- Animals: shellfish
- Animal Production: animal protection and health, aquaculture
Foreign competition makes shrimp farming in the USA economically tenuous. The small inland shrimp industry in Alabama can be sustainable only if production techniques are extremely efficient and niche markets are solidified. Shrimp are usually harvested by draining ponds through a net or screening device. Shrimp come out of ponds primarily during the last 10 percent of pond volume because they are not concentrated before then, and because they swim against the discharge current. Often, a high biomass of shrimp remains in little water volume and become easily stressed from low dissolved oxygen and high temperatures. If the shrimp die during this phase of the harvest, they will remain in the mud where they are very difficult to remove before they spoil. Shrimp harvest is often an inefficient use of water and especially labor, and it is not uncommon to leave several percent of the produced volume of shrimp behind to spoil in the mud. Mortality at harvest is particularly disheartening, because it is wasteful of a living product and results in a direct economic loss. Inefficiency and mortality at harvest cannot be sustained by a successful producer. Shrimp are highly perishable. To assure a very high quality product for market, harvested product must be placed on ice immediately and transported to market or to a plant for processing. The fresh shrimp market offers reasonable prices and there is potential for selling shrimp into the higher priced live markets, but these business options can not be well exercised during a total pond harvest. Neither the fresh nor live markets can absorb a large quantity of shrimp at one point in time because of short shelf lives for fresh shrimp and distribution logistics. Partial harvesting of ponds by a typical drag seine is terribly inefficient, because the nets are heavy and slow, and hence shrimp are able to escape them. Shrimp can be trawl-harvested using a medium size boat equipped with an outboard motor, but the typical trawl is cumbersome, the catch per unit effort is relatively small, escaping shrimp are killed by the dragline and otter boards, and two laborers are required to manage the vessel. Other techniques that are less labor intensive, more efficient, and less stressful to live shrimp have to be developed in order to frequently remove small quantities of shrimp for sale to the more profitable niche markets. The techniques have to minimize labor, because labor is a scarce commodity in west Alabama. We propose to test two alternative harvesting techniques that, to our knowledge, have not been applied to shrimp ponds. One technique is to use a small, 300' long purse seine for concentrating shrimp around the discharge pipe at harvest to increase harvest efficiency. Purse seines are different from the typical drag seine in that they envelope the harvested animals as they concentrate them. One end remains stationary and the other end encircles a given area and is slowly drawn together to form a large bag containing the animals. We think this method and material will allow us to significantly reduce shrimp biomass in the ponds while the ponds still remain predominately full of water. Shrimp will, therefore, not be stressed and mortality will be minimal. Ultimately, to greatly reduce water usage and minimize discharge, a larger version of this seine may allow us to totally harvest ponds without draining ponds at all. We will further utilize a modified Alabama skimmer trawl to partially/selectively harvest shrimp for both the fresh and live markets. A skimmer trawl is fitted on an aluminum frame mounted on the bow of a medium size outboard motor driven boat. Nets are attached on each side of the boat and may be drawn in by one person operating the boat. By contrast, a typical trawl is dragged behind the motor boat and is difficult to pull in and not kill or lose the shrimp, and re-deploy as a single crewman without tangling the tow lines. The skimmer trawl is a spin-off from a larger marine type apparatus currently in use in coastal waters. The skimmer trawl has been tested in crawfish harvest and was proven to catch approx. the equivalent of 500 hand-raised wire mesh traps in 1/3 the time. We think the skimmer net will allow us to make frequent harvests of relatively small quantities of shrimp required for fresh and live markets. The net will be particularly important for the live market where shrimp must be handled with minimal stress in order to survive transport and storage in live tanks. Because the nets can be handled by one person, labor will be minimized. Catch (lbs) per unit of effort (people-hours) will be used to evaluate both techniques. We weight all shrimp harvested from ponds. We produce in 16 ponds. Therefore, we will measure the biomass harvested and the time and labor required to deploy and retrieve a purse seine in at least 4 of the ponds at harvest compared with a standard harvest in at least 4 of the ponds. The purse seine will be tested similarly in a partial pond harvest. The skimmer trawl will be similarly tested and compared with a standard tow behind trawl that we also have tried. If these alternative harvesting techniques perform well in our ponds, then we know that the other farmers in the area will also want to use the nets and techniques in their ponds as well.