Pond Boss Forums STOCKING A NEW POND Types of fish to choose Tilapia with Winterkill

I will be interested in the study results. Often people find what they are looking for and bias is often exhibited in studies. Not suggesting this one is such but have seen it often in the many years of reading studies. Here is one very counter intuitive study which was reported on in PB mag some time back. If you want to learn - get PB mag !

Tilapia – stealth predator - revisited

Several years ago, in The Cutting Edge an article appeared, named Tilapia – Stealth Predator which provided study results where the data presented clearly indicate rapid digestion of fish prey in the stomach and suggest strong stomach acids in the digestive process as the reason. The study titled Rapid Digestion of Fish Prey by the Highly Invasive 'Detritivore' Oreochromis Mossambicus by R. G. Doupe and M. J. Knott, Australian Centre for Tropical Freshwater Research, James Cook University, Queensland, Australia (November 2009) Journal of Fish Biology: 2010 v76 - p1019-1024 also suggested that Mozambique Tilapia is more likely a functional omnivore (channel catfish are omnivores) and supports the notion of it being, under some conditions a piscivore (fish eater). This issue revisits the conclusions contained in the study discussed in this prior Cutting Edge article.

Stockings in recreational ponds are often in conjunction with other forage sources like Bluegill, Golden Shiners and Shads so the relationship between these species and Tilapia is important. Tilapia are used in ponds mostly as yearly supplemental forage stocking because they have a high lethal low water temperature threshold around 10°C or about 50° F. Thus, in most of the U.S. range (other than Florida and south Texas) Tilapia don’t survive winter. Further Tilapia are generally thought to be herbivores and we assumed they did not prey much on other pond fishes. We knew they ate a few fish fry and eggs but mostly they ate plant material and have been described as a true detritivore, with the ability to assimilate free nonprotein amino acids directly from detritus. The study above contradicts this common knowledge. Here the prey fish were consumed but no prey fish were found in the stomachs of any size class of Mozambique Tilapia at one-hour post-consumption, and none were detected in the stomachs when examined at either 2, 4,6,8, 12 or 24-hours following consumption. It seems highly likely that all prey fish were digested within 1 hour of ingestion by Mozambique Tilapia.


Yes, there is always more to learn, and assumptions are sometimes incorrect, and studies have different results. So this issue we note a contrary study titled, Foraging in non-native environments: comparison of Nile Tilapia and three co-occurring native centrarchids in invaded coastal Mississippi watersheds by Mark S. Peterson, William T. Slack, Gretchen L. Waggy, Jeremy Finley, Christa M. Woodley and Melissa L. Partyka in Environ Biol Fish (2006) 76:283–301 DOI 10.1007/s10641-006-9033-4. Here the authors examined the diet of Nile Tilapia and bluegill, redear sunfish, and largemouth bass over a two-year period in coastal Mississippi. The study contained the following findings. Nile Tilapia diet was clearly separated from the three natives based on group-average linkage cluster analysis. Sequential two-way nested analysis of similarities indicated there was no seasonal effect, there was a moderate size class effect and most importantly, a strong species effect. Pairwise tests indicated species fed on different components of and locations within the environment, with bluegill, redear sunfish and largemouth bass having the most similar dietary components and Nile Tilapia having the most distinct. The stomach contents for these species provide an interesting comparison of their diets. Nile Tilapia examined for stomach contents ranged from 1/3rd to 17 inches, 590 fish, in 24 size classes. Frequently eaten prey types in all size classes were small prey like rotifers, nematodes hydrozoa, and bryozoa plus various insect stages and parts. Additionally, microcrustaceans like copepods, cladocera and ostracods were consumed quite frequently as were fish scales. The most frequent stomach items were amorphous debris, detritus, sand grains and mud clumps. This indicates that Nile Tilapia consume bottom sediment directly which reflects the diverse prey types in all fish, particularly the large individuals. Nile Tilapia had a distinct diet from all three native centrarchids. Nile Tilapia clearly foraged on lower trophic levels (mud, sand, bryozoans, nematodes, hydrozoans, and rotifers) whereas largemouth bass fed on larger invertebrates and fishes (insect parts, fish scales, unidentified fish, fish parts) at small sizes. Prey of bluegill (chironomids, calanoid copepods, insect parts, sand, cladocerans) and redear sunfish (chironomids, insect parts, sand, snails and mollusks) do not overlap to a great degree with Nile Tilapia. The main cause for this separation stems from the primary foraging of Nile Tilapia on the bottom resources whereas bluegill and redear sunfish forage more on pelagic species in addition to epi-benthic resources. The authors do note other studies showing some limited competition and interference with sportfish.

From these different studies and others on topic it is apparent that we don’t have all the answers about Tilapia. Depending on location there can be some competition between Tilapia and other pond species, but it appears only at a low level with tilapia being efficient generalist bottom foragers with great adaptability.


Here is more on a very complex subject in this thread.


Effects of Cover and Prey Size on Preferences of Juvenile
Largemouth
Bass for Blue Tilapias and Bluegills in Tanks !
HAROLD L. SCHRAMM, JR.
Department of Fisheries and Aquaculture
School of Forest Resources and Conservation
ALEXANDER V. ZALE
Florida Cooperative Fish and Wildlife Research Unit
School of Forest Resources and Conservation
University of Florida, Gainesville, Florida 32611
Abstract

The effects of vegetative cover and relative size of prey were tested on the forage preference of
juvenile largemouth bass Micropterus salmoides offered blue tilapias Tilapia aurea and bluegills
Lepomis macrochirus in laboratory electivity experiments. When offered forage at or near the
maximum consumable size in tanks without vegetative cover, largemouth bass preferred bluegills,
but consumed blue tilapias in the presence of vegetation. When offered forage smaller than the
maximum consumable size in tanks without vegetation, largemouth bass selected blue tilapias.
Differences between the forage species in body morphology and effective use of protective cover
apparently caused the changes in prey selection. Our results suggest blue tilapias may be a suitable
forage for largemouth bass, but that habitat characteristics
and relative size distributions of other
available forage may affect their use.

+1 to that! I've learned a lot since subscribing.

During late September and October the intestinal contents of the tilapia(TP) has consisted almost exclusively of dark brown mud organic like sediment. Little if any FA algae or delicate submerged plant like materials are now present due to the feeding activities of the TP.

My larger TP are still very happy to hit the pellets but the smaller ones were definitely shorter in numbers at the water inlet and high water outlet this evening. Not sure if they have pulled off a little to deeper water or if they have started to become snacks for the LMB. Seemed to be about 1/2 the normal population of what was present before the cooler weather started rolling through. Tuesday afternoon water temp 1' down was at 72.5.

Very interesting, Bill!

Are tilapia like carp, in the situation where there is little remaining food in the water column, they will stir up the bottom sediments to get at the interspersed organic content?

So, how do the Nile Tilapia and Blue Tilapia differ in stomach contents??

Question was I am not sure what is meant by little remaining food in the water column. I think TP manure creates more phytoplankton that results in more zooplankton. I have never did a study of how the zooplankton community changes with the activities of TP. It would be a very interesting small research study if I had more time. Just as a note - the zooplankton species composition changes weekly and monthly as the water temp, day length and phytoplankton composition changes. As the phytoplankton changes so goes the zooplankton populations. Both are very dynamic. Nutrient concentrations and water temperatures are big influencers.

TP, I think, provide excellent forage for 12" and longer LMB. The benefits of TP, I think, are much more muted for 1st year growth of 2" LMB fingerlings. I just base that on some of Swingle's age old research and a couple of anecdotes here where the effects either didn't seem to contribute to faster growth of 2" fingerlings than with BG and/or minnows and in one case the addition of MOZ TP in the initial year backfired and was detrimental. In that case, MOZ TP consumed FHM and grew to sizes that the 2" LMB could not keep up with. Seems like the pond owner also thought the TP may have consumed some of his LMB fingerlings. Lot's of forage for 2nd year and 3rd year LMB were produced in that pond but unfortunately, there were none of the sizes of LMB that could fully benefit from the TP resource.

With regard to escape speeds and probability of escape and so on. What I have found by reviewing the literature is that the realized consumption frequency curves for fusiform and laterally compressed prey can be normalized by reformatting the curves to proportionate weight instead of proportionate length. IOWs, when plotted versus proportionate weight, the curves lay one over the other with similar distributions. To be sure, proportionate weight is the primary variable of specific energy content but the probability to escape a predatory encounter must also be very sensitive to the variable of proportionate weight. In as much as this is true, fish of same weight have very similar probabilities of escape and have similar energy content. Still regardless of energy density, the primary factor affecting peak frequency of realized consumed sizes (presumably the most optimum forage size) is the probably of escape.

How much a forage fish weighs matters for the probability of surviving a predatory encounter. The heavier the prey fish ... the more likely it is that it will survive and the predator fail to consume it. Here just assuming that the health of the prey fish is good. TP in chilled water, it is safe to say, are compromised in the health category and thus are less capable of evading a predatory encounter. But under favorable conditions where one examines the difference between species on the basis of proportionate weight, the species which is heavier at the same length stands a better chance of surviving. Also prey fish in good condition (higher RW) are less vulnerable to predation than prey of the same species and same length that are in poorer condition. Generally, one should expect that MOZ TP will be heavier than BG of the same length. Enough so, for example, that a MOZ TP of 2 1/4" has a similar probability of escape as does a BG that is 2 5/8". Also MOZ TP can grow to 3" in 60 days where excellent growth for BG over the same span of time is 2". MOZ TP thus are better suited for larger LMB which tend to consume them at shorter lengths than they would consume BG.

I don't have lots of experience with TP but from my personal experience and observations with my first year stocking them here's what I think and what we did.

We stocked 10 lbs of 6-9" TP this year in the spring along with 50 2" LMB about a month later.

I think it is possible that the TP were large enough to consume the fingerlings on our initial stocking but that window was also very small. The growth rate of the LMB from fingerling stage was approx 1" every 16 days and have maintained that rate as best as I can tell up to now. Next check is Oct 19 to confirm our season growth weight and length.

As to which is easier for the LMB to catch between BG and TP - I'm leaning to BG being more subject to forage of the LMB than TP. I haven't been able to catch much in the way of BG in traps is where I'm leaning to on this. Visually not seeing many YoY in the pond either. Conversely, the TP were roaming in packs of like size fish all spring, summer and early fall. My observations from my inability to trap BG and lack of them visually in the pond. Would have better info if I seined or shocked but I haven't done either to date.

I did make it out to the pond today to feed the fish around noon as well as try to see populations of the small fish and species. It appears as though the small TP numbers have been halved with our cooler overnight temps over the past 7-10 days. Water temps are still in the lower 70's in the afternoon but likely dipping overnight. With the lower numbers of smaller TP I am not seeing more YoY BG however. The areas the TP were really visible just have fewer fish in them.

Interesting sidenote was that I was reaching out to one of the other PB members about his Titan Bass so see how he was doing on growth rates and in the discussion he mentioned that some of his fingerlings escaped and got into the TP grow out pond upstream. I don't know what other forage was in the pond with the TP but it sounds like the growth rates on those LMB were outstanding.

In reference to some of the older threads on TP I remember there was some discussion on what is a good stocking rate for the TP. One owner was concerned that if he stocked to many TP catchability rates would suffer but the responses in the thread were actually the opposite saying that a higher stocking rate of TP at 20lbs vs 5-10lbs per acre could actually improve catch rates.

I do wonder if there is something to the higher stocking rate of TP being validated by the two above conditions. I would assume the TP grow out pond had loads of TP in it and as a result the LMB used them as forage. Further validated by the older post(s) with stocking rates.

Again, my personal observations and conclusions here. I don't have lots of experience but thought I would relay what I suspect is happening at our place as well as some anecdotal info from other sources.

BD,

Bottomline.

Can you expand on your experience in the form of a recommendation for the initial year?

Your LMB have grown very, very, well. So one question would be, is this because you stocked TP? Or would the LMB have made similar growth without the TP this initial year? Another question might be, were they necessary to control FA this year? Could an alternative prey species that consumes FA (e.g. GSH) have provided sufficient control in this initial year? To be sure, there should be no regrets, but would you repeat this recipe with another pond?

There is no need for concern with regard to growth of the LMB thus far. That piece was fulfilled and was completed very successfully. Even so, it would be naïve to think that the TP had no effect that will reach into next year. So as we approach the winter period it is worth asking if the TP have better prepared you for the forage needs that will take place after the TP die off. In your opinion, did TP fulfill the promise of increasing survival of YOY BG? If not, what are your thoughts on the reason?

All things considered, would you recommend to others to stock TP as part of the initial year stocking?

Here are some thoughts for this before BD replies.

1. He says the stocked TP were large enough to MAYBE eat some of the stocker 2" LMB. If that did happen then IMO it reduced the density of LMB stockers that in turn resulted in more food available for the surviving LMB that allowed them to grow better at a rate considered near maximum for LMB at this geographical location.

2. If YOY TP are better able to elude predation compared to BG, this escapement factor is IMO compensated for later when the YOY TP are easy captured in cooler water compared to small BG who in cooler water better more agile swimmers than the struggling edible sized TP. We have seen numerous species of predator fish die in fall with oversized TP stuck in their throat.

3. I don't think GSH are very affective or efficient at controlling FA. I have a 0.3ac pond near me that has a strong population of GSH due to the SMB numbers have diminished and the YP are not very effective at eating healthy 3"+ GSH that serve as brood stock. The owner has been increasing his purchase of TP each year to now 7lbs as 23 TP to control the FA. I think the FA that has been reportedly eaten by GSH has been FA in stomachs as mainly filaments consumed incidentally by the GSH as they are wanting to eat mainly the myriad of invertebrate that are living in and among the clumps of FA. IMO TP are firstly primarily vegetarians and detritovores and when those preferred food items are lacking their hunger causes them to resort to eating whatever animal foods they are able to capture.

I'm in the undecided category for recommending TP in 1st year which would likely mean I could share my experience and that's about it. I could be completely wrong on my lack of YoY BG from tapping, I just wasn't able to locate much of a qty of them in the sets I made.



We did have a little bit of FA started in the pond before I stocked the TP. I had zero FA floating mats in the pond this year though we would see a little bit of it on rocks or submerged vegetation and trees in the water.
Our stocking of TP was to both keep the FA from overwhelming the pond (had family stuff going on at the property with dad's passing), everything I read was they were a great forage option and one of their key benefits was that they outproduced BG which ultimately saved the BG as forage for later in the year.
*** Perhaps the YoY TP have pushed the YoY BG to a different area of the pond or habitat and they are present but I'm not seeing them.
*** Perhaps my stocking rate wasn't high enough to provide a dense enough forage base for the LMB to really key in on them.
*** Perhaps my traps were just not the right style for the YoY BG.
*** It is possible that you are correct that LMB are more effective at catching the TP once the LMB get to the 12"+ size and they pick off smaller TP as their optimal forage.
*** Very likely that some of the growth we saw in the LMB is attributable to the TP being present. I can't imagine a scenario where none of the YoY TP were eaten. As they are seemingly shorter in numbers now I can only guess that the LMB are starting to pick them off with the cooler fall temps.

Sadly, my perhaps above won't be answered this year. Once the TP are gone from winterkill I suspect that the fish will be in deeper water which will also prevent visual efforts to locate and I assume that trapping them in cool temps would have the same results as stocking them at low temps ultimately leading to death of trapped BG. My suspicions, assumptions, and guesses left me with a conclusion that I would need to supplement forage to make sure there were no hungry mouths to feed over the winter. Hopefully giving the fish time to correct any issue with a shortage of YoY BG before it manifests itself with low RWs.


I have no regrets in trying to find ways to "push" the fish this year on growth. I think if a pond owner is going to push LMB growth he or she is going to have to make calls along the way based on what the pond and the fish are telling them. In my initial samples of the fish I was seeing an avg RW of 162% (3 fish Aug 3rd - 12th). Those RW's changed to an avg of 124% (4 fish Sept 21st - 23rd). In the second set all the fish seemed to generally have the same appearance of thick back, filled out tail and a little thin on the belly. My call based on the notable reduction in RWs between the above dates and visual condition of the fish was to bump the forage. Reposted a pic of the fish from previous that needs to eat a supersized value meal!


I have no proof to offer here other that what I've stated above. My personal belief is that the TP didn't fulfill the promise of increasing survival of YoY BG. The only thing that makes sense to me is that the BG were easier to prey on. There could be several reasons for this however. One that I have spent time pondering is - If the YoY BG and the TP didn't occupy the same habitat then the YoY BG were displaced into areas that may have made them easier to prey upon as the YoY TP were at all of the complex structure, and shallow water riprap (inlet and outlet).

My feeling of lack of successful use isn't in anyway changing my plan to use them in 2025. In fact I'm looking forward to trying them again next year at the same 10lb rate and size if there is no LMB spawn. If there is a LMB spawn I'll likely double the TP to 20lbs. I'd love to see if there is any difference with the amounts of TP produced through the year. If it's less production I would guess that there's been increased consumption which is a good thing.

Glad to see you say this. TP will contribute much more to the consumption of prey next year. Production includes mortality by consumption. This will be at least partially evident in the growth of your LMB (which will be blend of consumption of all available consumable forage).