SURVIVAL AND GROWTH PERFORMANCE OF THREE DIFFERENT SOURCES OF PACIFIC WHITE SHRIMP Litopenaeus vannamei CULTURED IN ON-SHORE TANKS IN LOW SALINITY WATERS OF WEST ALABAMA

Inland, low salinity shrimp farmers in west Alabama, that produce the Pacific white shrimp, Litopenaeus vannamei, have been reporting abnormally low survivals at harvest. This phenomenon is not restricted to one farm, but has been observed across all farms culturing this species in west Alabama. Multiple theories exist as to the cause of increased mortality on Alabama shrimp farms including disease, toxic algae blooms, water quality, shrimp source, and reduced robustness of shrimp in later stages of production. In order to compare the survival and growth performance of shrimp from different sources, shrimp were obtained from three different hatcheries and stocked on the same day in three different 12-tank (700 L each) flow-through systems. Each source of shrimp was replicated four times in each system. Two of the 12-tank systems (TS) were installed on two different pond banks of one farm (Farm1-TS1; Farm1-TS2), and another was installed on a pond bank of a neighboring farm (Farm2-TS). The culture systems operated flow-through by pumping low salinity pond water through the tanks at a flow rate which exchanged water in the tank twice per day. Thirty-four shrimp were stocked in each tank and shrimp were offered a commercial feed once per day. Shrimp in tanks on each system were offered the same amount of feed.  Shrimp were supplied with aeration via two air stones and a regenerative blower. Throughout the trial, tanks were sampled periodically to track growth and survival. At the end of the trial shrimp were harvested, counted, and group weighed. A composite sample of hemolymph was taken from shrimp in each tank to determine hemolymph osmolality and blood ion levels. In order to assess survival following stocking, after 30 days tanks were drained to count and weigh shrimp in each tank system. Survival ranged from 85-94%, 95-97%, and 61-81% for Farm1-TS1, Farm1-TS2, and Farm2-TS, respectively. Following 107 days of culture on Farm1-TS1 there were no statistical differences in survival (72.8 - 91.2 %) or final weight (21.2 - 24.6 g) among shrimp sourced from three different hatcheries.  Likewise, in Farm1-TS2 no differences in survival (83.1 - 86.8%) or final weight (19.8 - 20.7 g) were observed. At Farm2-TS, following 111 days of culture there were significant differences in survival from shrimp sourced from one hatchery (40.5%) compared to the other two hatcheries (61.0 - 69.8%).  However, no significant differences in final weight were observed among treatments at Farm 2 (18.3 - 22.1 g). A large percentage of the observed mortality in the trial occurred in the first thirty days for two of the tank systems (Farm1-TS1 and Farm2-TS).  Hemolymph osmolality and analysis of whole body proximate composition are currently ongoing and will be discussed.