Backyard Aquaponics
A place to discuss aquaponics

I am collecting eggs from my female Tilapia every 2 weeks. I seem to have got the formula just right because my females are producing a steady stream of eggs. This time I rinsed eggs from 13 females and placed them (the female fish) into a container. If the female wasn't holding eggs I placed her in another container. 18 females were holding no eggs. This is a fantastic ratio (42%) There must have also been 9 females that I didn't catch as I should have 40 females in this tank.

What I need is a third container to place the captured males because I find myself catching the same males over and over again and at the end of the process the fish seemed rather stressed.

Amongst the eggs there are always some hatched or partially hatched babies. These I catch and put directly into the hatchery tank. The eggs go into the trusty incubator. I am a little concerned this time because I have quite a few thousand eggs and I am worried that the water flow in the incubator won't be sufficient to turn all the eggs over. This results in a fungus forming and killing the eggs before they hatch.

My last batch of fry I treated with MT (Methyl Testosterone) feed for 2 weeks which converts them all into males. These males are much faster growing and seem to show no ill effects from the "tweaking" of their sexual orientation. I have found that the mortalities amongst treated fry is quite high (about 30%) compared to untreated fry (under 10%). I have decided to split todays batch and treat only half of them to get a direct comparison.

Attached are some shots of the eggs collected today (Batch 2008/12/B)

Now I need a beer.

didn't realise they had such big eggs... no wonder they're so adept at spreading through an ecosystem...

Yes, they are quite big. The variations in colour appears to indicate the degree of maturity. The darker colour eggs are just about to hatch. What you can depend on is the fact that 100% of them are fertilized. The females will only hold fertilized eggs in their mouths and seem to have an uncanny ability to sort the eggs and spit out unfertilized eggs. Collecting from a variety of females (in this case 13) is a problem because the earlier hatched fry seem to pick at the later hatchlings struggling to get out of their eggs. Ideally I should place each females eggs in separate incubators but I just don't have the resources (or patience).

Now that's not like you Synapto... we expect better of you than that sort of laziness...

Yep, you're right. Pure laziness. I've just popped out (at 10:20PM) and whipped up a few more incubators, sorted the eggs by hand and put them in the appropriate ages.

So how exactly does the incubator setup work Synapto...

Well Rupe, when a boy tilapia and a girl tilapia like each a whole lot...

... no I didn't say "explain the mating ritual"... I said "How is the incubator" setup... ...

The idea is to gently roll the eggs around like the female would do in her mouth. A concave bottom is better because the eggs will always roll towards the center. I just use an ordinary bucket and use a little more water pressure to prevent any dead spots around the edges. Water enters the bucket through the center downpipe. I have a valve on this line to regulate the flow. The eggs naturally sink, whereas the hatched fry tend to float towards the surface. The water overflows through the spout taking the hatchlings safely out and the unhatched eggs remain. My slight modification to the system ***patented** is to place a large airstone directly next to the pump inlet to aid oxygenation. Temperature 28 - 30 deg and the water must flow 24/7.

I get close to 100% hatching from this system.

Goeie more Synapto!
I have zero experience with the plant part but have kept fish for a number of years. If you are having problems with fungus in the eggs the old trick in the aqaurium circles (mostly with the various Malawi mouthbrooders) is to add either Acriflavine or Methylene Blue to your hatching setup. Do a google to check the amounts but it is very little.
As to the newly hatched fry picking at the other eggs...yip they are carnivores as juveniles and they will pick at the other eggs in an attempt to eat them...and do loads of damage.
You may not want place each females eggs in a seperate hatcher but if you could setup 3-4 hatchers as in the pic above (taken from Skelmbosch ) and then put similar eggs together it may help.
The alternative is to split your males and females and then condition them seperately. Add male to female for a massive orgy of spawning and then strip the eggs that are all the same age.
I hope this helps!
Cheers,
KarelM
PS: If I can I would like to make a plan to visit your set-ups some time in the new year. My set-up is still a long time off but it will be nice to have a look at one that is functioning so well!

I am so impressed with all you are doing S!
A question..... Do you think you gain back the 20% loss in faster male grow-out... kilo for kilo?.... hard to judge I guess ....... but must be so or people wouldn't do it.
Where do you get hold of something like MT? How is it given?
Also what is the brand name of your test kit you are using?
Thanks for all the help on the flow bins..... really appreciated. I have reallised it is not the best economy for my set-up ..... but was worth investigating. Much thanks...

Something you may want to investigate instead of adding MT (not sure what the longterm effects on consumption would be...it is a hormone after all) is to see if it is possible to change the fish into triploids. Not sure if it has been done with mouthbrooders but it is common amongst salmanoids.
Basically it involves either heat treating or pressurising the vertilised eggs. This then ensures that the fish is in effect sexless. All the energy goes into building muscle so fish grow faster and bigger.
Cheers,
KarelM

Yes. True Karel. MT is much debated. Your note of caution is well-spoken.

I follow Synaptoman's threads with great interest and became curious that he has tried it. Seems easily available and easy to use. I do not wish to bring any dispute over his efforts cos I have an enormous respect for his capability. I sense you do too.....

You ever tried your alternate process personally? Sounds very interesting. How would you set this up practically? How would you prevent the eggs being completely destroyed? Sounds like great precision would be needed but definitely worth looking into for a commercial enterprise.

I would love to breed Oreochromis mossambicus into faster growing fish. The O. Niloticus seems to outstrip OM in growth enormously. Seems to be a problem to obtain ON though. And then to obtain O Honorum males.... to breed 94%-97% males .... so it is said. A further rapid increase in size. Be superb....

I've done extensive research in this regard and the minute amount of hormone ingested by one fish over the first 2 weeks of it's life will leave absolutely zero trace in the flesh once it reaches it's market size in 5-7 months. To give you an idea it only takes 1g of MT per 2kg of feed to have the effect. 2kg of MT treated feed will last me YEARS. I've probably only used less than one teaspoon of this feed to convert over 2000 fry. For interest sake, the MT is extracted from bulls testicles !!!

As far as the higher than normal mortalities, this was merely an observation. Whether I have a 10% or a 99% survival rate for the first 2 weeks is irrelevant. The big difference is investing money in feeding fish that just don't grow (ie. females or mixed sex)

I am extremely careful and treat the fish in a small aquarium for the 2 weeks. Thereafter they go to a rearing tank for another 2 weeks and thereafter I move to my home or commercial AP system. I only treat every 2nd batch of fry and sterilize everything afterwards just in case.

The success rate is apparently 99.7% and in my opinion is the easiest and most reliable method.

PM me if you need some treated feed.

@Cyara:
I have never done triploids myself but I know several of the trout hatcheries in Mmpumalanga do them on a DIY basis. As mentioned I am not even sure that this is possible for mouthbrooders BUT due to the growth that is produced it may be worth speaking to Stellenbosch or Grahamstown Uni's to find out what they think. For the home grown system I am not sure that this is a viableoption but I believe you are also planning a large system so it may be worth looking at this. It would be very intresting to compare the growth achieved with MT vs trips!
@Cynapto:
Ok having seen what you say regrading the amount needed i believe (as it seems you do) that it would be save to use MT. Would be intresting to see if trips are possible in mouthbrooders though.
For anyone in SA (that is South Africa NOT SOuth Australia ) , please have a look at : http://www.sanbi.org/frames/whatsnewcurfram.htm
This is the new "black list" contemplating which fish may or may not be kept in South Africa and what will be banned outright, what will require a license and what is free to be kept. Also have a look (Cyara!) if you can find an invert list on that site, I know most of the yabbies etc are currently banned/restricted not sure what the future holds for them! If you find that fish that you want/need etc are wrongly on the list you still have an opp to give inputs!
Cheers,
KarelM