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.

Last edited by Bill Cody; 10/10/24 07:31 PM.