A 'natural' way to have more male tilapia.

[David Hart]

I found this article at another site, and I thought some here, may also be interested in it.

 

Male tilapias tend to grow faster and bigger. So, if we are going to eat them, why not get the best bang for the buck ?

There is a 'natural way' to increase the percentage of male fry, without using chemicals.  Also,  'super males' are just too costly, to justify the price, for the average backyard aquapon. 

It just involves heating the water the fry are kept in.....for details, check out this PDF....

 

http://www.waset.org/journals/ijbls/v6/v6-1-7.pdf

 

 

[TCLynx]

Hum, I wonder how well that translates to Blue Tilapia since the article is about tests on Nile Tilapia.

[David Hart]

It may aplly to them too TCL..I didn't read this one, word for word. Just skimmed and it looked like it would.

http://www.biodiversite2007.org/IMG/pdf/Environment_sex_determinati...

 

[Teresa N Florida]

Oh how I worry, when we start playing 'God'.  Inevitably we cause an unexpected negative. After reading some of those articles, I did a further search and found 'that unexpected negative'.

If I read it correctly, doing such experimentation could later affect the number of offspring:

In many species, females determine the number of offspring for the next generation and so the viability of some fish populations with TSD can be compromised through alterations in their sex ratios due to temperature fluctuations of the magnitude predicted by climate change.

See the article in full > http://www.sciencedaily.com/releases/2008/07/080729234256.htm

Perhaps Greg, (mail4mema) could share some of his experience on this subject.

Of course if you KNOW what the negative impact will be, steps can be taken to mitigate them. 

 

Great topic David!

[David Hart]

Good points Tersea.

One way to avoid what you mentioned.....don't 'heat treat' your future breeders.

A way to avoid the 'heat treatment' and still get the females to grow a little quicker, 'naturally'....is to suspend a net 3 or 4 inches off the bottom of your grow out tanks. The females won't be able to pick up their eggs. Then they won't go the few weeks without eating, while carrying eggs and fry.

I found the article interesting, but, I doubt most backyard aquapons would go to the effort to do it. I just pick out the 'biggest' ones first, when I'm ready for a fish dinner....

[Dave Lindstedt]

Back on July 20th, 2011, I purchased 220 guppy size tilapia.  Most now have grown to 5 to 6 inches in length.  So my big question is when can I expect these guys to start reproducing.  Currently my water temp. varries from 74 to 76 degrees F.

[David Hart]

Hi Dave, I'm no expert....it does sound like they are getting about big enough....

If the are crowded , they are less likely to re-produce. I think my breeder tank is a degree or two warmer then yours. Before you know it....you'll have too many fry...

[Dave Lindstedt]

The bulk of my fish are in my self constructed 330 gal. tank, my guess is 100 to 120.  Next is my 100 galon tank I have about 30 to 40. 

 Then I have two aquariums a 40 gal. and a 20 gallon. Initially I had 30 in the 40 gallon tank Over the aquarium I installed a 18 inch x 35 inch under bed storage container cut for 16 2inch net pots.  A 70 GPH fountain pump pumped water into the container and it gravitated back into the aquarium from the other end.  Oct 4th I spotted a dead fish floating.  After riping everything apart, I managed to rescue 5 fish all others were dead. The 5 remaining I moved into the 20 gallon aquairum with 6 pre existing.  I scrubbed out the 40 gallon even did a wipe down of the walls with a light bleach solution.  Flushed everything and refilled it with fresh water in a spotless clean aquairum. Now I pulledd 5 fish out of the 20 gallon and put them into the 40 gallon. Then captured 5 more from my 330 tank and added them to the 40 gal for total of 10 fish. 

Next day found 1 dead fish in the 20 gal.  My guess he was one of the 5 I rescued.  So quickly syphoned out the 20 gal and refilled with fresh water. today I have 6 fish in the 20 gal. They are very active as one jumped out and died overnight.

Today I lost another that jumped out of my 100 gal. tank.  I use the 330 & 100 gal tanks to feed my grow troughs.

[TCLynx]

This probably isn't the best thread for it but,

What do your water tests say?  What sort of filtration do you have going?

Dave Lindstedt said:

The bulk of my fish are in my self constructed 330 gal. tank, my guess is 100 to 120.  Next is my 100 galon tank I have about 30 to 40. 

 Then I have two aquariums a 40 gal. and a 20 gallon. Initially I had 30 in the 40 gallon tank Over the aquarium I installed a 18 inch x 35 inch under bed storage container cut for 16 2inch net pots.  A 70 GPH fountain pump pumped water into the container and it gravitated back into the aquarium from the other end.  Oct 4th I spotted a dead fish floating.  After riping everything apart, I managed to rescue 5 fish all others were dead. The 5 remaining I moved into the 20 gallon aquairum with 6 pre existing.  I scrubbed out the 40 gallon even did a wipe down of the walls with a light bleach solution.  Flushed everything and refilled it with fresh water in a spotless clean aquairum. Now I pulledd 5 fish out of the 20 gallon and put them into the 40 gallon. Then captured 5 more from my 330 tank and added them to the 40 gal for total of 10 fish. 

Next day found 1 dead fish in the 20 gal.  My guess he was one of the 5 I rescued.  So quickly syphoned out the 20 gal and refilled with fresh water. today I have 6 fish in the 20 gal. They are very active as one jumped out and died overnight.

Today I lost another that jumped out of my 100 gal. tank.  I use the 330 & 100 gal tanks to feed my grow troughs.

[Dave Lindstedt]

The only filtration for my large tanks are my 4 grow troughts and the 528 plants growing in them. On the aquaiums I have standard fish tank filters a total of 3 between the 2 tanks.  Only test I have done is for ammonia.  And I know I am not checking that often enough.  I do try and replace 50% of the water,, with fresh water in the two aquariums once a week. My larger tanks are on a deck 2 foot above my grow troughts.  These gravitate into the troughts which drain into a 35 gal. "tote bin" where I have installed a sump pump, which pumps water back to the fish tanks. Today I wrapped the lower half of my 330 gal. tank with R-13 building insulation.  I intend to do this with all the tanks & aquariums.  The outside tanks I will cover the insulation with clear plastic to protect it from the rain.  I may do the same with the grow troughts.

I plan to build a solar water heater out of 2 15ft lenghs of 1&1/4 black flex PVC, that will be roof mounted on the Park model RV I am using as my opperations center.

I am located 3 miles from Gulf of Mexico, about 30 miles north west of Tampa, FL. We do get about 10 nights a year when night time temp will fall below freezing for 6 or more hours.  My  grow troughts are located inside a 10x20 ft plastic "car port"  which will be enclosed.  Next problem will be source of heat that doesn't put me in the poor house. Up north I had a kerosene "torpeto heater", electric fired pluged into a seperate electric thermostat. (I used that to keep pipes from freezing in vacant houses.)  I may do that again, here for my plants.    

TCLynx said:

This probably isn't the best thread for it but,

What do your water tests say?  What sort of filtration do you have going?

Dave Lindstedt said:

The bulk of my fish are in my self constructed 330 gal. tank, my guess is 100 to 120.  Next is my 100 galon tank I have about 30 to 40. 

 Then I have two aquariums a 40 gal. and a 20 gallon. Initially I had 30 in the 40 gallon tank Over the aquarium I installed a 18 inch x 35 inch under bed storage container cut for 16 2inch net pots.  A 70 GPH fountain pump pumped water into the container and it gravitated back into the aquarium from the other end.  Oct 4th I spotted a dead fish floating.  After riping everything apart, I managed to rescue 5 fish all others were dead. The 5 remaining I moved into the 20 gallon aquairum with 6 pre existing.  I scrubbed out the 40 gallon even did a wipe down of the walls with a light bleach solution.  Flushed everything and refilled it with fresh water in a spotless clean aquairum. Now I pulledd 5 fish out of the 20 gallon and put them into the 40 gallon. Then captured 5 more from my 330 tank and added them to the 40 gal for total of 10 fish. 

Next day found 1 dead fish in the 20 gal.  My guess he was one of the 5 I rescued.  So quickly syphoned out the 20 gal and refilled with fresh water. today I have 6 fish in the 20 gal. They are very active as one jumped out and died overnight.

Today I lost another that jumped out of my 100 gal. tank.  I use the 330 & 100 gal tanks to feed my grow troughs.

[TCLynx]

When you started finding dead fish did you run an ammonia test?  I know sometimes a pH crash can cause ammonia to spike again after things have been running for a while and when the pH is down below 4 the fish might not survive well.

 

I gave up on tilapia here but I'm inland central FL and running flood and drain aquaponics.  Now I grow Catfish and Bluegill and have given up the greenhouse so I can enjoy growing all the nice cool weather crops that grow best between now and April.

 

Hope things settle down in your tanks and the fish survive well for you.

[Dave Lindstedt]

I check the ammonia  every couple or 3  weeks.  I have little doubt it spiked when I lost 25 fish.  My guess is fish weigh 4 to 6 oz.  So 30 in a 40 gallon aquarium was over crowded.  But I had not kept their growth in consideration. But that is why I have them spread over 4 tanks.  Early on, I had kept my sump pump running 24/7.  I showed up to about 50 gallons of water in my 330 gal tank.  I had lost power for a while over night and sump pump shut down.  The discharge hose was laying in the bottom of the tank.  With the tank about 4 ft above the sump.  Well it cause the discharge hose to syphon back and overflow the sump.  Another mad panic getting water back in the tank.  Fortunately I did not loose any fish. But now I only keep the system circulating 8 to 12 hours a day.  I also don't let the discharge hose lay in the fish tank. 

TCLynx said:

When you started finding dead fish did you run an ammonia test?  I know sometimes a pH crash can cause ammonia to spike again after things have been running for a while and when the pH is down below 4 the fish might not survive well.

 

I gave up on tilapia here but I'm inland central FL and running flood and drain aquaponics.  Now I grow Catfish and Bluegill and have given up the greenhouse so I can enjoy growing all the nice cool weather crops that grow best between now and April.

 

Hope things settle down in your tanks and the fish survive well for you.

[SW]

Hi Dave,

Nice article!  I think next season I'll give it a try on some fry if I can find a heater that will get that hot!