  Coral reefs are fast-changing and complex ecosystems that are crucial to
monitor and study. Biological hotspot detection can help coral reef managers
prioritize limited resources for monitoring and intervention tasks. Here, we
explore the use of autonomous underwater vehicles (AUVs) with cameras, coupled
with visual detectors and photogrammetry, to map and identify these hotspots.
This approach can provide high spatial resolution information in fast feedback
cycles. To the best of our knowledge, we present one of the first attempts at
using an AUV to gather visually-observed, fine-grain biological hotspot maps in
concert with topography of a coral reefs. Our hotspot maps correlate with
rugosity, an established proxy metric for coral reef biodiversity and
abundance, as well as with our visual inspections of the 3D reconstruction. We
also investigate issues of scaling this approach when applied to new reefs by
using these visual detectors pre-trained on large public datasets.
