How to get all-male tilapia
All-male tilapia can only be obtained by hand sexing. Period. You can get really close to all-male using sex reversal hormones like 17a-Methyltestosterone, but there will always be individuals that are "so female" that they can't be converted. Even our own Wami hybrids only get to 89% male, which is still good, but it isn't all-male. In fact, even Mike Sipe, the creator of the Red tilapia and of our Wami hybrids was very clear that the best one-time occurrence of male hybrids from a single brood that he had ever seen was 98 out of 100. That still means that two percent or more will always be female.
Reader note: I recently read a page on the Internet in which the author states that a breeding colony similar to the ones that produce our Wami hybrids "will produce fry that are almost all male naturally". He goes on to state that "I have never seen a female hybrid. However, there is a 2% chance that a female hybrid can occur". In parentheses and bold text, he emphasizes that this 2% chance is "over the life time of a particular female", which has no bearing on the percentage of females produced.
I make a note of it here because the author prefaced his claim with "The number one issue in aquaponics is the uncontrolled reproduction of Tilapia in the system", a statement that is not supported in actual practice, and would not be solved with anything less than a 100% male tilapia population. It only takes one female to spawn.
Do I need all-male tilapia?
Chances are, you don't. But let's have a look at your operation, just to make sure.
There are only two situations where having an all-male, or even a mostly-male, tilapia population may prove beneficial:
- You farm over 20,000 tilapia annually
- You have very large floating raft beds
If you're raising 20,000 tilapia annually, harvesting roughly 12,000 pounds of filets at a time, and generating about $40,000 per year of income, it's safe to say that you've gone well beyond the typical home tilapia farmer. Even though your operation is small by comparison to other aquaculture operations, you are at the mercy of the very same economics. Your 20,000 tilapia probably cost you about $8000 to raise to a harvestable size, and when the time comes to reap the rewards of your investment, you can't afford to have large numbers of tilapia turn out to be under-sized females and un-useable juveniles.
So let's do the math. Twenty thousand male tilapia come in at an average weight of 20 ounces each. At a yield of 48%, each tilapia gives 9.6 ounces of edible filets. That's a total of 192,000 ounces, or 12,000 pounds. At $3.40 per pound wholesale, that's an income of $40,800. Subtract the $8000 already invested, and you are left with $32,800 gross profit. Now, let's change things around with a bunch of female tilapia in the mix.
This time lets pretend that 50% of the tilapia are females, that weigh in at 12 ounces each when the pond is harvested. This puts the filet yield for 10,000 of the tilapia at only 5.76 ounces each; a total of 57,600 ounces. The remaining 10,000 male tilapia still gave 9.6 ounces each, for a total of 96,000 ounces. When you add the yield together, you get 153,600 ounces, or 9,600 pounds. At $3.40 per pound wholesale, this gives you an income of $32,400. So now when you factor in the $8000 previously invested, you are only left with $24,640 gross profit. A pay cut of $8,160 that could have been avoided.
Note: In the above example, I intentionally didn't include any offspring that might have hatched in the mixed-sex system. I did this to keep the numbers easy to follow. In an actual system, a portion of the $8000 budget would have also been lost to raising juvenile tilapia that were far too small to be harvested.
It should also be noted that the only tilapia that yields 48 percent edible filets is a particular hybrid of Wami and Mossambica that would require hand sexing to remove unwanted females. I used these as the basis for my calculations to create a best-case scenario, any other hybrid combination or species will result in even greater losses.
Of course, the larger the operation, the more valuable an all-male or predominantly-male tilapia population becomes. It's important to remember that there are major differences between large and small aquaculture, in both scope and methodology. Typically, a large tilapia farm harvests fish in huge batches all at once, whereas smaller operations tend to be more "catch of the day". For smaller tilapia farmers, with a few hundred fish, the benefits of a male tilapia population is reduced to an inconsequential level.
If you're an aquaponic farmer, who uses very large floating rafts, the real danger comes from tilapia eggs and fry that get past the tilapia side and into the vegetable side of your system. In beds that contain soil-less media, such as expanded clay, tilapia eggs and fry don't usually survive long enough to cause any significant problems. However, in floating raft beds, these unwanted fish will munch away on plant roots, destroying far more than their own value. In narrow floating raft beds, about 48 inches wide, tilapia fry can be easily removed, however in systems that utilize wider beds, they may prove impossible to eradicate. Of course, even the largest systems can be drained and re-filled to eliminate unwanted fry, but in many situations, this may be just as detrimental as leaving the fry in the raft beds.
Hint: A small screen placed over the water outlet of the fish tank, or if applicable, over the water pump, will prevent eggs from drifting into the floating raft beds.
Other than the above two situations, keeping a male tilapia population is of little benefit.
Anyone searching for an all-male tilapia population should study our page about tilapia genetics first. Click or touch here to learn more about tilapia genetics.