The Shrimp List
A Mailing List for the Shrimp Farming Industry
The Shrimp List is a free, email-based, unmoderated, mailing list for shrimp farmers that distributes information posted by one member of the list to all the other members of the list. Anyone can use the lists to ask and answer questions, to keep participants up-to-date on a conference, to coordinate a project or to pass industry news around. You don't have to participate in the discussion. You can just sit back and read the messages that interest you. Your email address is not completely exposed, so you can remain anonymous.
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Excerpts from the Shrimp List
Shrimp News International frequently summarizes discussions from the Shrimp List. Here are some excerpts from the Shrimp List that have appeared on the Free News Page:
United States
Florida—The Half-Wit Who Works About 18 Hours Every Day
Gintautas Stasys Zavadzkas Leon (gleon@yahoo.com): The Shrimp List has been rather quiet lately...so:
A man owns a small shrimp farm in central Florida.
The Florida State Wage and Hour Department heard that he was not paying proper wages to his help and sent an agent out to investigate.
“I need a complete list of your employees and how much you pay each of them,” demanded the agent.
“Well,” replied the farmer, “there’s the farm hand who’s been with me for three years. I pay him $400 a week, plus I give him free room and board.”
“Then there’s the cook. She has been here for 18 months, and I pay her $250 per week, plus I give her free room and board.”
“Finally, there’s the half-wit who works about 18 hours every day and does about 90% of all the work around here. He makes about $50 per week, pays his own room and board, and I buy him a bottle of Vodka every Saturday night. He also gets to sleep with my wife occasionally.”
“That’s the guy I want to talk to—the half-wit,” says the agent.
“That would be me,” replied the farmer.
Source: The Shrimp List (a mailing list for shrimp farmers, “shrimp-subscribe@yahoogroups.com”). Subject: [shrimp] The reality. From: Gintautas Stasys Zavadzkas Leon. January 4, 2008.
Ecuador
Moving Juveniles from Nursery to Growout
Herry Samudra (herrysamudra@yahoo.com): How does one safely transfer juvenile Penaeus vannamei from nursery ponds to growout ponds? The distance at our location is about 400 meters. We have a problem with low survivals during transfer, and the animals that do survive don’t get back on feed for over a week.
Francisco Pons Zevallos (panchopons@hotmail.com): I have done it over a distance of 200 meters, manually, by foot, with a total biomass of no more than 80 kilos of 0.2-gram animals. How much biomass are you transferring and how big are your animals?
Fernando Huerta (fernandohuerta_dorman@hotmail.com): I transfer two-gram animals through a 1,200-meter, eight-inch pipe with excellent results. A few hours after the transfer, the animals are back on their feed. In one night you can transfer 6,000 kilos with just four people. You have to make sure that the pipe has a consistent slope and a constant flow of water.
Herry Samudra (herrysamudra@yahoo.com): Would you gentlemen describe your protocols before and during the transfer?
Francisco Pons Zevallos (panchopons@hotmail.com): The pipe system used by Fernando Huerta is the best system for juvenile transfer. I have seen it and wish I had the resources to do it.
Here is how I do it. Our juveniles are produced in 100-ton raceways, and it is easy to collect them with nets without stressing them. Nets should be a long and “U” shaped to give the juveniles room to swim. First we drain 40% of the water from the raceway, and then we start collecting the juveniles with the nets. We collect roughly four kilos of shrimp per pass, using two nets. We lift them out of the water for 20-30 seconds to let water run off and then weigh them. A sample of about 50 shrimp is taken aside by another person who weighs and counts them and then returns them to the raceway. This way we know how many shrimp we have per gram and can calculate the total weight transferred. Next we fill two, 25-liter buckets with 12 liters of new water, or use water directly from the raceways. We add one tablespoon of hydrogen peroxide to each bucket. The water in the bucket should contain around 20 mg/L oxygen. Then we quickly put approximately two kilos of shrimp in each bucket.
We cover the buckets with a lid, and then two men with one bucket each jog them to the pond, which takes about two minutes. The dissolved oxygen in the buckets is checked again at the ponds. It should be around 10 mg/L. The lid is removed, and the bucket is placed in the pond. Then we tip the bucket and spread the juveniles around with our hands, all the while observing their condition. We try to have no more than two degrees Celsius difference in water temperature between raceway and pond. As you can see, it’s a very simple and cheap procedure. We haven’t had any big problems with this method.
Ramon Macaraig (monmac52@yahoo.com): What’s the largest size shrimp that can be transferred using your method? I want to transfer two to three-gram juvenile Penaeus vannamei.
Francisco Pons Zevallos (panchopons@hotmail.com): I have only transferred animals that weighed less than a gram with the bucket technique. I don’t think it would work with larger animals.
Herry Samudra (herrysamudra@yahoo.com): What are the dimensions of your “U” shaped nets? Are they shaped like condoms?
Francisco Pons Zevallos (panchopons@hotmail.com): Yes, exactly, the “U” shaped nets are shaped like condoms. I use 3/4” PVC pipe as a frame for the net, which is made with 600-micron mesh. It is around 90cm long. When we collect the shrimp, we use two nets, side-by-side, so they cover a wider area and make it harder for the juveniles to escape. You have to drag the net fast enough so that the juveniles don’t escape, but not so fast that the juveniles are pressed against the end of the net.
Source: The Shrimp List (a mailing list for shrimp farmers, “shrimp-subscribe@yahoogroups.com”). Subject: [shrimp] Safe transfer from nursery to growout pond. November 14 to 21, 2007.
Algal Feeds
For Shrimp Larvae
Todd Blacher (toddblacher1@yahoo.com): Has anyone ever used Thalassiosira pseudonana for the production of Penaeus vannamei larvae?
John Scarpa (jscarpa@hboi.edu): I heard of some work done many years ago by Mary Schilling Clark at Harbor Branch Oceanographic Institution on using Thalassiosira weissflogii, a larger species than T. pseudonana, for P. vannamei larvae culture. There may be an abstract on this somewhere in the World Aquaculture Society archives.
Todd Blacher (toddblacher1@yahoo.com): I have also used T. weissflogii as a complementary species to Chaetoceros gracilis and/or C. muelleri. My culturing area, however, is very small and the T. weissflogii do not reach high concentrations. I have been culturing T. pseudonana for about four weeks and am getting amazing results (up to 16 million cells per ml), but have not tried to feed them to larvae because I have not cranked up the hatchery yet. Have any of you used T. pseudonana?
Dallas Weaver (deweaver@scientifichatcheries.com): Does anyone have experience feeding Spirulina, live or frozen, to penaeid larvae. If yes, to which stages?
John Scarpa (jscarpa@hboi.edu): Just remember that cell density is related to cell size. Although weissflogii does not get to the high densities of other species, it does offer a larger chunk (volume, mass), compared to pseudonana. Do you want a dozen White Castle hamburgers or just one Whopper?
Josh Wilkenfeld (josh.wilkenfeld@gmail.com): Cell size is important, especially during the early zoea stages, and so is the availability of particles for the larvae to encounter, since the early stages of shrimp larvae in particular are continuous filter feeders. Shrimp larvae are not very efficient at digestion and assimilation; they pretty much have to have a constant flow of feed going through their gut to get sufficient energy.
It’s true that weissflogii is one of the most nutritious species of phytoplankton, but its large cell size and relatively low densities in mass culture present two problems: early larval stages have a bit of a problem eating the larger cells and it takes much more floor space to grow them. Also, the cells would have to be concentrated to ensure that the larvae encounter them. Weissflogii usually works best starting at zoea-2 or zoea-3. It’s not a good idea, however, to use weissflogii as the sole, live algae species, at least until the mysis-2 stage, because of the size and availability issues.
I usually start by feeding at about 75-100,000 cells/ml and then add between 2,500-7,500 cells per ml of weissflogii when the larvae reach late Z-2 or Z-3. In the mysis stages, I’ll usually let the muelleri or gracilis densities drop to about 50K/ml, with 5-7.5K/ml weissflogii.
I’ve never worked with pseudonana and can’t say that I know of anyone who has, but that doesn’t mean that it would not be a great species for larval rearing. I tried to find some data on the lipid analyses of various species of diatoms (including weissflogii and pseudonana), but didn’t come up with anything useful during a quick Internet search. I heard a presentation sometime in the early 1980s that gave an analysis of various species of algae, and it was at that point that I decided to adopt the use of weissflogii into my feeding regime because, as I recall, it was second only to Skeletonema costatum in terms of its fatty acid profile. Weissflogii has always been much easier for me to handle in commercial-scale mass culture systems than S. costatum. I love the idea of the small size of pseudonana and the high cell densities, but lacking any definitive information on its food value or comments from anyone who actually has the experience of using this species with shrimp larvae, I guess what you have to do is give it a try. Todd, it would really be great if you ran some comparative trials with muelleri or gracilis.
Regarding Dallas’s question about the use of live or frozen Spirulina in larval feeding, many shrimp hatchery operators, including me, use commercially available dry Spirulina (INVE has a very good product) on a regular basis as a standard feed supplement beginning with zoea-1. I’ve also used Spirulina as a component of a moist maturation pellet that we produce on site. I’ve never tried culturing or feeding live Spirulina, and I’m afraid I’m not a big fan of frozen algae. I believe that the cell quality and nutritional value is diminished in the process of freezing, and you just end up with very dirty tanks and underfed larvae.
Phil Boeing (pboeing@dc.rr.com): I concur with all the other postings on this subject and would like to add the following:
Pseudonana is excellent algae for all stages of penaeid larvae. It is most widely cultured for feeding various species of bivalves because it is more of a coldwater species than the higher temperature tolerant weissflogii and the various Chaetoceros species. In some earlier work, weissflogii was used as a complete Artemia replacement for penaeid larvae at the Oceanic Institute. The Thalassiosiras are very high in cholesterol and HUFAs.
Todd Blacher (toddblacher1@yahoo.com): Thanks. I appreciate your comments. Once I start culturing larvae, if I come up with anything interesting, I’ll share it with all of you.
Samir Kuri (sk270965@yahoo.com): In Belize, I used Spirulina (frozen), pseudonana and weissflogii from zoea 1-2 onward with no muelleri or gracilis. I also used Daphnia with postlarvae and had very good results.
B. Sakthi Mohan Ganesh (saklynmon@yahoo.com): On Mafia Island, off Tanzania, I used frozen Spirulina from Z-1 to Z-3 along with supplements and got good performance.
Dallas Weaver (deweaver@scientifichatcheries.com): Thanks for the information. I am consulting for a group that hopes to significantly decrease the production cost of Spirulina. Being a much larger algae (50 to 100 µ long), perhaps it could be fed to later stages as a partial Artemia replacement. Frozen Spirulina should be cheaper that Artemia, or any locally produced live algae. I know this market wouldn’t be big, but it could be a fun market. What is your opinion based upon your experience regarding this possible market?
Source: The Shrimp List. Subjects: Unknown, Algae Feeds and Thalassiosira sp. November 1-2, 2007.
India
Fungal Infections and Probiotics
B. Sakthi Mohan Ganesh (saklynmon@yahoo.com): How can I avoid fungal infections in shrimp larval rearing tanks that also contain probiotics?
Satish Kumar (skbodapati@yahoo.com): With fungal infections, prevention is better than cure. If you properly dry the tanks and carefully wash the eggs and nauplii, the chances of getting fungal infections are minimal. You must also take care in feed management and avoid contaminants. If the fungi are a species of Lagenidium, I would suggest Treflan at 0.05 to 0.1 parts per million once or twice a day, depending on the severity, but you may still get low survivals.
Durwood Dugger (duggerdm@bellsouth.net): Mr. Kumar makes a very valid point regarding the priority of prevention. Assuming that you have already sterilized and filtered your hatchery water, high fungal levels in shrimp larval tanks are generally associated with open air hatcheries where there is insect contamination of the larval tanks. If it isn’t feasible to have a completely biosecure hatchery, then at least cover your tanks sufficiently to prevent insect access and contamination, especially if you have lights over the larval tanks that might attract insects. That should cut down on fungal inoculations significantly.
B. Sakthi Mohan Ganesh (saklynmon@yahoo.com): We can’t use Treflan in the tanks because it would kill the probiotic populations (Bacillus) that we encourage.
Source: The Shrimp List (a mailing list for shrimp farmers, “shrimp-subscribe@yahoogroups.com”). Subject: Re: [shrimp] Re.Fungal infection at shrimp larval rearing tanks. October 26-30, 2007.
