This article is a study by Dr. Chau Tai Tao (Faculty of Fisheries - Can Tho University) on the effect of alkalinity on the growth and survival rate of black tiger shrimp and whiteleg shrimp larvae and postlarvae.
What is alkalinity?
- Total alkalinity indicates the acid-neutralizing capacity of water.
- Alkalinity in water is created by 3 ions: OH-, CO32-, HCO3-. Among these, HCO3- is the main form.
Effects of alkalinity:
- Alkalinity affects the buffering system in the aquatic environment.
- It maintains pH fluctuations and helps stabilize water pH.
- Changes in water alkalinity will affect physical and chemical factors, as well as the survival rate and growth of shrimp.
- In marine shrimp larval rearing, lower alkalinity makes it difficult for shrimp to harden their shells after molting. If alkalinity is too high, shrimp larvae and postlarvae grow slowly, have difficulty molting, or fail to molt, leading to death.
Experiment evaluating the effect of alkalinity on the growth and survival rate of black tiger shrimp and whiteleg shrimp larvae:
Experimental setup:
- Shrimp rearing water salinity 30‰.
- Soda (NaHCO3) was used to adjust alkalinity to suit each treatment before larval stocking.
The experiment included the following treatments:
- For the black tiger shrimp experiment: Larval rearing water alkalinity of 80, 100, 120, 140 mg CaCO3/L corresponding to treatments 1, 2, 3, 4.
- For the whiteleg shrimp experiment: Larval rearing water alkalinity of 100, 120, 140, 160, 180 mg CaCO3/L corresponding to treatments 1, 2, 3, 4, 5.
Monitored parameters:
Environmental monitoring: Temperature, TAN, NO2-, alkalinity.
Shrimp monitoring:
- Total length of larvae and postlarvae was measured at stages Z3, M2, PL1, PL5, PL10, PL15 (for black tiger shrimp) and Z1, M1, PL1, PL6, PL12 (for whiteleg shrimp).
- Survival rate was determined at PL15 (for black tiger shrimp) and M1, PL1, PL12 (for whiteleg shrimp).
Results:
Table 1. Environmental parameters in the black tiger shrimp experiment
