Some one asked about breeding fish not too long ago and I realized I haven’t yet talked much about breeding tilapia. Breeding tilapia is easy and the normal question that follows is how do I keep them from breeding? This can be a blessing or a curse in aquaponics so it is best to do some research.
Tilapia are mouth brooders. The male will make a “nest” by clearing a space on the bottom and enticing a female to come lay eggs for him to fertilize, then the female will pick the eggs back up in her mouth to care for them. It is important to note that Female tilapia don’t grow nearly as fast as Male tilapia in the first place and then when breeding, the female tilapia don’t get to eat so they are not going to be growing well at all. Also when the males are putting energy and effort into breeding behavior, they will also not be eating and growing as much either. These are kinda important points to those people who are expecting to get large tilapia out of a system in a short period of time.
One way to keep tilapia from breeding is to get all male stock. There are a few ways to do this. One would be to grow the fingerlings out to a certain size and then by hand go through and check their gender. This is rather labor intensive and prone to errors and the fish need to be large enough for the gender to be obvious. More commonly people buy fry that have been treated with hormone laced feed to get the fish to all develop as males, this is the way most commercial operations do it. Finally there are some breeding operations that create all male stock by cross breeding different species of tilapia, sometimes with one of the parents being a hormone treated fish.
Now I didn’t get all male stock because I thought I would want to breed some of my own stock. So to keep my main population of tilapia from breeding, I kept them in a cage so the fish could not access a bottom surface from which to pick the eggs back up. This actually worked fairly well as long as I didn’t drop a piece of pipe into the cage as a hide for them (they can use a pipe fitting as a breeding cave.) Now the problems with cage culture have to do with feeding. How do you keep the feed from floating out of the cage before it’s eaten? There are some possible methods but none of them perfect.
I would not depend on using temperature to stop them from breeding since that only seems to work when one is trying to get them to breed and not when one doesn’t want it to happen in a big tank.
Next article I’ll talk a bit about what worked for me in breeding tilapia and what resulted in battered fish.