Print This Page


November 22, 2015

United States

Kentucky State University’s RAS Shrimp System

 

Researchers at Kentucky State University (KSU) are exploring the production and marketing aspects of an indoor shrimp production system.  Their newly equipped, 1,300-square-meter, Aquaculture Production Technologies Laboratory houses a variety of recirculating aquaculture systems.  Using electric boilers, the air temperature in the lab is maintained at approximately 23° C year-round.

 

In a recent experiment, a 3.1-cubic-meter, rectangular raceway was used as a nursery and outfitted with an external 190-liter settling chamber and a 190-liter biological filter filled with plastic biomedia.  Ten-day-old postlarvae (Penaeus vannamei) were obtained from a hatchery in Florida, USA, and stocked into the nursery at a density of 2,500/m3.

 

After the nursery phase, 5,250 shrimp weighing an average of 0.55 grams each were stocked in a 20-m3 fiberglass growout raceway with water containing artificial sea salt at a salinity of 20 parts per thousand.

 

The raceway was equipped with a 1-horsepower pump, which delivered water to three aeration nozzles distributed around the raceway and one nozzle that fed a foam fractionator.

 

The nozzles inside the raceway drew air in through snorkels extending above the water surface and directed water around a central wail.  The fractionator nozzle delivered aerated water into the foam fractionator, which was used as needed to maintain turbidity at approximately 40 nephelometric turbidity units.

 

Two 3,000-watt submersible heaters in the growout raceway maintained a water temperature of approximately 28.5° C.  A dry probiotic was initially added to the water over a two-week period, and 3 liters of biomedia from the nursery were placed in a mesh bag and submerged in the water to help establish a bacterial community.

 

Results

 

The growout tank was managed as a biofloc system, with the only external filtration being the foam fractionator to remove dissolved and suspended solids.  There was a 1.3-milligram-per-liter spike of total ammonia nitrogen one week after stocking shrimp, and a 3.5-mg/liter spike in nitrite-nitrogen concentration one month later.  Neither spike resulted in noticeable mortality.  Sodium bicarbonate was used to maintain pH, which got as low as 7.0.  The aeration system was effective at maintaining dissolved-oxygen levels above 6.5 mg/liter.

 

There were 15 centimeters of tank freeboard above the water surface and 46 cm of vertical netting surrounding the tank.  Regardless, 457 shrimp jumped out of the growout tank during this project, mostly on two occasions.  Netting was then placed tightly over the top of the tank, which prevented shrimp from escaping.  Lights turned on and off in the building may have startled the shrimp, resulting in much of the jumping.

 

Shrimp were grown in the growout tank for 98 days.  Shrimp weighed 24.3 grams at harvest and 91.8 kilograms of shrimp were harvested.  Survival was 69.1%, although adding the shrimp that jumped out of the tank would have made the survival 80%.  The feed-conversion rate was 1.3:1, and the growth rate was 1.7 grams a week.

 

Harvested shrimp were sold at a farmers market in Frankfort, Kentucky, which has a population of approximately 27,500 residents with a per capita income of  $24,100 (2013).  The shrimp were sold fresh on ice at $26.40 a kilo.  A total of 37.2 kilos were sold in an hour and a half.

 

The recurring costs of nursery and growout production for this project were approximately $12.10 a kilo.  As a percentage of total costs, electricity accounted for 25%, labor (at $10.00 an hour) for 28%, feed for 29%, postlarvae for 16% and other consumables for 2%.

 

If 14 growout tanks had been used, one tank could be harvested weekly all year.  If more tanks were used, an economy of scale effect should be realized, bringing down costs.  Other cost considerations include heating the air, infrastructure, taxes and distribution.  These should be considered carefully and vary depending on a farmer's circumstances.

 

Survey respondents were very accepting of the product and scored it highly.  Consumers appeared willing to pay more than chefs, possibly because chefs are motivated more by the profitability of their restaurants.  A direct-to-consumer approach for shrimp sales could prove to be profitable.  At a sale price of $26.40 a kilo, there appears to be room for profit, and according to survey responses, a higher price may be acceptable to consumers.

 

Future efforts at KSU will focus on increasing shrimp stocking densities and survivals to enhance production output and augment the potential profitability.  The sale of live shrimp will also be explored.

 

Information: Andrew J. Ray, Ph.D., Assistant Professor, Kentucky State University, Aquaculture Research Center, 103 Athletic Road, Frankfort, Kentucky 40601 USA (email andrew.ray@kysu.edu, webpage Kentucky State University (KSU).

 

Source: The Global Aquaculture Advocate (The Global Magazine for Farmed Seafood).  Editor, Darryl Jory (dejry2525@aol.com).  Innovation: Indoor-Raised Shrimp Find Potential Market In Kentucky State University Test.  Andrew J. Ray.  Volume 18, Issue 6, Page 76, November/December 2015.

Print This Page