Tzachi M. Samocha

Review of Some Recent Developments in Sustainable Shrimp Farming Practices in Texas, Arizona, and Florida

Abstract The world shrimp-farming industry is currently experiencing major crop losses due to disease outbreaks, which are often associated with environmental degradation. Such losses can be minimized through the adaptation of technologies that enhance biosecurity and environmental control. Current technologies suggest that a shrimp yield as high as 10 kg/m2/crop can be achieved in indoor, super-intensive, closed-recirculation systems in which environmental parameters are controlled. Nevertheless, high construction and operating costs make the financial viability of these systems questionable. Production of shrimp with reduced water exchange in outdoor ponds is another promising method to minimize monetary losses and environmental degradation. Data from commercial shrimp farms in south Texas suggest that significant reduction in water exchange and nutrient release is feasible with no impact on production when an adequate level of aeration is provided. Researchers of the Texas Agricultural Experiment Station, Corpus Christi, Texas, are currently testing other potential management tools for intensification of outdoor pond productions. These trials demonstrated the feasibility of producing ayield of almost 0.9 kg/m2 of marketable size shrimp with no water exchange. Inland production of shrimp in low-salinity ground water can provide another potential solution to disease and environmental problems, as production is conducted in isolated areas away from other host species and where effluent water can be used for crop irrigation. Recent studies with this water showed that high-density nursery and grow-out of Pacific white shrimp, Litopenaeus vannamei are feasible, with excellent survival and yield.

Variability in growth and survival of early postlarval shrimp (Penaeus vannamei Boone 1931)

Abstract Growth trials with early PL (postlarvae) suggested that growth and size variability may be used as sensitive indicators of PL quality. For PL produced from a broodstock population in which IHHNV (Infectious Hypodermal and Hematopoietic Necrosis Virus) had been identified, growth was lower and size variability was greater than for PL produced from a broodstock population free of IHHNV. Histological examinations of PL confirmed that the slower growing PL were infected with IHHNV, and that the faster growing PL were free of intranuclear inclusions characteristic of IHHNV infection. Survival of PL did not differ between the two populations. Differences in both survival and growth between batches of PL within populations were significant but did not mask differences in growth between the populations. Growth of early PL was exponential rather than linear and was appropriately characterized by the instantaneous growth rate. An additional growth trial conducted with juvenile shrimp indicated that differences observed in PL growth between the two populations continued to be expressed during juvenile growth. Correlations of PL growth to larval survival and duration suggested that larval survival was a good indicator of PL quality but that larval duration was inadequate to predict growth of PL.

Effects of two commercially available low-protein diets (21% and 31%) on water and sediment quality, and on the production of Litopenaeus vannamei in an outdoor tank system with limited water discharge

Abstract Effects of feeding Litopenaeus vannamei with commercial low-protein diets on shrimp performance and on water and sediment quality were studied under high shrimp density with limited water discharge. Twelve tanks (each 10.5 m 2 ) were stocked with juvenile shrimp (average weight, 1.69 g) at a density of 40/m 2 . Shrimp in six tanks were fed a 21% protein diet, and shrimp in the other six tanks were fed a 31% protein diet. Selected water quality parameters were monitored over a 94-day period. Shrimp growth, survival, feed conversion ratio (FCR) and selected sediment quality parameters were evaluated at harvest. Shrimp survival was significantly higher ( P =0.041) in the 31% treatment (96.2%) than in the 21% treatment (90.6%). Mean final weight of the shrimp in the 31% treatment (14.04 g) also was significantly higher ( P P 2 ) was 22% higher than that of the 21% protein diet (441 g/m 2 ). No significant differences were found between the 21 and 31% treatments in the daily-measured water quality parameters (dissolved oxygen, temperature, pH, Secchi readings, and salinity) and the weekly-measured parameters (total ammonia-N, nitrite-N, nitrate-N, reactive and total phosphorus, 5-day carbonaceous biochemical oxygen demand (cBOD 5 ), chemical oxygen demand (COD), total suspended solids and volatile suspended solids (VSS)). Differences in sediment quality parameters (volume of sediment, COD, cBOD 5 and VSS) between treatments were not statistically significant. This work shows that the 31% protein diet provided better production results than the 21% protein diet, yet it did not significantly deteriorate the water or sediment quality.