To maintain a quality product and preserve the marketability of bait shrimp, water quality must be maintained. Several parameters should be monitored, including salinity, dissolved oxygen (DO), temperature, ammonia, nitrite, and pH. DO levels should be maintained above 3 parts per million, but should typically be maintained near saturation. To accomplish this, suitable aeration should be available in each pond, and stocking rates and feeding inputs should be based on pond size and aeration capacity. As shrimp age, their ability to tolerate lower salinities increases. Initially, larvae and PLs must be maintained at high salinities for proper growth and development. However, a 15-day-old PL will typically be able to cope with reduced salinities, so the salinity can be gradually reduced to 4 parts per thousand. This is important because it expands the area in which shrimp can be cultured.
As farm locations move inland, property values decline. Hatchery stocks of PLs available for sale or to grow out farms, range in age from 6 to 15 days. It is important for an operation to maintain these younger PLs at higher salinities until they are at least a PL 15. Shrimp will grow best at temperatures of 28 to 30 degrees C and will tolerate much lower temperatures. The primary growing season is from early spring to late fall when temperatures are adequate for good growth. Salinity should be maintained from 4 to 32 parts per thousand and ammonia and nitrite at less than 0.5 parts per million.
Stocking rates depend on the degree of culture intensity within a particular farm. Bait shrimp operations may stock grow-out ponds at 50 to 100 shrimp per square meter. The key to stocking density is to have enough animals at harvest to satisfy demand. Stocking too few animals may leave a farm unable to fulfill all commitments. Stocking too many may exceed a farm’s ability to maintain water quality or harvest the production system. Factors to consider when determining stocking densities include pond size, expected mortality, and a farm’s ability to monitor and react to changes in water quality. The higher the density stocked, the greater the risk for water quality problems and the loss of a crop. New farms should consider a lower initial stocking density while they gain experience and grow their markets.
The growing season varies by location. Typically, it ranges from 5 to 7 months, but can be extended with the addition of a nursery phase. Degrees of management for bait shrimp ponds change with culture intensity. In most cases, daily water quality and feeding will be required. Periodic sampling of animals allows the farmer to evaluate growth rates and relative health of the crop and to adjust
feeding. Feeding is generally based on estimated biomass. It is necessary to update this estimate to ensure appropriate feeding rates. Excessive feeding will lead to the deterioration of water quality and reduced production. Additionally, excessive feeding will add costs to the overall budget.
Nursery Phase Option
Recent research has indicated the benefits of adding a nursery phase to a bait shrimp operation go beyond simply extending the growing season. By incorporating a nursery phase, a producer can stock larger shrimp for grow out, which increases survival rates while reducing the time required to reach a predetermined market size. In addition to a hardier shrimp, adding a nursery phase in an overall production scheme will better use land resources, which, along the Gulf Coast, can be a significant cost consideration in the business plan.
The drawbacks to the nursery system revolve around the additional costs. The cost of tanks, labor, utilities, and filtration must be considered when evaluating the effectiveness of adding a nursery phase to a grow-out operation. A good plan for nursery harvest and transfer to grow out is necessary for an effective nursery operation. Instead of absorbing the costs of a nursery system, a grow-out operation may be better suited to stock at space maximization rates rather than growth rates. Individual commercial operations should consider all the costs and benefits of the nursery phase in the business model before production.
Several species of shrimp have been cultured for food and research. The non-indigenous shrimp Litopenaeus vannamei is one of the most commonly cultured species of shrimp in the region. Food-size L. vannamei, grown to a final size of 12 to 25 grams, can produce yields of 4,000 to 6,000 pounds per acre when stocked at densities between 25 to 45 shrimp per square meter. For the native shrimp species Litopenaeus setiferus, research has shown that 12- to 15-gram shrimp produced at yields of 1,555; 5,259; and 7,995 kilograms per hectare are possible when stocked at 12, 40, and 60 shrimp per square meter, respectively (Journal of the World Aquaculture Society 24:295–303). In Alabama, bait shrimp are typically marketed at a 5- to 10-gram size. Because this is considerably smaller
than food-size shrimp, the growing season is reduced, possibly allowing for multiple crops during the warmer summer months. A management plan should consider site-specific conditions and provide adequate aeration to support the final biomass of shrimp, adjust feed inputs that will maximize growth but do not exceed 100 kilograms perhectare (80 lbs/acre), include routine crop sampling to adjust feeding rates, and use harvesting technologies that minimize stress on the shrimp.
The suggestion of on-site water exchange is still debated. Though the water quality can be improved, in particular related to ammonia, through water exchanges, a pond will lose important algae and bacteria in the process. Storing exchanged water for reuse may be a good idea. It will allow for water to remain onsite, reducing the risk of importing disease agents with new water. It will also help a farm reduce its overall discharge, which may be of concern with the Environmental Protection Agency’s new and developing effluent regulations for aquaculture.
Bait shrimp harvest is a critical time. A farm must minimize handling stress to keep the shrimp alive. Bait retailers will be loyal to farms that deliver a healthy, live product. Harvesting in the early morning or late evening when temperatures are cooler will help to reduce stress.Harvesting falls into two categories: partial harvest and complete harvest. A seine or trap is used in partial harvest. Seining involves considerable handling stress; it can disturb the sediment, which reduces water quality. However, large numbers of shrimp can be captured in a short time. Trapping reduces the impact on water quality and minimizes handling stress; however, smaller numbers of shrimp can be captured per unit effort. Complete harvesting may be the best choice. If ponds are designed well, the farmer can reduce handling stress and capture large numbers of shrimp. An Alabama Cooperative Extension System aquaculture specialist can provide additional information about harvest options.
Marketing bait shrimp is an important process the farmer often overlooks. Knowing the market and having buyers lined up should be done well before the first PL is stocked. Because these animals must be delivered alive and healthy, harvest time is not the time to market the product. Most retail bait shops will pay a little more for quality and reliability. Some 2001 estimates indicated that a farm would have to receive $50 per thousand live shrimp to be profitable. Market price, order size, and delivery times should be agreed upon before harvest to protect both the wholesale and retail firms.