Feeding Freshwater Prawns through Mechanical Means to Increase Yields and Size

Feeding Freshwater Prawns through Mechanical Means to Increase Yields and Size

Summary

90% of all shrimp/prawns that are sold in the US are imported! Most imported shrimp comes from Southeast Asia (Thailand, Vietnam, China and India).  These and other countries are not known for following best practices in production especially with the use of “not for human consumption antibiotic drugs”.

According to the Kentucky State University Prawn Production Manual, two of the issues facing producers of freshwater prawns are 1) producing consistently sized product and 2) decreased yields (as high as 50%).

If we could determine the cause for the widely varying size and yield, we could develop best practices that would benefit our farm and the US industry as a whole. If successful, this project could result in a value-added revenue stream from a sustainable product with a small investment of time.

This would not only lessen the environmental impact of overfishing the oceans by producing an aquaculture product that is locally grown, but help eliminate any disruption in the food chain by creating food chain security and reduce the environmental impact on planet Earth.

With my proposal, I believe the end result will increase yields and produce a more consistent-sized prawn.

A Freshwater Prawn is territorial and cannibalistic and because of these traits, some studies suggest as much as a fifty percent loss after the initial stocking quantity.

We plan to compare two feeding protocols – the first to distribute the feed by hand and the second to distribute the feed mechanically in a more uniform fashion. The end result is to see which produces freshwater prawns of more consistent size, weight and higher yield.

Most feeding is done by hand which entails slinging feed from a scoop over as much area as possible of the pond.  This has an inherent problem with large areas of the pond not being covered with any feed at all, making it an inconsistent way of feeding.

We created a low cost device that evenly spreads feed over the pond. We started calling this device “The Shrimpshooter”.  To view the “Shrimpshooter” in action go to www.donsprawns.com and under the photo and video section click on the video.

Jim Cotugno is a Prawn producer about 10 miles north.  We’ve worked together and supported each other since I started raising prawns.  Jim feeds by hand. This information presented is anecdotal and most certainly not statistical; but we felt my prawns were generally larger and had a more consistent size than his hand fed harvest. The only way to prove this “competition” was to have two ponds stocked using the same water supply and feeds to test the theory. One prawn pond fed by hand and the other prawn pond fed using the mechanical device.

When thinking about this logically, the prawn by nature is cannibalistic and territorial. If you could deliver the feed to individual living areas, you should be able to reduce the cannibalistic behaviors with the result being larger and more consistent sized prawns at harvest-time. 

Again, with evenly spread feed, the prawns do not have to go out and search for food because it is delivered to them, and they do not have to go into another prawn’s territory with a high probability (as much as 50%) of not returning to their own territory.

Reducing food induced territorial fighting will likely result in increased overall yields.

Objectives/Performance Targets

Prawns (shrimp) are sold and categorized by size and weight.  A 16 Count is an average of 16 prawns per pound.  A 25 to 30 Count would be much smaller in size and 25 to 30 prawns per pound.

One pond will be fed by hand, and the other pond fed by the mechanical device we invented that evenly distributes feed throughout the pond. We feel the evenly distributed pond will have more consistently sized prawns and a higher yield.

A higher yield means we can sell to more customers. More uniform sized prawns could also make the prawns more marketable to commercial organizations such as restaurants, an avenue of sales we have not even touched because they typically want and need a consistent size.

We will drain the first pond (hand fed) and as in previous years, keep a record of the number of pounds taken from the pond. Prior to selling, we will do a count of how many prawns per pound. We will also do a physical count (prawns per pound) four to five times during the harvest and sale. We will also use a size indicator to check consistency and uniformity of size. A simple ruler would work. As in the Average Count, size samples would be taken through out the harvest (approximately 10% of the total yield). The second pond would then be drained and the same records kept. This will determine if even distributed feed has an effect on the general size of prawns and a higher yield rate. Photos could also be taken.

Accomplishments/Milestones

June 5, 2014- The prawn hatchlings were delivered. Before putting into the ponds, we did a physical count to make sure we were putting the same amount in each pond. This was a time-consuming task because the hatchlings are very small ranging from 1/16 to ½ inch. It requires patience and paying attention to detail pouring tiny sized prawns from small containers to buckets and then eventually placing them into the ponds

Impacts and Contributions/Outcomes

The physical count paid off with even distribution into two ponds, and I was compensated for ones that had arrived no longer alive. (Yes, the dead ones were also counted.)

 July 8, 2014-The prawns have grown approximately one inch and can now be seen darting around during feeding.

• The count

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