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Everything You Ever Wanted to Know
about EMS in Mexico

Shrimp News Interviews Scott Horton




At the Tenth Central American Aquaculture Symposium (Tegucigalpa, Honduras, August 27–29, 2014), I interviewed, Scott Horton, technical manager at Nutricion Marina, part of Grupo Acuicola Mexicano (GAM), a large, vertically integrated shrimp farming company in Mexico.  After the interview, Scott forwarded more information on the EMS situation in Mexico, and that information has been incorporated into this report.


Shrimp News: What is your official title and job?


Scott Horton: Technical Manager for Nutrimar, which is part of Grupo Acuicola Mexicano.  We’re a vertically integrated company that has a genetic program, broodstock facilities, shrimp hatchery, farms, client farms, a processing plant and a feed mill licensed to use Zeigler’s technology and feed formulas for shrimp in Mexico.  We also sell shrimp hatchery and growout feed and postlarvae to other farms, and offer financing, insurance and consulting services.  We’re the only vertically integrated shrimp farming company in Mexico.



Our hatchery produces a high-growth line of animals that is working very well for us on certain farms.  We have two farms on the Baja Peninsula.  Granmar on the Pacific Coast has 350 hectares of ponds, with another 200 under construction right now.  It’s a high-density, semi-intensive farm, stocking 40 to 50 postlarvae (PLs) per hectare.  Sureño, the other Baja farm, is on the Sea of Cortez, on the other side of the peninsula.  It has 145 hectares of intensive ponds, stocked at 125 PLs per square meter and producing 28 metric tons of shrimp per hectare.  The hatchery is also located in Baja, but at a separate site for biosecurity reasons.  There are no reported cases of EMS on the Baja Peninsula.  The Baja peninsula had been relatively free of WSSV but outbreaks are becoming more frequent.  Our Sureño farm has remained free of WSSV.


Our company also has two farms on the mainland: one in Sinaloa, a seventy-seven-hectare, experimental farm; and one in Sonora, also a small farm.  In 2013, our farms in Sinaloa and Sonora got clobbered by EMS.  At the beginning of 2014, we experienced poor survival then switched to using postlarvae from the Ecuadorian lines produced by Primo Broodstock in Texas and cultured by the  Genitech hatchery in Sonora.  From direct stocking, these animals reached 30 grams at 20 weeks with 65% survival and a feed conversion ratio of 1.6.


We are building two new farms in the state of Colima.  They will have intensive, biosecure, three-phase systems.


Shrimp News: On September 14–16, 2014, Hurricane Odile blew up the west coast of the Baja Peninsula.  Were you there when it hit?  How did it affect your farms?


The hurricane hit Cabo San Lucas on the southern tip of the Baja Peninsula and then crossed over to the Sea of Cortez.  Our farm on the Pacific side was undamaged. The storm did cause considerable damage at the hatchery.  It is in the process of being repaired. We have taken advantage of the reconstruction to incorporate improvements in the facility.   The Sureño farm was cut off from the outside world for three days and suffered damage to the internal electrical grid.  We were at partial power for several days but lost very little shrimp thanks to the dedication of the workers on-site.  There were no injuries to personal at either site.


Shrimp News: Are you using any live feeds in your hatchery?


Scott Horton: Except for algae, we don’t use any live feeds.  Our maturation facility uses frozen and artificial diets.  The frozen ones are certified before use.  In larva culture we use 50% Artemia that are cooked and frozen for a minimum of seven days and 50% Zeigler’s Artemia replacement called" “EZ Artemia”.  There are several hatcheries in Mexico that are not using live feeds.


At our maturation facility we never bring in animals from ponds; we keep our closed maturation facility completely separated from our farms.  The Mexican Government checks hatcheries on a constant basis for whitespot, IHHN, yellowhead—and all the major shrimp diseases.  If a laboratory is found positive, it has to destroy its broodstock.  There is no government  revision for EMS and no government policy.  However, our hatchery has been checked for EMS by external labs (the University of Arizona Shrimp Pathology Research Lab (USA)  and the Centro de Investigaciones Biológicas del Noroeste S.C. (Mexico) and certified free.


Shrimp News: I’m very interested in the early mortality syndrome (EMS) situation in Mexico.  Is it getting any better?  Are you finding any solutions?


Scott Horton: Last year, I told people that there was light at the end of the tunnel but that it was a speeding freight train coming straight at us.  Now, there seems to be some sunshine at the end of that tunnel.  This year, Mexico brought in a new genetic line of shrimp from Texas Primo Broodstock in the United States.  Even though Primo’s animals are certified as specific pathogen free (SPF) by Dr. Donald Lightner’s lab at the University of Arizona in the United States, they went through the Mexican government’s quarantine system.  The quarantine facilities in use are one in Sonora, one in Monterrey (operated by Dr. Fernando Jimenez at the Universidad Autonoma de Nuevo Leon) and one in La Paz (CIBNOR).  There were two different imports from Primo Broodstock.  A limited number of families was brought in by ANPLAC (shrimp hatchery association) and distributed to six hatcheries. A large number of families was brought in independently to the Genitech lab.   There were some trials done at the end of 2013.  It was too cold to get much information, but it was clear that they were surviving better than the animals coming out of other Mexican hatcheries.  In 2014, many farms in Mexico stocked Primo animals.


The genetic line that we developed in-house (in conjunction with Onelab in Ecuador) with a family selection program using genetic microsatellites was designed for high growth.  With this line, we’ve been able to control whitespot and get growth rates ranging from 1.8 to 2 grams a week.  Our genetic line is not EMS tolerant, so we switched to the genetic line from Primo Broodstock, through Genitech, on our mainland farms.


The graph below compares the general survival curves for large, semi-intensive earthen ponds, without additional protocols.



During 2014, two solutions to the EMS crisis showed good results:


1. Biosecure, high-density farms with lined ponds and tight controls had good success.  Some of them were biofloc farms; some were mixed systems; some kept everything in suspension; some exchanged water; some practiced zero exchange; and some had  center drains.  When managed correctly, they all had some degree of success.


2. The other solution involved genetically improved animals.  I believe that a sustainable success rate is only possible through a combination of one and two.


Over the last 23 years, we’ve been through five shrimp pandemics, with the sixth starting in Asia this year, along with several rounds of minor disease problems, and basically, in the Western Hemisphere, we’re growing shrimp the same way we did 23 years ago, in large, shallow earthen ponds.  EMS is really going to be a game changer.  Five years from now, you’re not going to see the same people in shrimp farming.  Only 10 to 20 percent of the current farms are going to survive.  There’s definitely going to be a shake out in the industry.  The solution is going to be complicated, so right there you’re going to eliminate a lot of people that don’t have the technical capacity or discipline to deal with the problem.  If I said, “Here are the protocols you need to implement to solve this problem”, about 85% to 90% of the farms would not be able to implement them.


Shrimp News: You seem to be doing a lot of work with high densities.  Do you think all of Mexico will eventually switch to high-density farms?


Scott Horton: Yes, I think the industry in Mexico is going to become more intensive and use protected facilities, like greenhouses, to increase biosecurity and prolong the growout season.  EMS is enormously complicated.  If we wait around until the scientists figure out what’s going on with EMS, we’ll all be dead.  Looking at the clues from Asia and what’s already working in Mexico, high densities in controlled environments appear to be the answer.  There has been a movement in Mexico over the last few years to build indoor nursery units to head-start animals to combat whitespot.  As mentioned before, these units have also turned out to be successful in combating EMS.  Animals grown in greenhouses under controlled conditions usually do not get EMS.  Clean pond bottoms, high-quality feeds, high oxygen levels and controlled microbial conditions (bioflocs) all come into play here.


The experts say intensive systems are expensive to build, but if you look at them on a cost-to-produce-a-kilo-of-shrimp basis, they are less expensive that semi-intensive systems.  In 2012, before EMS, the Mexican state of Sinaloa produced 50,000 tons of shrimp in 32,000 hectares of big ponds.  With a hyper-intensive system, you would only need a little over 300 hectares of ponds to produce 50,000 tons of shrimp.


Shrimp News: Can EMS travel through the air?


Scott Horton: Yes, the bacteria can be carried on water particles in the air.  We’ve seen cases of ponds that were downwind from EMS-infected ponds break with the disease.


Shrimp News: What mistakes are the farmers making?


Scott Horton: A lot of Mexican farms use disinfectants to prevent disease.  The disinfectants kill off some of the bacteria types, but Vibrio bacteria are the first to recover.  They are opportunistic.  The reproduction time for Vibrios is one or two hours.  The disinfectants are only good for a couple of minutes, so they’re not the answer.  Antibiotics are not the answer, either.  The Vibrios are there, and we have to keep them in check with balanced systems.


Shrimp News: What are some of things that are working to control EMS in Mexico?


Scott Horton: We’re still climbing the learning curve on EMS, but in general, intensive growout systems are EMS free!  In large earthen ponds, it’s much more challenging to get something to work against EMS.  In all of Mexico right now, there’s probably not more than twenty-five hectares of super-intensive growout facilities.  Most of them are one-hectare or one-and-a-half-hectare farms.  None of them, however, has problems with EMS.  The pioneers and visionaries in Mexico who did intensive systems this year were not really sure that they would work, but when other farmers learn that they were successful, you’re going to see more and more people using them.


Right now, shrimp farmers are taking a shotgun approach to EMS, trying anything that sounds logical to find something that works.  Some farms have experimented with frequent water exchanges or water exchanges and then recirculation, and that seems to work against EMS.  I think it works because they’re washing the bottom of the pond clean.


There’s also a lot of interest in using systems that include tilapia, in the hope that the tilapia will stabilize the water quality.  Some of these systems have gotten pretty good results against EMS.  There’s a correlation between blue-green algae and EMS; tilapia reduce the number of blue-greens and encourage the growth of green and brown algae.  The tilapia are generally not in contact with the shrimp; they are in the reservoirs from which the shrimp ponds get their water, or they are in cages within the shrimp ponds.  This practice is not in use but will be on several farms in 2015.


Shrimp News: Does that suggest that the bacterium that causes EMS, Vibrio parahaemolyticus, likes higher salinities?


Scott Horton: Yes.  In the state of Colima, they have a small, intensive shrimp farming industry with about 200 hectares of ponds.  The farms there are small, and all of them use low-salinity well water.  The growth of Vibrios seems to be stunted at salinities below six parts per thousand (PPT), and below two ppt, they just disappear.  Those farms have been successful in preventing EMS.  In Sonora, there’s a farm about two kilometers inland from the coast that’s working with well water at salinities of seven to ten parts per thousand.  At those salinity levels, Vibrio will still grow, and the farm has had some problems, but it has been successful using square, earthen ponds and well water.  Most of the farms in Mexico don’t have the option of working with lower salinities.  Most of the farms, in fact almost all of the farms, are working with high salinities because they have no other choice.


Shrimp News: A couple of times you’ve mentioned clean pond bottom conditions as an important factor in preventing EMS.  How important do you think that is?


Scott Horton: The problem is the pond bottom, not the water column.  I’ve seen data from farms that show the occurrence of flood tides, which tend to stir up the bottoms of shrimp ponds.  Whenever that happens, they have problems with EMS.  Vibrios like bottom conditions; they like substrate and they like the shells of shrimp.  In fact Vibrio parahaemolyticus attaches itself to the chitinous portions of the shrimp’s esophagus, and that’s where it releases the toxins that kill the shrimp.  Only after it’s been there for awhile will it infect the hepatopancreas as a secondary infection.


I’ve learned recently that other bacteria can produce the same toxin that Vibrio parahaemolyticus produces.  The gene within V. parahaemolyticus that produces the toxin is in a plasmid and that plasmid can be transferred to other bacteria by bacteriophages.  There are many strains of parahaemolyticus, some toxic, some not, and some are more toxic than others.  Some are toxic today and not tomorrow.  I learn more every day, but the more I learn, the less I understand.


There are certain organisms, for example, rotifers and the larvae of mollusks, that are bio-concentrators of Vibrios.  That’s why it’s important to eliminate or reduce them before stocking a pond with shrimp.


Shrimp News: The Mexican shrimp farming industry got hit hard by EMS in 2013 and again in 2014.  Did it to anything different in 2014?


Scott Horton: In 2014, a majority of shrimp farmers in Mexico did not change anything.  They followed the same procedures that they used in 2013.  Einstein once said something like, “If you don’t change something, you can’t expect a different outcome.”  In 2014, farmers restocked, and they really didn’t do anything different, and again they got hit very hard by disease.  It looks to me like Mexico will produce the same amount of shrimp in 2014 that it produced in 2013.


Some groups had the conviction, courage and money to close their large, semi-intensive farms because they knew what they were doing was not working.  No one knew that the genetic line from Primo would have the success that it is having.  Some farmers did build new, intensive systems, and almost a hundred percent of them were successful in controlling EMS.  Once you go to high density and plastic bottoms, you’re able to keep the bottom clean, and that takes you a long way toward avoiding EMS.  I also think oxygen plays a big role in preventing EMS.  If you keep the oxygen level above three or four per million around the clock, you have a much better chance against EMS.


Shrimp News: Thailand has small intensive farms, and it’s having huge problems with EMS.  Why do you think the same thing is not going to happen to intensive shrimp farms in Mexico, Guatemala and the rest of Central America?


Scott Horton: I don’t have a good answer for that.  Overall, Thailand and Vietnam are not controlling EMS.  However, there are success stories.  Farms in Thailand that have subdivided ponds down to a size of under 3,000 square meters  and applied good management practices with good quality PLs are successful.  In Vietnam there is a zone where the farms use small, intensive, lined ponds, good genetics, good quality PLs, excellent feeding protocols, and well water.  These farms implemented this strategy ten years ago and have never known WSSV or EMS!


Shrimp News: Before taking your current position with Grupo Acuicola Mexicano, you farmed shrimp in Guatemala.  I understand that the farmers there are not having problems with EMS.  What can we learn from them?


Scott Horton: The big shrimp farms in Guatemala went from almost 100 percent semi-intensive farming to 100 percent intensive farming.  The original farms were semi-intensive and they subdivided their ponds and went intensive.  I read something the other day that said Guatemala’s production levels per hectare were the highest in the world.  I was at the same company and with the same people (Jose Luis Valdes, President of the Tecojate Group) in Guatemala for twenty years, and we went from a fifty-hectare, semi-intensive farm to five farms (and a hatchery) covering 550 hectares that were completely intensive.  In the last year that I worked for the company, we produced about 24 million pounds of shrimp.


Interestingly, a new wave of small-scale intensive farms has established a foothold in Guatemala.  They are generally 1,000 to 3,000-square-meter farms, using plastic lined ponds and lots of aeration.  There are now about 100 hectares of these new intensive farms that produce fifteen to eighteen tons per hectare per crop.  In Mexico, I am involved on a project with a social group, the UGOCP, and working with funds from the Mexican Government (CONAPESCA, FIRA), and financing for operations through Nutrimar, to build a small Guatemalan-style production facility to show that the technology for intensive culture can prevent the EMS problem, work in Mexico, and be duplicated on many sites.  The facility will be used to certify biologists in this type of production.  It’s in conjunction with the social sector in Mexico, the ejidos (farms that were built by the  government and given to rural groups of individuals).  We were looking for a solution that the ejidos could use to restructure their large extensive and semi-intensive farms, which have become obsolete and a waste of money.  The best option for them is to build small, intensive farms with plastic-lined ponds.  The new, small-scale, intensive shrimp farming industry in Guatemala is in the hands of people who are not highly trained or educated, and they are succeeding.  The farms are relatively inexpensive to build and they work.


Guatemala has gone intensive for a number of reasons: land is expensive, it doesn't have the broad estuary areas for farm construction, security is a problem and theft is a big issue.  When land is expensive, the shrimp farmer is pushed in the direction of intensive farming.  If the footprint of a farm is small, security costs per hectare go down dramatically.


Shrimp News: How come I never hear anything about security problems on shrimp farms in Mexico?


Scott Horton: It happens, but it’s so limited that almost nobody has security guards on shrimp farms.  They might have a night watchman or two, but in general, farms don’t even have fences around them.  The new hyper-intensive farms have fences around them, but they’re more for biosecurity than anything else.  In the future, I think you’ll hear more about thievery in Mexico because when you have so much high-value shrimp concentrated in a small space, you’re going to have to protect it from the bad guys.


In conclusion, Mexico is fast coming to grips with solutions for EMS.  Lack of financing (not available, not affordable) is a major constraint.  However, Mexico has the tools at hand to quickly recover its place as a world leader in farmed shrimp production.


We need honesty and collaboration.  We need to analyze our successes and failures to gain a better understanding of what needs to be changed.   We need research dealing with not only the bacteria but also with the ecosystem, the role of blue-greens and the bioconcentrators.  We need better feeds, feeding methods and additives.  We need to learn more about using probiotics.


And finally, we need to think and to question everything!


Information: Scott Edward Horton.  Nutrimar (Km 6.5, Carr. Fed. Libre, Los Mochis, Mexico, phone 52-668-817-5471, mobile 52-668-137-0112,  company email scott.horton@gpbo.com.mx, private email guategringo@gmail.com, webpage http://www.grupoacuicolamexicano.com.mx).


Sources: 1. Scott Edward Horton.  Interview by Bob Rosenberry, Shrimp News International.  Tegucigalpa, Honduras.  August 28, 2014.  2. The Tenth Central American Aquaculture Symposium (Tegucigalpa, Honduras, August 27–29, 2014).  EMS in Mexico: Situación Actual, Avances in Concocimiento y Casos de Éxito.  Scott Horton.  August 29, 2014. 3. EMS/AHPNS/ in Mexico.  Scott Edward Horton and Craig Browdy. International Forum on Aquaculture, Latin American Chapter, WAS, Guadalajara, Mexico, November 5-7, 2014. 4. Bob Rosenberry, Shrimp News International, November 25, 2014.

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