THE FISH WE EAT ~ COUNTERPOINT

crock_babies
Crock Babies ~ Their sex is determined by the heat generated in the nest

The fish we eat counterpoint to some voiced opinions. Prejudices are numerous against a lot of the new methods of food production in America today.  Most of it, in my humble opinion, is rooted in fear and ignorance.  The new technologies take a lot of work to understand, so anyone throwing a fear bomb can score points with those not schooled in what is actually going on.

Let’s take this quote from a post in my former forum, (Science Project Tilapia..!) “First off, I wouldn’t want to put something in my mouth, nevertheless my stomach that might have been a female, but was chemically altered to make it a male. That kind of genetic alteration just leads to problems, diseases, malformations, or chemical imbalances 20 or 30 years down the road.”

This statement reminds me of an exchange between Edith and Archie Bunker when she brought him a tongue sandwich. He said, “I don’t want to eat anything that has been in a cow’s mouth!” Edith asked him, “what do you want instead?” Archie replied, “How about some hard boiled eggs?”

If you don’t see the comparison between the first position and Archie’s, I’m talking to the wrong audience. Throwing fear bombs about what might happen 30 years from now is pure conjecture and has not been borne out through research. Farmers are constantly searching and selecting the best strains, so inferior genes are always being sorted out.

Here are the facts. The determination of sex in many animals such as fish, alligators, and crocodiles is not totally determined by genetics. I’m sure when you go to the store you don’t see tags on your food that tell you that the animal was genetically female but ended up male or that it was a male or female animal at all.  RIGHT..?

Almost no one cares that they are eating a neutered male bovine (bull), which is at least 50% of the beef you eat. The fact is that many animals outward sexual expression is determined by temperature, not genetics. The quality of the meat does have something to do with the sexual genetics of the animal as well as how it was raised and what it was fed.

Tilapia can be sex-reversed by using temperature. It happens in the wild every year. Once the water temperature reaches 96F nearly all fry will be male. Chemical sex reversal may seem repugnant, but hormones are common practice in animal husbandry. To sex reverse fry, you feed them a small amount of testosterone for their first month of life. Testosterone is a natural male hormone and many men take it to keep sexually active as they age. Should we isolate these people? A silly thought I think.

Hormonal treatment stops with the fish at far less than one gram in body weight.   They are harvested at around 1000 grams. What is in the adult fish’s system in a year has nothing to do with what it was fed as a fry. Thoughts to the otherwise are fear mongering. Chemically sex-reversed fish are safe. What needs to be considered is the safety of the workers that administer the drug. They need to be protected from exposure to such chemicals and in 3rd world nations; they don’t have the protections we enjoy here.

Let’s talk about hybrids. In today’s world, if you don’t want to eat hybrids, you’ll starve. Even if you grow your own feed 95% of the seed you buy is a hybrid. Hybrids are crosses between either similar subspecies or compatible genus’ to produce plants or animals that grow bigger or faster than the parents. Hybrids generally don’t breed true, but it is possible to select offspring that eventually do breed true. In general, the greatest benefit is seen in the first generation, or F1 hybrid. The Mule animal, for example, is a hybrid cross between a horse and a donkey.  Mules, however, are sterile.

In the case of tilapia, there are several hybrids of limited importance.  In some cases, these produce all male hybrid fish. This is of interest because the males grow bigger and faster than the females. The downside of this is that you need to keep two genetically pure strains. This has proved to be humanly impossible and no pure strains are left that can provide these crosses. All O. horanoram and O’ aurea in the USA are contaminated and no longer produce significant numbers of all male fish. What is left is the Super Male.

In humans, a super male would have a YY genotype. They would be sickly and die before they reached reproductive age if they live to birth at all. The Y chromosome in humans has little to offer except for sex determination. In fish, this isn’t the case and there is no clear Y chromosome.  In some rather than use XY they use WZ so things take a little more consideration to sort out.

Let us suppose that a tilapia has an XY chromosome system, but that both chromosomes are fully functional (genetic testing has borne this out).  A healthy super male can be made that is YY. Cross it with standard females XX and all offspring are genetically male. All that remains is to raise the fry in warm water to have 95%+ male fish.

So where do super males come from?  There are several ways to do it, but let’s see how it happens in the wild. There is a warm spell in the spring which leads to breeding. Once the females are holding the temperature drops to 70F. Due to the temperature, most of the fry are sex-reversed to female. 50% are genetically male. When the generically male females breed with normal male fish, 25% will be YY supermales. This process can also be done artificially with estrogen or more exotic laboratory methods.

Bottom line is that super males can’t pass anything unsafe to their offspring. Count yourself as a villager with a torch and pitchfork going after things (Frankenstein Fish) if you haven’t taken the time to understand and you still disagree with the facts above.

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