LOW-INPUT SHRIMP FARMING IN Kent

Before the early 1980s, pond aeration was not a standard practice for freshwater shrimp farming. 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 aeration and water quality monitoring equipment. Initial start-up and production costs, including pond construction but excluding land purchase, can be more than $12,500 per acre. Since 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.

Researchers and farmers produced between 300 and 900 lb of freshwater shrimp per acre in the 1970s and early 1980s. Although harvest yields were inconsistent, shrimp could be produced without aeration. In Kentucky, several field trials were conducted from 2002-2005 to explore the potential of low-input shrimp farming. The data collected from 2002-2003 suggested that 400 lb of shrimp could be produced per acre with organic fertilization, no aeration, and feeding no more than 25 lb feed/ac daily. The results from these early demonstrations indicated that improvements could be made and the practices refined.

Stocking, fertilization (see schedule below), and feeding practices were modified in 2004. Shrimp were stocked at 10,000 to 14,000 per acre in six (6) ponds, one 1/4-acre and five 1/2-acre. 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 400 and 810 lb of shrimp per acre, without aeration. Average yield was slightly above 500 lb/ac. Shrimp size ranged from 9 to 22 count (shrimp per pound). 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, plastic bags, gloves, and ice) from gross sales.

This year in Todd County (2005), some new records were set for low-input shrimp farming. 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 1) and continued until harvest. Shrimp were harvested from September 24-25, 2005. Harvest yields ranged from 700 to 900 lb of shrimp per acre. The average yield was 808 lb per acre. Shrimp size ranged from 8 to 10 count.

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 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.

The stocking, fertilization, and feeding practices described below were used for the low-input shrimp farming demonstrations conducted in 2004 and 2005.

· Feed no more than 20 lb/acre daily (Table 1) using 28 % protein, sinking catfish pellets.

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 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.

Table 1. Daily feeding rates, adjusted weekly, using 28 % protein sinking catfish pellets for freshwater shrimp stocked at 10,000 shrimp per acre.

Week

Total amount fed

Daily Feed (lb/ac)

1820 lb/acre

Published as, Organic fertilization in culture ponds. World Aquaculture, 35(2): 64-65 .

(PowerPoint slide show) Presentation at: Aquaculture '04; Honolulu, HI; March 4, 2004. Book of Abstracts, p. 652.