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PL Counting

A Discussion from the Shrimp List


Nelson Gerundo ( The scoop method of counting shrimp postlarvae (PLs) provides rough estimates only, but I do not doubt the accuracy of the XperCount, an electronic counter made by XpertSea Solutions, Inc., that provides accurate counts of Artemia, rotifers, microalgae, eggs, nauplii, postlarvae and juveniles.  Here is a link to a video on how easy it is to use.


Daniel Gruenberg ( Nelson, I suspect that XpertSea Solutions is no longer in business.  I sent them an inquiry about purchasing one of their counters, but I got no response.


Also, you say that you don’t doubt the accuracy of their counter, but there are no peer reviewed papers on its accuracy, and the only “proof” you offer is the manufacturer’s naked claim.


Anyway, if I do eventually hear from them, I will buy one and conduct my own tests and let the group know my results.


Has anyone in this group purchased an XpertSea counter?  Can anyone vouch for its accuracy?


Nelson Gerundo ( Régis Bador, a reliable name in aquaculture, has given it a positive review.  I consider Régis’s approval as the equivalent of peer review.  He gave it his stamp of approval.  You can view Régis’s résumé here, his Linkedin page here, and his webpage here.


Daniel Gruenberg ( Nelson, Régis Bador is marketing the XpertSea counter.  He’s not an independent, third-party validator.


Just how many shrimp farmers are using this device?  Where did you get the 95%+ accuracy figure?  What’s it based on?


Nelson Gerundo ( Daniel, I got the 95%+ accuracy figure from one of Régis’s posts to this list (Shrimp List message #15178).  It was for counting shrimp nauplii.


To get information about the XpertSea counter from Régis, here is what you should do.


• Fill out the form at his website:

• Or you could email him at


Daniel Gruenberg ( Nelson, in case you have difficulty understanding, I am looking for scientific, peer reviewed, third-party, independent validation of the manufacturer’s claims.


I am unaware of any shrimp farmer that has used the XpertSea counter and can vouch for its accuracy.  Where did you get the 95% accuracy figure?  Compared to what?


I have contacted the manufacturer in Canada, but have not received a response.


Nelson Gerundo ( Daniel, Other than the XpertSea counter, you might also want to look at the Larco-PL Counter.


Daniel Gruenberg ( Thanks for that very interesting information, but the Larco-PL Counter is still under development, and I suspect it won’t find too many buyers at $20,000 per unit—if and when it is released for sale.


Matthew Briggs ( Hello Daniel, I have used the XpertSea counter, and the accuracy is not 95%.  My result with a range of PLs from 0.005 to 0.7 grams was 75-80% accuracy.  It still needs refinement to give more accurate results.  It’s a great idea with lots of potential, but still not accurate enough for my needs.


Daniel Gruenberg ( Thanks Matt, that’s what I suspected.  At 75-80% accuracy, it is still no better than the “scoop” method.


Most commercial shrimp farms in the world have no idea what their true survival rate is, because they don’t know the number of PLs they stocked.  And even those that purchased the XpertSea counter don’t know because its accuracy in the field is only 75 to 80%.


I don’t think the $20,000 Larco-PL Counter is going to appeal to many shrimp farmers, although, theoretically, its image processing approach is probably capable of a much higher accuracy than the optical density approach used by XpertSea.


Our industry really does need an accurate and economical method for counting PLs.


Nelson Gerundo ( We have a choice, an expensive and more accurate PL counter like the $20,000 Larco-PL Counter that is being developed or the cheaper, versatile, handy, portable, bucket-type XpertSea counter.  Some of us will stick with the tedious and laborious “scoop” method, shown in this picture of an improvised PL scoop for estimating the quantity of juvenile giant tiger shrimp at a hatchery in the Philippines.


Picture in Graphics = Philippines/Scoop Method


Régis Bador ( Nelson, the link does work.  I just tested it five minutes ago.


Daniel, yes, I am the XpertSea distributor for Oceania and Latin America.  For Asia, please contact George Chamberlain ( the XpertSea distributor in Thailand, or just contact XpertSea directly.


I do confirm that this is a reliable device for small sizes and homogenous organisms like, fish eggs, shrimp nauplii, Artemia nauplii, pure microalgae and the young larval stages of any aquatic animal.


I also confirm that it has to be calibrated for larger animals, especially if there is an abnormal size distribution.  It’s least effective when batches of different sized PLs have been mixed together.


I am about to run new tests with the XpertSea Counter in New Caledonia, my home country, and I’ll keep you posted on the results.


Daniel Gruenberg ( Hi Régis, it’s nice to hear that people are at least thinking about PL counting, and I also thank you for the comments on the calibration of the XpertSea counter.  If we are going to fix the PL counting problem, we are going to need good, high-quality, economical solutions.  Keep us updated on your progress.


Nelson Gerundo ( The XpertSea counter is an ingenious invention of Valerie Robitaille, Cody Andrews, Sylvie Lavigne and Francois Robitaille, a group of very young and talented Canadians.  Their invention won the grand prize in the 50th Canadian DevTech Competition in 2011, organized by Quebec International, whose aim is to identify and give recognition to new promising technological companies in Canada.  Thirty-eight Canadian companies participated in the competition and XpertSea was awarded first place from among the ten finalists that were selected by the committee.


Here is a picture of three of the brilliant young people who invented the XpertSea Counter.  From Left: Cody Andrews, Valerie Robitaille and John Robitaille.


Daniel Gruenberg ( Régis, how much does the XpertSea counter cost?


Do you have any comments on Dr. Brigg’s contention that the unit is only 75-80% accurate?


How often does the counter need to be calibrated?


Do things like PL pigmentation affect accuracy?


I am interested in accuracy under typical field conditions, not ideal laboratory conditions.


Nelson Gerundo ( Here is the contact address for XpertSea Solutions, Inc.


XpertSea Solutions Inc.

2700 Jean-Perrin Street, Suite 170

Quebec PQ G2C 1S9 CANADA


Phone: +1-418-915-8028

Fax: +1-418-915-8028




Matthew Briggs ( I think Régis is right when he says these devices are good at counting small things that are all the same size.  Unreliable counting occurs with larger PLs that vary in size.  The XpertSea counter requires individual calibration, which can be time consuming, thereby somewhat negating its practicality.  If your requirements are for counting Artemia, algae or naups, the XpertSea counter is more accurate.


Daniel Gruenberg ( Again, I don’t think you can claim blanket 95% accuracy for the XpertSea counter unless the size and species of the test animals are identified.  The video at the bottom of XpertSea’s Home Page shows 200–300 fish being counted with very high accuracy.  The 95% figure may hold for those fish, but you can count that amount of fish by hand, so where’s the utility.  When you are trying to count millions of PLs in the real world under actual working conditions, the XpertSea counter does not seem to perform at 95% accuracy.  It’s more like 75-80% as quoted by Dr. Briggs.


My contention that there is no practical way to count millions of PLs prior to stocking still holds.  Let’s hope the technology keeps moving forward.


Matthew Briggs ( That’s a good point Daniel.  Even if the XpertSea counter were 100% accurate, it would still not be a very useful tool for counting the millions of PLs that big shrimp farms stock.  You cannot use it to count all your PLs, unless your production is very small.  It is, however, useful for sampling and estimating the number of PLs in a large order.


We already have volumetric methods, along with the perforated spoon method for estimating the number of PLs, but these methods result in inaccuracies when extrapolated to the total number of PLs in a shipment.


To my mind, the XpertSea counter is a good tool for counting algae, Artemia and maybe naups, but not that useful for PLs.


So Daniel, I agree with you.  We still don’t have a good, automated way of counting large numbers of PLs.


Ramon Macaraig ( It’s time for some comic relief here—Why don’t you guys just count the eyes and divide by two.


Matthew Briggs ( Oh Ramon, that would be too fast.  Why not count the legs and divide by ten!


Bocuan Orapopo ( I’m harvesting ponds right now.  I was pretty happy with the survivals of the first few ponds until one pond had survivals of 120%.  Then, all of a sudden I felt like a fool.  Obviously, my estimate of the number of PLs stocked in those ponds was way off.


Régis Bador ( Pigment, or any other characteristic of the external appearance of larvae, has no impact on the XpertSea counter because its counts, simply stated, are based on the volume of the animals.  It is important to understand that the counter does not focus on viewing the animals.  It uses the volume of water and animals (or algae) to make its counts.  That’s the great advantage of the system: you can count millions of shrimp nauplii at once as long as you can “concentrate” them in the ten liters of water inside the XpertSea bucket.  You don’t have to rely on the little samples that your biologist uses to extrapolate a total.  Don’t ask a statistician about the method we traditionally use to get the total number of PLs from such limited and tiny samples; he may have a heart attack.


For any stage of organisms with a consistent size, for example recently hatched Artemia nauplii, shrimp nauplii, pure algae cultures and fish eggs, most of the calibration has already been done by XpertSea.  You only need to check or confirm the calibration at your site once.  After that, as long as you’re counting the same size and species, you don’t have to recalibrate.  The XpertSea counter keeps a record of your calibrations for different species and sizes and allows you to choose the right one each time.


If you work with a new species or size, you only need to recalibrate the counter once because the XpertSea counter keeps a record of each new calibration.


I want to remind everyone that there are two limitations to the XpertSea counter for PLs, especially for large PLs:


1. When the size distribution is too wide or abnormal or when you’re working with mixed batches of PLs, the XpertSea counter is not as accurate.


2. If you’re counting millions of PLS, you may not be able to afford the time and expense of counting them in ten-liter buckets, even if the count only takes ten seconds.  If you’re accustomed to transferring tens of thousands of PLs in buckets to large tanks on trucks, however, you may want to consider buying several XpertSea buckets, but just one of the lids that contains all of the electronics for doing the counting.


If you’re shipping in plastic bags with several thousand PLs in each bag, then the XperCount is not the ideal tool.  It could be used, however, to randomly sample a few plastic bags to estimate the total.  Remember, all these counts only take ten seconds.  So, even if you only count every tenth bag, you still get a good estimate.


Ramon Macaraig ( We just purchased an XpertSea counter and will test it in September 2013 when we stock our ponds.  One thing my engineers told me though is you can’t use it out of the box.  You have to test it with your PLs and send the data back to XpertSea for them to calibrate it.  I think this is a rather cumbersome process that we didn’t know about when we purchased the unit.  Anyway, I will give you my accuracy report once we have used the unit.


Juan Aguirre ( Hello Matt, you say you got 75-80% accuracy.  Compared to what counting method?  Dilution?  Volumetric?  Weighing?  Manual counts?  Did you count a range of different sizes and batches?


Matthew Briggs ( Hi Juan, my counts were compared to hand counting.  There was considerable size variation within the PL batches that we counted and maybe this led to less accurate counting.  We counted a large number of batches and the results were +/- 15-20% off what we hand counted.


Brian Boudreau ( Hello shrimp group, the only two pieces of information you need for an accurate PL count are the total biomass weight and the average PL weight for each PL tank harvested.  The total biomass weight is obtained during the harvest of the PL tank by weighing PLs in batches in a bucket of water on a digital platform scale and zeroing the scale with a bucket of water before adding about a kilo of PLs at a time.  The average weight can be obtained by weighing a small sample of about ten grams of PLs in one liter of water in a two-liter plastic pitcher on a smaller scale.  Then transfer these animals and water into a clean, white, larger bucket.  Make sure they are distributed evenly and then take a picture of them.  You need crystal clear water less than one centimeter deep for the picture.  Load the picture into your computer, magnify and count the PLs with a red dot.  The picture can be shared electronically between hatchery and farm, so the person receiving PLs has the opportunity to observe the uniformity and quality aspects of the PLs and can do his own count to cross check your count.


Source: The Shrimp List (a mailing list for shrimp farmers).  Subjects: (1) Larvae feeds vs. Growout Performance and (2) PL Counting.  July 15 to July 20, 2013.


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