So you need more fish...
Say you just harvested 100 lbs of your Tilapia for a local restaurant.
Maybe a couple died of old age. (Or maybe you accidentally froze one of your fish tanks…cough cough.)
Maybe your current stock is getting old and less productive, and you want some young fish in there to keep nitrification pumping along.
(Don’t know what your stocking density is? Dr. Nate says, “Weigh them.” Yes, really. We weighed our fish one-by-one to measure our stocking density.)
Regardless of why your stocking density is low, you’re going to need to replace those fish, right?
But buying fry (i.e. baby fish) can get pricey, and as a startup farmer, that’s usually not the most appropriate option.
So you decide to breed your existing stock. That’s great! But... how?
Here’s what you need to know.
First of all: How do you keep your tilapia from breeding?
We just decided that breeding was a good thing, right? So why not just let your fish breed all the time?
Because when Tilapia are getting environmental cues to breed, that becomes their top biological priority.
Which - unless you want fry - is bad news for you. Breeding tilapia will stop gaining weight and if un-managed, can cause all kinds of trouble.
Male tilapia show extreme aggression to the fish around them and will kill other males and other females.
Quick tip: If you choose to isolate your breeding individuals in a brood tank, always put in more mature females and less mature males, so that the male is less likely to damage the female. (A good size ratio is about 20 to 6 inches.)
There are two ways that you can keep your Tilapia from reproducing.
- The first is keeping your water cool. (You can read more about ideal temperatures here.)
- Keep your tanks in the dark. As you'll see, light acts as a cue for the fish to breed.
Before you start breeding, select the stock that you want to breed.
You'll want to identify several traits that you value. (For us, a valuable trait is cold tolerance. If you're selling your fish, that trait may be size.) Then, you want to isolate those traits.
You can isolate a trait by first selecting some candidates from our tanks and putting them in a separate tank, and applying a factor that eliminates the individuals that don't possess that trait.
For cold tolerance, this means that “You freeze the tank and the ones that are left over you breed.”
P.S. - This is a very loose definition of selective breeding! There is a certain amount of chance involved. If you're in a hurry to get a specific breed, you're better off getting tilapia from a breeder.
Optimal conditions for breeding tilapia
Okay, so you know how to keep your tilapia calm. How do you get them to breed?
Just like you keep the water cold and the lights off for calm tilapia, you can use warm water and light as an "on switch."
Both the warmth (75-85 degrees) and the light cycle (at least 12 hours a day) act as environmental cues to your fish that it's time to make fry.
There's one more thing that you need to facilitate reproduction for your fish: a substrate.
Female tilapia "mouth-brood" their fry- that is, they lay unfertilized eggs on the bed of the lake or tank. The eggs are then fertilized by a male, and the female returns and scoops the eggs into her mouth, where she broods them until after they hatch.
Of course, the female needs a safe place to lay those eggs. In conical tanks like ours, laid eggs would drift to the bottom of the tank and be drained away or picked up by an SLO.
Even in flat tanks, the eggs drift and are both poorly fertilized and difficult for the female to collect.
You can compensate for this by giving the fish a substrate of some kind- something like a gravel bed where water movement is slowed and the eggs are sheltered.
Separate fry from mature fish
Once the fry have hatched and emerged from the mother's mouth, you'll want to separate the fry from the mature fish so that they are not preyed upon.
You can do this either by netting the mature fish out of a fry tank or vice versa.
An alternative option is producing fry manually- obtain the eggs and sperm by milking, then combining the two in a container.
Ready to bump up your stocking density?
What other questions do you have about breeding tilapia? Leave them in the comments below!
Ready for more?
Check out our other aquaponic resources for more helpful information.