Exploring Bioethics - NIH Office of Science Education - National ...

Super-Sized SalmonSalmon can be bred and raised in tanks on fishfarms. Most salmon consumed in the UnitedStates are from fish farms. Fish farming is anover-$100-million-a-year industry. The farmshave separate tanks for fertilized eggs, for newlyhatched fish, and for each size fish as they grow.Scientists have been able to make transgenicsalmon that grow 11 times bigger, on average,than a regular salmon of the same age. Agrowth-hormone gene is injected into fertilizedeggs to produce the super-sized fish. Not onlydo they grow larger than wild-type salmon, butthey reach sexual maturity more quickly and canbe bred earlier. Because of their large size andtheir ability to reproduce earlier, these transgenicfish can help meet the growing consumerdemand for salmon.The three fish on top have been genetically engineered and arelarger than the bottom fish of the same age.Photo: Courtesy Huntsman Marine Science CentreCopyright © 2009 Education Development Center, Inc. Exploring Bioethics.Permission granted for classroom use.The risks of genetic engineering are not well defined but may include altering the appropriateexpression of the salmon genome, which could have undesirable consequences for the fish and itswell-being. Researchers at Purdue University have investigated the effects of transgenic fish on wildpopulations of the same species. Using a fish called the Japanese medaka, scientists found thatjust 60 transgenic fish could drive a population of 60,000 wild fish extinct in only 40 generations.Whether these results would be the same for salmon is not yet known.People disagree over the health benefits of farmed compared with wild salmon. Farmed salmonhave more omega-3 fatty acids, which have proven health benefits, but also higher levels of chemicalcontaminants known to cause cancer. However, some studies indicate that transgenic organismsmay have adverse health effects on consumers, such as unexpected allergic reactions.Alternatives to the super-sized salmon include farming nontransgenic fish or continuing to catchwild salmon, which has environmental consequences of its own.Is it ethically acceptable to genetically engineer fish to grow larger and thus provide morefood for humans? Why or why not?Master 6.2 (Page 11 of 12)