Tilapia Ponds - Over Population

[DailyLunatic]

A little background.

I'm in Thailand, so it's warm all the time. Temps is not an issue. I'm raising Tilapia in two 5x15m open air ponds, not any kind of hydroponic situation. Well water is being pumped into both ponds during daylight hours. Solar, so no additional costs for water or electricity. I do not do a full harvest and do not intend to do so. Meaning that I use a perpetual method of taking only the larger fish, and keep the pond with mixed sizes. This allows for fresh fish throughout the year, but creates a problem...

Problem:
Over population. Tilapia breed very quickly, and long before a harvestable size. Thus, I have many more times the number of fish the pond can sustain comfortably. I do not discourage the Egrets, or King Fishers, and actually enjoy the bird watching. I've tried ducks to keep the population under control, but wife did not care for the way they soiled the benches and walkways (they are now caged). Besides they seemed more interested in the fish food than in the actual fish.

I have heard that predator fish can be introduced (i.e. Catfish) but that they work best if the pond is drained and all fish harvested on a regular basis, else they end up taking over the pond. I can't find Bass here. I will keep looking. Maybe they consider them to be an invasive species...

What suggestions do you have for this issue?

-sterling

 

[Magnum Man]

Good to hear you have too many now… I would look at netting, with a large pond sized net… keeping the ones big enough to harvest, and put together a holding tank for the fingerlings and fry, that are deemed “extra” and see if you can sell any of those to your neighbors… me personally, I would keep the mid sized and larger to put back into the pond, and sell the smaller

 

[DailyLunatic]

Good to hear you have too many now… I would look at netting, with a large pond sized net… keeping the ones big enough to harvest, and put together a holding tank for the fingerlings and fry, that are deemed “extra” and see if you can sell any of those to your neighbors… me personally, I would keep the mid sized and larger to put back into the pond, and sell the smaller

I have considered a 'lift net' similar to pictured below, but would prefer a solution other than manual separation.

That said, I was planning on doing that for the purposes of animal protein in the chicken and fish feed.

 

[Colin_T]

Fish breed when there is plenty of food and lots of space for everyone to live.
Reduce the food and you reduce the number of fry being produced.

Reducing the size of the environment can reduce the number of fry being produced by stressing the fish so they either don't breed or are less inclined to breed. In crowded conditions, fry are more likely to be eaten but diseases are more likely to occur.

Reducing the water temperature will shorten the breeding period but that can't really be done in equatorial regions like Thailand where it's always warm.

You can have adults in smaller ponds or aquariums breeding and then put the young out in the big ponds to grow. Harvest the medium sized fish to eat and use the bigger fish for future breeding.

Most ducks don't eat fish and if they do, it's usually small fish (less than 1 inch long). Adding a predatory fish to the ponds won't help. It will stress the adults and stop them breeding and you won't have anything to harvest.

If you have a chest freezer, then harvest a number of them and freeze them for later use. A restaurant might buy them from you if they are cultured without chemicals. Apart from that you're kind of stuck unless you can find someone who wants young fish on a regular basis.

An option is to have one pond of Tilapia and one pond with a different species in. You won't have as many Tilapia to deal with and the other pond could provide income from the sale of aquarium fish or a different type of food fish. If you have spare land and are allowed to have more than 2 ponds (this depends on your partner), have a lot of ponds and set up 2 with Tilapia and have other types of fish in other ponds. You harvest fish from one Tilapia pond while the second pond is left alone. When you have harvested enough fish from the first pond, you stop taking fish from there and take them from the second pond while the numbers build back up in the first pond.

 

[DailyLunatic]

Fish breed when there is plenty of food and lots of space for everyone to live.
Reduce the food and you reduce the number of fry being produced.

Yeah, but these are being raise as food, not as ornamentals. The idea is to get them up to size as quickly as possible. Feeding less will postpone that, and result in smaller yields.

Adding a predatory fish to the ponds won't help. It will stress the adults and stop them breeding and you won't have anything to harvest.

I don't believe that to be a true statement. Here is a quote from an article posted to Langston Universities site:

The most practical method of reproductive control of tilapia for the small scale farmer may be through the use of predatory fish. Large mouth bass (Micropteris salmoides) is probably the most popular and is effective in controlling fry and young tilapia fingerlings. Stocking rates will vary with the stocking rate of tilapia, water clarity and size of bass. 25 to 100 bass per acre should provide adequate control. However, the fish culturist will have to fine tune the rate to local conditions.

Bluegill and green sunfish can also be effective controls on tilapia reproduction. Like the large mouth bass, the sunfish will consume the fry, however, the sunfish will also very efficiently remove the eggs. This may be more effective than control of the fry because there are no young tilapia to compete for food and also the mouth brooding of the fry by the female cannot occur. This allows her to feed on a more continuous basis and gain more weight. More research needs to be conducted on optimum stocking rates for sun fish in tilapia ponds. Five hundred per acre would be a good starting point. Again, fine tuning to local conditions by the fish culturist will be necessary.

The full article can be found here: https://www.langston.edu/tilapia-culture-cages-and-open-ponds
Discussion on Open Air Ponds begins about halfway down.

My original intent for having two ponds was to have one pond with Tilapia, and the other with Catfish. After reading that Catfish are not a good predator for Tilapia, that they tend to take over a pond, and that they walk, I abandoned that idea. Now both ponds are combination Tilapia/Prawn. Looking for a source for Bass, Sunfish, or another suited for this region.

The over population is affecting water quality, reducing growth rates, and consuming recourses. Unfortunately, I'm having trouble locating any of the named fish locally. There is an invasive species being fished in some areas call a Peacock Bass. Despite its name, it is actually a Cichlid. I need more research to evaluate its viability as a predator and that is will be controllable.

What you were proposing is a grow-out pond. Not what I am trying to do. Partially because it would have the same issues I am facing now and the grow-out pond would required a way to remove the juveniles as well, or large scale fish moves back and forth. As I said, this is a perpetual system I am trying to set up. Not one where one does large scale harvests.

Fish reach sexual maturity at around 3" (12 weeks). A female lays every 4 weeks thereafter. She lays between 300 - 2000 eggs per clutch. If only 1% survive, it will outpace what the pond can support.

I will continue manual sorting (the ducks will be happy. They love the fish.) but it is labor intensive, slow and not very effective.

-sterling

 

[GaryE]

"Peacock bass" will eat everything they can,, but Tilapia are famous for thriving in poor water conditions, and Cichla are not. Cichla aren't bass but were tagged as such to bring American anglers in to fish for them, and spend money. They are powerful fish, but they don't come from dirty water.

You can't win. Tilapia are cultured to be eaten, and the whole system of keeping them thousands of km from their natural range is based on constantly removing fish for consumption. They are being farmed, as you well know. It's harvest time..

Outside of their native ranges in different regions of Africa, they may be the most destructive fish on the planet. Introduced "Tilapia" are one of the ways we humans have been driving small fish to extinction. You're seeing their ability to reproduce and survive.

 

[Magnum Man]

I read that actually stress may help them reproduce that they have strong survival skills, and if they feel threatened, it will increase their reproduction

 

[Colin_T]

Outside of their native ranges in different regions of Africa, they may be the most destructive fish on the planet. Introduced "Tilapia" are one of the ways we humans have been driving small fish to extinction. You're seeing their ability to reproduce and survive.

That happened in Lake Wanam in New Guinea. The government introduced Tilapia into the lake as a food source but the Tilapia ate the native fishes and the local people didn't like the taste of Tilapia. Lake Wanam now has no native fishes left in it.