Aqua-Feed Wastes: Impact on Natural Systems and Practical Mitigations—A Review

Dietary composition of aquaculture feeds (aquafeeds) determines the quality of wastes from aquaculture production systems. These wastes, which are derived mainly from nitrogenous and phosphorus compounds subsequently affect water quality in the culture systems and the ambient environment. Depending on the type of culture systems and management practices employed, the aquafeed wastes can influence the water pH, algal turbidity, biological oxygen demand (BOD) and may cause fish mortality. The aquafeed wastes also can facilitate eutrophication leading into harmful algal blooms. Moreover, large quantities of aqua-waste are discharged as fish cannot retain all the food they consume which means a significant portion of the feed remains uneaten. In this paper, we review and discuss practical nutritional strategies and mitigation measures to reduce aquafeed wastes including controlled formulation using high-quality ingredients, enzyme-based aquafeed, processing, reduction of anti-nutrition factors and precision feeding. The paper further recommends strategies for enhancing the resilience of aquaculture production systems and mitigation measures to reduce the effects of aqua-wastes on ambient natural environments.