The article abstracted below should , based on web search results , include a comparison/analysis of a pond with BG and tilapia mosb. and LMB. I don't have access to the paper and did not want to buy it.
Not much on these points in US research (or it is hard to find) but I will keep looking. Have been checking on this off and on for 6 mths.
My 2 cents worth based on what I have found so far. Read the abstract below --it sets out how to determine the answer from a biological factor method .
One article (not a scientific study) by very respected fisheries scientists who happen to run a hatchery and write and cousult on southern ponds concludes that tilapia (so long as they are subject to winter die off) do help improve greatly the BG forage base because they reduce predation of BG by LMB . This was not a long term study or conclusion but I would rely and have on these authors. There are other articles that draw this conclusion also. What they seem to be reporting is that both quantity and quality of BG 3 in. and over are easily seen. After all that is what is visible ( it is hard to see very small BG). Other info from FishBase and studies on what juiv. ( less tha 3in. BG and Tilapia eat clearly indicate that juiv. BG and tilapia eat some (? how much) of the same things including the range of zoo/planktonic diets. There is no indication they both eat FA (BG don't-- tilapia do) but they do compete for some food at this life stage. BG also eat small tilapia. In the long run this may help or hurt with the recruitment of BG -- who knows. Even if BG rect. is reduced and it causes a negative effect it can easily be managed around. One thing I am sure of is that once you start a program of increased forage base whether by feeding or fert. or stocking ( no matter what type of forage fish BG , TS, tilapia etc, )you will get an increase in predator biomass which to remain healthy must continue to get the increased forage unless you intend to remove a lot of predators. But that is ok -- it is one of the recognized facts and advantages (? disadvantages) of an active pond management approach. If I find more I will repost. ewest
Date: April 1992 Pages: 177 - 186 Ecological aspects of fish species interactions in polyculture ponds Ana Milstein1
(1) Fish & Aquaculture Research Station, Dor M.P., 30820 Hof HaCarmel, Israel
Received: 12 December 1990 Revised: 19 June 1991 Accepted: 3 July 1991
Abstract The relationships between cultivated fish species and their environment is largely dependent on the biological characteristics of the fish and the degree of intensification of the culture. In extensive and semi-intensive systems, based on natural production, stocking fish species of different feeding habits together enables a more efficient utilization of pond resources. In polyculture systems only a proper combination of ecologically different species at adequate densities will utilize the available resources efficiently, maximize the synergistic fish-fish and fish-environment relationships and minimize the antagonistic ones. Synergistic interactions among fish species may be explained on the basis of two interrelated processes: increase of food resources and improvement of environmental conditions. Antagonistic interactions occur between incompatible species combinations and when the stocking rates are balanced; in this case, the way the system is affected depends on the food chain level were the imbalance occurs. Several examples of synergism and antagonism at different levels of the food chain are analyzed in this paper. The knowledge of fish-fish and fish-environment quantitative relationships enables choosing adequate combinations of fish species, stocking rates, input types and rates, and other management decisions according to the specific local conditions: climate, quality of water supply and pond fertility, availability of fish fry and fingerlings, availability of feeds and fertilizers, and market requirements.
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