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Penaeus monodon Sightings in the Western Hemisphere

A Discussion from the Shrimp List


Craig Browdy ( We had an interesting visitor to South Carolina a couple of weeks ago.  A very large and healthy Penaeus monodon was caught by one of our shrimp trawlers.  A few more turned up in North Carolina a while later.  Does anyone know where these shrimp came from?


Osires de Melo ( A couple of years ago, some P. monodon were caught in northeast Brazil, a region where no one farms them.  A plausible guess was that the monodon were released with ballast water from vessels that had been in Asia.


Leland Lai ( So much for biosecurity and quarantine.  It’s bound to happen and I wouldn’t be surprised if monodon is eventually found off Hawaii and stylies [P. stylirostris] off New Caledonia and/or Tahiti.  And P. vannamei is in ponds all over the world, silently plotting escape plans!  It’s called the globalization of shrimp.  Sounds kind of like Atlantic salmon and Cobia doesn’t it!  Ok, Ok, I’m just having fun during my lunch break.


Josh Wilkenfeld ( I remember hearing or reading the stories of the mysterious appearance of monodon off the coast of Brazil, and the theory that they might have come in with the ballast water of large ships.  I don’t really know about the mechanics of ocean going vessels, but I wonder how these ballast tanks are filled and emptied, how clean they are kept (free of toxic substances) and how good of an environment this might be for shrimp to survive in for any length of time.  If the ballasts are filled and emptied by pump, it would surprise me if mature shrimp could survive the trip through a pump and impellor.  PLs might be able to make it through the pumps, but might still have a difficult time finding enough to feed on over a period of days or weeks in this environment, unless, of course, they were feeding on other dying organisms, which is possible.


Again, I know nothing about how these large ships work, but just thinking logically, I’m guessing that they draw water into the ballast tanks when they are moving away from harbor, and though their draft can be quite deep, they are probably not drawing water from areas where they are likely to suck up large shrimp that are bottom dwellers.  So I suppose the most likely case that can be made for transoceanic ballast transport of shrimp is by pulling in near-coast PLs that may be on their way into nursery grounds.  Interesting idea, but I still wonder about how well they would do in a ballast tank environment.


I assume that ballast tanks are very well painted with the same types of materials that are used to protect the outer hull from corrosion and fouling, and tanks may also include, in one form or another, substances meant to discourage the settling of barnacles on the inner surfaces of the tanks.  I wonder if, in order to reduce maintenance, there are other procedures or substances used by marine engineers to keep the ballasts clean and discourage survival of hitchhikers, and if such antifouling measures might also be toxic to shrimp.


Contrary to the above considerations, it does not seem to me at all far-fetched to think that monodon have made their way into culture systems in South America, both in the early days, when not much thought was given to regulating the introduction of nonindigenous species, or even today, when some aquaculturists are willing to move animals illegally, thinking this will somehow give them a business advantage.  I think it’s been correctly assumed (if not scientifically proven) that the origin of IHHN virus in the Western Hemisphere was from early importation of monodon, and more recently, it’s probable that the Taura virus made its way into Asia by the extralegal importation of non-SPF (specific pathogen free) vannamei, most likely from somewhere in Central or South America.  The point is that it never surprises me to hear that people are willing to ignore the risks to the environment and potential negative impact to their own livelihood to bring in animals illegally, using whatever form of rationalization is convenient for them at the moment.


Illegal importation of exotic species is much more difficult to do in the USA, though perhaps still not impossible.  And there certainly have been monodon in various places in mainland USA in the past.  There were monodon and stylirostris at the National Marine Fisheries Service facility in Galveston, Texas, when I first went to work there in 1980, and I would guess that there were monodon (and other species) at other research facilities at various times as well.  Certainly, less attention was paid in those days to accidental escapes, although I do recall that we eventually installed a rather primitive chlorinator for treatment of water discharged from the hatchery at the Galveston facility.


If monodon were inadvertently transported by ship, or accidentally released from research facilities or early commercial trials at one time or another, it would be interesting to know if they have been able to survive and reproduce in their “new” environment.  I have a few follow-up questions for Craig Browdy (above):


1. Were the specimens captured in North and South Carolina sexually mature, and if so, was there any sign of ovarian development and presence of spermatophores?


2. Were the specimens in good enough condition so that tissue could be used for testing by PCR to see if they were carrying any known pathogens?


3. This is probably expensive, but I wonder if it might be possible to determine the origins of these mystery animals by communicating with someone from Moana Technologies, High Health Shrimp, or other groups that have done significant genetics work with monodon, to see if certain loci or markers could be used to characterize specific populations from different regions?


I started this reply much earlier in the morning, but had to drop it for a while, so just now saw Leland’s comments (above), which I agree with completely.


Patrick Wood ( At the end of the day, does it make any difference?  The world is too complex to regulate everything.  The rules are bound to be broken, naturally or unnaturally, voluntarily or involuntarily.  The sum total of the earth is what one should look at—not man-made boundaries.


Josh Wilkenfeld ( I don’t know, Patrick.  I can agree that the planet and evolution set up their own set of rules, which if left untouched by humans, would have kept things running just fine.  As you pointed out, it’s probably impossible to reverse damage already done by thoughtless and sometimes inadvertent movement of exotic species from place to place, but that doesn’t mean that we should give up completely on attempting to do a better job of minimizing the environmental impact of our activities.


You are correct in pointing out that even the movement of SPF (specific pathogen free) animals poses risks, since accidental and/or intentional release of animals is almost impossible to prevent.  We would be tilting at windmills, however, if we attempted to completely eliminate the movement of exotic species throughout the world.  I think that some progress has been made in terms of educating people about the need to move animals in a responsible and safe manner (SPF and strict quarantine rules for non-SPF seems to be the only logical way).  We should continue to emphasize the importance of using SPF animals when working with exotic species, as well as working to improve performance of endemic species, so that they will be as commercially and economically attractive to use as foreign species may be, in this case, vannamei.


Regulations and laws are often ineffective because they are too difficult to enforce, and getting people to cooperate for the good of their environment or the planet as a whole, just doesn’t seem to fly.  The only thing that seems likely to work is economic incentives (or penalties).  The goal should probably be to make it as easy and preferably even more profitable for hatchery and farm operators to work either with SPF animals when using exotic species, or with SPF and/or SPF/SPR (specific pathogen resistant) local species, as it is to work with “illegal” and potentially dangerous imports.


At this point, I’m not really concerned about who may be responsible for the appearance of monodon on the Atlantic Coast of the USA.  These animals may be illegal immigrants (if they were released from a USA-based installation), but there is no deporting them at this point.  Like Craig, however, I am very curious to know their geographical origin and, if possible, the approximate time and location of their release or escape, so that we can begin to learn about and keep track of their progress, both in terms of movement and assimilation and their health.  After all, not all immigration is bad, and now that they are here, we should know as much about their past and future as possible.


Victor Suresh ( Does anyone know of adult vannamei in fisheries off the coasts of Brazil or Venezuela?  Vannamei is an exotic species in these two countries, but I have not seen reports that it is established in the local fisheries there.


I was recently in Brazil and heard a comment similar to what Osires de Melo said (above) about the whitespot virus in southern Brazil being attributed to ballast water.  Hard to believe, but the Brazilians swear on it, saying that there has been no live shrimp importation into southern Brazil for a long time.


Stephen Newman ( It is my understanding that the animals off the coast of Brazil were there as a result of a failed shrimp farm several decades ago.  It is also my understanding that wild monodon are routinely caught off the northern coast of Brazil and have established themselves off the coast of Guyana (northeast coast of South America) as well.  There is no practical way to restrain the movement of animals as long as there is a value to someone for doing so.  There will be a strong trade in illegal animals and the movement of pathogens will continue to be an issue.  Tight regulation and extreme consequences for getting caught will deter some, but the existence of a thriving global black market ensures that these practices will continue to some degree.


David Griffith ( I understand that monodon was imported into Venezuela and other parts of the Caribbean in the late 1970s and early 1980s.  About three years ago a couple of monodon were caught in Lake Maracaibo by artesanal fisherman (I saw one of these and have photos if interested), and I know of at least one monodon being caught off the Península de Paraguaná (Venezuela).  The issue was discussed on the Shrimp List (see Source below) a few years ago; the general consensus was that while monodon may be occasionally found, it hasn’t been caught in sufficient numbers to suggest established populations.


Alain Michel ( It is well known that monodon has extended its range to the west coast of Africa where it is frequently found in the trawler catches.  This new population is clearly a result of the escapement from shrimp farms in West Africa.  Maybe they got to the Americas by following logs across the Atlantic.  Concerning a potential settlement of all the exotic species that have been imported and reared as captive broodstock in Tahiti, it has never occurred just because there is no continental shelf.  The lagoon is very small and the slope out of the barrier reef goes straight down to a thousand meters.


In the South Pacific, monodon has just extended its range to Fiji, where there are enough mangrove areas suitable for them to make a living.


Mario Aguirre ( David Griffith’s comments are correct except that monodon was imported in the late 1980s by the Aquacam (now closed) shrimp farm in the Cariaco Gulf in Venezuela.  Also, three monodon have been caught on a shrimp farm in Venezuela.


Victor Suresh ( Do you know of any vannamei caught from the ocean by fishermen in Venezuela or the Caribbean?  The reason I am asking this question is that one of the concerns expressed in using nonnative stocks is the possibility that the stocks will escape into the wild, become established and compete with local species.  Has the long presence of vannamei in countries like Venezuela and Brazil shown the potential of vannamei getting established in the wild?


Hervé Lucien-Brun ( Monodon is now relatively common on the west coast of Africa.  A monodon fishing industry has developed in West Africa, especially in Nigeria.  Several people think the origin of the West African monodon was a farming project in Gambia.  The farm failed and the technicians released the stock into the sea.  I don’t know if it’s true because several other monodon projects were initiated in the same area, the Ivory Coast, for example, without success.  After failing, the Gambian project was reborn, and it is now in operation again, this time with wild-captured monodon broodstock from Gambian estuaries.


Juan Aguirre ( In Ecuador, the Morrison group (Fincacua, Semacua) brought in monodon in the early 1980s and tried it in farms.  It wasn’t very successful and no sightings have been reported.  There are others (Phil Boeing, Bobby Padua) who should know the full story.


Camaxdron ( Monodon are in Guyana, Trinidad, Venezuela and Colombia (Caribbean side).  They are breeding and surviving with no apparent harm to wild shrimp.  They are entering and growing in vannamei ponds, being caught by trawler fleets, and increasingly, appearing at shrimp processing plants.  They’ve been here a long time.  They command better prices and grow faster than vannamei, and they may have acquired some resistance to our Vibrios and viruses.  How did they get here?  It doesn’t matter.  They may help us escape the current plague of low prices—and help us compete with the millions of tons of vannamei that are coming in from Asia.  Let’s turn the “tortilla” on them.


See: Who's Got the Biggest Monodon?


Source: The Shrimp List (a mailing list for shrimp farmers, “”).  Subject: [shrimp] Monodon culture in the Americas.  October 16-25, 2007.


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