4th quarter 2004
Transgenic fish
Every year, around 80 million tonnes of fish are caught worldwide; a further 40 million tonnes are produced in fish-breeding facilities. In the case of the latter, great efforts are made to adapt the fish to the specific conditions in which they are bred, with emphasis on faster growth, better feed conversion and resistance to disease. Genetic engineering has little effect on existing fish-breeding objectives, but it accelerates breeding work and makes it possible to transfer genes from other species.
Fish have several advantages over mammals when it comes to genetic engineering: fertilisation of eggs and development of embryos do not take place in utero but in the water. This means the eggs do not have to be extracted, processed and then re-implanted in the mother. What is more, a large number of eggs are available, so that several experiments can be conducted in parallel. So far, the main types of fish to be genetically modified are the Atlantic salmon, the trout and the carp.
Breeding objectives:
Quicker growth and larger fish through transfer of a growth hormoneCold tolerance through transfer of an "antifreeze protein AFP" from the flounderResistance to illnessSterility to prevent cross-breeding with existing wild populationsFluorescence in zebra fish for aquariums — the first genetically modified fish to be licensed. So far there are no other licences apart from those for the zebra fish, although some fish are ready for the market.
An American firm (A/F Protein) has already produced a market-ripe transgenic salmon in Canada (Aqua Bounty Farms). The AFP protein was transferred to the fish, which also exhibits an overproduction of the growth hormone. It grows four to six times more quickly than fellow members of its species in a natural state. The firm has been waiting since 1999 for a licence for the salmon from the US Food and Drugs Administration, FDA. But the longer the proceedings have lasted, the more resistance has grown. There are fears of environmental risks resulting from the transfer of the gene to wild salmon through cross-breeding. Computer simulations have even shown a "Trojan gene effect": if a gene increases reproductive capacity (of larger fish) on the one hand but impairs survival capacity on the other (for example, because the fish are slower in escaping from enemies), stocks could die out. There are also concerns about tumours and deformities that recurrently appear. Last but not least, a further increase in salmon production would put even greater pressure on prices.
As already mentioned, the zebra fish is the only genetically modified fish currently licensed. Fluorescent fish were originally developed in Singapore to determine pollution in bodies of water, where the fish used only changed colour when the water contained pollutants. A fluorescent aquarium fish — Night Pearl, containing the gene of a jelly fish — was first marketed in Taiwan in mid-2003. Since the beginning of 2004, it has been possible in the USA to buy Yorktown Technologies' GloFish, which contains a gene from sea coral/anemone and glows red when light falls on it. Organisations, associations and interest groups have protested vehemently and even filed a suit against the government to stop the sale of GloFish. Proceedings are still pending.
| Table: Genetically modified aquatic species (FAO, 2003) |
| Name | Latin name | Number of genetic
constructs used |
| Atlantic Salmon | Salmo Salar | 6 |
| Coho Salmon | Oncorhynchus kisutch | 4 |
| Chinook Salmon | Oncorhynchus tshawytscha | 3 |
| Tilapia | Oreochromis spp. | 12 |
| Medaka | Oryzias latipes | 17 |
| Zebra fish | Brachydanio rerio | 14 |
| Common Carp | Cyprinus Carpio | 14 |
| Channel catfish | Ictalurus punctatus | 9 |
| African catfish | Clarias gariepinus | 1 |
| Rainbow trout | Oncorhyncus mykiss | 7 |
| Cutthroat trout | Oncorhyncus clarki | 1 |
| Goldfish | Carrassius auratus | 5 |
| Northern pike | Esox lucius | 2 |
| Loach | Misgurnus anguillicaudatus | 2 |
| Sea bream | Sparus aurata | 2 |
| Red sea bream | Pagrus major | 1 |
| Blunt snout bream | Megalobroma amblycephala | 1 |
| Nigorobuna | Carrassius auratus grandoculis | 1 |
| Walleye | Stizostedion vitreum | 1 |
| Brine shrimp | Artemia franciscana | 1 |
| Seaweed | Laminaria japonica | 1 |
| Sea Urchin | Strongylocentrotus purpuratus | 1 |
| Abalone | Haliotus rufescens | 1 |