Structure from motion images collected during follow-up marine debris surveys at coral reef sites at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands from 2021-09-13 to 2021-09-14

The photographs described in this dataset were collected using a Structure from Motion (SfM) approach during in-water marine debris swim surveys conducted by snorkelers in 2021, at sites where entangled nets were removed in 2018. Surveys were conducted by the NOAA Fisheries, Ecosystem Sciences Division (ESD) at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands (NWHI). The photographs in this collection are from follow-up surveys that occurred from September 13-14, 2021 on a joint mission with non-profit organization Papahānaumokuākea Marine Debris Project aboard the M/V IMUA, to assess reef recovery. Impact images are those taken from sites which were previously entangled with nets, and control images were either relocated or newly established to fulfill the paired study design.

The 2021 mission attempted to relocate all paired sites where "after" and "control" photos were taken in 2018; if found, the permanent 3 x 3m plot was reimaged using the same SfM approach. Only a subset of 2018 sites were successfully relocated in 2021 (12 "after" sites, 8 "control" sites), and five new nearby "control" sites had to be established to fulfill the paired study design.