Addressing Phosphorus Waste in Open Flow Freshwater Fish Farms: Challenges and Solutions

Legislation and interest to protect and restore freshwater and marine ecosystems from aquaculture's environmental impact is global. However, aquaculture induced eutrophication continues to be a major environmental issue. Open freshwater fish farms in particular, providing fish with phosphorus-rich feeds pollute aquatic ecosystems since water soluble phosphorus, uneaten feed, feces, and metabolic waste from farmed fish increase phosphorus concentration in the adjacent waters. Several intestinal enzymes, transporters, and regulating factors are implicated in dietary phosphorus retention of farmed fish. For example, alkaline phosphatase and other transporters help the anterior intestine absorb phosphorus, while pH, calcium, and vitamin D affect these enzymes and transporters. Intestinal morphology and gut microbiome may also affect this process. Reducing phosphorus pollution from open-flow fish farms requires a thorough understanding of processes that affect nutrient retention and absorption as well as of the impact of dietary factors, anti-nutritional substances, and intestinal morphology. Optimizing feed composition, adding functional feed ingredients, and managing gut health can reduce phosphorus release and improve aquaculture sustainability. Processing and functional feed additives can mitigate anti-nutritional factors and, addressing these issues will reduce aquaculture's environmental impact, ensuring aquatic ecosystem health and global food security