Aquaculture systems as mesocosms

Abstract

AbstractThe boundary between aquaculture and capture fisheries is becoming blurred as wild populations of aquatic organisms are ever more impacted (unintended) and managed (intended) by humans who have irreversibly changed the trajectory of the biosphere. Most current aquaculture systems are semi-intensive, open systems that depend to a very high degree on natural ecosystem services. A mismatch between a significant human-induced decline of natural ecosystems on the one hand and increased human demand for ecosystem services on the other hand calls for solutions that minimize the reliance on ecosystem services for all purposes, including aquaculture. Low-yield, extensive aquaculture systems are sustainable in suitable areas, but they are not economical on a global scale unless the human population declines significantly. The most ecologically sustainable aquaculture systems for a growing human population are intensive, closed recirculating aquaculture systems (RAS), which are human-managed mesocosms that require constant balancing of energy and matter in inputs and outputs. Knowledge generated and technologies developed for culture of ornamental organisms in aquaria at microcosm scale have advanced ecologically sustainable aquaculture at larger mesocosm scales. Ecosystem succession must be managed when establishing aquaculture mesocosms to maintain optimal conditions for growth, health, and development of aquaculture organisms. Since trophic level transfer efficiency (TLTE) is only 10–20%, aquaculture systems for top-level carnivores are least energetically efficient and most resource intensive. Balancing trophic levels in closed aquaculture mesocosms requires proportional matching of primary producers, consumers, and decomposers to minimize reliance on ecosystem services.