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Moving Penaeus vannamei from Nursery to Growout
(Some Pictures at the End of This Report)
Saji Chacko (email@example.com): Dear Listers, I am from India, presently farming Penaeus vannamei in a single-stage system (no nursery ponds), using stocking densities of between 30 to 60 postlarvae (PLs) a square meter (m2) in one-hectare earthen ponds. Would a two-stage system with nursery ponds be more efficient?
Pamindangan Farm (firstname.lastname@example.orgPamindangan” happens to be the area where my farm is located. It is better to use that name, kinda like Clarke Kent, especially in my country where there are many busybodies):
Dear Saji, the effectiveness of two-stage culture depends on your system for transferring juveniles to the growout ponds and your knowledge of managing nursery systems. I tried to implement a nursery system at my farm in Indonesia, and, after a couple of failures, I gave up and converted the nursery ponds to growout ponds.
While there are presumably plenty of experiments and wonderful results out there for two-stage systems, one has to consider the risks and possible losses when implementing them. You need a lot of ponds, and they should be lined or concrete. Instead of using nursery ponds, I think you should increase the stocking density of your growout ponds to 70 or 80 PLs m2.
Eric De Muylder (email@example.com): Hello Everybody, I think the primary problem with nursery systems is transferring the juveniles from nursery to growout without stressing them. This means moving small shrimp from one tank to another without capturing them and with only minor water quality changes. You may have a shorter growout cycle, but anything that causes stress will result in mortality, synchronized molting and some growth loss.
Saji Chacko (firstname.lastname@example.org): Dear Pamindangan, thanks for the insight. I’m in India, where I farmed tiger shrimp (Penaeus monodon) for over 20 years. In 2009, I switched to P. vannamei. I’m still learning “vannamei” and will soon upgrade to a more intensive system. Last month, I went to Indonesia to see its vannamei farming systems.
I ran some trials on a two-stage system and had mortality problems when transferring juveniles. Here in Gujarat, we have extreme conditions with summer temperature as high as 45° Celsius and winter temperature as low as 10°C. The difference in temperature between the pond water and atmosphere causes cramping in juvenile shrimps.
One idea I had was to use HDPE (high density polyethylene) lined raceways on the partition dyke between two ponds and transfer the juveniles by gravity to the growout pond. Do you think that makes sense? If so what is the ideal raceway size? I am not using bioflocs.
The main reason for using a nursery cycle here is the slightly lower growth rate that we get during summer when salinities rise as high as 50 parts per thousand (ppt). The shrimp reach 16 to 18 grams in 100 days at densities of 40 to 60 m2 with a water depth of 1.6 meters. Growth rate is slightly higher (by about 2 grams) at densities below 40. During the winter crop, when the water temperature drops to as low as 16°C for short periods, it takes almost 150 days to produce 20-gram shrimp. I wonder if a nursery phase would shorten the growout period? Research reports indicate that it would.
By doing a partial harvest during mid crop, I could improve the growth rate marginally.
After starting with crumbled feeds, I use auto feeders and have experienced better feed conversion ratios with them, compared to manually broadcasting feed. I use SPF seedstock from Shrimp Improvement Systems’ broodstock. Information: Dr. G. Subba Rao, General Manager, Shrimp Improvement Systems India, Pvt., Ltd., 4-70-3 Lawsons Bay Colony, Visakhapatnam 530017, Andhra Pradesh, India; Hatchery, Mukkam Village, Bogapuram, Vizianagaram District, Andhra Pradesh, India, (phone/fax 0891 6641589, mobile +91-9848193090, email email@example.com).
I have also come across a few instances where the HDPE lining got lifted up during mid crop due to gas formation below the lining, which resulted in crop loss. What precautions should one take during installation to prevent such incidences?
Hervé Lucien-Brun (firstname.lastname@example.org): Two-stage culture is very common in Latin America. It allows better use of the growout ponds by making the growout cycle shorter, and it also allows for more flexibility with hatchery production and the restocking of growout ponds. Nurseries are mostly 5,000 m2 to one-hectare earthen ponds, stocked at a density of 100PL/m2. Some big farms use circular or raceway-type concrete tanks and nurse the PLs for between 10 to 20 days at 5,000 m2, feeding them high-protein crumble feeds and sometimes with Artemia. The water is fertilized to promote plankton growth.
It’s important to transfer the juveniles to the growout ponds during their early hard-shell stage of the molt cycle and at night or early morning when temperatures are lower and the light less intense. One important key is to always keep the juveniles in water to avoid thermal stress resulting from the evaporation of moisture from their bodies if they are exposed directly to the atmosphere. Juveniles are transferred from the nursery ponds in baskets, placed in tanks on a vehicle and driven to the growout ponds, where they are acclimated to the pond water over a twenty-minute period. The transfer should be a gentle process, done by an well-trained team that’s looking for signs of stress. On our 600-hectare farm, we do the transfers as quickly as reasonable and do not experience significant mortalities.
Pamindangan Farm (email@example.com): Kudos, Hervé, impressive details! My problem was mortalities during transport from the nursery to the growout ponds, probably caused by my lack of experience in doing it right. Consequently, I now do direct stocking and have converted my nursery ponds to growout ponds.
Saji, your conditions sound pretty extreme in terms of temperature and salinity fluctuations from summer to winter. How have you been doing so far? Have you tried adding depth to your ponds? I have zero experience in growing shrimp under such extreme conditions. Here in Indonesia we only have two seasons: hot and rainy. I can’t give you any insight on biofloc either because I have yet to produce it on a consistent basis.
Partial harvests are becoming the norm here. They lower densities and improve water quality. I normally do two or three partial harvests per crop, depending on the condition of the shrimp and growth data. To condition my ponds for liners, I dried them out for two months before I lined the banks with HDPE. If your HDPE lining gets lifted up, you might want to shorten the distance between the holders. I use bamboo to “nail” them to the banks of the pond. What is the cost of labor and cement in your area? I have found that concrete ponds are way more stable and cost only a little more than the price of thick HDPE lining.
Saji Chacko (firstname.lastname@example.org): Dear Hervé, would you please elaborate on your method of harvesting the juveniles from the nursery ponds? For example, what type of net do you use and what is its mesh size? How heavily do you stock the growout ponds? On our farm, where the stocking density is between 40 to 60 m2, we need one nursery pond for every two growout ponds, which results in a huge reduction in the total area we need to farm shrimp. What is your suggestion?
Dear Pamindangan, in India, we have three pronounced seasons: summer, monsoon and winter. In the summer water temperatures do not go above 32°C in the ponds. During the monsoon, the salinity drops to as low as 3 ppt. Despite the changes in season, I have been producing around 1,000 metric tons of vannamei a year.
One more question on HDPE lining: Do you run breather pipes under it?
Cement and labor are expensive here compared to 500-micron HDPE. What is the thickness of your HDPE?
Pamindangan Farm (email@example.com): Saji, I only use HDPE on the banks of my ponds, not on the pond bottoms, which are either earthen or concrete. I heard that those who totally line their ponds with HDPE here in Indonesia use some sort of breather pipes to release any excess gas from the pond bottom. Since I don’t use such methods, I cannot comment much on them. If your ponds have air pipes running from one end of the pond to the other, you might be able to use them to help pin down the HDPE, but you will probably need some sort of heavy duty pinning or weights to make sure they do not float up.
As to the thickness of the HDPD, I found that the more durable 0.75 mm HDPE is better than the 0.5 mm HDPE. The cost of installation including the material and labor for me was around $4.00 a square meter, depending on the cost of good quality imported material. There are cheaper versions of HDPE on the market now, but I have not tried them. I can cover the bottom with concrete for around $5.50/m2. The price of cement has increased drastically lately, but because we are now in the rainy season, I have stopped construction work.
Saji Chacko (firstname.lastname@example.org): Dear Pamindangan, thanks a lot and best of luck with your operations.
Luis Rafael Giovanni Chasin Valencia (email@example.com): I agree with most of what Hervé said about nursery ponds, but disagree with his comments about transporting juveniles in water. From around 1987 to 1990, I did it in Ecuador without any problems, but now in Brazil, even though we do everything right, we are experiencing some transfer mortalities. I found that it’s much more reliable to transfer 0.5-2.0-gram juveniles without water in 2-kg, slotted plastic containers, carrying no more than 6-7 kg of juveniles per container. I use a motorcycle and carry two containers per trip. Each trip never lasts longer than two minutes. One night I transferred 1.0-1.5 million juveniles in five hours. Our mortality rate is usually zero. Our nursery ponds are between 0.7-1.6 hectares. Keeping the nursery ponds close to the growout ponds is the key to success for this protocol.
Jorge Cordova (firstname.lastname@example.org): Hi Giovanni, could you send me a picture of the plastic containers that you use to transfer juveniles.
Glen Bieber (email@example.com): Jorge, I now work in East Africa, but a long time ago, I worked for years in Nicaragua and Panama. Your idea of transferring juveniles without water has many applications. I also would like to see a picture of the containers.
Luis Rafael Giovanni Chasin Valencia (firstname.lastname@example.org): Jorge and Glen, I posted three pictures of the slotted plastic baskets to the photo section of “The List”.
Shrimp News: I had to do some guessing while summarizing this report. If I made a mistake on any of your comments, please let me know and I’ll correct them.
Also, there was a previous discussion on “The List” that covered moving juveniles from nursery to growout. check it out.
Sources: 1. The Shrimp List (a mailing list for shrimp farmers). Subjects: Nursery Systems for L. Vannamei and Plastic Container for Transference of Juveniles. December 11-19, 2012. 2. Email to Shrimp News International from Shrimp Improvement Systems India. Subject: Christmas Greetings. December 31. 2012. 3. Summarized by 2. Bob Rosenberry, Shrimp News International, December 31, 2012.
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