Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Tilapia source near Iowa Missouri border?

Good question, Dave. I don't know why all the research checked noted them as zooplankton foragers...they don't spit out the veges, do they?

IIRC it has to do with the size of particles the paddlefish gillrakers can filter. They filter out the "larger" zooplankton while the phytoplankton is typically too small to be retained and passes thru. So I guess you might say, in a round about way, they actually do spit out the veggies.

I also think some of the small zooplankton will pass through - size filtering selection based on the paddlefish filtering mechanics. Particle size retention by paddlefish has probably been researched. Don't forget protozoans and rotifers are also part of the zooplankton community.

I sent an email to Alan Johnson, as suggested above. Here was his response:

"Dear Mr Perrin,
To write a response to your question about stocking tilapia into your farm pond in Iowa to control filamentous algae I have consulted Fisheries Chief Joe Larscheid and my supervisor Jay Rudacille. We understand the temperature tolerance of tilapia. However Joe stated that stocking tilapia into Iowa�s waters will not be allowed under any condition.

There is a lack of scientific data on the effects of tilapia as a management tool for farm ponds. Digestion of the filamentous algae will release the nutrients bound in them, likely causing more single-celled algae to bloom causing water to become green. Tilapia may diminish the filamentous algae then turn to other food sources which could compete with the other game fish in the pond, example would be consumption of zooplankton important to larval bass and bluegill. If the tilapia did result in a population of large bass, when the tilapia die there would be no forage until tilapia are restocked and spawn again.

Use of the bass and bluegill system with removal of bluegill by angling can result in the large bass you seek. Contact your local fisheries biologist to discuss pond management techniques further.

Sincerely,
Alan

J. Alan Johnson | Natural Resource Biologist
Iowa Department of Natural Resources
P 641-647-2658 | F 641-647-2690 | 15053 Hatchery Place, Moravia, IA 52571
www.iowadnr.gov"

It was curious to see that Fisheries Chief Joe Larscheid stated
"stocking tilapia into Iowa�s waters will not be allowed under any condition." Doesn't seem very scientific. Must be some political issue here I am unaware of. I did also send an email to Iowa State University, which has a wildlife R&D department (and fisheries program), regarding research on tilapia and FA. I await a response.

ok, I got an email about the research just after posting. Here was the response:

"Good morning!

Thank you for your email. I will pass it along to our scientists. I�m also passing it along to our Fisheries Extension Biologist, Allen Pattillo. Allen is out of the office on vacation at the moment, so he won�t respond immediately, however he can be reached at [email protected] or 515-294-8616 when he returns.

Have a great day!

USGS
Iowa Cooperative Fish & Wildlife Research Unit
Iowa State University | 338 Science II | 2310 Pammel Drive | Ames, IA 50011
[email protected]
www.cfwru.iastate.edu"

A bit more hopeful response here. I will try and contact Allen Pattillo as well. I would suggest another other Iowegians with interest in this topic might contact him as well..

Appears that the Iowa Fisheries Chief is talking in absolutes by saying "not be allowed under any condition". Before making such a strong statement, too bad the Iowa DNR can't approach it with an open mind and at least research/look at the other states that do allow Tilapia. Their decision doesn't totally surprise me though, especially considering the invasive species (zebra mussels, asian carp)that they are dealing with right now.

Brad-
I wrote back to Allen J regarding that exact perception. I also asked him if the Iowa DNR had ever discussed this with neighboring states that DO allow tilapia, to learn from their actual experience. I would have to defer to Bill Cody and others regarding his premise about algal blooms resulting from tilapia, but it seems a weak argument.

But what about those BOW with an established forage base, like mine, with BG and BCP? Another topic of research: comparison of (new) pond lacking established forage base vs. established pond with forage base, and the effect of tilapia as FA control on other algal species growth..

Umm... not so sure about the removing BG part to get big bass.

Agreed Bocomo.

I've wondered the same thing regarding digestion of algae....don't tilapia poop? And it seems there have been a few posts of late regarding the absence of floaters after the water cools. How can one be sure that all those dead tilapia aren't decomposing on the bottom, out of the reach of terrestrial predators, releasing all those consumed nutrients back into the pond?

Are Tilapia a solution that once implemented, need to be continously stocked from that point on, or do they ever get "done??" With the job?

I think Tp are like most everything else, +'s and -'s. Last year I had a pond full of them and could catch them using a fly rod around the feeders. I thought they were good eating with out that strong fish taste that some fish have. But this year I did not have so many in the pond and I did not catch a single one this year.

Sprkplug
I think TP are just another tool in the toolbox, potentially. I could see them as a way to break the viscous cycle of FA, by having nutrients in the form of FA converted to TP instead vs just having FA die and sink to the bottom, only to start again. Like Tracy says, pluses and minuses to everything. I don't really have a dog (? fish) in this fight, but the science (or lack of it) has my curiosity peaked. There are some really awesome, detailed threads in this forum on biomass, which is part of what this discussion is coming down to.

So, I got a response back from Iowa State University, regarding tilapia research:
---------------------------
"Mr. Perrin,

Your email came to me from the Iowa COOP unit for possible input.

There have a been some studies done on the use of tilapia for filamentous algae control as well as alternative prey base for largemouth bass in southern states. While the smaller tilapia have been able to consume the algae, complete control has not always been possible due to the inherent fertility of the pond as well as algae�s growth rate. In addition, complete algae control will not in itself cure the pond fertility issues as other forms of plankton or vascular plant can still take place as the nutrients will remain in place. Tilapia use as an alternative prey base has not always been successful for a number of reasons.

As for Tilapia not being legal in Iowa, agency staff are cautious about possible impacts of non-native fish on the native ecosystem. Some state agencies have not shared this same concern. For myself, I did my earlier graduate work on grass carp for vegetation control in Texas. At the time, we were informed that this fish would not be able to reproduce in Texas streams due to salinity and water flow requirement. Unfortunately, this species has been able to reproduce in waterways not considered as spawning opportunities based on earlier research. Thus, some state agencies have taken a very conservative approach to the use of any non-native species in management due to unforeseen consequences.

Sincerely,
Joe

Joseph E. Morris, Professor � Natural Resource Ecology and Management (NREM)
Director � North Central Regional Aquaculture Center (NCRAC)
339 Science II, Iowa State University
Ames, IA 50011-3221"
----------------------------
Another rather tepid response. I get the impression they think I am looking for tilapia to be a 'cure all' for FA. When I wrote him back, my response was that tilapia could be part of a complete plan for FA management. But, given the above responses, I think I'll just let this issue go.

Wow, I haven't checked in here for a while! Good to see other Iowans are interested and taking the time to reach out to the DNR. I find it interesting that Alan reached out to his supervisor, must be getting a few more questions about Tilapia lately! It's too bad Joe Larscheid is basically saying it'll never happen. It seems the Iowa DNR just isn't what it used to be. Not sure if it's political or financial pressure but I used to consider us one of the best in the country. I, and hopefully others, will continue to contact the DNR and try and do our part.

sorry Dr. Luke you have to deal with such non-sense.