can also be used to produce single sex groups of fish, when
the sex-determining mechanisms in the parental lines are different (for
example, hybridisation 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 genetically
modified organisms (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.
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.
4.2 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 characterisation and diagnosis.
DNA-based technologies are being used now to characterise different species
and strains of pathogens. Genetic characterisation 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 characterised, 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 immunisation 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 immunising 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 Organisation 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.
4.3 Farming systems
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. 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 polyploidisation 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, fertilising with frozen sperm from the
endangered species and then duplicating the chromosome-set of the fertilised
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
The question of appropriateness should consider the following elements:
- How does the farming system influence the use of genetic biotechnologies
in developing countries ?
- What are the factors that determine or influence the appropriateness of
the different biotechnologies in developing countries e.g. their
environmental impact; their impact on human health; the status with respect
to intellectual property rights; the status with respect to biosafety
regulations and controls; the degree of access to the biotechnologies; the
level of capacity-building or resources required to use them; their
financial cost; their impact on food production and food security;
- The relative costs (financial, social, political or otherwise) of the
biotechnologies versus the relative benefits (productivity, food security or
- Whether they are more (or less) appropriate than existing conventional
methods in the fishery sector in developing countries;
- Whether some of the biotechnologies are more (or less) appropriate than
- Whether some biotechnologies are more (or less) suited to certain regions
in the developing world than others.
NB: When submitting messages, members of the Forum are requested to ensure
that their messages address some of the above elements.
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