From pond to table.
Post-larval shrimp, about 3/4 the size of a mosquito larvae, are purchased from a specific pathogen-free hatchery in the USA by the 1st of May. These young are transported to our farm and placed in acclimation tanks where the salinity is slowly decreased from shipping salinity (15 to 32 parts per thousand, ppt) to the farm salinity (3.5 ppt). The larvae are then transferred to earthen ponds where they grow until harvest. In recent years we have begun nursing shrimp in solar-heated houses in order to increase shrimp survival and get larger shrimp at harvest. In this case, we begin the acclimation process in March.
The ponds are excavated in prairie soil composed of tight clay with minimal percolation. Water is pumped from wells that reach 650 to 680 ft below ground. Hydrostatic pressure forces the water to about 35 feet below the ground surface. The salinity of the well water is 3.5 ppt, which is about 10% of seawater strength. We have to amend the water with potassium salts for the shrimp to survive.
The growth phase comprises 4 to 5.5 months. Management consists principally of feeding shrimp twice a day and maintaining good water quality. Dissolved oxygen is the principle water quality variable that we actively manage through the use of automated data logging and control devices, and mechanical aerators. We limit production to moderate levels to minimize water quality problems and reduce the occurrence of noxious algal blooms.
Shrimp are fed a sinking pellet that is formulated and fabricated specifically for shrimp. The feed is composed principally of plant products and about 5% fish meal. We have participated in research that has decreased the quantity of fish meal by substituting plant protein. No mammalian by-products are used in our feed. Shrimp are sampled for growth every week and feed allotments are adjusted accordingly.
Shrimp are harvested during a 6 to 7 week period that begins in September and usually ends by the beginning of November. These shrimp are a tropical animal that would normally die as the water cools in the fall. Before harvest, we first transfer most of the pond water to another pond in order to conserve water and to minimize environmental impact by water discharge.
Shrimp are harvested by draining the remaining pond water. Water is drained through a cage fitted with a pump that transfers the shrimp in water to a dewatering tower located on the pond dike.
In the tower, the shrimp are separated from the water by a grate and fall into a bin where they are covered immediately with ice. The shrimp are then packed for the fresh market or shipped to a processing plant to be flash frozen.