RESULT DEMONSTRATION: USING AN IN SITU BIOASSAY SYSTEM TO DETERMINE A WATER AMENDMENT APPLICATION RATE FOR IMPROVING SURVIVAL AND PRODUCTION ON AN INLAND SHRIMP FARM IN LOWNDES COUNTY, ALABAMA

An inland shrimp producer in central Alabama has grown Pacific white shrimp, Litopenaeus vannamei, for the past several years, utilizing an aquifer that typically yields 7-8 ppt salinity. Previous attempts have consistently yielded poor results for survival and overall production. Research and field trials on other Alabama inland shrimp farms indicate the absolute necessity to amend well water with potassium and magnesium to obtain good survival and growth.  Given that this farm in Lowndes County is one hundred miles distant from other more productive inland shrimp farms, the authors recognized the necessity of performing an in-situ bioassay to determine the best amendment rates for improving survival. Nine limnocorrals and twelve limnocorrals were placed in two established ponds in 2016. The limnocorrals had a pond mud interface, were continuously aerated, stocked and fed identically for forty days. There were four triplicate treatments in one pond system—10 ppt artificial salt mix, untreated pond water, KMAG at 375 mg/l and muriate of potash at 135 mg/l. In the second pond, the artificial salt mix treatment was absent. Statistically, given that some of the replicates were failures, it appeared the KMAG treatment may have outperformed the muriate of potash treatment in terms of survival.

In 2017, both ponds were treated with 375 mg per liter (1000 lbs per acre-foot) of KMAG. Potassium and magnesium concentrations following KMAG treatment increased from 18 ppm to 56 ppm and 62 to 113 ppm, respectively. Sodium concentrations in both ponds ranged from 2505 to 2588 mg/l.  One month prior to stocking, ponds were treated with HTH (pool chlorine) at 10 mg per liter for eradication of aquatic insects and fish. Pond production results in the fall of 2018 were 4908 pounds per acre, a net feed conversion of 1.19 with an estimated survival of 62%. However, it is quite possible the pool chlorine treatment prior to post larval stocking may have had a contributing positive impact on survival.