Nutrient Loading From a Sustainably Certified Aquaculture Operation Dwarfs Annual Nutrient Inputs From a Large Multi-Use Watershed, Lake Yojoa, Honduras

Net-pen aquaculture is a popular and increasingly prevalent method for producing large quantities of low-fat protein in freshwater ecosystems across the tropics. While there are numerable social and economic advantages associated with aquaculture, there are also challenges related to the environmental sustainability of aquaculture operations which supply pens with externally produced feed. For example, excessive nutrient loading, which can drive rapid eutrophication in aquatic ecosystems, is a major risk. In this study, we compare the estimated annual nutrient loads from the six principal tributaries that contribute to Lake Yojoa to the estimated nutrient load of a large net-pen Tilapia operation located in the central region of the lake. The Tilapia farm was responsible for ∼86% of the nitrogen (N) and ∼95% of the phosphorus (P) contributions to Lake Yojoa for the year of our study. This excessive nutrient loading of both N and P suggests that this single aquaculture operation, more so than changes in nutrient inputs from the watershed, was responsible for the previously documented deterioration of Lake Yojoa. This study shows the potential for net-pen aquaculture to have significant negative impacts on freshwater ecosystems, even when operations meet the current sustainability certifications standards. We suggest shifts in metrics that could improve the impact of the certification process so that best practices can reduce the impact of net-pen aquaculture on freshwater ecosystems and arrive at the intended goal of long-term environmental sustainability. La versión en español de esta publicación se encuentra disponible en los materiales suplementarios.