Earth observation based mapping of coastal aquaculture ponds in Asian hotspots – An object-based analysis of high spatial resolution Sentinel-1A SAR data

Kurzfassung

Aquaculture is one of the fastest-growing animal food production sectors worldwide, became the main source of valuable animal protein in many countries and offers great potentials for global food security. While capture fisheries production stagnated over the past years, aquaculture has seen a remarkably increase from 6.2 Mio tones in 1983 to 70.2 Mio tones in 2013 and contributes nearly half of the total volume of aquatic foods in human consumption today. Asia alone generates nearly 90 percent of the total global aquaculture production, with a large share being produced in pond systems which were mainly built in valuable fertile coastal environments. However, this has also led to large-scale land use change, destruction and loss of coastal wetlands, and pollution of waters and soils. In this context earth observation instruments have great capabilities for mapping and monitoring aquaculture areas on even very large spatial scales and can be used for quantitative assessment of aquaculture inventory information. In this study we present an object-based approach to map pond structures analyzing multi-temporal, high spatial resolution radar data for significant aquaculture hotspots along the coasts of East and Southeast Asia. High spatial resolution SAR data allows for the detection of even narrow linear aquaculture structures such as levees or dikes surrounding ponds or other aquaculture systems. The different backscatter response for the components of a typical aquaculture site (dikes, levees and enclosed water surface) and its distinct shape and size allow for the identification and separation of aquaculture areas from other natural water bodies. Open source segmentation algorithms have been applied to high resolution Sentinel-1A interferometric wide swath mode data with a pixel size of 10m to delineate coastal aquaculture structures. Remote sensing based mapping of coastal ponds can effectively support sustainable aquaculture development and add great value for environmental protection.