WetmanNY, Maybe that's why scientists are always so hairy
I didn't know that testosterone could be so efficiently used to affect fish gender, but I guess if the concentrations are high enough, or even low enough...a whole new world of information just opened up to me!
Oriongirl, that was my initial thought cause I didn't know much about the 'drug' possibilities. Kribs from my own experience are always affected by higher pH's, but I still don't know if Bettas also are.
ok, two posts and I've already learned a hell of a lot. After reading Wetman's post, I did a google search and found some interesting stuff I'd like pass on to those interested.
I didn't know it's uses were that far-fetched since many fish farms use it, especially on Tilapia (only works for the pure line breeds).
A little of what I learned. Female tilapia grow slower than male tilapia, so scientists came up with a method of treating all of the tilapia fingerlings with male hormones so those fish that would have been female now turn out to be male. Then all of the fish in the growing tanks or ponds will be male, and the average growth rate will be higher than it would have been with half males and half females. Now even the US government supports the use of reversal techniques by allowing all of the tilapia hatcheries who wish it to participate in what is known as an INAD. This basically means they have the right to put chemicals into the food of the fish that are not yet cleared as being safe, as long as they send results in to the government.
And in general I'm in complete awe at what can be done. Hormones, testosterone, endocrinve, LH-RH, SPE, CPE, HCG, 17 alpha methyl testosterone, 17 beta estradiol, etc. etc. all are well used, and apparently at will, and still being tested. One company advertised products over the net and argued it could work for a variety of different fish, 'especially hormones synthesized in the laboratory can be utilized to induce sexual maturation, ovulation, and spermiation, produce all male, all female, or sterile stocks, induce metamorphosis, facilitate osmoregulation and accelerate growth in cultured finfish.' These drugs seem t be a huge aid to the profitability of aquaculture and the business, which ofcourse in some ways, is not a bad thing, or is it?
It is also used to produce a female stock
http://www.fawc.org.uk/reports/fish/FISHR038.htm
Female-only technique This technique is used to produce female fish only, avoiding the production of males which perform poorly and which can become sexually mature in less than one year. To start the process the male hormone, methyl testosterone, is introduced into fry food; this turns all these fish into males. Those fish which would have been males anyway are identified by the presence of males in their subsequent offspring and they and their offspring are not used in production. On the other hand the male fish which, without the hormone treatment would have been females, produce only female offspring when mated with females. This technique is now commonly used and each year a small group of female fry is set aside for masculinisation so as to provide males for continuing the line. In effect the Y chromosome (male determining) has been eliminated from the stock.
To top it off Aquatext,The Free Online Aquaculture Dictionary says the following about hormones used on fish:
"Most countries however permit the use of hormones in potential brood fish that are not to be used for human consumption. Treated fish, which would otherwise have been female, cannot be stripped of sperm, and these fish are dissected and the milt used to fertilise eggs which results in the production of all female off spring. This is desirable in some species where the females mature later than the males, or grow larger, faster. The most common hormone used for masculinisation is 17a-methyl testosterone, which is used at a rate of between 1-60mg/kg feed for a period of between 25 and 100days following first feeding. The administration of very high levels will have the effect of sterilising the fish. The hormone is fully dissolved with ethyl alcohol prior to mixing with the feed. A more even mix can be achieved if the feed is spread out and the hormone sprayed onto the feed. After mixing the food is dried to allow the ethyl alcohol to evaporate off before feeding it to the fish. The feed can be stored in a freezer for later use."
Pretty soon we're gonna be pressing a button to get our fish to be 'the way' we want them
