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ISIS Report 15/12/03
Transgenic Fish Coming
Prof. Joe Cummins exposes the
regulatory vacuum behind the rush for commercial release of transgenic
fish
Sources
for this report are available in the ISIS members site.
Full details here
Glofish for the new year
The tiny zebra fish that lives in aquariums, a popular laboratory
animal, was genetically modified to produce a fluorescent red pigment, and is
being promoted for sale as a household aquarium pet, the "glofish". The glofish
caused a stir in the United States because regulation of such transgenic pets
is murky and none of the major regulatory agencies: FDA, USDA or EPA has been
willing to take the lead in regulating the glofish (even though USDA does deal
with pet animals). The glofish is set to go on sale January 5, 2004 without
regulatory approval.
FDA announced: "Because tropical aquarium fish are not used for food
purposes, they pose no threat to the food supply. There is no evidence that
these genetically engineered zebra danio fish pose any more threat to the
environment than their unmodified counterparts which have long been widely sold
in the United States. In the absence of a clear risk to the public health, the
FDA finds no reason to regulate these particular fish."
The FDA position that transgenic glofish are substantially equivalent to
unmodified fish is hypothetical and no effort has been made to test the
transgenic fish in contained, but wild-like environments. Fish pigmentation
with "poster" colors is an aphrodisiac to wild fish and may even provide
protection from predators in certain light conditions, or the pigment
fluorescence may signal toxic defence as in the stinging sea anemone from which
the glofish transgene was prepared and in that way discourage predators.
FDA was presumptuous in washing its hands of the regulation of the
transgenic zebra fish, which is likely to become a major pest of warm water
areas.
Other transgenic fish to follow in droves
The release of glofish may signal relaxation of the regulation of
transgenic fish now being promoted for commercial release. To ensure that
transgenic fish do not overpower or seriously pollute the gene pool, both
promoters and regulators stress the safety of "sterile" transgenic fish
released to bodies of water. Previously, "sterile" fish are produced using
synthetic triploid strains of fish produced from treatment of eggs pressure
or temperature shock and with sex hormones. As ISIS reported, the sterile
triploids were "leaky" and tend to produce a few fertile progeny, which can
establish transgenic populations.
In spite of these problems, the transgenic fish are being promoted as
the first marketable transgenic animals for human consumption. More effort
seems to have been spent on promoting the existing defective transgenic fish
than on improving them so that they can be safely released for commercial
production. Muir and Howard defined conditions under which transgenic fish can
cause rapid extinction to wild fish stock, thus posing extreme risk; but this
has been ignored in the rush to commercialization.
Development of transgenic fish has focused on a few species including
salmon, trout, carp, tilapia and a few others. Salmon and trout are cash crops
while the others primarily provide sources of protein. The salmon nearest to
commercial release is the Atlantic salmon engineered with a pacific salmon
growth hormone driven by the arctic antifreeze promoter gene. The rapid growth
of that transgenic salmon is achieved, not so much by the transgenic growth
hormone as by the antifreeze gene promoter that functions in the cool water
desirable for salmon flavor. The commercial release of transgenic salmon, even
in somewhat contained fish farms, is likely to lead to problems similar to
those experienced in the Atlantic salmon farms of the northwest Pacific. A
number of studies indicate that salmon produced in sea pens escape and breed
with native species, introducing new disease and spreading pollution from the
culture pens. These problems will probably be amplified in the fast growing
transgenic stocks.
Tilapia fish, native to Africa, are cultured world wide as "poor
man’s food", second only to carp as warm water food fish, and exceeding
the production of Atlantic salmon (whose market value is twice that of
tilapia). Tilapia has been extensively genetically modified and promoted as a
transgenic fish exclusive for isolated or contained production. Transgenic
tilapia, modified with pig growth-hormone, were three times larger than their
non transgenic siblings. Tilapia genetically modified with human insulin grew
faster than non-transgenic siblings, and could also serve as a source of islet
cells for transplantation to human subjects. Trout growth hormone was used to
produce transgenic carp with improved dressing properties. Such transgenic carp
are recommended for production in earthen ponds.
Giant mud loach was produced by linking the mud loach growth hormone
with its actin promoter. These giant fish are not, technically speaking,
"transgenic", as they contain no foreign genes even though the inserted
construct is artificial, and pose a paradox for regulators.
Silk moth genes were introduced into Medaka fish to create resistance to
bacterial pathogens. Some commercially desirable fish and crustaceans have been
difficult to genetically engineer because embryonic tissue is difficult to
manipulate. But it has been found that the parental gonads of such animals
could be modified using replication defective pantropic retroviral vectors.
Pantropic vectors can transform an array of species they are modified forms of
the Moloney mouse leukemia virus used extensively in gene therapy. Such vectors
have proven useful in modification of a range of edible marine animals
including mollusks. Animals produced using modified mammalian leukemia viruses
will require extensive testing and long-term evaluation prior to release for
human consumption. This is particularly important in view of the leukemia cases
found among the handful of successes in human gene therapy, which were done
with a retroviral vector (see "Gene therapy risks exposed",
Science in Society
19).
Contained cultures of transgenic fish
The current generation of transgenic fish has not passed the test of
complete sterility if released or escaped to the environment. Fish production
in inland earthen ponds may prove acceptable for contained transgenic fish
culture. But such facilities should be provided with fail-safe destruction of
the pond animals in the event of flooding and adequate protection from theft.
Pond commercial culture is effective for carp and tilapia, but more difficult
with salmon and trout. Currently, pond culture is suitable for carp and tilapia
because the fish are vegetarians, carnivorous salmon and trout depend on a diet
of fish and fishmeal but the worldwide stock of feed fish has diminished and
suitable vegetable meat substitutes must be found. Atlantic salmon (as typical
cold water carnivores) cannot thrive on a diet of rapeseed oils but the fish
can achieve maturity if finished with fish oils at least 20 weeks near the end
of their maturity cycle. GM oil rape seed with enhanced production of long
chain fatty acids are proposed to serve as feed for pond cultured fish. And
glyphosate-tolerant GM canola meal has been pronounced substantially equivalent
to non-GM canola as feed for rainbow trout.
Aquaculture can help feed the world without diminishing ocean
resources, but premature releases of transgenic fish stocks will do more harm
than good. Bad decisions have plagued aquaculture, resulting in pollution and
extensive damage to native stocks. International agencies such as the World
Bank, the International Development Bank and the Food and Agriculture
Organization of the United Nations have created harm by ill- advised projects
that led to damage to native resources and pollution. Scientists Julio E.
Pérez and Mauro Nirchio of Venezuala along with Juan A. Gomez of Panama
commented in Nature: "However, if the aquaculture industry is going to
reduce the pressure on wild fish stocks and provide food for the world’s
growing population, substantial changes must be made by governments, the
private sector and international funding agencies. They must protect coastal
ecosystems; promote research and development of native species; and encourage
farming of low-trophic-level fish — those low on the food chain.
International technical funding agencies can exert great influence in changing
practices". Without such constructive thinking, the aquaculture industry poses
a threat, not only to ocean fisheries but also to itself.
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