Essential role of seaweed cultivation in integrated multi-trophic aquaculture farms for global expansion of mariculture: an analysis

Ecologically friendly aquaculture crops, such as seaweeds, herbivores, omnivores, and detritivores can be cultured using relatively less of our limited natural resources and produce relatively less pollution. They also top FAO’s estimates of aquaculture crops for the 21st century. These crops already comprise nearly 90% of global aquaculture tonnage, >90% of all aquaculture production in China and >60% of production even in North America. Consumers prefer them, most likely due to their low prices. Production costs of organisms low on the food chain are low due to the ability of these organisms to efficiently utilize low-cost, mostly plant-based diets and to recycle their own waste. Thus, ecologically friendly aquaculture is not a dream but a dominant global reality. The less ecologically-friendly aquaculture of salmon, sea bream, fed shrimp, among others, has attracted public opposition to aquaculture, but these crops totaled approximately only 10% of global production in 2004. The profitability of industrialized monocultures of these crops is threatened further by rising costs of energy and feed, environmental regulation compliance, disease, and public opposition. Current monoculture practices and perceptions intrinsic to the aquaculture industry can be turned around into a vision of sustained profitable expansion of carnivores production with trophically lower organisms in ecologically-balanced aquaculture farms. This category of aquaculture, which is the modern intensive form of polyculture practiced in Asia, feeds the waste of carnivore culture to lower trophic level organisms, primarily algae and mollusks. Species are selected based on their ecological functions in addition to their economic potential. Ecologically-balanced farms turn the costly treatment of carnivore waste outside the farm to a revenue-generating process of biofiltration, conversion, and resource recovery into plant and mollusk crops inside the farm. In doing so, they solve several of the major problems faced by modern aquaculture. The aquaculture industry can protect its own interests – and reap major benefits – by understanding the importance of ecological balance, the potential of seaweeds as components in feeds, and the importance of the culture and R&D of low trophic level organisms. The industry should also accept the relevance of environmental, social, and image aspects of aquaculture to its success. Governments have the tools to reward multi-trophic farms with seaweeds by means of tax credits and nutrient credits and to penalize unbalanced monoculture approaches by means of ‘polluter pays’ fines, thereby providing the multi-trophic farms with a significant economic advantage. Such measures have been discussed, but their implementation has been slow.