How to Grow and Harvest Vannamei Prawns

How to Grow and Harvest Vannamei Prawns

In our fish farm in Pangasinan, we grow what the locals call “vannamei” in addition to milkfish ("bangus"). Vannameis are part of the shrimp/prawn family which includes the more famous tiger prawn (Penaeus monodon). Vannameis are more correctly called Whiteleg shrimp or Pacific white shrimp because of their transluscent white body. Scientists used to call it Penaeus vannamei (old name), and recently as Litopenaeus vannamei (new scientific name).

A number of fully grown tiger prawns (penaeus monodon) taken out after complete draining of one of our ponds. These are part of a few samples of tiger prawns given by a dealer for free several months ago. From post larvae, they grew up into adults shown in the photo. We were actually surprised they survived.

Freshly caught vannamei shrimps/prawns from one of our ponds using the shrimp net trap described in this post

Crustaceans like tiger prawns and vannameis are bottom feeders and stay at the pond bottom. They dive deep into the sediments or muck at the bottom to escape predators and rely on the organisms at this substrate layer for their food.

From experience, we learned that growing vannameis in polyculture with (i.e., grown together with) our home-grown bangus is more advantageous to us pond operators/owners. They add to our revenues and help increase the productivity of our ponds, with minimal increases in costs.

Vannameis are now the most farmed species globally. But why not grow the tiger prawns instead, which command a higher selling price per kilo? We did in our closed system ponds when we were just starting, but unfortunately with very discouraging results (very low survival rates).

For comparison, tiger prawns (“sugpo” in Tagalog and “bingalo” in Pangasinense) are more sensitive to water quality (that is, they demand higher quality). Vannameis are less so and can be produced in closed system ponds like ours. In Class A ponds, they can be grown in higher stocking densities (intensive environment).

Tiger prawns require a costlier feeding regimen since they need high protein feeds. In the case of vannameis, they have lower needs for proteins. In fact, in our ponds where vannameis are grown extensively, they can make do with the natural food in the pond.

Vannameis are more resistant to various diseases, compared to tiger prawns. Thus, survival rate for the latter tends to be quite low, whereas vannameis have been enjoying much higher survival rates in recent years.

Vannameis can grow as fast as tiger prawns but when they reach 20 grams apiece, the vannamei’s growth rate slows. However, tiger prawns can grow to a large size, thus commanding a higher selling price at the Dagupan fish center.

The above comparisons between tiger prawns and vannameis are not mine, but were drawn from conclusions made by the FAO’s Fisheries and Aquaculture Department.

As a layman-farmer, my own actual experiences (though limited) however, are consistent with these observations.

But to be sure, it’s best to choose suppliers who sell only SPF (specific pathogen free) vannamei stock. According to experts (FAO, SEAFDEC, BFAR), SPF vannameis are certified free from six known shrimp diseases. It’s no guarantee that they won’t get infected in the future, but right now, the odds are stacked in our favor.

For the list of accredited suppliers, refer to the Bureau of Fisheries and Aquatic Resources (BFAR)’s On-Line Info System. For us fish farmers from Binmaley, Pangasinan, there is one located in Bonuan Gueset in nearby Dagupan City.

Vannameis are usually stocked in our ponds at the start of the cropping year after the ponds are cleaned up. Ponds where the vannameis are released have undergone the usual preliminary activities during pond preparation (click this to see the step-by-step procedures on how to prepare the pond).

Vannameis for growing are usually purchased as post-larvaes (usually PL-10 to 15). From hatching in a hatchery, it takes about 25 days to produce a PL-15. Upon receipt of the stock from our dealer, we keep them first in a large "saplar" (or sorting net) and feed them with boiled egg yolk and oyster meat. After 2 weeks, the vannameis are released into the ponds.

We follow the stocking density for extensive system of 4 to 10 pieces per square meter. After 4 months, we can do initial harvesting when the vannameis reach about 11 to 12 grams apiece.

How to Harvest Vannameis in Ponds

We normally do a thorough harvesting of our vannameis (or what remains of them to be exact) during the end of our cropping year – using the complete drain method (“limas”) (for the related blog post on how to do pond draining (“limas”), click this.)

Note: In Class A and B ponds, vannameis are harvested by draining the pond at low tide through a bag net installed at the outlet gate, either through the natural flow of outgoing tide water or with the help of a water pump.

During intervening months, when we harvest our bangus, we do catch a number of vannameis that are entangled with the bangus, using the usual haul seine net method (“kalokor”). Click this and go to the section "How to Harvest Bangus" to give you an idea of how it is done.

But for harvesting of vannameis specifically, we also do cull-harvesting of subadult vannameis, and later, even adults (around 20 gram weight per piece), using a shrimp trap device that I discovered recently – the so-called “bubo” in Pangasinense or extended shrimp net trap (it looks roughly like a large accordion net).

How do we do it? Below are the step-by-step procedures.

1. Buy or rent “bubo” trap. You can buy at Lingayen market at Php2,000 to 3,000 per piece.

2. For bait, buy half a kilo of salted dried fish (“tuyo”).

3. Also for bait, pick a fallen brown mature nut (“niyog”), cut out some pieces (meat with shell) and roast them over fire.

4. Spread out the “bubo” net trap to its maximum length. Make sure that both ends of the trap are closed by tying with string to later prevent escape of trapped vannameis.

A "bubo" shrimp net trap fully stretched out and being checked out by my caretaker and aide. We borrowed this trapping device from my harvest workers the first time we used one.

 

Our own "bubo" net trap fully stretched out

5. Attach the baits (salted dried fish and roasted coconut meat on shell) on every other compartment in the “bubo” net trap.

A piece of roasted coconut meat in shell ("niyog") (above) and a piece of salted dried fish ("tuyo") (below) as baits

6. Refold the trap and place it in a plastic basin.

Net trap being folded after placing the baits inside

 7. Take the trap in basin to the targeted pond and choose the specific location for the trap.

"Bubo" net trap folded in plastic basin by the side of the pond, ready for set-up

8. Use two pieces of bamboo poles or stakes (“onoon” or “tulos”) and tie each end of the net trap to a bamboo pole.

Tying one end of the trap to a bamboo pole or stake; other bamboo pole is for the other end of the trap

9. Go down the pond and insert one bamboo pole (to which one end of the net trap is tied) into the pond bottom near the side of the pond. The pole is used to hold down the net at the bottom.

One end of the net trap being held in place by a bamboo pole

10. Unfold the rest of “bubo” net trap slowly, stretching it to its full length by moving the basin farther down along the side of the pond. 

Rest of the trap being unfolded and stretched to the other end; see first bamboo pole holding down the trap at left of photo

11. Plant the second bamboo pole (to which the other end of the “bubo” net trap is tied) at the pond bottom when the net is fully stretched.

Preparing to set up the second bamboo pole to hold down the other end of the net trap

Note: The “bubo” net trap must sit right on the pond bottom to allow entry of the vannameis into the trap, as they are lured by the baits. Remember that the vannameis are bottom feeders and stay at the benthic (bottom) layer of the pond.

12. Leave the trap at the site and wait for 4 hours.

13. Retrieve the trap by the doing Steps 9 to 11 in reverse. That is, pull out the second bamboo pole. Refold the trap (with the vannameis inside) in the basin. Wade toward the first bamboo pole and pull it out. Then put the entire trap with the catch in the basin.

14. Have a weighing scale ready. Make sure that enough quantity of crushed ice has been purchased and on stand by.

Note: The ice will prevent onset of melanosis (blackspot discoloration in shrimps that can turn off buyers and bring down selling price) and ensure that the quality of vannameis is maintained before and during sale at the fish center.

15. Untie both ends of the net trap. Shake out the “bubo” net to dislodge the trapped vannamei prawns. Unload the vannameis into the plastic basin. Count the number of pieces caught and get total weight in kilos. Divide total kilos by number of pieces to get the weight per piece in grams.

Retrieved net trap being untied at both ends

Vannamei prawns being dislodged into the plastic basin by shaking them loose from the net trap

Vannamei prawns caught using "bubo" net trap

16. Repeat Steps 4 to 15 to do a second harvest. Make sure to choose a different pond or location (if trapping is done in the same pond). 

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