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Copepods and Early Mortality Syndrome

 

Daniel Gruenberg (seagardenfoods@mac.com): I want it to be clear about one thing: copepods are far and away the best feed for penaeid shrimp larvae and postlarvae.  They are the “gold standard”.  All other larval feeds are measured against them.  Both Penaeus monodon and P. vannamei fed copepods show superior pigmentation, growth and survival compared to alternative feed sources.  Providing a cost-effective and stable supply of copepods for shrimp hatcheries is the “holy grail” of penaeid larvae nutrition.

 

I have been feeding copepod nauplii to postlarvae (PLs) shrimp for many years.  Many times we see tiny PLs with a copepod in each cheliped.  Copepods may be speedy, but they can only travel some hundreds of microns at a time.  Shrimp become detritivores in their later life stages, but PLs like live foods, and they are extremely efficient predators of copepod nauplii.

 

Laurence Evans (ecotao@yahoo.com): Hi Daniel, I would like to know how to select for the development of large numbers of copepods in new ponds?  If copepod production in new ponds could be developed to a repeatable and transferable technology, it could be very beneficial for the shrimp farming industry.

 

Daniel Gruenberg (seagardenfoods@mac.com): Lawrence, I have fought a long battle trying to convince shrimp hatcheries and shrimp farmers of the benefits of copepods.  If you are already convinced of the benefits of copepods, I would be willing to send you a sample of a product that can consistently result in a significant bloom of copepods in your shrimp ponds.  Contact me directly for more details.

 

Although copepod blooms are difficult to manage in open ponds, they are part of our complete concept of “natural pond management” or NPM. Despite some major successes at large farms, in the past, I find it difficult to convince farmers of the significant benefits of copepods in shrimp farming.

 

Recently, we begun to make some new strides in this regard, and now we have set up a demonstration farm (currently only 12 days into the growout cycle) to specifically model our NPM concept of aeration and feed control.  This pond is lined, but the concept works in all soil types.

 

Our technology was originally developed for certified organic production, but now we are trying to promote it more broadly as simply a better and more economical way to produce shrimp sustainably.

 

We would like to help more farmers learn the natural way to grow shrimp without lime, dipthrex, copper sulphate, chlorine, antibiotics and a host of other toxic chemicals that a put in ponds, so that shrimp farmers can achieve consistent, high quality harvests with reduced feed conversion ratios, better quality and lower costs of production.

 

If I ever find the time to get our new website up and running, I plan to post all our information on natural pond management there.

 

Here’s a little tidbit: On the farm where I’m doing my demonstration, the owner and managers knew the benefits of copepods, but followed C.P. Foods’ strategy of killing everything in the pond first, which resulted in plankton blooms that varied qualitatively and quantitatively, even in adjacent ponds during the same crop.  I assured the demonstration farm that I could create copepods for them, but they were skeptical.  Then the farmer’s brother, who operates a tilapia operation, developed problems with blue-green algae, while working with a different water source with a salinity around four parts per thousand.  I fertilized one of his low-salinity, tilapia ponds, and after four days, it looked like an Artemia tank, but instead of Artemia, it was full of copepod nauplii.  Microscopic examination of the water revealed massive amounts of diatoms (Chaetoceros sp.).  Oh, and the blue-green algae also disappeared!

 

It convinced the shrimp farmer to follow our natural pond management (NPM) concept.  I am quite confident that I can create copepods for you in any pond!

 

Louis Botero (botero_fernando@yahoo.com): I just remembered an interesting and very intriguing event that occurred around 27 years ago.  On very rare occasions, we would find extraordinary blooms of copepods in some of the ponds at our brackish water shrimp farm in Cartagena, Colombia.  The lucky shrimp in those ponds would show extraordinary growth; it did not take advanced science to conclude that it was the huge copepod populations that were causing such amazing results.  The events would drive our biologists crazy because they could not explain why the explosion of copepods happened.  We missed a great opportunity to do the research and write some new science!

 

Larry Drazba (ldrazba@ibw.com.ni): It is our experience that dense copepod blooms promote extraordinary shrimp growth in pre-adult shrimp.  The animals actually turn upside down (pleopods and pereiopods toward the water surface) to harvest them.  For many years, before whitespot became a big problem, we used simple organic fertilizers like wastes from flourmills and occasionally rice wastes to promote the copepod blooms.  We suspended the practice for some years because we were afraid that copepods were active whitespot carriers because they show positive for whitespot in PCR tests for about 5-10 days after stocking.  More recently, we were informed that they are only passive carriers, and if we waited five days after stocking, they were not a threat.  We resumed using organic fertilizing several years back.

 

Daniel Gruenberg (seagardenfoods@mac.com): Yes Larry, each cheliped grasps one copepod and these animals multitask quite well as one cheliped moves the copepod to the mouth, another is poised to grab one from the water column.  It’s really an amazing thing to watch.

 

You bring up an excellent point, and it was the arrival of the whitespot virus (WSSV) that put the wrench in the gears for our NPM method of shrimp farming.  What I contend now and did so then was that presence of WSSV is not something to panic over.  We would find WSSV in our P. monodon ponds, but had less than 2% mortalities over hundreds of crops.

 

This is why I have been telling everybody that they are looking at the wrong side of the equation when they kill everything in the pond before stocking.  In an open pond system, it’s ludicrous to think that your can maintain relative sterility over the growout cycle.  The virus is there, and modern diagnostic tools can find it, but that doesn’t mean the animals will break with the disease.  I am happy to see that I’m not the only one who has recognized the “passive carrier” principle!

 

We like to use inorganic fertilizers because they are “clean” and don’t present any additional benthic loads for the pond.  Our results are consistent.  We typically prepare our ponds with 30 kilograms per hectare of ammonium (NH4-N) and about half that much phosphorus pentoxide (P2O5).  Micronutrients are added to achieve diatom/copepod blooms, followed by weekly additions to manage them.

 

I used to grow P. monodon at low, semi-intensive densities of 15 to 20 postlarvae stocked per square meter, and sometimes they reached 10 grams in 30 days.  When I did this at the Thai Department of Fisheries (DOF) ponds, the DOF scientist, who is now my good friend, asked if I had purchased larger animals and put them in the pond at night to make myself look good!  We look back at that and laugh about it these days.  Now that I have found a good source of P. monodon SPF broodstock, I am seriously looking forward to trying it again.

 

Hank Bauman (hank_bauman55@yahoo.com): Daniel does seem to be onto something here.  So, in the prevention of EMS/AHPNS, is it the nutritional benefit of the copepods that prevents the disease?  Or is it the fast growth of the juvenile shrimp?  Or does the presence of massive amounts of copepods indicate an environment that is unsuitable for Vibrio parahaemolyticus, and/or the “turning-on” phase of the phages that cause the toxin production?

 

The fact that polyculturing shrimp with tilapia has a positive effect on EMS seems to indicate that creating an environment not suitable for V. parahaemolyticus and/or the phage may be the key.

 

Daniel Gruenberg (seagardenfoods@mac.com): Hank, of course I cannot be certain and have been known to be wrong now and then, but it is my belief that the copepod system is helping with EMS on multiple levels, most of which you correctly pointed out with your excellent questions.

 

So far, I have had no takers on EMS affected farms wanting to try my free samples.  I guess they don’t read this list or I don’t have enough credibility yet, but as you mentioned there are more ways than one to skin this cat.

 

If test results from our feed come back positive, we intend to market our anti-EMS feed product along with our micronutrients as not just an EMS solution but as an overall shrimp health solution and hopefully a new paradigm for shrimp farming.

 

Larry Drazba (ldrazba@ibw.com.ni): I am convinced that out competing the pathogens is our principal concern.  Out competing them can mean many things as Daniel has pointed out.   Promoting a “better” pond environment is one of them.  A better pond environment can mean more plentiful nutritive feeds, biological exclusion of pathogens, zero exchange biofloc systems—and I am sure there are others.  In its most extreme form, it was the “kill everything” concept (somebody else’s term) that was very successful and profitable for many years.  The kill everything approach has at least one major drawback.  When you kill everything you have to replace it quickly with something else that is pathogen excluding or you will have given all the opportunistic bad algae and bad bacteria free rein and left yourself open to ponds that crash.  If the system that you are developing is as easy to cookbook as the kill everything system—fantastic!  If not, we have been looking for systems to guarantee pond succession for many years and we are obviously not there yet.

 

Durwood Dugger (ddugger@biocepts.com): I’m following this discussion on copepods.  For those of you that participate in the Linkedin discussion groups, I have started a group there on Economically Optimized Integrated Species in Recirculating Aquaculture Systems, where similar discussions would be appropriate.

 

Hank Bauman (hank_bauman55@yahoo.com): Is it possible that the “kill everything” concept can still work?  Before EMS/APHNS, the first organisms to populate the pond after chlorination were at worst blue-green algae, which resulted in slower shrimp growth. That’s what we observed at Belize Aquaculture back in 2002-2003.  But now, it may be that V. parahaemolyticus may be one of the first organisms to populate a pond after everything else has been killed.  Unless, as mentioned by Larry, you quickly seed it with known beneficial plankton, flock, or whatever.

 

However, if you “kill everything” and let it settle before pumping to your culture pond you won’t have all the organic fertilizer from the dead organisms left in the pond bottom.  If I merely chlorinated and pumped in water to our hatchery without filtration, it wouldn’t work at all.  I believe most “kill everything” type operators are doing this in the growout pond.  If they are pumping in mangrove or plankton rich water, there will be a lot of dead flock on the pond bottom.  It’s only feed for other organisms at that point.

 

And yes, we have been looking for the “magic formula” for years.  But fortunately up to now the consequences of missing the bulls-eye haven’t been too devastating, except for the necessary adjustments to new viral attacks.

 

Dallas Weaver (deweaver@mac.com): All the “kill everything” approaches are crapshoots unless you immediately seed the pond with desirable organisms.  In my recycle systems for larval fish, I would wash the walls of a new tank with a concentrated solution of hydrogen peroxide (HCL/H2O2), and fill it with sand-filtered, biofiltered, UV-treated water.  There was nothing living in the water after this treatment.  I would then aerate the tank and feed it a variety of plant and fungal-based protein and general biomass full of bacteria and protozoans, but no vertebrates, to create a stable decomposing ecology.  I measured and controlled oxidation, pH, dissolve oxygen, ammonia, the carbon:nitrogen ratio and volatile suspended solids.  Adding general biomass to the clean tank stopped the crapshoot problem.  The walls of the clean tank became colonized in less than 24 hours and competitively suppressed pathogen transmission.  The protozoans in the culture that were eating bacteria would also eat any opportunist or obligate pathogens that accidentally entered the system.  It became an instant diverse microbiological ecology.

 

Larry Drazba (ldrazba@ibw.com.ni): Basically, in aquaculture systems, there are two approaches. The first approach is to dry out, sanitize and sterilize and then harvest as soon as possible. The other approach is more “homeopathic”: you let everything get dirty, let nature bring the system into equilibrium, and then run it until it crashes. It appears that both systems are affected by EMS.

 

Since the early days of the Waddell Mariculture Center in South Carolina, USA, and Belize Aquaculture, Ltd., in Belize, we have learned that using pond water from successful ponds—“conditioned water”— produces successful crops. Why then, as Dallas Weaver (above) suggested, didn’t a market for conditioned water or specific pathogen free biofloc develop to inoculate new ponds?

 

Daniel Gruenberg (seagardenfoods@mac.com): The key is diatoms.  They have a profound effect on the microbiology of the pond water and benthos as well as the zooplankton.  It is not just the bacteria that are the issue.  If you have diatoms and copepods, everything else falls into place.  It is not quite that simple but close.

 

Dallas is referring to a recirculating aquaculture system, not an open pond.  I contend that if you have that much trouble controlling the microbiology of a relatively closed system, the idea that you can even get close to that in an open pond system is ludicrous.

 

Again, anyone that doubts the power of copepods and diatoms, I will send you some samples to create them your ponds, with the request that you report your results back to the list.

 

Bernhard (redbee@cyberni.de): Daniel, please send me some samples.

 

Source: 1. The Shrimp List (a mailing list for shrimp farmers).  Subject: Copepods.  June 6 to 8, 2013. 2. Bob Rosenberry, Shrimp News International, June 9, 2013

 

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