THE EFFECTS OF VERTICAL SUBSTRATE AND SHRIMP Litopenaeus vannamei DENSITY ON WATER QUALITY AND PRODUCTION DYNAMICS IN INTENSIVE GREENHOUSE-BASED BIOFLOC SYSTEMS

Leo J. Fleckenstein*, Nathan A. Kring, Andrew J. Ray
 
Division of Aquaculture, Kentucky State University Land Grant Program
Frankfort KY 40601 USA
leo.fleckenstein@kysu.edu
 

The use of artificial substrates in shrimp aquaculture has been shown to have beneficial effects on the animals being cultured. Increased growth and decreased FCRs have been recorded in multiple studies. In intensive shrimp production systems the use of substrates has been proposed as a method to allow increased densities of shrimp while reducing negative effects of over-crowding. Substrates also increase the surface area available for periphyton growth that could impact shrimp production and water quality. This study evaluated the effects of substrate and density on water quality and shrimp production in greenhouse-based biofloc systems located in Kentucky, USA.

Four 11.04 m³, wood frame, polyethylene-lined tanks were constructed in each of four high tunnel greenhouses for a total of 16 tanks. Four treatments were created using two factors:  substrate and density. The four treatments were: High Density Substrate (HDS), High Density No Substrate (HDNS), Low Density Substrate (LDS), and Low Density No Substrate (LDNS). High density systems had 200 shrimp/m³ and low density tanks had 100 shrimp/m³. Tanks with substrate had an added 18.1m² of surface area created by vertically oriented plastic construction barrier material. The experiment was blocked by greenhouse, such that each of the four treatments was randomly assigned to one tank per greenhouse.  All tanks were chemoautotrophic-based biofloc systems with a 470-L settling chamber to control suspended solids levels in the systems. No heaters were used in the experiment, all tanks relied on ambient air and solar energy to maintain water temperature. All systems were fed twice daily at 12:00 and 16:00 and feed amounts were based on initial stocking density. Dissolved oxygen, pH, salinity and temperature were measured twice daily. Total ammonia nitrogen, nitrite, nitrate and turbidity were measured weekly.

Shrimp were stocked at 7.15g, and harvested after 119 days.  There were significant (p<.05) differences in shrimp production due to density but no significant differences due to substrate.  Average weights in high density tanks were 24.1g (HDS) and 24.8g (HDNS) and average weights in low density tanks were 26.4g (LDS) and 25.7g (LDNS). Peak nitrite levels and overall mean nitrite levels were significantly higher in high density treatments compared to low density treatments. Dissolved oxygen levels and pH were significantly lower in high density systems over the course of the study. Results from further shrimp production and water quality analyses are pending.