Aquaculture management by integrating seaweed with shrimp

Aquaculture is the fastest growing food production sector in the world and has come under increasing scrutiny and criticism because of coastal pollution. Effluents' from intensive farming contain much organic matter, nitrogen compounds, phosphorus and other nutrients, makes the water unfit for aquaculture and lead to eutrophication. Macroalgae plays a vital role in controlling toxic wastes to reasonable and cultivable limits and also improves water quality. Aquaculture - management can be done effectively by integrating seaweeds into aquaculture systems. This method can be done either by stocking seaweeds along with shrimp in optimum stocking density or by recycling the water through a pond supplemented with seaweeds. In the present study an attempt has been made to find out the species of seaweed suitable for integrated farming with shrimp in brackish water tide-fed system on southwest coast and sea water in pump-fed system on southeast coast of India.

The removal of nitrogenous compounds such as ammonia, nitrate, nitrite and total nitrogen was found to be 65 to 82%, 34 to 53%, 28 to 77% and 53 to 60% respectively by seaweeds in the treatment ponds inrhen compared to the control ponds. The species of Gracilaria verrucosa, proved to be an ideal seaweed for integrated farming with shrimp in the brackishwater ponds and post monsoon period is the most favourable period for integrated farming as the growth performance of seaweed and shrimp were found to be more than the monsoon period in the tide-fed system of southeast coast of India. Eventhough the accumulation of toxic waste was less compared to southwest coast, the growth rate was comparatively lower in sea water system of southeast coast of India. G. verrucosa integrated with Enteromorpha intestinalis in optimum stocking density can reduce stress on shrimp by utilizing excess nitrogenous wastes either through bacterial mineralization or direct use by seaweeds.

In the Present context, luxuriant growth of G. verrucosa in the first year of experiment leading to harvest of 880kg was due to the heavy amount of nutrient loaded in the Pond for age long aquaculture activity, which enabled the proliferation of algal growth and maximum removal of nitrogenous load from the system. It was also observed that growth of alga in the pond was able to minimize the disease problems in shrimp.