The effects of stocking density and artifical substrate on production of pacific white shrimp Litopenaeus vannamei and water quality dynamics in greenhouse-based biofloc systems

Abstract

Inland shrimp aquaculture has increased in popularity in recent years as a means of providing fresh seafood to consumers away from the coasts. With adequate marketing,fresh shrimp fetch relatively high prices and can give farmers a means of diversifying, production. In temperate regions such as Kentucky, low-cost high tunnel greenhouses may be used to extend the growing season of warm-weather crops, including tropical animals such as penaeid shrimp. To optimize investments, inland producers are constantly exploring methods to increase overall production. A 100 day-long study examined the effects of stocking density and artificial substrates on water quality, stable isotope dynamics, and production of Litopenaeus vannamei using biofloc-based aquaculture systems in greenhouses. Four treatments were compared: High Density Substrate (HD/S), High Density No-Substrate (HD/NS), Low, Density Substrate (LD/S), and Low Density No-Substrate (LD/NS). Four high tunnel greenhouses each contained four 10.9 m3 tanks. The experiment was blocked by location such that one replicate from each treatment was randomly assigned within each greenhouse to account for potential environmental variation. Each tank was outfitted with a settling chamber for solids filtration, and 13.1 m2 of polypropylene, construction safety fencing was used as substrate in the substrate-containing tanks. Shrimp were stocked into the experimental systems at 2.71 g mean weight; high density treatments were stocked with 300 shrimp/m3, while low density treatments were stocked with 200 shrimp/m3. Water temperatures were significantly lower over the course of the entire study within substrate treatments. pH throughout the study was significantly lower within substrate treatments and high density treatments. Stable isotope data indicated that very little of the carbon and nitrogen in shrimp tissues was likely sourced from biofloc and periphyton material. Low density treatments had significantly lower FCRs than high density treatments. However, the addition of substrate in the HD/S treatment resulted in significantly more efficient shrimp FCR than was observed in the HD/NS treatment. The HD/S treatment also had significantly higher, shrimp biomass than all other treatments. High density treatments had significantly higher FCR and lower survival than low density treatments. This study demonstrates that artificial substrates can reduce some of the negative effects of high shrimp stocking density, with significant improvements in FCR and biomass production. Although it is important to note the implications for water quality, adding substrate to facilitate high density shrimp culture in high tunnel greenhouses can facilitate higher stocking density without compromising the size of the animals