Laboratory Holding Procedure 



In the laboratory the shrimp were stocked in four raceway tanks. 

 Each tank was 10 feet (3.05 m) long, 4 feet (1.22 m) wide, and 2 feet 

 (0.61 m) high and held about 450 gallons (1703 L) of water. Under 

 ambient temperature (25°C) conditions, a maximum of 1000 shrimp were 

 stocked in each raceway tank. Stocking densities were changed with 

 holding temperature conditions. At high temperature (32°C), the den- 

 sity was lowered to 600 shrimp per tank, while at 18°C the density 

 could be increased to more than 1000 animals. 



Often there was an initial high mortality during the first 48 

 hours, primarily due to physical stress either in trawling or in 

 transportation. The initial mortality ranged from 10 to 25% of the 

 total stock per day. By the third day the rate decreased to 5% under 

 normal conditions and then to 1% on succeeding days. The phenomenon 

 of mass molting which occurred sometimes had resulted in heavy mor- 

 talities. In a single night as many as 15 to 20% of the normal ani- 

 mals would molt and die. Although some of these deaths occurred from 

 natural stress of temperature and salinity changes, a great majority 

 of the shrimp were vulnerable to attacks by the other shrimp at this 

 time and were killed. In general there was a low incidence of mass 

 molting at 18°C and a high incidence at 32°C. 



The shrimp were allowed to adjust to laboratory conditions at 

 15°/ooS and 25°C for about 48 hours. They were then transferred to 

 the respective control temperatures 25°, 18°, or 32°C for acclimation. 

 The temperature was changed gradually from ambient to the control 

 within 24 hours. After the shrimp were kept for seven days in the 

 control or acclimation conditions, they were tested. 



Animals in the laboratory conditions or under acclimation re- 

 ceived dry food pellets at a rate of approximately 5% of their body 



34 



