Ocean sprawl: The global footprint of shellfish and algae aquaculture and its implications for production, environmental impact, and biosecurity
Michelle Harvey, Luke T. Barrett, Rebecca L. Morris, Stephen E. Swearer, Tim Dempster
Abstract
Shellfish and algae aquaculture is widespread in marine waters with an extensive footprint that interacts in complex ways with the surrounding environment. Potential impacts include habitat alteration via modifications to flows, nutrients and sediment, and changes in the occurrence of parasites, disease, and other organisms in the food web. To quantify the impact of suspended aquaculture, understanding its scale and spatial arrangement is key. Using satellite imagery, we identified suspended aquaculture structures and assessed their density, type, and distance from shore in countries that produce >90% of global shellfish and algae (China, South Korea, Chile, Japan, and Vietnam). China and Vietnam contained the highest number of farms, with structure density greatest in South Korea and China. On average, longlines were 8 times more common than rafts, and were the dominant production type in all countries except Japan. Farms were located closest to shore in Vietnam (mean ± SE = 469 ± 458 m), and furthest from the coast in China (2010 ± 2157 m). Characterising cultivation techniques and the sprawl of infrastructure across major production regions informs farm placement, management, and regulation to mitigate risks and maximise the benefits associated with suspended aquaculture.