Stunting Hormone

[Jdubz]

When do the fry stop producing the hormone which stunts the others or do they keep producing it till they are fully grown?

Edit typo

 

[jourdy288]

I would like to know that...

 

[Inchworm]

This is an interesting question, but no one replied. I'll give it a bump and maybe someone will tell us today.

 

[Schmill]

I didn't know that they even produced it.
Perhaps ask over in the Scientific section, (or post in there pointing them over here), and you might get a better response

 

[saltynay]

I would imagine it depends on fish species. I know that endlers and I would assume it generalises to guppies should have the sexes kept seperate as if combined once one male has mated he starts producing the hormone and releasing it to prevent other males from becoming larger then him and being more dominant, It also affects the females in the same way. If kept seperately then both sexes will reach full size then they can be mixed and mate again. The difference in size is actually quite minimal and not genetic so it won't be past on to the spawn of ta 3rd gen stunted pair unless the sexes are again kept mixed upto sexual maturity.

 

[jonnyf84]

When do the fry stop producing the hormone which stunts the others or do they keep producing it till they are fully grown?

Edit typo

As with humans, when fish reach maturity they seriously slow down the production of growth hormones. The debate of stunted growth and growth hormones in fish is a complicated one that has never been 100% proven.I think it's a big mix of genetics, diet, general health and environment. With the first 'growth spurt' couple of years being important. I think thats why the whole stunting thing is difficult to pin down because there are many factors to take in to account.

The whole point of the growth inhibiting pheromone is that it inhibits growth in crowded situations, this won't happen in large lakes or rivers and as such the fish there grow normally. Only in aquariums or small garden ponds where water changes are neglected is it likely to reach concentrations where it has an affect. Without regular and frequent water changes the result of growth hormones (pheromones) will build up in the water, in a compact space this is widely regarded to stunt the growth of fish (some more than others). I am a firm believer that if you have two test tanks with exactly the same species and number of fry, equal volumes of water and the same feeding regime, but in one tank you do a 50% water change twice a week, in the other a 30% water change once a week then the first tank will provide a higher growth rate and healthier fry.

This youtube clip is interesting if nothing else, a 43 year old goldfish, this clears tells you that it has stopped producing growth hormones, possibly due to cramped conditions or irregular water changes, but other goldfish will continue growing and growing providing they have enough space and good water quality - that is my opinion anyway. How the hell it got to 43 is beyond me!!!! Amazing stuff though huh.

[URL="http/youtube.com/watch?v=SL3Fpt4tspc"]http/youtube.com/watch?v=SL3Fpt4tspc[/URL]


This link is a fascinating piece if you've got the time and brain cells to read and understand it, it shines a different light on the debate. This indicates that the Goldfish has bursts of growth hormones released after a cold spell has ended (ie Spring). Therefore if the animal is fed well at that point, it will grow.
So no cold spell - little to no growth.

[URL="http/jeb.biologists.org/cgi/reprint/203/9/1477.pdf"]http/jeb.biologists.org/cgi/reprint/203/9/1477.pdf[/URL]

There is no deffinative answer to your question jdubz but the info is there to make your own mind up.

 

[Jdubz]

Thats great thanks.

At the mo i have 4 fry about 1/2 inch in size in a 70 litre tank they are growing nicely.

But.... when my swordtails drop i will have about 70/80 in there what sort of water change and how ofter will it be needed?

 

[jonnyf84]

But.... when my swordtails drop i will have about 70/80 in there what sort of water change and how ofter will it be needed?

You should be fine with a weekly 40-50% water change, although like i said in my previous post i am a firm believer that the more water changes you do when keeping fry the better, two 40% changes a week would be beneficial but not essential. Unless your tank is very well planted then I imagine you will lose almost half your fry, a lot will be eaten by their parents in the first few days and a few of the weaker ones will just die.

 

[Jdubz]

The tank is bare but a few stones and moss, im going to catch the female and put her into a breeding trap as ive had loads of luck with them.

 

[jourdy288]

Thank you! I have this problem with my guppies, I'll try separating them now, thank you!

 

[OldMan47]

The generally accepted way to deal with the unknown of growth inhibiting hormones is to do lots of water changes for fry that are being grown out. Whether it is growth inhibiting hormones or just good water quality, it is well demonstrated that lots of water changes gets growth moving well and keeps the fish growing.