Earth Observation for the Assessment of Pond Aquaculture in Coastal Asia - Status and Future Potentials

Abstract

Aquaculture is the fastest growing sector in the global food industry. Growing global population and changing consumer behavior lead to a sharp increase of worldwide production of aquatic products from 13 to 76 million tonnes during the past 25 years at an annual growth rate of 6.7 percent. Today every second fish comes from aquaculture, which became a vital source of essential fatty acids and protein for the world's population with great significance for global food security and nutrition. Asia supplies almost 90 percent of global aquaculture products, and aquaculture is a rapidly growing economic factor in the coastal zone that promises high income but entails high environmental risks: mangrove deforestation, water pollution, and the use of antibiotics and pesticides threaten vulnerable coastal ecosystems. The Copernicus Sentinel-1 mission allows continuous and wide-swath radar mapping, enabling the exploitation of a large data volume for the detection and mapping of aquaculture. We focus on coastal land-based aquaculture ponds, appearing as generally rectangular, permanent water-covered surfaces surrounded by dams, dikes or levees. Open source clustering-based image thresholding and segmentation algorithms were applied to extract single pond objects from Sentinel-1 IW GRDH high resolution time series data based on object and shape metrics. In view of aquaculture's growing contribution to global nutrition and food security, an important research objective is the estimation of pond production quantities. With the collection of sub-national and in-situ aquaculture production and yield statistics this study aims to estimate pond production - exemplified by the Mekong Delta in Vietnam as one of the world's most important aquaculture hotspots. Earth observation holds great potential as a helping tool for future approximation of pond production estimates and for the sustainable management of resources along our planet's coasts.