Over the past several years, freshwater shrimp farming has become very popular. Aerators, pond-side electricity, substrate, and high stocking densities are used to raise shrimp intensively. Most of the people contacting extension specialists for information about shrimp production do not have or can not afford the resources needed for intensive culture practices.
Pond aeration was not a standard practice for freshwater shrimp farming before the early 1980s. Stocking densities and feeding were managed to prevent water quality problems, especially, low dissolved oxygen. However stocking densities, feeding rates, and technical inputs have increased significantly for prawn farming with the development of efficient electric aerators. Water quality management becomes the limiting factor because of higher feeding rates and greater stocking densities. The objective has been to maximize the number of pounds harvested per surface acre. This intensive approach to production requires large initial investments associated with high stocking densities, high feeding rates, addition of artificial substrate, installation of electrical power on pond banks, and the purchase of water quality monitoring and aeration equipment. Initial start-up and production costs, including pond construction but excluding land purchase, can be more than $12,500 per acre. Because these costs are so high, the majority of small-scale and limited resource farmers are priced out of intensive freshwater shrimp production. Furthermore, the risk of financial loss can be significant.
In the 1970s and early 1980s, researchers and farmers produced between 300 and 900 lb of freshwater shrimp per acre. Harvest yields were related to the number and size of shrimp stocked. The data indicated that bigger animals could be grown if ponds were stocked at lower densities, or with larger juveniles rather than 7-day post larvae (pL). Although harvest yields were inconsistent, shrimp could be produced without aeration.
The risk of low oxygen concentrations and the loss of a shrimp crop is significant with high stocking densities, aggressive feeding schedules, and no aeration. However, it is generally accepted that poor water quality and low oxygen are uncommon when daily feeding is no more than 25 lb/acre. Several field trials were conducted from 2002-2005 to explore the potential of low-input shrimp farming in Kentucky.
Low Input Demonstrations, 2002 & 2003
Low-input shrimp farming practices were first demonstrated in Hopkins County, Kentucky (Wurts et. al.). A 0.5-acre pond was stocked with 4000, 0.5-g freshwater shrimp (8,000 shrimp/acre). The pond was fertilized with 125 lb (250 lb/ac) of alfalfa meal 14 days before stocking. Juvenile shrimp were released into the pond on June 13, 2002. Daily feeding began at 10 lb/acre but did not exceed 25 lb/acre. Aeration was not used.
The pond was harvested on September 28 -- 107 days after stocking. Roughly 200 lb of shrimp (400 lb/ac) were captured. The average size of each animal was 35.2 g, or 13 shrimp to the pound (13 count). Shrimp were fed a 35% protein, sinking pellet and a total of 723 lb commercial catfish feed. The food conversion ratio was 3.6 (lb feed/lb gain). Survival was approximately 60%. It seems likely that harvest yield and shrimp size would have been significantly larger if the juveniles had been stocked before June 1 rather than on June 13.
Water quality was measured during August and September when feeding, temperature and oxygen demand were greatest. The dissolved oxygen concentration averaged 6.8 mg/L (temperature, 76-81F) with the lowest value at 4.8 mg/L. Total ammonia nitrogen concentration was never higher than 0.3 mg/L and pH ranged from 7.8-8.5. Total alkalinity and total hardness were 27 mg/L and 230 mg/L, respectively.
The cooperator in this demonstration produced shrimp for home consumption. However, assuming a price of $7.00-8.00/lb for 400 lb of shrimp and subtracting the costs of food, fertilization, and juvenile shrimp (Table 1), the value of shrimp harvested by this producer was between $1,695 and $2,095 per acre. The farmer owned a pond that already contained water, possessed the equipment and supplies needed, and had family help for harvest. A potential producer must consider additional expenses such as: loan financing, pond construction, liming, pumping, mowing, harvest labor, nets, purging tanks, gloves, plastic bags, and ice. However, with low-input farming, there are no costs associated with installing electric power on pond banks, the purchase of aeration equipment and substrate, or electricity to operate aerators.
Table 1. Stocking, fertilization and feeding costs (per acre) for a low-input freshwater shrimp farming demonstration in Hopkins County, Kentucky -- 2002.
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Item
|
Quantity
|
Price
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Juvenile shrimp
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8,000
|
$ 800
|
Alfalfa meal
|
250 lb
|
$ 35
|
Feed
|
1450 lb
|
$ 270
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Total
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$1105
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In 2003, four demonstration ponds (one 0.75 and three 0.5 acre ponds) were stocked with 45-60 day pL at 8,000 and 10,000 shrimp/acre. Ponds were located in Hopkins County and Grayson County, Kentucky. The growing season ranged from 110 to 124 days. Survival was 56 % in ponds stocked with 10,000 pL/acre and 33-40 % for ponds stocked with 8,000 pL/acre. However, dense filamentous algae or the presence of several largemouth bass may have been responsible for the poor survival observed in ponds stocked with 8000 pL/acre. Temperatures in June were significantly cooler than normal and harvest yields and shrimp size, 146-348 lb/acre and 16-18 count, were smaller than in 2002. However, because shrimp size and yields were greatest in ponds that had the best survival and highest stocking densities, it seemed clear that shrimp were overfed at a maximum daily feeding rate of 25 lb/ac. Furthermore in 2003, another Kentucky producer stocked a 1.0 acre pond with 10,666 pL/ac, used aeration, and had approximately the same yield (332 lb/ac) as the demonstration ponds stocked at 10,000 pL/acre without aeration (326-348 Lb/ac). The data collected from 2002-2003 suggested that 400 lb of shrimp could be produced per acre with organic fertilization, no aeration, and feeding less than 25 lb feed/ac daily. The results from these early demonstrations indicated that improvements could be made and the practices refined.
Low Input Demonstrations, 2004 & 2005
Stocking, fertilization (see schedule below), and feeding practices were modified in 2004 (Wurts, 2005). Shrimp (45-60day pLs) were stocked at 10,000 to 14,000 per acre in six (6) ponds, one 1/4-acre and five 1/2-acre. The demonstrations took place in Hopkins County and Todd County, Kentucky. Ponds were stocked between May 21 and June 1, 2004. Daily feeding started at 10 lb per acre and was capped at 20 lb per acre. The growing season ranged from 110 to 133 days. However, it is unlikely that there was any significant growth during the last 14 days of the 133-day period (133 -14 = 119 days). Low-input farmers harvested between 454 and 820 lb of shrimp per acre, without aeration. Average yield was 580 lb/ac. Shrimp size ranged from 9 to 22 count (shrimp per pound). Shrimp size was 9-10 count in Todd County ponds. Shrimp were sold at the pond bank for $7.50 - $8.00/lb, heads-on. The cooperating producers reported that profits ranged from $1,600 - $2,200 per acre. Profit estimates were determined by subtracting basic costs (i.e. juvenile shrimp, feed, fertilizer, copper sulfate, plastic bags, gloves, and ice) from gross sales.
Some new records were set in Todd County for low-input shrimp farming in 2005. Four, ½-acre ponds were stocked with 10,000 shrimp per acre on May 21, 2005. Ponds were fertilized with alfalfa and triple super-phosphate before stocking, as practiced in 2004. Ponds were not aerated. Daily feeding was capped at 20 lb/ac on week 11 (Table 2) and continued until harvest. Shrimp were harvested 125 to 126 days after stocking from September 24-25, 2005. Harvest yields ranged from 697 to 912 lb of shrimp per acre. The average yield was 809 lb per acre. Shrimp size ranged from 8 to 10 count. Even with 500 lb of unsold shrimp, the producers reported profits a little above $3,400 per acre.
Table 2. Daily feeding rates, adjusted weekly, for freshwater shrimp stocked at 10,000 shrimp/ac.
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Week
|
Daily Feed (lb/ac)
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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
|
10
10
12
12
14
14
16
16
18
18
20
20
20
20
20
20
|
Total amount fed
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1820 lb/acre
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Also in 2005, a harvest yield of 994 lb/acre of shrimp was achieved in a ¼-acre pond. Shrimp size at harvest was 10 count. The pond was fertilized as in 2004. Shrimp were stocked at a density of 16,000/acre on May 21, 2005. Daily feeding was capped at 24 lb/acre beginning on week 11 (Table 3) and continued until harvest (9/23/05). While the pond was aerated, it is unlikely that the aeration used (type and placement) had any significant impact on pond dissolved oxygen concentrations.
Table 3. Daily feeding rates, adjusted weekly, for freshwater shrimp stocked at 16,000 shrimp/ac.
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Week
|
Daily Feed (lb/ac)
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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
|
10
10
12
12
14
14
16
18
20
22
24
24
24
24
24
24
|
Total amount fed
|
2044 lb/acre
|
The stocking, fertilization, and feeding practices described below were used for the low-input shrimp farming demonstrations conducted in 2004 and 2005.
· Stock 10,000 shrimp/acre.
· Fertilize ponds with alfalfa and triple super-phosphate before stocking.
· Feed no more than 20 lb/acre daily (Table 2) using 28 % protein, sinking catfish pellets.
· This is for a 16-18 week growing season.
Fertilization with Alfalfa and 0:46:0 (N:P:K) for Low-input Shrimp Production
1.) 14 days before stocking juvenile shrimp: fertilize ponds by spreading 250 lb/ac of alfalfa pellets over the entire pond bottom, as evenly as possible. The pond must be free of aquatic weeds before fertilizing.
2.) 14 days before stocking, “slowly dissolve” 10 lb/ac of triple super-phosphate (0:46:0, N:P:K) into the pond water. If a pond has a history of dense phytoplankton blooms, omit the triple super-phosphate. However, if the pond water is still clear one week after stocking, triple super-phosphate should be “slowly dissolved” into the water. The pond must be free of aquatic weeds before fertilizing.
3.) 13 days before stocking, evenly distribute 6 lb/ac of alfalfa pellets over the entire pond daily, for 6 days (day 13 to day 8, pre-stocking).
4.) 7 days before stocking, evenly distribute 8 lb/ac of alfalfa pellets over the entire pond daily, for the last 7 days before stocking shrimp.
5.) To summarize, a total of 342 lb of alfalfa pellets and 10 lb of triple super-phosphate will be required to fertilize each acre of low-input shrimp production before stocking. However, fertilization must be done over a 14-day period as described above.
2005 vs. 2004 in Todd County, Kentucky
There were two significant differences in 2005 that may have accounted for the substantially improved harvest yields in Todd County. First, 0.7 - 0.8 g post larvae were stocked, bigger than previous years (0.25 to 0.5 g). Todd County cooperators stocked their ponds 10 to 17 days earlier than most Kentucky shrimp farmers. Because they stocked earlier on May 21, substantially larger post larvae were available to them. Second, survival was higher in 2005 than in 2004 (43-58% vs. 64-75 %) for ponds stocked with the same density of shrimp (10,000/ac). This would suggest that stocking larger post larvae improved survival. It is interesting to note that even though the post larvae stocked in 2005 were larger than those stocked in 2004, individual shrimp sizes at harvest were the same for both years. Also, it seems likely that 8-10 count shrimp are the maximum sizes attainable in an 18-week, Kentucky growing season. This observation was supported by the presence of algal growth on the shells of larger shrimp harvested in 2005 (molting had stopped).
Todd County Demonstrations: Ideal Conditions?
It is not likely that all shrimp farmers would have the same results as the producers in Todd County, Kentucky. Because the ponds in Todd Co were adjacent to the Tennessee border (Figure 1) in the southwest region of Kentucky (plant hardiness zone 6b; USDA, 1990), they may have had a 2-3 week longer growing season than areas in Kentucky that were farther north. The ponds were refilled for the winter to control pond bank erosion. As a result, the ponds had substantial filamentous algal blooms prior to fertilization and had to be treated with copper sulfate. In addition to eliminating algae, it is likely that the copper treatment also killed many of the predators that threaten post-larval shrimp. After fertilization, the producers topped off their ponds with screened water from a 65-acre reservoir. This inoculated the ponds with a wide variety of plankton, improving the availability of natural food for the juvenile shrimp. An external collection system fabricated from heavy gauge screen simplified harvest. Sales at the pond-bank allowed cooperators to charge a premium retail price ($8.00/lb) for their 8-10 count shrimp. Furthermore, the ponds were in close proximity to Clarksville, Tennessee – a relatively large urban population center – which provided a ready market for “freshly harvested” jumbo shrimp.
In regions with climates similar to the northern latitudes of Kentucky, it may be necessary to use higher stocking densities to achieve 700 to 900 lb/ac yields for low input shrimp farming. Shrimp are not likely to reach the 8-10 count size in a 15 to 16 week growing season and cooler temperatures. Therefore, with survivals similar to those observed in these demonstrations, harvest yields would be lower. It might be necessary to stock these ponds with 16,000 shrimp per acre (or higher) and cap daily feeding at 24-25 lb per acre. While it is likely that individual size will be reduced (higher count), it still may be possible to produce 800 lb of freshwater shrimp per acre using low input practices.
Advantages of Low Input Aquaculture
Poor water quality can cause the death of a crop and the loss of an investment (juvenile shrimp, feed, fertilizer, etc.). Low oxygen levels could occur using intensive or low-input methods, with or without aeration. While the risk is small for low-input farming, oxygen problems are possible, especially in ponds greater than 6 feet deep. Nonetheless, low-input practices could provide an opportunity for farmers with limited resources, or ponds in remote locations, to profit from freshwater shrimp farming. At 2.0 acres per county, there could be 240 acres of low-input shrimp ponds in Kentucky alone. With production levels of 700 to 900 lb/ac and retail prices from $6.50 to $8.00 per pound, low-input farmers could harvest 168,000 to 216,000 pounds of shrimp with a gross value between $1,092,000 and $1,728,000 annually. Expected average yields of 800 lb/ac should be of larger size, higher value shrimp (8-13 shrimp/lb). But, harvests would not be so large as to saturate small, local retail markets. Higher stocking densities might increase harvest yields to 800-1000 lb/ac but could reduce individual size and increase count depending on climate and length of growing season. Basic start-up and initial production costs, excluding land purchase and pond construction, are as much as 73 % lower for low-input shrimp farming. Therefore, the return on an initial investment can be significantly higher than for intensive culture practices.
Aeration, substrate, high stocking densities, and high feeding rates are eliminated for low input shrimp farming. Ponds are managed at or below their biological or environmental limits. Enhanced natural productivity improves harvest yields and profits without significantly increasing inputs. There should be no waste effluent discharge problems. Wastes serve as pond nutrients rather than pollutants, and augment natural productivity. Practices can be sustained without producing detrimental impacts on the environment. Advanced technical skills and highly specialized education are not required by farmers adopting these practices. Furthermore, it has been observed in Kentucky that shrimp ponds in the 0.25-0.5 acre range may have higher yields per acre than larger ponds. With niche marketing and retail sales at the local or county level, profit potential and the return on an investment could be relatively high for a small-scale farmer. Low-input practices can provide significant opportunities for producers with small farms or limited resources to profit from freshwater shrimp farming.
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