Caught this little tilapia this morning-about three inches long. I haven't stocked any this spring 2011. It tells me two things-some are still in there and obviously they are spawning.

Has anyone seen this occur this far north?

thanks

Last winter was very mild, doesn't suprise me...

I have not heard of anyone that far north having over wintering unless they have springs. That can cause a real problem with carrying capicity.

I just hope that some are getting adjusted/evolving an ability to withstand cooler conditions. How nice would it be to have full time Talapia in the north? IIRC some Eel grass was originally only native so of the Ohio river but thru the yrs (and I believe Bill Codys coaxing) it is now doing well up here.

CODY note: The eel grass that Bob-O refers to above is not the standard eel grass aka Valisneria americana . The eel grass I am working with is corkscrew or spiral eel grass a southern variety or subspecies adapted to warmer water, although it will survive much further north and in colder water than tilapia.

If they are overwintering it may cause a problem especially if any get out of the ponds and in other sources of water.

I think that is the fear most places try to put on us.

I am sure mine will not have a chance as my ponds are not that deep, do not have springs or wells tied to them.

I'm pretty sure that is it. Nothing to be concerned about as a continuous problem year after year. That is unless mild winters will be the norm, which I doubt.

A few over wintering tilapia can fill up a pond and cause extreme biomass problems. One reason they work well is they don't over winter. If 75% of your carrying capacity is tied up in tilapia you might not like that very much.

This would be horrible! Might result in tilapia being banned in more states than they are already.

Caught 4 more last night about 6 inches long.

Eat'em before it gets to cold or they overpopulate

I missed this thread......Tilapia are the oldest recorded farmed fish...in over 6000 years, they have never acclimated to cooler climates. Also, reproduction in overwintering tilapia will rarely occur in northern latitudes due to a short photo-period.

As a side note to what ewest mentioned about tilapia taking up carrying capacity...what is often forgotten is that with tilapia consuming normally non-utilized nutrients in the pond, the "carrying capacity is drastically raised....generally, tilapia are ignored for carrying capacity concerns.

Unless you're pushing things in a non-aerated pond during the summer....... Then I believe they should be considered part of the carrying capacity because they need DO too!

esshup, Do you think they need as much DO as the regular pond fish? I've only been around these fish the last three years and I still learn something new about them every day. Us old dogs can learn new tricks every once in a while .

Rex???? A little help here!

I know that the ones that we raised in a RAS over the winter went off feed if there wasn't enough aeration. I didn't have an O2 tester, but the other water parameters were O.K.

I've had thoughts along a similar line. I don't know the first thing about Tilapia, other than I don't want them competing with my BG, but if they reproduce like gangbusters and eat FA....isn't the FA introducing or elevating the DO content to some degree?

It almost sounds like adding the initial brooders (the same as adding any other fish) will impact the biomass of the BOW immediately, then as reproduction takes hold and their numbers increase, AND they aggressively target the oxygen producing FA, the carrying capacity of the pond will be reduced?

What am I missing? Is it a case of having the Tilapia die out over winter and hoping that they don't contribute to eating themselves out of DO before they expire?

If stocked together with GC in an unaerated smaller BOW, is there cause for concern regarding too drastic reduction of aquatic growth, resulting in reduced DO available for the other fish species present?

I have seen about 6 in the 8 inch category in the last few days. I guess they are moving to the warmer shallows during the day now.

I hope to get out soon and see if mine are moving into shallow water yet and if any vegetation has come back. Pond seems clean this year.

sprkplug, yes the FA makes O2, but I'll bet that if a study was done (ewest, has one?) you'd find that the majority of DO that is in a pond is "produced" by two things - the interaction between the pond surface and the air, and phytoplankton (i.e. "the bloom").

There are three main sources of oxygen in the aquatic environment: 1) direct diffusion from the atmosphere; 2) wind and wave action; and
3) photosynthesis. Of these, photosynthesis by aquatic plants and phytoplankton is the most important.
Oxygen, derived from photosynthesis, is produced during the day when sunlight shines on the plants in the water. Oxygen levels drop at night because of respiration by plants and animals, including fish. These predictable changes in DO that occur every 24 hours are called the diurnal oxygen cycle

Aquaculture of Tilapia and Pangasius; A Comparative Assessment

Michael V. McGee, PhD
Caribe Fisheries Inc.
Lajas, PR

Tilapia can survive exposure to as little as 0.6 mg / L D.O. for short periods of time and levels of 2.0 mg/ L are adequate to prevent significant stress. However, chronic exposure to D.O. levels below 3.0 mg/L will compromise feed utilization and growth rates as well as disease resistance. Thus, Tilapia are dependent on dissolved oxygen in water. Under conditions of intensive production Tilapia ponds are aerated to increase or sustain dissolved oxygen levels. Although effective, use of mechanical aeration can significantly increase production costs.

So theoretically speaking, is it a plausible assumption that an herbivorous fish species of high fecundity, like Tilapia, might negatively impact their environment in regards to DO production?

Particularly if exacerbating circumstances existed, such as in a small, unaerated, shallow BOW, or perhaps when stocked together with another herbivorous species, (GC)? Or if the Tilapia were to overwinter?

I realize the chances of such an occurence may be miniscule, but does the potential exist?

I've wondered this for some time.

I put some in a 1/4 pond so maybe we will se how they do in a small body of water. I am sure that none will overwinter here but you never know. If I decide not to add them next year we may find out if some did. But I think even if the water did not get cold enough to kill them, it would slow them down enough to be eaten by either the LMB or CC.

Any water system with plants and or animals has the potential for BOD to be more than supply. The more living organisms and the more static the water the higher the chance. That is the exact reason overwintering tilapia can be a problem (to much biomass - BOD - for the available supply). It is simple - a water system is like a car engine - you can run it a long time at low RPM but if you run it at high RPM it is likely to break sooner.

That's what I thought. Thanks Ewest.

The following is all based on tilapia in a "typical" sport fishing BOW, and NOT overwintering...


This thread personifies why so many states classify Tilapia as an "invasive"..State biologists like to look at the papers, and deduce that Tilapia compete directly with every native species in a pond's ecosystem, so they are banned without further thought and ignoring real world proof. In the pond (where annual death of tilapia is a near certainty), the paper theories dissolve and leave the paper pushers scratching their heads in bewilderment, because every species that SHOULD be displaced (on paper) thrives.

Just some of the almost countless benefits to a pond is when tilapia aerate a pond to "farm" bacteria and Macrophytes, which become a "new" food source that would not otherwise exist absent tilapia. Tilapia fry/fingerlings also become the primary prey, greatly reducing pressure on "native" prey. Tilapia primarily only consume plants and nutrients no "native" specie can (thus, they are neither a load nor consideration on the "normal" carrying capacity or BOD). Tilapia DRASTICALLY increase water quality by increasing aerated water, aerobic bacteria and by reducing the toxins, such as hydrogen sulfides formed by anaerobic bacterias.

Stockings of 100 pounds, or more, per surface acre have yet to be shown detrimental in any pond or lake I am aware of. SEPM actually suggests stocking Tilapia at 100 pounds (or more) per surface acre in trophy bass waters on their website.

The fears and worries mentioned in this thread "seem" logical, yet the way tilapia function in water, not on paper, makes the fears a non issue.


In a sport fishing pond, consider Tilapia as adding a supplemental feed program, aeration and as a nuisance plant eradication program and NOT as a "Fish". And in the same way as supplemental feed and aeration create an "unnatural" increase in a BOW's carrying capacity, so will annual use of Tilapia...after 3 years of adding tilapia, the BOW will have a far higher carrying capacity (NOT including the tilapia weight).

Extremely little scientific study has been done on tilapia in a pond setting as we use Tilapia, and that is outside of the food fish production industry. From what I have seen in ponds, Tilapia seem to be somewhat self-limiting through cannibalism, from being so territorial and aggressive toward each other....they virtually ignore other species, even when nesting. I think Bob Lusk would agree, tilapia seem to defy all the rules other fish play by.

Tilapia, in short are not a burden on a carrying capaicity in a pond, they are a missing link in our waters that bring out a ponds true carrying capacity capabilty Without adding Tilapia in the weight, and after 3 years use, probably at a level at least 2-3 times higher....all with no effort other than writing the check to cover annual stocking...

How in the dickens can a tilapia increase aerated water?

Dave, the Tilapia swim rapidly up and down, from breaking the surface down to detritus laden muck and flash, or "slap" the newly oygenated water into anoxic areas, heavily mixing the stagnated waters while doing so...If you see tilapia in clear waters, they appear like they scratching their sides on the leaves and other detritus lying compacted on the pond bottom. Tilapia do this to promote aerobic bacterial growth on detritus. The tilapia consume the bacteria and as a bonus like when adding aeration, the aerobic bacteria also more rapidly digests the detritus...

What about a trophy BG pond... It is my understanding that Tilapia readily consume artificial pellet feed, which directly takes food away from the BG, and/or increases the amount of feed which must be dispensed, thereby driving up costs. AND, a well managed BG pond will rely on a predatory species to control BG offspring.... It is often touted as an advantage to have Tilapia present as forage for your Bass, when dealing with a LMB orientated goal, or at least in a more traditional balanced scenario, but when trophy BG are the goal LMB considerations are secondary at best, aside from maintaining their numbers. It would seem that the forage provided by yoy Tilapia would reduce the pressure on the BG yoy, which would appear counterproductive.

I'm still not following the reasons why Tilapia don't count towards carrying capacity. Don't they breathe too? Wouldn't that impact the available biomass a given BOW could support?

sprkplug, There are 2 ways to look at a trophy BG fishery....Tilapia are indeed pellet hogs, yet convert the pellets at roughly a 1.2:1 rate where BG convert around 4:1....If larger BG eat tilapia, you may gain more bang for your buck on tilapia being foraged over the pellets, but BG would probably expend more calories eating live food.

The second view is that with the increased caryying capacity, your pond could theoretically carry twice the trophies with more total available forage along with more, larger, over-abundant LMB to still control the excess BG recruitment.

As for affecting the biomass, tilapia do..they increase it as much as 5 fold in fish, but offset by the larger amount of biomass they consumed to grow, much of it detritus, which often comsumes more oxygen than the Tilapia will...plus as said above, the Tilapia will bring oxgenated water to areas it never existed....in an already aerated pond, the additional oxygen is a moot point.

Tilapia simply allow a pond to find a new, higher carrying capacity by consuming available nutrient other species cannot digest and utilize, moving it into the food chain for the"normal" fish to consume.

There is no succinct way to state all the interactions.