Camera Configuration and Use of AUVs to Census Mobile Fauna

There is a diversity of shapes and sensor configurations used in the design of autonomous underwater vehicles (AUVs). Cameras and lighting (for both still and video imaging) are common sensor systems and have traditionally been configured to produce orthogonal images of the seafloor. Such imagery provides invaluable small-scale, high-resolution data for studies of seafloor geology and sessile invertebrate communities. However, using orthogonal imagery to census the diversity of mobile fauna has limitations caused by avoidance. A simple analysis using species-individual curves demonstrated that species richness was generally lower in surveys using orthogonal images when compared to forward-looking oblique images despite encountering the same number of individual fishes. This pattern was consistent when contrasting data from separate AUV and ROV surveys at boulder reefs in the Gulf of Maine as well as from down-looking and forward-looking cameras simultaneously collecting video imagery from a camera sled in a variety of habitats. These results indicate a need to evaluate the effects of camera configuration on the performance of abundance and diversity indicators developed from image data acquired using AUVs and other vehicles. Further, we recommend that AUV designers endeavor to accommodate oblique angles for cameras and associated lighting within vehicle design parameters in order to support missions that improve detection of mobile fauna.