9. Acoustic Applications

In the past few decades aerial and satellite imagery have been the primary source for producing regional scale maps of coral reefs. Although these tools are well-suited for the clear and shallow waters of the typical coral reef setting, they are less useful for mapping in shallow turbid coastal waters or in mesophotic depths (30–75 m), where considerable coral reefs are known to exist. Acoustic remote sensing systems are relatively insensitive to water column transparency and turbidity, making them ideal tools for mapping reefs in settings inappropriate for optical mapping. Acoustic mapping of coral reefs was in its nascent stage in the 1990s at the time when optical aerial, satellite, and more recently LiDAR technologies were maturing into widely accepted methods for coral reef mapping. Recent developments in hardware, software, and post-processing, however, have rapidly elevated acoustic remote sensing to a viable alternative for producing accurate high-resolution maps of coral reefs. In addition to delineating habitats, the information encoded in acoustic echoes can also provide information about the water column and substrate, including suspended solids, fish size and biomass, bathymetry, grain size, and epifaunal height and abundance.