David Flushing

David Flushing (retired) in a T-6 Texan Navy Trainer, about to perform some aerial acrobatics.


David Flushing worked at Ralston Purina for nineteen years, seven of them at the Agromarina de Panama shrimp farm in Aguadulce, Panama, where he eventually became Director of Operations (Gerente de Operaciones). His recollections provide an interesting look at some of the non-biological challenges of developing a successful shrimp farm in Latin America during the 1970s and early 1980s.


Shrimp News: How did you get started in mariculture and shrimp farming?


David Flushing: I was fascinated by biology ever since I can remember and by marine biology, in particular.  I grew up next to the ocean and amassed a large collection of marine specimens from the shoreline and while snorkeling.  I've had numerous saltwater aquariums for as long as I can remember.  I won the science award at my 6th, 9th and 12th grade graduations and a marine science scholarship for a summer at the Woods Hole Oceanographic Institution.  Becoming a marine biologist was what I wanted to be, and I never gave a thought to anything else.



David Flushing at Vera Cruz Hatchery in March 1975

My professional career in mariculture began in June 1968 when I was a marine biologist working for Inmont Chemical in Northport, Long Island, New York, USA.  Long Island Oyster Farms, Inc. (LIOF) was a subsidiary of Inmont and was aggressively developing a commercially viable oyster (Crassostrea virginica) farming business.  In addition to oysters, LIOF developed commercial clam culture (Mercenaria mercenaria) and experimented with commercially growing scallops (Argopecten irradians) and shrimp (Penaeus monodon).  By 1969, I was doing field research year-round in Long Island Sound studying oyster and clam growth, causes of winter mortality, oyster and clam predator biology and efficacy of predator control methods.  This multifaceted practical field research involved daily dives to the bottom of the sound and often times under the ice floe.  In 1970, I became involved in the start-up of a new oyster hatchery built on Long Island Lighting Company's new coal-powered electric power generating station's warm water effluent lagoon in Northport, New York..  In 1971, I was involved with the development of a patented automated oyster-opening machine.  I subsequently started up a commercial production facility using six of these machines to process fresh oysters into a variety of ready-to-cook and serve-on-the-half-shell frozen entrees for the restaurant trade.


In 1972, I worked for OMI (Oceanography Mariculture Industries) in Riviera Beach, Florida, researching the culture of Florida pompano (Tachinotus carolinus), Malaysian prawns (Macrobrachium rosenbergii) and lobster (Homarus americanus).  In 1973, I moved to the Dominican Republic to help oversee construction and start-up a new commercial-scale, fully integrated, high-density culture, pompano-production facility for OMI.


In 1974, I interviewed with Harvey Persyn, Dr. Bill MacGrath and Dennis Zensen for a position with Ralston Purina's Mariculture Research Center in Crystal River, Florida.  I became involved with almost everything from feeding studies, diet formulations, water quality, pond management to broodstock sourcing in Apalachicola for maturation studies.  I also supervised the construction and start-up of a postlarvae growth test facility in Vera Cruz,  Panama, and performed survival and growth experiments while training local employees to continue doing them.


Ralston Purina's Crystal Crystal River, Florida, Maricluture Research Center (lower left corner) in 1974


I also had the opportunity to work with over a dozen marine animals including nine different species of shrimp.  But, most importantly, in Crystal River I had the honor of working with folks like Rodney Levins, Randy Aungst, Joe Mountain, Rod Bruce, Harvey Persyn and Ron Wulff, all of whom launched successful careers in shrimp farming based on their experiences in Crystal River.



In 1975, I moved to Aguadulce, Panama, to help manage Ralston Purina's shrimp pilot plant operations at Agromarina de Panama.  In fact, my trip to Aguadulce was also my honeymoon.  My new wife Barbara and I spent our first two months living with as many as seven men in a two bedroom apartment in downtown Aguadulce.  You can only imagine the looks and rumors as eight men left the apartment every morning in this conservative Roman Catholic town.  When our household goods finally arrived two months later, we quickly moved out to a rented house.  I spent seven years in Panama managing or supporting Agromarina's shrimp farming operations.


Shrimp News: Your wife sounds like a good sport.  Tell me a little bit about her.


David Flushing: In 1974 when working for Purina in Crystal River, Barbara, who was my girlfriend at the time, asked me to take care of her freshwater aquarium while she went home for the summer.  I decided to surprise her and added a beautiful freshwater shrimp to her collection of dime-store fish.  Over the next seven weeks, the shrimp systematically killed all of her fish except for one freshwater shark.  When Barbara returned, she was devastated.  She told everyone that she figured a guy who was a marine biologist and had an apartment full of aquariums would at least know how to take care of a few simple fish.  I sheepishly told her it wasn't saltwater. It was embarrassing.  Barbara accepted my proposal for marriage anyway, which was the best thing that ever happened to me—and 37 years later, it still is.  She still tells this story whenever the subject of aquariums arises.



Shrimp News: Tell me about your overall experience working for Ralston Purina in both Crystal River and in Panama for Agromarina.


David Flushing: The professionals I worked with in Crystal River and in Panama were exceptional.  There was a sense of excitement that facilitated both synergy and healthy competition.  Innovation and experimentation were in everyone's blood and we were ecstatic with almost daily discoveries.  Due to our diverse backgrounds and personalities, we studied problems from many different angles, and we were free to try anything that may have had merit.  So things were never boring or routine.  There was no requirement to publish anything (except to apply for selected patents) as we were focused on achieving a profitable business.


Our various backgrounds merged into such a diverse skill set that we never realized how quickly we were advancing shrimp culture technology.  Looking back it was almost magical how quickly and naturally we jumped to the next obstacle, never doubting that it too could be solved.  Not that we always agreed on everything; quite the contrary.  It was often the abundance of hubris and ego that made things work.  It took a lot of work and countless hours, but we all loved what we were doing and we sacrificed more time with our families than we realized or ever intended.


Addison Lawrence 1975

We also reached out and shared information with others in the industry around the world.  I became friends with Dr. Addison Lawrence (Texas A&M University) and others with whom we had long standing symbiotic relationships.  Without these disparate sources of ideas and sharing of research discoveries, we may have slowed down and over analyzed things.  We were constantly looking for and sharing publications that had anything to do with marine species and aquaculture.  Reading these publications was a rich source of ideas to apply to shrimp.  Without resources like the Internet back then, our sources for these publications were mostly limited to our collective network of colleagues and contacts from around the world.




While in Crystal River I had an opportunity to experiment with Macrobrachium rosenbergii (the blue Malaysian Prawn) culture.  We were successful in duplicating the efforts of others in breeding and raising postlarvae.  Ron Wulff and I ran extensive feeding, growth and survival studies for postlarvae and juveniles and harvested adults from one freshwater pond.  I recall becoming unpopular with several of my colleagues when I answered Dennis Zensen's request for a commercial viability assessment of rosenbergii.  The report was not favorable for a number of valid reasons.  We stopped all work on freshwater shrimp a month later.  I reported to Harvey Persyn at the time and fortunately he supported my assessment.


Shrimp News: You mentioned you almost turned down the job at Purina.  Why?


David Flushing: My first meeting with Dennis Zensen, the father of Ralston Purina's success in shrimp farming, was why.  It took three separate interviews over a three week period to be hired by Purina.  When I was asked to fly to St. Louis for a third meeting with the "big guy in the big office", I thought Purina was too bureaucratic.  After Bill MacGrath introduced me to everyone involved with shrimp research and finance in St. Louis, I found myself sitting in a chair in a large office facing a stone-faced gentleman named Dennis Zensen.  Dennis relentlessly quizzed me for almost an hour.  He showed no reaction to my answers and immediately fired off another question that had no relevance to his previous question or my answer.  He volunteered nothing and looked like he would be a formidable poker player.  It was intimidating, and I left his office convinced this was not a place where I wanted to invest my career.


As I left Dennis's office Bill MacGrath anxiously asked me how the interview went, so I told him.  He said don't worry, he's just like that.  I was then asked to wait while Bill MacGrath, Bob Biddlingmeyer and several other direct reports to Dennis went into his office.  A few minutes later they came out and congratulated me.  Dennis was impressed and told them to make an offer to hire me immediately.  They did and I accepted it.  Best impromptu decision reversal I ever made.


I was later informed that my understanding of why the two previous commercial endeavors I worked on were successful, what mistakes were made and why OMI eventually failed to realize a profit is what impressed him.



Dennis Zensen the Father of Modern Shrimp Farming


I quickly learned to respect and admire Dennis's business acumen and insight.  He was always a gentleman whose business vision and managerial style provided us with the financial and technical resources we needed to move forward.  He was involved with every major decision made as we developed Agromarina, yet he was never an obstacle.  Dennis Zensen came up with the Agromarina name in December 1973.  According to Fritz Schwartz, Dennis's business development manager, Dennis used a combination of "agriculture" and "marine."  Agromarina de Panama, S.A. was born.


I'm convinced that without Dennis Zensen at the helm, Agromarina may never have gone past our 85-acre pilot plant in Panama.  Dennis also successfully developed several other unlikely new businesses for Ralston Purina, including a successful mushroom farm that dominated the fresh mushroom retail market in the USA and a hydroponics tropical plant business.  Today, Dennis remains revered by all who were there during Purina's heady days of discovery as the man that enabled it all to happen.


Shrimp News: What do you think were some of the discoveries that proved pivotal to Purina's success in shrimp farming?


David Flushing: Obviously there were a lot of them.  Foremost it was the assemblage of talent, the latitude to explore wherever our discoveries led us and the resources to follow through that allowed us to succeed.  However, three technical discoveries come to mind as truly pivotal.  Maturing and spawning shrimp in captivity involved several key milestones that were only possible due to the skills and keen observations of some very talented and hardworking colleagues.


The singular most significant discovery was Penaeus vannamei’s unlikely potential for commercial shrimp farming.  The story about how Agromarina focused on vannamei has become legend, and as such, it has evolved as memories of the details merge and fade.  My recollections from March 1974 when I joined Purina were recently collaborated with Dave Drennan, Bill More and Ron Staha.  Here is the story as I currently understand it.


Prior to Agromarina, Dave Drennan was Purina’s eyes and ears in Panama.  He enjoyed “hunting” the local waters for gravid shrimp, and he had an amazing knack for finding them.  According to Dave, vannamei, or “patiblanco” as they were known locally, represented only about one to two percent of the shrimp caught in Panama.  The balance of the commercial catch was about 12 to 15% Penaeus stylirostris and about 85% Penaeus occidentalis.  Furthermore, vannamei was a smaller species caught at a deeper depth (45 to 25 feet deeper than occidentalis or stylirostris) and required longer trawls.  It was a commercially insignificant species.  So naturally, little attention was paid to vannamei (too small, too deep and too few).  But a couple of important discoveries in 1971 and 1972 soon changed that.


Here is Dave Drennan's recollection of the first discovery in late 1971:



One day Yosuke Hirono came down to Panama to go out on the shrimp boat.  It was about five o’clock in the afternoon.  After several trawls I pointed out to Yoshi that a female occidentalis didn’t have a spermatophore, but it had glistening gelatinous material adjacent to her thelycum (genitalia) where the spermatophore should be.  That was the awakening that the apparatus used to attach the spermatophore on the female breaks off after mating, especially when the female is manhandled in the trawling net.  So actually a lot more captured females were mated than I had previously thought.  After breaking off, the spermatophore sperm pack was almost invisible, especially in occidentalis.



Previously, capturing mated females for any species of white shrimp was difficult and infrequent.  This discovery led the way for capturing more mated females in the wild, and Dave quickly became very successful in catching and spawning occidentalis and stylirostris as needed to support Purina’s research efforts in Crystal River.


In May of 1972 Dave Drennan decided to try to catch a mated vannamei.  Generally vannamei were not caught in the same areas as occidentalis or stylirostris, so local fisherman advised Dave where he was most likely to catch the largest vannamei specimens.  Armed with this information, one night Dave set out with Captain Hilario, his son Pedroza Hilario and a crewman called Viejo on the M/N Patricia shrimp boat.  They caught the first mated vannamei on the southeast corner of Chepillo Island on a 96-foot drop-off.  Dave observed that the vannamei sperm pack was more of a white translucent color compared to occidentalis and stylirostris, so it was more visible and easier to detect.  Dave caught three mated vannamei that night; one of them became the genesis of a worldwide revolution in shrimp farming.


The three mated females were taken back to the small lab that Dave operated at the Smithsonian Institute’s research station on Naos Island.  That night only one of them spawned.  Dave hatched the fertile eggs and collected the nauplii.  He noted that the vannamei nauplii were different in appearance from the other white shrimp species caught in Panama; they had a distinct reddish spot.  Dave shipped the nauplii to our hatchery in Crystal River, Florida, and asked that they be evaluated.


The Crystal River research team successfully reared these vannamei from nauplii to postlarvae.  Ron Staha and Ron Wulff both recalled that this first batch of vannamei were unremarkable and performed in the hatchery as well as the other species under evaluation.


Harvey Persyn nicknamed them “the red light special” based on how the red spot in the nauplii glowed when viewed under a microscope.  But they were destined to go down the drain because they were just a smaller insignificant species with a very limited source of mated females.  During this period Purina had evaluated 13 penaeid species in the hatchery for possible commercial culture.


Ron Wulff and Harvey Persyn worked together to convince Bill More to let them stock one of our 1/4-acre, lined research ponds with this lesser known, unpromising and commercially inferior species.  Over the next couple months, pond samples indicated a high survival with a rapid and uniform growth rate.  The shrimp were more golden in color than other species—a color that proved to be a good omen.  After about 120 days the pond yielded a calculated 3,960 pounds per acre of 17-to-20-gram shrimp.  This did not seem possible because it was double the yield from previous harvests from the same ponds using other species.  Harvey weighed and checked the harvest several times to make sure there were no errors while Ron Wulff measured and re-measured the surface area of the pond to make sure it was accurate.  Shrimp farming history was made!


It is important to note that no one person was responsible for the discovery of vannamei's suitability for shrimp farming.  A number of people played significant roles in making it happen.  Since it was considered an experiment borne out of curiosity and then opportunity (a pond happened to be available), the pond was not as closely monitored as more promising research on other species and bait shrimp production in the raceways.  Therefore most vivid recollections begin after the harvest when its significance was first appreciated.  Some of the Ralston Purina employees who were involved in this historic discovery are: Dave Drennan (sourcing manager), Ron Staha (hatchery manager), Harvey Persyn (research manager), Ron Wulff, Rodney Levins, Durwood Dugger, Yosuke Hirono and Bill More.


Purina management (Dennis Zensen) quickly became excited and wanted to capitalize on the commercial potential of this discovery.  The search was on for a location to develop a commercial farm while research on vannamei was accelerated in Crystal River.  The results of this research were initially kept quiet because Purina knew we had a winning species that had heretofore escaped serious evaluation.  The rest is fairly well documented shrimp farming history.


In the 1970s vannamei was a curiosity outside of Ralston Purina and was not actively farmed.  Today it is estimated that over 95% of the farmed shrimp in Latin America and over 80% of the shrimp farmed worldwide are vannamei.  According to the Food and Agriculture Organization's Data and Statistics Unit, the farming of vannamei in 2010 exceeded three million tons with a wholesale value of 23 billion dollars.  The total global economic impact is far greater.  That's quite a legacy for the Purina Pioneers that helped take vannamei from insignificance in the 1970s to the predominate commercially farmed species 35 years later.


Members of the Team That First Raised Penaeus vannamei in Captivity
David Drennen 1975 Ron Staha 1975 Harvey Persyn 1975


The second pivotal discovery was eye ablation.  The unexpected vannamei yield and survival rate in Crystal River immediately focused Purina's attention on this little lesser known shrimp.  Due to continued difficulties in capturing mated vannamei, the Crystal River team focused on maturation of females.  A review of published literature indicated that eye ablation in other crustaceans could induce maturation.  Ablating both eyestalks did induce maturation, but survival rates were low.  Then in January 1975 a shrimp with only one ablated eye matured.  I recall Joe Mountain being ecstatic about this, so I took a quick photo of the now famous female.  She spawned and the first nauplii from a shrimp matured in captivity were born.  (I wonder why we never named her?)


The third key discovery was the use of polychaete worms in our maturation broodstock diet.  Joe Mountain traveled to Tahiti to follow up on a report that the French had achieved monodon maturation in captivity.  Joe observed the use of the gonads from a local mollusk from the Trochidae family, probably Trochus niloticus.  The female of this species is a popular source of food in Tahiti and the Philippines and was readily available.  The following is Joe's account:



My trip to Tahiti demonstrated the benefits of adding the female gonadal material from a univalve mollusk called "Trocha" (also called "top shells", used in making pearl buttons for clothing) to the diet of monodon to greatly improve maturation.  When I returned to Panama I began looking for other local dietary supplements to add to the evolving maturation diet we were using: frozen Artemia, oysters and squid. Dave Drennan told me that local fishermen used two types of worms as bait—white worms and red (blood) worms.  One of our night watchmen (Batista, a big and really nice guy) made arrangements for us to try some worms.  We received some bloodworms (tripas de sangre) and the first time I fed them to our broodstock the reaction was amazing.  The shrimp were literally fighting over a worm!


The way the local worm collectors caught the bloodworms was using a bicycle air pump with one end of the airline inserted into the freshly cut-off end of the protruding worm case which was visible at low tide.  One man would put down a piece of flat material on which the pump was placed, and then he would start pumping.  Seconds later the worm would seem to fly out of the other (hidden) end of the tube.  The second member of the two-man team would then collect the worm.  I never did get to try the white worm.



Joe eventually created a small local worming business in Vera Cruz with dozens of entrepreneurs harvesting worms for our maturation program (we were their closest customer and probably paid more for them than the fishing bait industry, but we never ran out of them and had access to exactly what we needed).  Joe Mountain was soon operating 50 maturation tanks, and his hoards of amorous females consumed polychaetes voraciously.  Joe really loved his job, and it showed in everything he did.


I vividly recall scouring over a dozen stores in south Florida to buy all the bicycle pumps I could find as Joe and his wormers had unexpectedly exhausted the supply of bicycle pumps in Panama.  I must have appeared crazy buying so many bicycle pumps at each checkout counter.  I air-freighted over 180 bicycle pumps to Panama in just one initial shipment.


The use of these common marine worms in the shrimp's diet was a key to launching Agromarina's successful shrimp maturation program and was a significant step towards closing the penaeid breeding cycle.  At the time it was believed that the richer proteins and complex amino acids in the bloodworm are what made it so effective in assisting shrimp maturation.  However, I often wondered if it may also have involved the polychaetes' unusually high copper content, since a marine shrimp's blood is copper based.  I'm sure someone has determined that by now.



The Construction of the Agromarina Shrimp Farm in Panama


Shrimp News: You were very involved with the expansion and construction of Agromarina; tell me about that.


David Flushing: Design and construction of the initial pilot facility in Aguadulce began in 1973 using a local company (Carmelio Amado Engineering).  Its onsite supervisor was Sammy Uruttia.  Ralston Purina contracted with Jay Arndt, a friend of Bill MacGrath's who had construction experience in St. Louis, to assist with getting things done quickly in what was considered a remote and laid back area of rural Panama.


Padge Beasley and Mel McKey moved from Crystal River to Aguadulce in early 1974 to help complete construction, get operations started and stock the first ponds.  Jay Arndt oversaw construction of the hatchery and helped Mel in Aguadulce.  Later in 1974, Ron Staha moved to Panama to help finish the new hatchery building in Vera Cruz and begin growing algae.


I relocated to Aguadulce in June 1975 shortly after Padge Beasley and Mel McKey had left Ralston Purina.  Padge moved on to manage growout ponds in Honduras and spent 15 years developing shrimp culture in Mozambique.  Yosuke Hirono and Bill More traveled to Aguadulce every week but lived in Panama City.  Ron Staha and David Drennan were stationed in Panama City and traveled to Vera Cruz.  My wife Barbara and I resided in Aguadulce for six years before moving to Las Cumbres outside of Panama City.


During my time in Panama, I had the opportunity to work directly with many of our employees in Vera Cruz. Ron Staha and Joe Mountain had assembled an impressive team, many of whom continued their careers in shrimp culture and are still active today. Unfortunately I am unable to remember all of their names, but the following colleagues who worked in Vera Cruz between 1975 to 1982 are a few I will never forget: Franklin Kwai Ben, Ricardo Yero, Roberto Chamorro, Arabia Greer, Juvenal Montessa, and Adriano Guerra.


I spent my first year in Aguadulce managing the nursery program and performing hundreds of experiments to improve shipping of postlarvae from Vera Cruz, stocking survival, feeding rates, water exchange and optimizing nursery transfer methods to the growout ponds to improve survival rates.  Shipping postlarvae was a closely coordinated effort among Ron Staha, Yosuke Hirono and me as we perfected the transfer parameters and stabilized nursery survival rates.


I also assumed responsibility for all of the Aguadulce's site maintenance and capital improvements.  Shortly thereafter, I was asked to take over all Aguadulce operations as Director of Operations (Gerente de Operaciones).  This helped free our research biologists and pond managers to focus on improvements and feeding studies.  During this period we also added several additional ponds and made incremental improvements to the facility.


Shrimp News: Were the pilot plant ponds in production when you arrived?


David Flushing: Yes.  By January 1975 many of the ponds were stocked with postlarvae, and the first growout ponds had been harvested.  A small deheading plant was built on the edge of town to process the harvest and truck it to Panama City.  A local pig farmer hauled away the heads to supplement his feedlot.  We were still experimenting with stocking densities and primarily used stylirostris.  Catching mated vannamei year round was not possible, so initially stylirostris and occidentalis were the predominant production species.


Early Developments at the Agromarine Shrimp Farm in Aguadulce, Panama
Harvesting a Pond 1981 85-Acre Pilot Farm in 1978
Feeding Trial in 1981 Processing Plant in 1981


Shrimp News: Who was working at Aguadulce when you arrived?


David Flushing: I arrived about the same time as Paul Maugle in June 1975.  We were the only permanent expatriate residents.  Paul had worked in Columbia for the Peace Corp teaching indigenous people how to farm shrimp using wild postlarvae and feeding the handmade ponds with manure.  Paul reported to Yosuke Hirono.  Yosuke spent part of his time in Aguadulce and part in Vera Cruz as a technical liaison between both operations.  Paul worked hard but seemed to struggle with transitioning to the dynamic environment that Purina fostered and the more precise discipline of intensive shrimp culture.  Paul left Agromarina about five months later.


In January 1976 Frank Follett arrived in Aguadulce to replace Paul Maugle.  Frank was involved in growout pond management and made significant improvements to production and survival rates.  Frank left Agromarina in September of 1979.


Alberto Ciniglio was hired in 1975 and resided for a while in Aguadulce.  Later he assisted Yosuke with fine tuning an optimum feed conversion ratio and feeding curves for our growout chow (Ralston Purina MR25) based on a formula involving feed protein, shrimp protein and shrimp weight.  Yosuke's famous "green line" feeding curve was developed and was successfully used for many years.  Alberto left Agromarina sometime in 1977.


In 1980 Glen Bieber was hired to assist with both Vera Cruz and Aguadulce operations.  He lived in Panama City and traveled to Aguadulce weekly for a while.  Glen left Agromarina in 1982.  He traveled around the world from Sri Lanka to Africa earning a living in the shrimp farming industry.  Glen currently raises shrimp in Tanzania.


Shrimp News: With the high stocking rates and pounds per acre others have reported for Agromarina, was the change from one-acre ponds to larger ponds a problem?


David Flushing: With significant expansions on the horizon we needed to understand how to scale one-to-two-acre  ponds to 10, 50 and 100 acres.  Not just physically, but in how we needed to manage and feed them effectively while maintaining two crops per year per pond.


From the onset, intensive pond management seemed more of an art than a science, an art that varied from person to person that was not going to scale up easily.  We needed to provide our local employees with some basic indicators and guidelines of what actions to take and when to get help.  We spent a lot of time trying to empirically come up with indicators of pond conditions that were easily documented and taught.


Our experiments ran the gamut, and several times we nearly lost a pond while testing some techniques.  We tested variables that were measurable and appeared to be factors in growth and survival, while distinguishing between the variables we could control and those that we could not.


These measurable variables included the usual things like turbidity (Secchi Disc), salinity (refractometer), temperature, water color (Yosuke's color gauge), dissolved oxygen (O2 meter), pH, water exchange rate (calibrated flumes and weirs) and weather.  Measurements were taken twice daily to capture solar diurnal rhythms (such as algae blooms).  Of course all the readily observable but not measurable indicators of a pond's "health" were also included in our data collection efforts, but they were not as readily quantified (i.e., sulfide smell, milky water, shrimp visible on pond's edge and fractionated protein foam).


Our ability to control some of these measured variables was clearly limited to things like water exchange rates, aerators and feeding rates—and to lesser degrees, pond preparation (drying, tilling, liming), stocking density and species.


We even kept a large supply of potassium permanganate on hand to help rescue an oxygen-starved pond when nothing else would respond fast enough.  We quickly learned that there were differences in sensitivity to these environmental variables among the species we were using (stylirostris, vannamei and occidentalis).


Collecting all this data was routine and fairly easy, and trending key variables was fairly straightforward, but analyzing the complex relationships between them statistically was difficult and time consuming.  I used a calculator and lots of graph paper, but the temptation to jump to a seemingly obvious conclusion was great.  Agreeing on what the data was telling us was rich fodder for passionate discussions long into the night.  How much easier and quicker it would have been to have a computer at our disposal with a statistical program back in the late 1970s!


Meaningful results from all our data collection and analysis did come, albeit slowly, and we formulated both remedial actions and predictive indicators of problems that could be readily taught.  We demystified some of the art and significantly improved pond performance, consistency and predictability.  Our local employees learned quickly and relished the responsibility to assume more control of daily decisions.  We also learned more about controlling water exchange rates, improving water distribution from entrada to salida and ideal pond water depths.  This information was incorporated into the design of our future shrimp ponds and water distribution systems.


During one of our periodic management team meetings we were discussing the increasing volume of data collected for sourcing, hatchery, maturation and pond management.  Bill More was clearly becoming frustrated with our discussion when he suddenly pounded his fists on the table and emphatically told us we were all "collecting too much erotic data and need to stop it!"  When we all laughed uncontrollably, Bill became even more frustrated until he realized he had meant to say "erratic data”.  It was one of those moments of unexpected but welcomed levity you never forget.



The First Major Expansion of the Agromarina Shrimp Farm

Shrimp News: When did the first expansion of Agromarina begin and how many expansions were there?


In 1977, I prepared a master plan for a commercially scaled facility that used most of our suitable leased land on El Gallo, the Aguadulce side of the El Tigre Estuary.  This also included expansion and improvements to both our Aguadulce and Vera Cruz operations.


The hatchery and maturation facilities required additional tanks and equipment, but Aguadulce was where the largest capital investments were made and naturally required the most attention to design, manage, schedule and budget.  Aguadulce's expansion included surveying for reservoirs, canals, ponds and roads, a new pumping station, bridges and improved water control structures.  We also had to procure construction equipment, train operators and hire from a limited-skilled workforce.


I received notice from Bill MacGrath that the capital funding request was going to be approved, so he told me to start work immediately.  I knew I couldn't commit capital money without formal approval from corporate, so I worked with Bill More to borrow operating funds until the capital budget was approved.  Both Bill More and I were uncomfortable with this, but sometimes we had to bend a few rules to get things done.  When Bill MacGrath learned that things were not going as fast as they could and that Bill More could not continue to fund the project from his operating budget without getting in trouble with the auditors, Bill MacGrath came to Aguadulce to meet with me.


Bill MacGrath Giving the Signal to Proceed with Construction


While gesturing in front of a temporary pond layout sign on the open mudflat, Bill MacGrath emphatically said:


Listen David, by the time anyone in St. Louis knows you started work without an approved capital budget, it’ll be approved!  Here, this is all the authorization you need.  Now let’s get started!


Jokingly, I took Bill MacGrath's picture to document his capital spending authorization and absolution.  Then Bill More and I proceeded to bend some more rules—rules with much larger price tags—and construction proceeded at full speed.


That was just one of the many great things about working with Bill MacGrath and Dennis Zensen; they were entrepreneurial mavericks in a corporate world who knew what it took to get things done.  They sheltered us from the requisite corporate bureaucracy so we could remain focused on the tasks ahead of us.  I learned later in my career just how instrumental Bill and Dennis were in helping us all succeed in making Agromarina a success and the political capital they had to risk to make it all happen.


The capital budget was approved rather quickly, and before I knew it I was in charge of it and everything that it funded.  At the time it was the second largest project I had managed in my career, but this time there were no resources available to assist with procurement and design.  Doing it alone was overwhelming.



The Second and Third Expansions of the Agromarine Shrimp Farm


Second Major Expansion of Agromarina in 1979

In 1978 a second expansion was made at Agromarina that brought the total acres of productive ponds to over 700.  It had been planned and laid out during the first expansion, and so it was a much easier project.  It was completed in less than a year and exhausted most of our economically developed land on the El Gallo side of the estuary.


In 1978 we began planning a third and much larger expansion on the other side of the El Tigre estuary.  It involved over 1,000 acres, a more comprehensive infrastructure to support operations and major expansions in Vera Cruz.


I worked with Ron Staha as he scaled up the hatchery in Vera Cruz to meet the forecasted demand, and managed the construction of the hatchery expansion and other infrastructure changes to accommodate it.  Working with Ron was a pleasure.  He knew exactly what he wanted, where he needed help, and he had a vision of a modern efficient hatchery operation.  I just helped provide the technical details to meet his vision and then got it constructed.


I also worked with Joe Mountain to expand the maturation facility and manage its construction.  Joe was always experimenting with his sexually active charges and trying new techniques.  Since our maturation technology was not as seasoned as our hatchery, Joe and I decided to build a more flexible and less permanent facility that would allow for potentially significant changes later on.  Joe was a consummate research biologist, and it was always a delight to work alongside him.


I spent about one to two days a week in Vera Cruz and five to six days in Aguadulce (there were no weekends) while tracking costs, schedules and reporting back to St. Louis on our progress.  While it was exhausting, I loved every minute of it.


There were no contractors large enough to take on a project of this magnitude, and the resources and construction equipment we had acquired on site were inadequate for such a large endeavor.  (You have to remember that back in 1979, 1,000 acres of intensive shrimp culture was pretty big, even though it may seem like a postage stamp compared to some of the farms in operation today).


We had to form a completely self-contained construction operation on site.  To meet the demands of this more challenging expansion, I formed an engineering and construction team on site.  I hired a construction manager from Panama City (José Perez), a structural engineer, an architect and draftsman, construction superintendents, a land surveyor, support clerks and a secretary.  I also turned over my remaining operations responsibilities to Frank Follett and Alexis Botacio so I could focus 100% of my time on design and construction.


Construction began in 1979 (when my first son was born) and continued non-stop for 20 months.  This expansion required a 300-foot bridge across the estuary and a 260-million-gallon-a-day pumping station, which at the time was reported to be the largest saltwater pumping station in the Western Hemisphere.  We also designed and constructed new operations buildings (maintenance facility, feed warehouse, an onsite shrimp processing plant and an office building).  We also ran our own utility lines from the town of Aguadulce (water, power and telephone) to the site.


The bridge (also called "the river crossing") had to come first as the only access to the other side of the river was a 20km drive that required crossing a large mudflat that was only passable for a few months of the year. Work on the bridge continued 20 hours a day six days a week until it was completed.


To add to the drama, the first vehicles to cross the bridge were my motorcycle followed by a tractor trailer carrying our 60,000-pound drag-line crane. This represented the maximum design load for the bridge! For the next 16 months we had traffic controllers on the bridge as trucks crossed back and forth hundreds of times daily with construction materials, supplies, fuel and rock for roads and rip rap.


El Tigre Bridge Completed in 1980


We serendipitously discovered a sedimentary rock formation on the El Gallo side of the river during the second expansion.  It quickly became a small rock quarry operation to supply gravel for roads and rip rap along the pond banks to prevent erosion.  Drilling, blasting, sorting and hauling were ongoing for more than two years as over two hundred thousand cubic yards of rock were hauled over the bridge to the other side of the estuary and graded onto miles of roads.  This discovery saved us significant capital and prolonged the life of the pond berms.  I had previous blasting experience gleaned from my project in the Dominican Republic, but not on this scale.  We shook the town of Aguadulce over five miles away a few times until we dialed in the ideal ratio of explosives.



Rock Quarry, First Blast, 1979 (Agromarina did two blasts a week for two years.)




Construction Supervisors at Agromarina in 1977


It was a very rewarding experience to witness how we improved the lives of hundreds of residents in Aguadulce and surrounding areas.  Living in Aguadulce had very few perks, especially for a gringo extranjero, but observing our impact on the community was one of them.


Agromarina quickly became the second largest employer in the area (second to the local sugar mill with hundreds of seasonal unskilled workers).  Unfortunately, that fact began attracting the attention of the local labor union.  In 1980 and 1981 we had over 160 construction workers and equipment operators, about 60 shrimp farm operation employees, 10 office personnel, and about 80 part-time employees for our onsite shrimp processing plant.


To support construction, we set up on-the-job training programs for local workers.  We trained men whose work skills were heretofore limited to cutting sugar cane with a machete to become welders, carpenters, mechanics, heavy equipment operators, truck drivers, masons and a host of other construction related skills.  These skills changed their lives as they earned more money,  elevated their position in the community and ultimately left Agromarina with valuable skills they could use elsewhere.


Shrimp News: What were some of your challenges to constructing the full-scale shrimp farm?


David Flushing: There were many.  Perhaps the most frustrating were those I could not control like limited local resources and limited expertise in St. Louis to help with engineering systems in our corrosive saltwater environment and resource limited rural economy.  I was compelled to research locally available solutions to many problems and then test them in the field before scaling them up to commercial size.  A few examples come to mind.


Procuring Equipment: Procuring heavy equipment that can operate in a soft mudflat, maintenance of that equipment when it is continuously exposed to high concentrations of salt, and training local people to operate and maintain the equipment required a lot of research and time.  At our peak in 1979 we owned and maintained 14 Caterpillar wide-track bulldozers, a Link Belt dragline, a Hitachi excavator, six John Deere backhoes, a front end loader, two P&H hydraulic cranes, a Caterpillar road grader, a rock drilling rig, fifteen Lincoln welders, eight dump trucks, seven  four-wheel-drive  trucks, four army jeeps, numerous pumps, concrete mixers, portable generators and lights. We quickly became the largest heavy equipment construction company in Panama!


Three of Eleven Bulldozers Building Dikes in 1979


Problems with Concrete: We needed to develop a concrete mix that limited the intrusion of salt ions. Once saltwater and the dissolved oxygen it carries contacts steel reinforcing rods (rebar) embedded in concrete structures, the steel begins to corrode and eventually spalls the concrete—essentially breaking it apart and compromising its structural integrity.  Combinations of air entrainment and some unusual density enhancing concrete additives combined with higher cement ratios and additional rebar coverage reduced this problem significantly.


Third Generation Water Control Structure

We also reduced our use of concrete pipe for our water control structures as it was becoming expensive to transport larger diameters from Panama City where it was made.  A third-generation water-control structure for the 50-acre growout ponds was designed that eliminated the use of concrete pipe, reduced costs, used pre-cast panels that were made on site and significantly reduced potential repairs for operations.


"Floating" Bridges: Building "floating" bridges on mudflats was also a challenge.  The conventional solution is to use concrete or creosote wood pilings.  But they were expensive, needed to be fifty feet long, and the necessary equipment to drive them wasn't available within a hundred miles.  We were unable to locate any contractor in Panama City willing to tackle this part of the job who would commit to a schedule.  I tested several "floating" foundation displacement designs and found one that worked on the expansive clay and silt that was 50 feet deep all over the mudflat.  As long as a heavy piece of equipment was not parked on the bridge, the hydration force of water acting on the super-fine expansive clay supported the dead load indefinitely and excessive live loads for over an hour.  These "floating" bridges remain in place today.


Sedimentation: Silt-laden water flowing down the estuary river accumulated in our 1974 pilot plant canals and reservoirs and soon became a serious problem.  The pilot plant filled the first 500 feet of its elongated reservoir with black anaerobic silt in just four years. This occurred despite a very low pumping capacity.  It was also partially due to anchoring the pump intake pipes just above the river bed.  Ponds closest to the pump station accumulated much more silt than those a considerable distance away.  The water supply gates (entradas) for the closest ponds were partially blocked within two years.  Remedying this was problematic, expensive and endangered continuing operations.


An effort to address the long term operational problems of silt accumulation was incorporated in our first major 600 acre expansion in El Gallo.  A considerably larger reservoir was designed and water was forced to take a slow circuitous route through the reservoir to allow silt to settle out before reaching the ponds.  The reservoir was also located so it could be dredged from roadways and the spoils placed in designated adjacent areas.  Furthermore, the pumping station was completely redesigned so that water was pulled from the middle of the river water column versus near the bottom as was done in the pilot facility.  Tests proved that when the intake pipe elevation was raised 3.5 meters from the bottom it reduced solids transported by the pumps by as much as 70% during downstream flows depending on the season.  There are only two seasons, very wet and very dry.


When designing the 1,500 acre El Tigre expansion two independent large reservoirs were used so that they could be alternated each year and accumulated material could be removed when the reservoir was completely dry.  This is far more economical than wet dredging and avoids exposing nursery and production ponds to oxygen-starved water laden with anaerobic sulfides.  If managed properly (keeping one reservoir dry at all times) this combination of elevated pump intakes and alternating reservoirs seemed to be the most effective approach to managing silt accumulation.


Managing two alternating reservoirs also solved another interesting problem.  After several years of continuous operation (as any shrimp farmer knows) the primary reservoir teems with a surprising variety of marine life, a thriving eclectic marine ecosystem in and of itself.  After several years, fishing in the pilot plant reservoir system was a great pastime.   Octopus, blue crabs, shrimp and mantis shrimp flourished on the bottom.  The ability to drain the reservoir each year and allowing it to dry reduced the growing demand this biomass placed on oxygen and plankton, both of which are beneficial to the shrimp ponds.


Driving Pilings: Driving pilings into the estuary to build a 300-foot bridge and a new pumping station was possibly the biggest challenge.  The tides changed the direction of flow in the estuary four times daily and often flowed in excess of six miles per hour.  The tides in the estuary also ranged between 15 and 24 feet twice daily. When this rapid rising and falling bi-directional flow is carrying debris and tree trunks from upstream jungle areas, a six mph velocity can exert tremendous forces on the bridge as debris collects against the bridge pilings.  After several scaled tests in the river, we designed and built a floating barge with an unusual 4,000 pound gravity drop hammer to drive battered steel pilings to a gravel layer 70 feet down.  The pile driving hammer had a 10-inch circular opening in the middle (like a donut) so that we could simultaneously drive the pipe piling while washing out material from inside the piling.  Corporate engineers found it to be a highly unorthodox piece of equipment, but agreed it worked and solved an unusual problem in a very cost effective way.  This design significantly reduced the forces required to drive the piling by as much as 50% while excavating the inside.  This allowed belling out the bottom of the piling and filling it with concrete.  This design solved several problems in construction and significantly improved the bridge's longevity.


Corrosion: We also used a low-alloy, high-strength steel called Cor-Ten that corroded very differently from conventional steel.  US Steel was the inventor of this product, and its initial market was primarily railway coal cars, architectural and roofing materials.  With some help we located some specially fabricated heavy-walled Cor-Ten pipe that was ordered by an oil refinery in Texas.  The price was astronomical, especially considering our budget.  But we identified several thousand feet in various lengths that had been rejected for use in the refinery due to subtle variances in its composition.  I went to Baltimore and negotiated the purchase of all the rejected steel for a small fraction of its costs (basically scrap value) and had it shipped to Aguadulce.  To further protect the bridge supports and enhance its longevity, we applied a special coating to the steel and attached 272-pound zinc-aluminum alloy sacrificial cathodes to each piling.  This same Cor-Ten battered pipe piling and cathodic protection system was also used to build the new pumping station.  The material has proven itself and has subsequently been used in other marine environments.



Largest Saltwater Pump Station in Western Hemisphere


Developing a large-scale pump that was efficient, that could survive pumping corrosive saltwater and that did not foul with marine growth was a challenge.  We had tried vacuum primed centrifugal pumps cast from iron and brass, hydraulically powered submersible pumps made from stainless steel and several variations with limited success in three previous pump stations on the El Gallo side of the river.  Most had maintenance and corrosion problems within a few years and required major repairs and replacement.


Pumping Station 1981



I met with the product development group of Allis Chalmers who manufactured some of the largest vertical lift pumps in the USA to explore development of a pump that would be reliable and economical in our seawater application.  We came up with an extended-shaft, axial-flow, submerged-propeller pump fabricated from Cor-Ten steel with sacrificial anodes.  Based on the pump we developed, I designed a six-pump station that discharged into three ten-foot-wide fiberglass flumes that extended 150 feet over the river (estuary), which carried seawater to a 110-foot-concrete-distribution channel.  The station was capable of pumping 260 million gallons daily and was still operational 20 years later when Agromarina ceased operations in 2001.


Work on the Pump Station in 1980
Panamanian Workers Celebrating the Completion of the Pumping Station in 1981


Shrimp News: What did you do for entertainment in Aguadulce?


David Flushing: In the 1970s entertainment in Aguadulce was very limited for Americans.  We basically created our own diversions.  While I was immersed in work for Agromarina, Barbara kept busy teaching English to the 5th grade class at Escuela Alejandro Tapia (the local public school), taking Spanish guitar lessons from an elderly gentlemen and participating as a member of the "prestigious" Club de Cocina (a local women’s cooking club).


Aguadulce Movie Theater in 1975

But then there was the Aguadulce Theater!  A venerable institution for decades located on the downtown square.  Admission on Saturday nights was just 25 cents.  A huge opening was left in the back of the theater after a truck had crashed through the back wall.  It was not repaired for years, and probably helped keep the building cool.  During each showing of third-rate 1960-era movies from Mexico and Brazil, dozens of bats would fly in front of the projection screen and within inches of our heads.  While this took some getting used to, they did help keep the blood-thirsty mosquito population down.  Watching movies in Aguadulce in the late 1970s was a memorable experience.



Ralston Purina's Interests in Ecuador


Shrimp News: I understand that Purina explored opening operations in Ecuador, but nothing ever happened.  What can you tell me about that?


Yosuke Hirono 1975

David Flushing: We clearly had an interest in Ecuador, and the potential was huge there.  I made several trips to Ecuador as did most of the principals in Agromarina.  We all recognized Ecuador’s potential as greater than Panama’s.  Furthermore, we could leverage the less capital sensitive components of our technology and realize a significant revenue stream fairly quickly and inexpensively.  We had feed manufacturing already in place, we were already shipping nauplii from Vera Cruz to Ecuador, and our pond management and feeding technologies were transferable.


Yosuke Hirono was very passionate about the possibilities in Ecuador and took the lead in pushing Purina to initiate a project, to fish or cut bait.  He relocated to St. Louis and for over a year spent all of his time managing feeding experiments in Ecuador, hiring qualified personnel and training them with what we had developed in Aguadulce.  This set the stage for Purina to enter the market by selling our feed, seed and experience with little to no capital expenditures.  Yosuke consulted with several farms in Ecuador that became successful using Purina's technology.  He basically had proven the market was viable and Agromarina's expertise was very marketable.


We decided that an important first step to getting into Ecuador was to establish a local hatchery operation.  Ron Staha and I went to Ecuador in 1978 to do some testing of the water and locate a suitable location for a new hatchery.  Peter Shayne invited us to use his vacation home in Salinas so we could perform hatchery field tests.  I helped Ron Staha set up a small field laboratory, and while he conducted baseline survival studies, I explored the entire coast of Ecuador by plane identifying potential hatchery locations.  I slowly flew along the coastline at low altitudes to photograph potential sites and locate them on detailed maps.


On one occasion, as my pilot approached the Peruvian border, a voice came on the radio and kept repeating something in an odd accented Spanish that was hard to understand.  My pilot said to pay no attention.  A few seconds later another voice spoke in stern clearly worded English: "Turn around now or you will be shot down!"  That sure got my attention and at my insistence my pilot immediately made a sharp 180 degree turn.  We were infringing on the airspace of an Ecuadorian military base near the Peruvian border, and by flying so low and erratically we received more than their usual amount of attention.


Then I visited the three most promising sites and identified availability of needed infrastructure (roads, power, local labor and housing as well as nearby industry, drainage outfalls and shoreline stability for the critical water intake pipe).  I took large water samples from these three promising locations, and Ron Staha tested them with nauplii.  Yosuke joined us in Salina and assisted with the testing.  Things looked very promising for all three locations, so the next step was to see which coastal property we could purchase.


Shrimp News: What was the relationship between Agromarina and Peter Shayne?


David Flushing: Peter Shayne managed a shrimp processing facility in Guayaquil (Empacadora Shayne, CIA., LTDA.) and was competing to process product from the vast Ecuadorian shrimping fleet.  Peter’s general manager was Carlos Raymond, an affable gentleman who was very helpful to us.  Peter saw shrimp farming as a means to expand his processing business and negotiate for exclusive processing contracts with shrimp farmers.  While Peter Shayne was a colorful character, he was shrewdly entrepreneurial and had a vision that helped change the shrimp industry in Ecuador.  He was a gracious host while I was in Ecuador, and he visited my home in Aguadulce several times as discussions with Purina management explored how we could work together.  He was prepared to put skin in the game and make things happen one way or the other.  I believe Purina International had an arrangement with him to sell Purina's shrimp chow (MR25), but most other agreements were probably informal.  Bill MacGrath and Yosuke Hirono headed most of our Ecuador initiatives and are more familiar with any agreements that may have existed.


Shrimp News: What do you believe stopped Purina from moving into Ecuador?


David Flushing: Unfortunately Purina was reluctant to commit additional technical resources in Ecuador without first expanding our base in Panama.  In 1978 and 1979 we were making substantial investments in expansions of all of our Panama based facilities.  Purina's business manager for mariculture Richard Moeller and his business analyst Fritz Schwartz believed that any significant initiative in Ecuador would dilute our limited technical resources in Panama and Crystal River.  They believed that it would potentially jeopardize our success in both countries.  Naturally, we did not agree and were hungry for another challenge.  When it became apparent in early 1979 that Ecuador was going to get ahead of us unless we acted promptly, Purina simply put further initiatives on hold.  Yosuke Hirono left Purina in 1979 to follow what he believed was a bigger and more lucrative opportunity in Ecuador.  Yosuke saw it as a "potential gold rush" and he wanted to be a part of it.  He became very instrumental in Ecuador's success in shrimp farming.


Shrimp News: Why was Purina willing to share their technology so freely?


David Flushing: Back then we were very open with our rapidly evolving technology.  We frequently visited shrimp operations all around the world and freely reciprocated by welcoming guests to see our operations.  The only area that had restricted access to outsiders was our maturation facility.  I visited numerous farms in Ecuador, Costa Rica, Venezuela and Honduras.  In fact, I first met Padge Beasley in Honduras (Sea Farms near Choluteca).  I also visited Red Lobster's top secret freshwater shrimp (Macrobrachium rosenbergii) farm outside San Pedro Sula, Honduras (Agua Finca de Camarones).  Ron Wulff, a Purina alumni and a good friend, was Red Lobster's Technical Director of Aquaculture.


Perhaps our openness was partly naive, but I believe we learned as much as we shared, and we were fortunate to have the resources of Ralston Purina to test whatever we found promising, and then integrate it into our growing technology base and make things happen quickly.  Folks like Dr. John Barcate (Director of Corporate R&D), Rolland Laramore (Senior Microbiologist), Albert Hotois (feed formulations), Bill MacGrath (animal nutritionist) and many other technical experts were at our disposal.  It was a "dream come true" scenario for any marine biologist.



Agromarina and the Environment


Shrimp News: Back in 2008 I heard you say that Agromarina was an environmentally sensitive farm.  What were some of the things you did to protect the environment?


David Flushing: While converting a pristine mudflat and estuary to a commercial shrimp farm certainly seems like an environmentally insensitive endeavor, we did some things that reflected our backgrounds as biologists.  I can think of a few small examples:


Unlike many shrimp farms that followed, Agromarina did not destroy mangrove areas along the estuary to construct ponds.  However, erosion of pond banks was a problem as our ponds grew in size with our ability to manage them.  Rock rip rap was used extensively, but it was expensive and was not always effective.  In an effort to find a more efficacious means to reduce erosion, I started planting different species of mangrove trees along the pond banks.  The results from one species looked promising.  We hired local fisherman to collect propagules (mangrove seeds) from the estuary and our employees planted them for a couple years.  Agromarina planted over 126,000 propagules between 1979 and 1981.  The resulting mangrove trees protected the shrimp ponds and reservoirs banks from wave erosion for 20 years with little maintenance.


Propane Cannons for Cormorant Control

Our ponds were frequently under attack by flocks of migrating cormorants.  Initially we did not believe they could consume as much shrimp each day as they did.  One day we used a shotgun to persuade a few to visit our laboratory for a dissection.  Their stomachs and throats were gorged with dozens of shrimp.  Many were so full they could not fly and evaded us by swimming away underwater.  After a few weeks of additional persuasion the cormorants learned to stay far away from us, but not from our shrimp ponds.


The growout acreage also attracted many other species of large birds including roseate spoonbills, flamingos and white ibises.  While they and several species of mammals consumed some shrimp along the waters edge, their comparative impact on pond yields was deemed to be negligible.


But those ravenous cormorants really ate our lunch!  I purchased six propane powered cannons (noise makers on steroids), mounted them on empty brightly painted 55-gallon drums and set them to automatically fire every 20 minutes or so.  At times it sounded like a civil war was raging in the distance, however the cormorants were eventually encouraged to feed elsewhere.  It did not prove to be a permanent solution (unconditioned newcomers kept coming), but it was a successful tactic that helped improve yields for a few years. Unfortunately local poachers eventually had an even greater impact on yields.


Teaching our employees to drive trucks and jeeps on narrow muddy roads with saltwater on either side was a challenge.  Many a vehicle ended up in a pond when feeding shrimp or transporting equipment and personnel.  This was very dangerous for our employees and it proved expensive.  Looking to the practices used in the sugar cane fields for over a hundred years, we began buying oxen and building ox carts.  We lowered our carbon footprint before Al Gore made it a popular expression.  Instead of a maintenance shed and a gasoline and diesel depot, we built fenced pastures, water troughs and feed sheds.  Several folks from St. Louis were amused by this backwoods initiative, but the results clearly spoke for themselves, and we purchased more oxen whenever we could.


Oxen Carts Loaded with Ralston Purina Feed for Delivery to Ponds in 1980


I'm reminded of a humorous event involving Agromarina's livestock herd.  It occurred when we had to sell a couple oxen due to their age and health.  We sold them for more than we paid for them; they simply grew larger and yielded more meat.  Corporate property accounting did not know how to cope with a profit from a depreciated asset and was stymied on how to report it.  We were subsequently told not to sell any more oxen, but to give them away instead.



The End Game

Shrimp News: Why did you leave Panama?


David Flushing: For a number of reasons.  The unbridled support for what we were doing was cooling off as Ralston Purina's management was changing.  Dennis Zensen had left the company and the mariculture group was placed under Paul Hatfield, a corporate president who also ran Ralston Purina's soy protein division.  I got to know Paul personally and had a lot of respect for him.  After the closing of Crystal River was announced and several key personnel had left Agromarina, the writing was on the wall.  Dick Redpath, Purina's corporate vice president of engineering, got to know me as I often consulted with corporate engineering on design challenges in Aguadulce.  He offered me a more promising career in corporate engineering in St. Louis and Paul Hatfield encouraged me to accept it.  So obviously I accepted.  I had many mixed feelings, but the ten-year love affair between Purina and shrimp farming was clearly cooling off rapidly.


Shrimp News: What did you do after you left Panama?


David Flushing: In 1982, I moved to St. Louis (Ralston Purina's world headquarters) and was a senior project manager for a wide variety of projects ranging from process improvement, quality control initiatives, a nation-wide maintenance management system, development of artificial intelligence based management tools and leading edge computer integrated manufacturing (CIM) in a joint venture with IBM.  I also performed technical evaluations of other mariculture operations owned by companies that were interested in partnering with Ralston Purina.


One of my favorite projects was a complete renovation, updating and significant expansion of Ralston Purina's world headquarters.  Working for an international company like Purina, I also found myself managing other large projects in Venezuela, Mexico, Honduras, Peru and Puerto Rico.


For the past 20 years I have been a Director of Projects and Engineering for Jacobs Engineering Group managing the design, construction and commissioning of large industrial facilities in the pharmaceutical, food and beverage, manufacturing, and civil infrastructure industries.  While this proved to be more lucrative for me and my family, in my heart I have always remained a shrimp farmer.


Shrimp News: Is there anything else you wish to share about the early history of Agromarina?


David Flushing: I could probably go on for hours since this was a very exciting and passionate time in my life, but I would like to say that to have been a part of Agromarina and all the technological and commercial firsts it realized was an honor.  It never would have happened without everyone working together and Purina's deep pockets.


I'd also like to comment about the eventual closing of Agromarina in 2001, 15 years after Purina sold it to Granada Corporation.  Agromarina changed hands several times over that period.  From what I understand the forced closing in 2001 was mostly a politically driven and economically myopic closure.  It was a period that I'm grateful I did not have to witness; however, two Purina pioneers were still there at the end: Bill More and Gustavo Bernal.


Bill More is one of the nicest, honest and most generous people I know; it was an honor to work for him.  His knowledge of shrimp farming is unsurpassed even today.  Bill was the first employee Purina hired to develop a mariculture business in 1969, and he was there when Agromarina was sold by Purina in 1986, 20 years later.  Bill then continued to work for Agromarina's new owners in varying capacities, and he was there when it was shutdown by local officials in 2001.


The last Purina employee working for Agromarina in 2001 was Gustavo Bernal, one of the first technicians hired in 1974.  Gustavo was promoted over the years as his skills and interests in shrimp farming grew.  Gustavo currently owns and operates a successful business near Aguadulce with his wife Maruja Bonilla.  Maruja was my administrative assistant and worked for Agromarina for more than 10 years.


During the almost 25 years that Agromarina operated (1974-2001), the total farm production was over 53,000,000 pounds of shrimp.  That's pretty impressive considering that nine of those years Agromarina had less than 700 acres of ponds and struggled with many obstacles during its last five years of operation, including the whitespot virus.  During Agromarina's peak production period in the early 1990s, it produced more than 6,000,000 million pounds of shrimp annually.


Had changes at the helm of Purina in January of 1982 been different (CEO Hal Dean stepped down, and Bill Stiritz was named CEO), perhaps Agromarina would be alive and productive today.  With the talent it attracted, Agromarina may have overcome the whitespot and Taura viral attacks that began to decimate shrimp culture in Panama in 2000 and remained a leader in shrimp farming today.


While that didn't happen, the Purina Pioneers went on to spawn a worldwide shrimp farming industry based on the technology they collectively developed, using what was once considered an insignificant and small penaeid species.  That's a gratifying legend for everyone who was involved.


As testimony to the caliber of Purina's mariculture alumni, an overwhelming majority of them have been successful in shrimp farming across the globe.  In February 2008 we gathered in Orlando, Florida, and had a "Purina Pioneers Reunion."  In attendance were 46 pioneers and their spouses, including Dennis Zensen and his wife Carol.  After sharing personal updates and watching a presentation about our history, we feasted on seafood and had a great time catching up and telling stories of the good old days.  Despite some of us having been incommunicado for decades, the conversations were lively, and we all agreed that in most ways none of us had changed very much.


Ralston Purina Reunion in Orlando Florida in February 2008
Front Row: David Flushing, Rodney Levins, Ron Wulff, Dennis Zensen, Carol Zensen, and Fritz Schwartz
Second Row: Mel Mackey, Padge Beasley, David Drennan, Bill More, Joe Fischer, Harvey Persyn, Peter Van Wyk, Durwood Dugger and Gabriela Hughes Schrader
Back Row: Reggie Markham, Roland Laramore, Ron Staha, Yosuke Hirono, Henry Clifford and Bill MacGrath




Information: David Flushing, P.O. Box 248, Grover, Missouri 63040, USA.


Source: David Flushing, Interviewed by Bob Rosenberry, Shrimp News International. Published July 23, 2012
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