Organic Manuring in Freshwater Aquaculture and Its Impact on Pond Ecosystem and Fish Health: An Overview

The use of organic manure in aquaculture had been practiced since centuries in India, China and other Far East countries. Sustainability of aquaculture farming depends upon ecofriendly, economically and socially viable culture systems. The recycling of organic wastes for fish culture serves the dual purpose of cleaning the environment by avoiding the problem of waste disposal and providing economic benefits. The recycling of animal dung/wastes in fish ponds for natural fish production is important to sustainable aquaculture and to reduce expenditure on costly feeds and fertilizers which form more than 60% of the total input cost. Integrating aquaculture with animal husbandry results in the most rational utilization of organic manures. However, the indiscriminate use of these manures in fish ponds, instead of improving the pond productivity, may also lead to pollution causing negative impact on the dissolved oxygen regime of the fish ponds and may cause problems to fish health. Therefore, it is necessary to understand the standard doses of these wastes which would keep the physico-chemical parameters of pond water in a favorable range required for the survival and growth of fish. When organic manure is applied in aquaculture ponds, best results are obtained with its frequent applications. Judicious organic manuring of fish ponds can eliminate the need for supplementary feeding. Although a lot of work has been done on the utilization in fish culture ponds, of animal manures, particularly farmyard manure, poultry droppings, cow dung and biogas slurry which are suitable substitutes for costly feeds and fertilizers. In the present review, an attempt has been made to elucidate the present status of organic manuring in fish culture systems and its impact on pond ecology and fish health.