Breeding with the help of hormones

[Francisco Andrade]

Hi everyone,

I am a "fishing enginier" (this is the best translation from portuguese I can think now), graduated in the Federal Rural University of Pernambuco. I also own a fish store here in Brazil.
I live in a area that is a source of many fish collected for the hobby, the most collected fish here is the french angel (pomacanthus paru) wich is sold here for the equivalent of US$ 1,10.
What I have in mind is that it´s completely possible, even commom place, to keep fish for many years and to see them to grow and get mature adult specimens in our aquariums. And they do not reproduce because of the lack of one or more things. However maybe it´s possible to use hormones to "fool" the fish´s brain and to make him "think" : wow, it´s time to breed!!
Ok, no more kiding, On the most harsh end of the thing maybe it´s possible to use HCG, which acts direct at the gonads, and change broodstock constantly to deal with the increasing immunization to this hormone. This easy for me to do with the french angel, an it´s harmless to the fish.
Maybe someone now something that acts at a higher level (hypotalamus) and do not develop such immune response through time.
Also, some experiments we made here with freshwater fish shown that it can be possible to put the inducing hormones (GTH, GnRH) in the food. Some fish seem to not destroy the hormone at the digestive tract, and this opens the possibility of using hormones in small fish, which do not put up with an injection.
What do you all think ?? Does anyone tried ??

Thanks,
Francisco Andrade

 

[FMarini]

Hi:
your suggestion is not far fetched. We have discussed the use of superovulating hormones and inducing agents (particularly GnRh and leutinHR peptides) to increase fecundity in fish in my other forum.
To my knowledge there have been a number of expt done on FW fish to induce eggs/sperm production. W/ FW fish this has not been a problem, however the fry (offspring) of many FW fish will eat commerical prepared/ obtainable foods.

So w/ saltwater fish we have a number of problems, many of the adult fish are too large for the ave home aquarium (and your french angel is a great example), 2)-many fish don't tolerate same species in the small confines of an ave home aquarium, and 3)- is correct sexing.
so lets assume you have a huge vat w/ plenty of space and a flow thru facility w/ sterilzed artifical saltwater. You add a few fish and get them to breed by injectinmg them w/ hormones, they lay their eggs, now what? Most angels fry are suitibly small that they require ciliates or smaller for first foods. There is currrently no commerical available first foods for these fish. The WAikki aquarium has successfully raised a centropyge angel and did so buy capturing/collecting and growing the appropiate first food. A little tough and very costly. Can it be done, Sure, the question is cost benefit ratios.
So can we try to get these fish to lay eggs and produce sperm-yes, it can be done. I ask you what next.

Hassin S, Holland MC, Zohar Y.
Early maturity in the male striped bass, Morone saxatilis: follicle-stimulating hormone and luteinizing hormone gene expression and their regulation by gonadotropin-releasing hormone analogue and testosterone.
Biol Reprod. 2000 Dec;63(6):1691-7.

Hassin S, Claire M, Holland H, Zohar Y.
Ontogeny of follicle-stimulating hormone and luteinizing hormone gene expression during pubertal development in the female striped bass, Morone saxatilis (Teleostei).
Biol Reprod. 1999 Dec;61(6):1608-15.

Antonopoulou E, Mayer I, Borg B, Swanson P, Murza I, Christoforov O.
Effects of testosterone on gonadotropins, testes, and plasma 17alpha,20beta-dihydroxy-4-pregnene-3-one levels in postbreeding mature Atlantic salmon, Salmo salar, male parr.
J Exp Zool. 1999 Sep 1;284(4):425-36.

[No authors listed]
The role of LH-RH in induction of spawning in grass carp (Ctenopharyngodon idellus). II. Ultrastructural study of pituitary gonadotrophs.
Sci Sin. 1978 May-Jun;21(3):397-400.

Ibrahim KH, Chaudhuri H.
Preservation of fish pituitary extract in glycerine for induced breeding of fish.
Indian J Exp Biol. 1966 Oct;4(4):249-50

 

[Francisco Andrade]

Hi Frank,
Thanks for replying.
As I told you, I live by the beach and it is prety easy to have a flowthru facility. It´s not necessary to keep the fish together and nor is necessary to know the sex prior to spawning. The gametes can be collected after the fish has been injected with the apropriate hormone. So the sperm can be diluted and put with the eggs the fertilizate them. The embrios can then be put in a incubator.
Of course the most difficult part is to feed the larvae. It have to be determined what and how much food will the larvae need. I know it´s very difficult to do this and maybe some years will be necessary for success to come. But this must be done.
I have been diving at least once a week for the last few years and I see with my own eyes that the populations of certain species, french angel included, are declining fast. A few years ago it was commom to take 20 lbs of live rock and find a baby french in a hole, it happened to me a few times. I used to freedive and see eight or ten french angels in an hour, two weeks ago I went to this same place and dove for three and a half hour, and guess: not even one french.
I am realy worried about this. For the fish, the environment and the people who survive fishing ornamentals.

Thanks for letting me know what you think.

Francisco Andrade

 

[Louis Z]

Francisco When I was diving off the coast of Belize I would see different sized pairs of French angels all the time. Sexing would not be the problem. I would think that you could work with a smaller sized pair. Of course you would need a wide/deep pond for the pair and work with their nutrition. Being so close to the beach makes the maintenance easier. I doubt that you would even need hormones to induce spawning. They would be in the same photoperiod and water temperature as in their natural location that they would spawn naturally. Nutrition for both adult and larvae is the important thing to concentrate on. You can collect water samples on your next dive and see what the larvae may be eating. By dumping microalgae into the samples you might be able to culture the larval food organisms. This is probably what the Hawaiian researchers did. I do have a question on where you live. Do you live in a big city that has a lot of pollution runoff into the beach area? These toxins could cause problems in culturing the live food organisms with filtered seawater. Louis Z.

 

[Francisco Andrade]

Hi Louis,
Even at the biggest city in my state the water at the beach is quite clean. But I don´t think this will be a problem as there is no pollution at all in my area (there are 3000 thousand people living here).
Even with the same water temperature and photoperiod, captive enviroment might lack something, (maybe area!!!) and even if nothing lacks, hormones can make us able to determine when the spawn will occur, off season f.ex., and thus make it easier to work with.
It´s a good idea to feed water samples with microalgae, I will try this and let´s see what happens.

Francisco

 

[Louis Z]

Francisco If you find any ciliates send me some. Id like to try tinnitids and vorticella. If you cant send me some hopefully you live next to Rio - Ive been dying to go for Mardi Gras- I could use you as an excuse. Just kidding about Mardi Gras but serious on the ciliates. Thanks Louis Z.

 

[Francisco Andrade]

Hi Louis,
I can send you some ciliates, if I find them at all, but it will take some time. Unfortunately I live 1800 miles away from Rio.
See ya

 

[Louis Z]

Francisco Just send me some of the water that you collect at depth- the ciliates will be there. Just before you send dump some green water in there for the trip. The ciliates would probably be the only thing that would survive the long trip. As for Rio thats ok I am pretty sure there are beautiful brazilian women on any beach down there. Dreaming Louis Z.