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Drug-Induced Fish: Hormone Causes Tilapia to Undergo Sex Change

Monday, April 06, 2009 by: Barbara L. Minton
Tags: fish, health news, Natural News

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(NewsTarget) Has the fish on you dinner table gone through a drug induced sex change? If the fish is tilapia, the answer is probably yes. Tilapia is a delicious, mild flavored fish that has become very popular because of its low price. This low price is achieved by converting the young females to males through the use of the hormone drug 17alpha-methytestosterone. Raising an all male population allows fish farmers to produce bigger fish in a shorter time period with less feed. It also allows them to produce fattened profits. The only problem is that consumers have no idea the fish they are eating have undergone hormone-induced sex changes, and the long term consequences of such changes to health and environment are as yet unknown.

Almost all tilapia sold in the U.S. is hormone drug treated

Tilapias are warm water fish originating from Africa and the Middle East. The main species cultured in ponds, cages and pens is the Nile tilapia. The problem with these fish is their quick maturation at two to three months of age, and their ability to start breeding at a rate of once a month. These characteristics result in the overpopulation of stocked tilapia ponds and the stunting of growth because of the crowding of the fish. Another problem associated with a mix of males and females is the sizes of the fish for harvest varying from small to large due to the faster growth of males. This makes it more difficult to establish uniformity of product. For producers wanting high yields of large-sized fish in three to four months, all male fry are preferred.

Production of all male tilapia can be accomplished by such techniques as separating the males and females manually, hybridization which mates two species to produce all-male offspring, or by artificial sex reversal. The most efficient and least expensive method is sex reversal with the use of 17 alpha-methyltestosterone.

To artificially create sex reversal, the physical sex direction of the fish is manipulated by the feeding of methyltestosterone prior to and during the early sexless stage of the baby fish, called fingerlings. This technique was first developed in Japan in the 1950s for sex reversal of aquarium fish and species of carp. It was demonstrated as commercially feasible in the 1970s. Fish raised in this manner grow bigger quicker because they do not need to expend energy in developing reproductive organs and require less feed. If properly applied, the sex reversal treatment can be 98 to 100% effective.

Treatment with methyltestosterone is now the chosen method of producing tilapia in fish farms worldwide. Virtually all tilapia sold in traditional American supermarkets and grocery stores is tilapia fed with methyltestosterone.

17 alpha-methyltestosterone is highly toxic to the human liver

Methyltestosterone was created in an attempt to modify the chemical structure of the predominantly male hormone testosterone so that it could be patented. It has been prescribed for several years as a hormone drug substitution for men and women with hormone deficiency, and has been a favorite of body builders. The joining of the 17 alpha-methyl group to testosterone allows testosterone to pass through the liver without being metabolized. However, it also makes the drug highly toxic to the liver and capable of causing liver cancer. The drug has been taken off the market in Germany due to its high liver toxicity.

Industry reports claim that after five days of withdrawal from the hormone laced feed, the levels of male sex hormone in the treated fish return to normal indicating that no hormone residues are present. According to these reports, the fish are therefore safe to eat. However, no long term studies have been completed to determine if this statement is indeed true.

Hormone drug treatment of fish is restricted in other countries

In some countries, restrictions exist on the sale of hormone treated fish unless it is proven that there are no risks to human health from consuming them. When such restrictions are in place, there is a problem created for the marketers of fish treated with hormone drugs. Marketing of treated fish is illegal in the EU countries and in India.

Many people do not want to eat food that has been altered with substances that change its basic biology. Although it can be argued that the ability of technology to provide cheap food is a good thing, new technologies often bring unintended and unwanted consequences. Little is know about the effects of the testosterone drug on the fish or on the environment. Clearly the hormone drug passes through the fish and enters environmental channels such as water and land. Unintended consequences from the use of sex changing drugs in fish would not be the first unintended consequence for the food industry. That industry thought it was a really good idea to use pulverized parts of cows in animal feed to help speed cheap food to market and fatten bottom lines. The result was cases of mad cow disease.

Industry representatives point out that if tilapia were not sex reversed, females would be farmed along with males. Their greater requirements for feed for reproductive organ development would put a greater environmental strain on the fish farm by creating a greater amount of waste. Since wild fish are used in fish feed, raising only males implies greater conservation.

There is awareness and outrage about the treatment of land animals raised to become part of the food chain. Land animals are enough like people to elicit human empathy. Even the treatment of lab rats has a vocal opposition. That fish are not being allowed to complete their biological destiny has not evoked our emotions, perhaps because the industry has done a good job of keeping their practices under cover.

One large health oriented grocery chain has made the decision to stand up for the rights of fish, even if only to attract more health oriented customers. The chain began banning testosterone in fish about three years ago, scouring the world to find fish farms that did not use methyltestosterone. They even stopped selling tilapia for a while before working out arrangements with farms in Ecuador and Costa Rica to supply hormone-free fish. No fish containing hormones are now sold in their fish case.

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About the author

Barbara is a school psychologist, a published author in the area of personal finance, a breast cancer survivor using "alternative" treatments, a born existentialist, and a student of nature and all things natural.

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