1. Influence of water temperature Penaeus vannamei has strong adaptability to water temperature. Generally, the growth temperature is 16℃-38℃, but too high or too low water temperature will affect it, mainly including the following aspects:
(1) on metabolism. When the water temperature is high (higher than 34℃), the activity of digestive enzymes is enhanced, which leads to high consumption, low efficiency, anorexia and easy to be frightened, and the recovery time of muscle whitening after stress is long, which affects growth; Low water temperature (below 65438 08℃), slow digestion, poor absorption, easy indigestion, blocked blood circulation, increased coagulation and poor blood flow, thus reducing its disease resistance and food intake.
(2) Effects on dissolved oxygen, ammonia nitrogen and nitrite nitrogen. When the water temperature is high, the dissolved oxygen in the water is low, and it is not easy to form saturated dissolved oxygen. Low dissolved oxygen is not conducive to the transformation of NH3 and nitrite nitrogen, while high NH3 and nitrite nitrogen are more toxic.
(3) Effects on phytoplankton. High water temperature has a great influence on phytoplankton in water, resulting in rapid reproductive death and short life cycle. Once the supply of nutrients is insufficient, the phenomenon of water exchange will occur, and its fluctuation is large, which is easy to cause stress and death of prawns. The low water temperature brings difficulties to the reproduction and cultivation of water color. Continuous rainy days may also cause "anti-water" phenomenon, that is, fat water becomes "crystal clear" overnight.
(4) the effect on drug efficacy. If the water temperature is low, the drug effect is generally low, or even ineffective, increase the dose; High water temperature increases toxicity, and some drugs are prone to phytotoxicity at high temperature. For example, every time the water temperature rises 10℃, the toxicity of copper sulfate increases by 1.7-1.8 times.
(5) Influence on environmental pathogens. At high temperature, some pathogenic microorganisms multiply in the humus of water, which leads to the occurrence of shrimp diseases, such as gill rot and red leg disease.
2. Influence of pH value: Penaeus vannamei requires a pH value of 7.0-8.6.
(1) Influence on chemicals: When the pH value is below 7, chlorine-containing disinfectants and quaternary ammonium salt disinfectants have better effects; When basic aluminum chloride is precipitated under acidic conditions, the water quality is better; Alum works at pH 7.0, while gentamicin and streptomycin are ineffective at pH 8.0, and chlortetracycline is the best at pH 7.0.
(2) that pH value of the wat body which affects the physiological function of the white shrimp is low, the carbon dioxide in the shrimp body is not easy to be release into the water, the oxygen exchange is poor, and the head is easy to float; When the pH value is high, ammonia exists in the form of NH3, which is toxic and easy to cause shrimp diseases.
3. The effect of dissolved oxygen The optimum dissolved oxygen for white shrimp is more than 5 mg/L. ..
(1) Effect of dissolved oxygen on digestive protease activity of prawn: When dissolved oxygen is above 3.5 mg/L, protease activity is higher; When the dissolved oxygen is high, the protease activity changes little; When the dissolved oxygen is about 1.6 mg/L or less, the protease activity is low.
(2) How low the dissolved oxygen is, it will cause the white shrimp to suffocate and die. When the dissolved oxygen is between 0.3mg/L- 1mg/L, white shrimp will suffocate and die, and its oxygen consumption will increase with the increase of individual white shrimp.
(3) The dissolved oxygen value fluctuates greatly, indicating that there is too much organic matter in the water, which needs to be changed in time. When the water quality is not well regulated, it is easy to have poor appetite and frequently-occurring diseases.