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Shrimp News Interviews Al Stokes and Craig Browdy
At Aquaculture America 2005 (New Orleans, Louisiana, USA, January 17-20, 2005), I interviewed Dr. Craig Browdy, senior marine scientist at the South Carolina Department of Natural Resources, and Al Stokes, manager of South Carolina’s Waddell Mariculture Center:
Shrimp News: Craig, tell me a little bit about your education and your first steps into shrimp farming.
Craig Browdy: As an undergraduate, I went to the University of Maryland, where I heard some lectures on aquaculture and really liked the idea of an applied science. When I graduated in 1981, Israel was one of the leading aquaculture countries in the world, so I did my Ph.D. at Tel Aviv University. Most of my research was done at the National Center for Mariculture, in Eilat, on the Red Sea. That’s where I met Tzachi Somocha, currently a shrimp researcher at Texas A&M University, who became my advisor. I worked on shrimp reproduction for the next eight years.
Shrimp News: How did you get from the National Center for Mariculture in Israel to the Waddell Mariculture Center in South Carolina?
Craig Browdy: I met Dr. Paul Sandifer, the force within the South Carolina Department of Natural Resources who started the Waddell Mariculture Center. He was looking for someone to do shrimp reproduction work at the Center. I got the job. It was a good fit. Paul was a wonderful person to work for until his retirement a few years ago.
Shrimp News: Hi Al, same question, tell me a little bit about your education and your first steps into aquaculture and shrimp farming.
Al Stokes: In 1977, I received a bachelor of science degree from Clemson University, where I studied recruitment of wild fish into farm ponds and pond ecology. About the same time, I was introduced to catfish pond management practices at Clemson. When I graduated, I applied for a job with the South Carolina Department of Natural Resources and was fortunate enough to get hired and work with Dr. Ted Smith and Dr. Paul Sandifer, who,at the time (1978), were studying freshwater prawns (Macrobrachium rosenbergii). We farmed prawns in ponds located at the Dennis Wildlife Center. We managed several ponds and raceways and performed studies focused on improving production numbers. We stocked nursed animals versus postlarvae and installed substrate in an attempt to increase stocking rates. We also wanted to determine optimum water quality management practices. We achieved good production, results with approximately 1,300 kilograms of large prawns per hectare during the summer. We also offered services to assist potential prawn farmers in the state.
In 1979, I was asked to review the plans for the proposed Waddell Mariculture Center, and, during construction, I became the on-site manager to get it furnished, equipped and running. The Center officially opened in 1984, and I was assigned the job of pond manager.
In our first year of operation, we began working with Penaeus setiferus that we received from Chris Howell in Florida. We stocked at a very low rate that first year. The second year, we accidentally double-stocked a pond and got very good production from it. From there, in an attempt to increase production, we began stocking nonnative species like P. vannamei, P. schmitti and P. monodon. We got better results with vannamei and have been intensifying our stocking and management efforts with it ever since.
Shrimp News: Craig, what was your job when you started at Waddell?
Craig Browdy: My first job was to set up shrimp maturation and spawning. At the time, one of the impediments to the development of shrimp farming in South Carolina was the supply of postlarvae. The Waddell Center wanted to stimulate the development of shrimp farming by providing larvae to the farms. I was hired to work on maturation and reproduction, and Kathleen McGovern was hired to work on the hatchery side. After a few years, we ramped up production during the two-month stocking window to twenty million postlarvae.
Shrimp News: Al, what became of the freshwater prawn industry in South Carolina?
Al Stokes: Carolinians were not familiar with freshwater prawns and prawns just never took off as a preferred product. When we started farming marine shrimp, we discovered we could produce two to three times the amount per production unit compared to freshwater prawns. Marine shrimp postlarvae were also less expensive and survival rates, in general, were higher. Farmers quickly lost interest in prawns and decided to stock marine shrimp instead.
Shrimp News: Craig, when did you realize the potential for greatly increasing intensification of shrimp farming while reducing water exchange?
Craig Browdy: A year or two after I arrived at the Mariculture Center, I took over the technical side of the Center’s US Marine Shrimp Farming Program grant. That was about 1990. Steve Hopkins, Al Stokes and Paul Sandifer were very much involved with the planning and the implementation of the research, so it was wonderful experience for me to learn from them. In 1992, we stocked some earthen ponds at 300 and 400 animals per square meter. The 300-per-meter pond produced a great harvest. We had so much aeration in those ponds that they looked like milkshakes. We got high survivals and produced the equivalent of 32,000 pounds per acre. We were still using water exchange and heavy aeration. The shrimp in the 400-per-meter pond had problems with blackspot and slowly succumbed to bacterial infections.
After achieving such high production, the issue changed. People became aware of the fact that shrimp farming had a potentially serious sustainability problem. It was now more important to protect the environment than to achieve maximum production. Steve Hopkins deserves a lot of the credit for being ahead of the curve on that issue. He’s the one who started shutting off the water valve. He realized that we don’t need to be running so much exchange water through the ponds. In fact, he addressed it as early as 1993 with one of the Center’s first studies on reducing water exchange. The series of Hopkins’s papers that came out over the next five years have had a lot to do with making world shrimp farming more sustainable.
One of the most important things that we learned was that when you stopped exchanging water, the whole system became more stable. After an initial succession, the blooms and crashes of the phytoplankton community disappeared. The bottom line was that the additional aeration necessary for a zero exchange system was less expensive than the energy needed to exchange water. But it really wasn’t the sustainability issue or the financial issue, the thing that made it take off around the world was the disease issue. Shrimp farms all over the world were getting hit with killer shrimp viruses. Farmers realized they could no longer pump in water that might be loaded with diseases.
Shrimp News: When did you realize that the shrimp were feeding on the bacteria in your closed systems, or was that just a serendipitous discovery?
Craig Browdy: I’m not convinced the shrimp are getting much of a nutritional contribution from the bacteria. I think the greatest contribution from the bacteria is water stability. This is one of the important areas of current research at the Waddell Center. Our current research suggests that these systems, although often called heterotrophic, have very significant algal communities. For production of P. vannamei it may be the algae much more than the bacteria which contribute to growth enhancement. We now have some new experimental systems for exploring these issues so stay tuned.
Shrimp News: Al, what have you learned from these new super-intensive ponds?
Al Stokes: Because we didn’t want to overfeed our zero exchange production system, we became much more efficient managers when applying feeds. Even at very high stocking densities, feed conversion ratios have dropped to approximately 1.5:1, ratios we never anticipated ten to fifteen years ago. In fact, in some of our low density studies (below 30 shrimp per square meter) we’ve seen feed conversion ratios below 1:1.
Shrimp News: What are the pros and cons of super-intensive systems in the USA?
Craig Browdy: USA shrimp farmers continue to face stiff competition from low priced imports. Super-intensive systems offer an opportunity to reduce production costs through the application of technology. This builds upon USA research and infrastructure strengths. The keys to commercialization in the short term will be establishing consistent commercial scale production at the 4-6 kg/m2 levels which have been demonstrated experimentally, coupled with innovative marketing strategies. Never before have USA consumers had access to fresh shrimp in close proximity to markets, at a variety of count sizes, on a continual basis, year round. These are the advantages offered by the advanced, environmentally sound technologies being demonstrated at the Waddell Center with support from the USA Marine Shrimp Farming Program.
Sources: 1. Bob Rosenberry, Shrimp News International. Interview with Alvin Stokes and Craig Browdy, January 18, 2005. 2. Bob Rosenberry, Shrimp News International. Interview with Alvin Stokes and Craig Browdy, a slightly modified version of the interview, posted to Shrimp News’ History of Shrimp Farming in the United States webpage on March 12, 2017.
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