Pond Boss Forums INTRO Questions & Observations tilapia blocking net?

I just got through reading eric's article on using blocking nets to raise bluegill and I had the idea of using blocking nets for tilapia. I love to eat tilapia but find them difficult to catch when I want to eat one. So how about not putting all of them in the pond but keeping some behind a blocking net for when you want to have dinner?

Jim the blocking net shound contain tilapia to a restricted area until they have babies. Then all bets are off.

Probably a silly question, but here goes: do tilapia spawn like BG etc?

No, tilapia spawn every six weeks when the temperature is warm.

Hmmm. BG spawn once a mth. in the south during April - Aug. +- . Tilapia are mouth brooders. There are several species of tilapia. Mozambique tilapia (O. Mossambicus) being the one most discussed here.

Tilapia
Life History and Biology
http://srac.tamu.edu/tmppdfs/127565-283f...37b071f2c79794c


Under
good growing conditions in ponds,
the Mozambique tilapia may reach
sexual maturity in as little as 3
months of age, when they seldom
weigh more than 2 to 4 ounces (60
to 100 grams). In poorly fertilized
ponds sexually mature Mozambique
tilapia may be as small as 1/2 ounce
(15 grams).

In all Oreochromis species the male
excavates a nest in the pond bottom
(generally in water shallower than 3
feet) and mates with several females.
After a short mating ritual the
female spawns in the nest (about
two to four eggs per gram of brood
female), the male fertilizes the eggs,
and she then holds and incubates the
eggs in her mouth (buccal cavity)
until they hatch. Fry remain in the
femaleÕs mouth through yolk sac
absorption and often seek refuge in
her mouth for several days after they
begin to feed.

AQUANIC
Maternal mouthbrooders, spawn twice a month, 2,500 eggs/lb body weight, eggs hatch in 5 to 7 days.

http://aquanic.org/publicat/state/il-in/as-494.htm

My limited understanding is 14 days for the female to develop eggs + plus the spawn ,+ 7 days to hatch , + a day or 2 before expulsion from her care , then start all over. One brood every 24 to 28 days.

Thats more often than I had been told but I did know they outbred the bluegill just not by how much. I think that they must also have a higher survival rate. By the end of the summer the edge of my pond was solid 3 to 4 inch tilapia and almost any bass or catfish we caught looked like a balloon from eating them. I wonder if there are any adverse effects on the bluegill from having so many tilapia? Even with a very heavy predator base the predators seemed to have no effect on their numbers. I can see how they could take over your pond if they didn't die in the winter.

James,

I haven't seen any adverse effects on BG from Tilapia...in fact the opposite, the BG numbers in my ponds improved each year and now have kind of stabilized at a high level after 4 years of stocking Tilapia.

The key may be in initial stocking rates and sizes of the initial stockers. Seems to me that very high stocking rates with relatively large Tilapia might indeed work against the BG. There is some evidence from lakes in Mexico that large Tilapia that overwinter each year may have an adverse effect on quality of LMB fishing...theory being that larger Tialpia in overpopulated waters may eat fry of other game fish.

In my own case, I've reduced Tilapia stocking rates to about 5 to 7 pounds per acre and things seem to be very stable for me at that rate. One pond stocked with 2 pounds per acre last summer, didn't get the algae control I wanted.

One of the great things about Tilapia I haven't seen mentioned is what you touched on...their survival rate. Mouth brooders that protect their young like Tilapia do, should have a higher survival rate in the young. I'm hoping to get some really good data/experience in the next few months on Tilapia reproduction and growing out young fish capable of surviving in the ponds with predators.

In my own case, I'm planning to produce young Tilapia in my indoor facility, transfer them to grow out tanks and then, if necessary, transfer them again to cages in the ponds for final growing before release. By the way, my indoor facility is also stocked with Gams to determine if Tilapia will eat them. So far, they haven't.

Meadowlark I am also thinking about stocking at a lower rate due to the huge numbers of fish that I had by the end of the summer. I think that I stocked too heavily and had no vegetation in the pond by the end of the summer. This year I will decrease to about five pounds an acre and see what happens at that level. Have you had any of your fish reproduce yet?

No, not yet. I haven't turned up the temps in the tank yet...running about 74 degrees. I'm fighting ammonia start-up problems which I expect/hope to get under control soon when the ammonia eating bacteria on the filters start really kicking in.

Finding the right balance in your pond is tricky...I like to have some vegetation, but not too much. Of course, we all like lots of forage also. Depends on how many predators you have and water quality, etc., etc. You may want to step down gradually and see how it goes. I've been playing with the numbers for 4 years in my ponds and think I'm about getting to where things need to be...until some disaster comes along to throw everything out the door!

Meadowlark, I put some small tilapia in a trough with lots of gambusia and the tilapia killed and ate every one. Stop feeding them and see what happens!

Ah, ha. Interesting piece of data BrianH. Thanks.

I have expected that would happen but wanted to test it out to be sure. Kind of tells me there may be an upper bound to the stocking rates, which is something I have suspected. Stocking levels at "too high" and "too large" may actually be detrimental to your BG and LMB fry...that is something I have hypothesized and suspected but haven't proven yet. The level of "too high" is certainly yet to be determined, if, in fact, it even exists....like you said, if they have nothing else to eat, then the Gams and maybe even other small fry may look as good as algae to a hungry Tilapia. One thing about Tilapia is they will find a way...some day, maybe decades or centuries away, they will survive 55 degrees and then 50 degrees, I predict.

BrianH, have you tried the same thing with Pacu?

No, I didn't get any pacu yet.

BrianH,

If you are interested in getting some larger Pacu, often for free, may I suggest you contact a fish supplier in your area that sells them to aquarium owners as little fish. In my area, those suppliers often have customers who are trying to find a home for their pet Pacu that has quickly outgrown their aquariums.

It would be interesting to know different experiences with filamentous algae control with different stocking rates of Tilapia. It would also be important to know if the pond is fertilized and how heavy the bloom is, as well as the species of Tilapia and when the stocking occurred.

In early June of '05, I stocked large T. nilotica (average about a pound)at a rate of 13 lb/acre. The pond was heavily fertilized, had a good phytoplankton bloom (visibility to about 18" using the "Auburn Arm Test"), and had very large mats of f.a. at the time of stocking. The f.a. was reduced by about 90% at the surface, but never entirely disappeared, and a pretty thick bottom mat remained.

In late April of '06, I stocked T. nilotica of the same size at a rate of 13.5 lb./acre. Fertilization and phytoplankton bloom were as the year before, but the f.a. had just begun to form fairly small mats. The pond was quickly completely cleared of surface f.a. except in very shallow areas that the larger Tilapia couldn't enter, and it stayed clear. There was moderate growth of bottom mats, not nearly as heavy as the year before. For the first summer ever, I didn’t once have to pull off stinking masses of algae that wrapped my trolling motor prop in shallow water.

I suspect that stocking time is an important variable in suppressing f.a. growth. I now hector my fish supplier to make me and my neighbors first on his Tilapia list, and have concluded that a really irritating whine is the most valuable factor in good f.a. control with Tilapia, but what if he quits taking my calls?
Lou

Lou,

You may be a candidate for a redneck aquaculture system That way you don't have to depend on anyone but yourself for your Tilapia.

A couple of factors I've observed after several years with Tilapia:

1) artificial feeding makes a huge difference in the degree of algae control you get with Tilapia....I have proven, to myself if no one else, that 5 pounds per acre in a no artificial feeding pond is equivalent to 10 to 15 pounds per acre in an artificial feeding pond, again in terms of algae control. Science also backs up this finding. In my indoor system, I am purposely NOT feeding floating pellets, but feeding sinking food to the fish that I am training to be future pond cleaners.

2) there is a cumulative effect of multiple years of stocking Tilapia on algae control. I began noticing that effect after two years of Tilpia stocking. I noticed that even in early spring, without Tilapia, I no longer was seeing the big mats of bottom algae and no longer needed early season chemicals to control algae before Tilapia stocking. It just wasn't there anymore. I attribute that to Tilapia even though they weren't even in the ponds when this normally happened.

Lou :

Very interesting. There are various types of tilapia in the US including Oreochromis aureus - Blue tilapia , Oreochromis mossambicus - Mozambique tilapia , Oreochromis niloticus niloticus - Nile tilapia , Tilapia rendalli - Redbreast tilapia and others. The names and species are confused at least to me. You are the first here that I recall that has niloticus as most info here is on mossambicus.

The sooner you start to break the FA cycle the more effective the control so start early if the tilapia will handle the water temps. In our ponds it seems the FA gets its head start by growing over winter and early spring on the bottom. Also I agree with ML on year to year suppression. Even though it looked like lots of FA on the bottom in 06 the 05 suppression helped reduce the amount of 05 that was there to reproduce. The tilapia eating FA in 05 plus your reduced visibilities shading it out on the bottom helped reduce the 06 crop. Send old Mudcat Joe down for a look-see at the FA so he can provide a cats-eye report.

I have seen the a huge drop in FA but have not seen the decline in bass population or of any other forage fish. I may not have reach my stocking limit of Tilapia though. I start conservatively with only putting 100 6-8" in a 25 acre pond. I still have them and that one and only stocking took place over two years ago now.

Meadowlark I also have seen a cumulative effect of stocking for three years. Last year I think I may have stocked too heavily because by the end of the summer there was almost no sign of any plantlife in the pond. Last year I stocked at 20# per acre and so this year I am planning to stock only 10# per acre.