Although commercial producers have tried to follow prawn management methods developed at aquaculture experiment stations in the U.S., small-scale commercial ponds are usually no match for well-supplied and well-managed experimental ponds.
Therefore, farm-level production is usually inferior to production at experiment stations.
Tables 1 and 2 summarize production data from commercial and experimental sources, respectively, for several states. In both tables, production has been segregated by stocking density.
From Table 1, low stocking densities (8,000 to 10,000 per acre) typically produce 200 to 700 pounds per acre, while experimental results for low stocking densities have produced about 800 pounds per acre (Table 2).
Low stocking densities in experimental ponds also resulted in large adult prawns—eight animals per pound or 8-count whole prawn—while commercial harvest weights were approximately 12 per pound or 12-count.
There were similar results for semi-intensive stocking densities. Commercial yields (500 to 800 pounds per acre) trailed behind experimental yields (900 to 1,000 pounds per acre).
Posadas (2004) highlighted cases in which commercial yields under semi-intensive and extensive production were similar, despite the almost two-fold stocking difference.
The reason was that semi-intensive stocking densities produced smaller prawns (14-count average size) than extensive production (8-count average size). Yield equals the number harvested per acre multiplied by the average size.
Intensive stocking in experimental ponds has often produced yields of more than 2,000 pounds per acre when artificial substrates were used (Table 2). These yields offset the high production costs and result in low break-even prices.
Intensive stocking is less common in commercial ponds, although yields have exceeded 1,000 pounds per acre in some cases and been comparable to extensive and semiintensive yields in other cases.
While the potential returns are high, the operating cost is also high, making intensive stocking less attractive to some small-scale producers.
Farm level economics:
Site selection, pond construction and water supply
Land costs vary widely, as do pond construction costs, which can be as high as $5,000 per water acre. In traditional aquaculture regions of the U.S., however, pond construction cost is $1,200 to $3,000 per water acre. Ponds used for prawn farming are usually small, less than 2 acres.
Feed can be distributed more uniformly in a small pond than in a large one, which is important because prawns, unlike catfish, do not congregate at feeding sites. Some producers culture prawns for supplemental income by adapting existing farm ponds to aquaculture.
However, experience has shown that ponds built for prawn production (with catch basins) are easier to manage and harvest and yield more prawns than typical farm ponds (Tidwell et al., 2002).
Well water is best for aquaculture. If small ponds must be filled from streams and creeks, the water should be screened to keep out predatory fish and treated to remove pollutants before prawns are stocked.
Equipment:
Equipment needed for prawn farming includes electric aerators, a 5-hp water pump, a feed storage area, a water quality kit, a dissolved oxygen meter, harvesting equipment, a pickup truck, a mower, and artificial substrates (Table 3).
Harvesting and holding equipment includes seines, baskets, tanks and oxygen cylinders. Growers who use large ponds also might need feed broadcasting equipment and several vehicles.
The cost of artificial substrate is a major expense in prawn farming. Orange construction fence, a standard substrate material, costs $22 per roll in Kentucky and one roll makes 400 square feet of fence.
Ninety-one rolls of this fence are required to provide 0.5 acre of additional surface area in a 1-acre pond. Table 3 outlines the cost of purchasing and installing enough artificial substrate to increase a pond’s surface area by 50 percent.
Electric in-pond aerators are usually adequate for supplemental aeration, but a PTO-powered aerator might be handy to have for emergencies. Research shows that sufficient aeration is achieved at the rate of 1 hp per water acre. Many producers use 1-hp paddlewheel aerators that typically cost $500 to $700 and have a 3- to 5-year lifespan.
Catfish-type paddlewheel aerators (5- to 10-hp) are more expensive ($3,000 to $6,000) and are usually not used.
Information Sourced From:
Southern Regional Aquaculture Centre
