Nitrite toxicity in Fresh water or Low Saline water Shrimp Farming and it's control strategies and preventive methods.

Hello everyone,

          Myself SRIHARI N C, B.F.Sc., Here we are about to discuss How Nitrite affects Shrimp farming and It's control strategies and Preventive methods.

(I) How Nitrite enters the aquaculture system?

• Nitrite (NO₂^- ) enters the system by Nitrification process, in which Total Ammonia (NH_{3 &} NH₄⁺) is oxidised to Nitrite by, Nitrosomonas and Nitrite is oxidised to Nitrate (NO₃^-) by Nitrobacter.

• Ammonia (NH_{3 &} NH₄⁺) enters the culture system through animal excreta, uneaten feed (excess feed), dead and decaying organisms, etc. and here the Nitrogen Cycle starts (Img.1)

(II) How does Nitrite (NO₂^-) affects animal metabolism:

• Tissue Hypoxia (Brown blood disease in Finfish) occurs when water contains high nitrite concentration. 

• Nitrite enters the blood stream through gills.

• Hemocyanin (Hemoglobin in Finfish) which transport oxygen in blood, combines with nitrite and forms Methemocyanin (Methemoglobin in Finfish) and losses it's ability to carry oxygen and there by resulting in inhibition of aerobic metabolism and initiation of anaerobic metabolism.

• This anaerobic metabolism results in mass mortality of Shrimp in culture system.

(III) Symptoms of nitrite toxicity in shrimps:

• Pale to dark brown colour gills

• Gasps for breath at water surface

• Reddish pigmentation on appendages

(IV) Treatment:

• Application of Common Salt could prevent a bad situation

• Increased dosage of probiotics (Nitrifying bacterial strains)

• Increased aeration

• Controlled feeding

• Application of oxygen enhancer to enhance dissolved oxygen

(V) How does Common Salt treatment prevents bad situation:

• In absence of Chloride, the animal's gill electron receptor has more affinity towards nitrite than oxygen.

• In presence of Chloride, the animal's gill electron receptor has more affinity towards chloride than nitrite and chloride gets eliminated from receptor when oxygen approaches the receptor.

(VI) Amount of Common Salt needed for the pond:

(VII) Preventive methods:

• Maintaining Dissolved oxygen level more than 5ppm (5mg/l)

• Controlled feeding

• Regular water sampling and applications

• Removal of waste (sludge) using Central drainage (shrimp toilet) method

• Maintain pH from 7.5 to 8.2

Conclusion

By following BMP in shrimp farming, we can control the nitrite toxicity in culture system and secure the animal. Applications of AHCP on scientific approach can reduce the cost of production effectively and can have better profit margin.

For further contact,

Mr. SRIHARI N C, B.F.Sc.,

+918270776354 (WhatsApp / Call)