WATER QUALITY AMONG DIFFERENT FEED MANAGEMENT TREATMENTS FOR PACIFIC WHITE SHRIMP Litopenaeus vannamei

Feed management applications can dictate the water quality within a pond. Increasing feeding rates provide an increase in production, thus nutrients such as nitrogen, phosphorus, and organic matter will also increase, respectively. These nutrients promote a greater oxygen demand and concentrations of toxic metabolites which can lead to frequent problems with low dissolved oxygen and an abundance of blue-green algae. Four feed management techniques were used among sixteen ponds culturing Pacific White Shrimp (Litopenaeus vannamei) at Gulf Shores, Alabama. The different feeding strategies included two treatments with hand feeding using the Standard Feeding Protocol (SFP) which is calculated with a predicted growth of 1.3 g/wk, and an estimated feed conversion ratio (FCR) of 1.2, assuming a survival rate of 75% over 16-wk culture period, and SFP plus 15% from 8-16 weeks. Two automatic feeder treatments included a solar timer feeding which fed SFP divided into 6 feedings per day and AQ1 acoustic demand feeding allowing up to 12 kg/day/pond based on shrimps feeding response.

These management practices were evaluated by a series of water quality analyses over a 16-week grow-out season; with feeding treatments starting at week 4. Samples were analyzed at weeks 0, 4, and 8-16 for the following parameters: chlorophyll a, total ammonia nitrogen, nitrite-nitrogen, nitrate-nitrogen, total nitrogen, total phosphorus, soluble reactive phosphorus, total suspended solids, total suspended volatile solids, turbidity, conductivity, salinity, and biological oxygen demand. Samples were collected and shipped overnight to Auburn, Alabama for off-site analysis. On-site water quality was also obtained at the farm. This included weekly levels of total ammonia nitrogen (probe), and daily measurements of temperature, dissolved oxygen, pH, feed inputs as well as final production.  No differences were found between treatments as of week 10 (Table 1). However, characterization of water quality over the 16-week production cycle and possible correlations with production and performance will be discussed.