|GM-fish possible problems and implications
In many cases, the scientists have inserted a gene that produces a growth hormone, to make the fish grow fester and attain a larger size at maturity. The intention is not to have a larger fish, but to have forms that could be hervested earlier and they expect the fast growth rate to be the desired trait. In some, the gene is a human growth harmone gene (hGH gene) from human beings. Several fast growing fishes have been made by not adding a new gene, but adding a new promoter region for an already existing gene. A promoter is the region of a gene that decides, where, when and for how long the gene should be active (or express itself). The purpose of adding a new promoter is to activate the gene out of turn, in order to get a result desired by the scientists. An example is a form of Atlentic Salmon which has a growth hormone benefitted with a promoter obtained from another species of fish. The growth hormone gene in Atlantic Salmon get activated only during the summer. The introduced promoter in the genetically-modified form keeps the gene active during the whole year, paving the way for a faster growing, larger fish.
It was recently reported in the media that a GM-Tilapia had been brought to Sri Lanka by the National Aquatic Resources Development Authority. In October last year, the Society for Enviornment Education (SEE) received information about an effort to import a GM-Tilapia that has a human growth hormone gene. This particular varient had been made by modifiying the Nile Tilapia (Oreochromis Niloticus) and has a fast growth rate. One form of it is of a pinkish-orange colour. It is not yet certain whether the Tilapia brought by the authority were a GM-fish. In an interview to The Observer (11.04.2001 - lead story) the director of the authority had stated that the Tilapia brought by them has a fast growth and breed rapidly but had not shown any potential dangers and that it could be used as an ornamental fish as well as a food item. However, these details are uncomfortably similar to the characters of the GM-Tilapia.
This incident illustrate the apparent case with which a new fish (whether GM or not) could be brought in without any check on control. Most of these come as ornamental varieties. About 40 species of exotic fish have been found in our waterways, and some of them are proving to be invasives except for the 18 species that are prohibited from import under the Fisheries and Aquatic Resources Act, there is no control at all. Under the Fisheries and Aquatic Resources Act., it is not necessary even to obtain a permit to import a fish. If new regulations are not made it is not possible for the Department of Fisheries and Aquatic Resources to stop the import of any GM-fish. This act is weak in another related aspect. Even if a prohibited fish is found within Sri Lanka, there is no way to prevent a person from keeping or breeding it, nor to seize such fish.
Therefore, it is important to get an idea of the possible implications of such an introduction of a GM-fish. Several issues that help make an assessment could be:
* Whether the GM-fish could (or would) hybridize with any native species?
* Will they, if released, compete with natives
* Will they become predators
* What could heppen if one consumes such fish.
The answers to these and other questions could be obtained only by perusing literature on GM-fish.
Tilapias belong to the family Cichlidae which have two native, non-endemics in Sri Lanka. They are the Green Chromide (Etroplus Surethensis), the well-known Koraliya and the Smaller Orange Chromide (Etroplus maculatus) valued mainly as an aquarium fish. They belong to a different genera than the Tilapias, have substrata-Spawning habits as opposed to the mouth-brooding habits of Tilapias. There is no possibility of any GM-Tilapia breeding with any of these native cichlids. However, several exotic species of Tilapias have been introduced to Sri Lanka as a food fish. Two of these, the Mossambique Tilapia (Oreochromis Mossambicus) and Nile Tilapia (O. nitoticus) are widespread in Sri Lanka. These two interbreed with each other. Therefore, it is possible that a GM-Nile Tilapia would hybridize with both these species.
The possible long-term implications of an introduced GM-fish to the populations of usual forms could be gathered from the results of a study by William Muir and Richard Howard of Purdue University in West Lafayette, Indiana, U.S.A. and published in the Proceedings of the National Academy of Sciences (1999) (Volume 96). They had inserted the hGH gene to the Japanese Madaka or Rice Fish (Oryzias Latipus), small aquarium fish that is often used in research due to the small size, hardiness and the high rate of reproduction. They found out that GM-Medaka grow faster and reached maturity earlier, and grew larger. These larger fish had been able to attract more mates, or more efficient in transferring their genes to others. At the same time, they saw that only 78% of the GM-fish reached maturity compared to non-GM Medakas and that after the rapid spread of this gene through a population, their numbers would decline and get wiped out. They then put the results into a computer model and found out that 60 GM-fish introduced into a population of 600,000 wild individuals could cause their extinction within 40 generations.
According to Dr. William Muir, they have called such genes as "Trojen Genes" as they resemble the Trojen Horse, by getting into a population looking like something good and ends up by destroying the population that harbours it. They found out that sexual selection drives these genes into populations and then the reduced viability drives the populations into extinction. Other research scientists have found supportive evidence and Dr. David Penman has discovered that some trans genic fish have decreased production of sperm and therefore, while they mate more, have less success in getting progeny.
It is possible that a TM-Tilapia could cause the eventual collapse of the introduced Tilapias that are found in Sri Lanka. Since all introduced Tilapias compete with natives for food and the species O.mossambicus is even listed as one of the 100 worst invasives of the world by IUCN in 2001, the wiping out of it could be argued to be a positive development. At the same time, other could argue that since there is a substantial inland fishery dependent on it, this could be detrimental to those who earn by it. Another possible argument could be that since GM-fish grow faster and larger they could possibly enhance production.
Any large and fast growing animal naturally needs more food. It could be much greater than the proportion of weight gained by them, as it is determined by other factors such as food conversion ratios and metabolic rates. This possibility had been shown by a research conducted by Robert Delvin at the Department of Fisheries and Oceans in Canada. He found out the genetically modified Coho Salmon consume nearly three times more food than required by non-transgenic ones. More food for these means, less food for other fishes and aquatic creatures that share its habitat. In addition, it could well become a predator of small creatures and the eggs and young of other fish that may hasten their demise. A larger, hungrier fish could well seek larger prey. Even if there is no problem of hybridization with native fishes, a GM-fish could bring about the destruction of native fishes by competition and predation. The GM-Tilapia made in Cuba are known to grow twice as large as their non-transgenic relatives (Ref; J. de La Fuente et al).
The other important issue is how they will effect the consumers. A person feeding on the flesh of any such fish that has more growth hormones could get an unwanted dose of it. The implications of such in the short and long-term cannot be ascertained with any certainty. This area needs a lot of careful research. So far, no trans genic fish had been approved for human consumption anywhere in the world. An application to rear a genetically modified form of Atlantic Salmon commercially for human consumption had been forwarded to the U.S. Food and Drug Administration (FDA) for approval. It had been made by Aqua Bounty Farms, a subsidiery of A/F Protein. It is interesting to note that the Centre for Veterinery Medicine of FDA had regarded this GM-Atlantic Salmon as an "animal drug" because of the increased production of growth harmones.
A country like Sri Lanka, that has a hospitable environment for many non-native species, has to be extremely careful and cautious about the importation of any such GM-animals, even for experiments. This is because there are no definitely fool-proof measures to prevent escapees to the wild who could probably establish populations. An accidental release could happen even from the most carefully controlled enclosures. In 1999, about 30,000 genetically modified Atlantic Salmon had escaped from a fish ferm in Washington, U.S.A. There are worries that these would breed with native populations of Atlantic Salmon, which may cause its extinction. The other is that consumers of Atlantic Salmon in the future would be unwittingly taking an 'animal drug'. The escapees from Canadian fish farms amounts to about 280,000 fish. It is uncertain how these will affect the wild, populations, which only could be assessed in the future.
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