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Summary

Short Citation
Pacific Islands Fisheries Science Center, 2025: Benthic cover derived from structure from motion images collected during marine debris surveys at coral reef sites entangled with derelict fishing nets at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands from missions in 2018 and 2021, https://www.fisheries.noaa.gov/inport/item/59172.
Full Citation Examples

DOI: https://doi.org/10.1016/j.marpolbul.2023.114703

Abstract

The benthic cover and fishing-net related data described in this dataset are derived from the GIS analysis of benthic orthophotos. The source imagery was collected by snorkelers using a Structure from Motion (SfM) approach during swim surveys in search of derelict fishing nets. Surveys were conducted by the NOAA Fisheries, Ecosystem Sciences Division (ESD) at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands (NWHI). Initial surveys occurred from September 24 - October 3, 2018 during an ESD-led marine debris removal mission aboard the NOAA Ship Oscar Elton Sette, and follow-up surveys occurred from September 13-14, 2021 on a joint mission with non-profit organization Papahanaumokuakea Marine Debris Project aboard the M/V IMUA.

During the 2018 mission, fishing nets were located during swim surveys and selected for SfM if the net was interacting with coral or hard substrate, the depth of the net was within ~1 - 4 m of the surface, and the area of the net fit within the 9 sq. meter SfM survey plot. During the SfM survey, a permanent 3 x 3 m plot was established around the center of the fishing net, and the net was photographed using a back and forth swim pattern ("before" photos) for later processing using a SfM approach. The net was then removed, the volume of net removed was estimated and recorded, and the same area was photographed again in the same way ("after" photos). A nearby (>50 m distant) paired control site was also photographed using the same method ("control" photos).

During the 2021 mission, we attempted to relocate all paired sites where "after" and "control" photos were taken in 2018 and if found, we reimaged the permanent 3 x 3m plot 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 our paired study design.

The photographs from each site were processed using Agisoft Metashape software to generate orthomosaic images that were analyzed in ArcGIS for benthic cover using a random point approach. In 2018, the number of points at net-impacted sites were constrained to the net coverage area and were scaled to the net area to ensure an equal point density among replicate net-impact sites. The same number of points were randomly assigned to the 3 by 3 m paired control site. In 2021, twenty random points were assigned to each orthophoto within the 2018 net polygon. Each point was classified into one of seven benthic categories: turf algae, macroalgae, sand, bare substrate, Porites compressa, sponge, or crustose coralline algae (CCA). In 2021, turf and macroalgae categories were merged into a single algae category and all coral species were assigned the coral category. The annotated points for each site were converted to percent cover for each benthic category. Fishing net size (sq. m) and degree of fouling were also calculated from the initial "before" orthophotos. Analyses were conducted to compare the benthic composition of net sites to control sites and to determine if fouling or net size contributed to these differences.

Distribution Information

  • CSV - Comma Separated Values (Text), 3 KB

    Benthic cover data from marine debris surveys conducted at coral reef sites entangled with derelict fishing nets at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands in 2021. Surveys were conducted by the NOAA Fisheries Ecosystem Sciences Division. Data include fishing net area and weight, and percent benthic cover data derived from structure from motion images collected during the marine debris surveys.

  • CSV - Comma Separated Values (Text)

    Benthic cover data from marine debris surveys conducted at coral reef sites entangled with derelict fishing nets at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands in 2018. Surveys were conducted by the NOAA Fisheries Ecosystem Sciences Division. Data include fishing net area and weight, and percent benthic cover data derived from structure from motion images collected during the marine debris surveys and processed using a structure from motion approach.

Use Constraints:

These marine debris survey data act as a proxy for area surveyed and have not been screened for accuracy based on environmental conditions or GPS accuracy. NOAA can not be held liable for use of these data in a manner other than for perusal of preliminary marine debris data for scientific research on coral reef ecosystems. When using this data, please credit the NOAA Fisheries, Ecosystem Sciences Division.

Suggested citation:

Pacific Islands Fisheries Science Center, 2022: Benthic cover derived from structure from motion images collected during marine debris surveys at coral reef sites entangled with derelict fishing nets at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands from missions in 2018 and 2021, https://www.fisheries.noaa.gov/inport/item/59172.

Controlled Theme Keywords

BENTHIC, CORAL REEF, environment, MARINE SUBMERGED DEBRIS

Child Items

Type Title
Entity SFM Debris: Benthic Cover entities

Contact Information

Point of Contact
Ariel Halperin
ariel.halperin@noaa.gov

Metadata Contact
Lori H Luers
lori.luers@noaa.gov

Extents

Geographic Area 1

-175.8211335° W, -175.7880926° E, 27.89404863° N, 27.82745706° S

Geographic extent of marine debris structure from motion surveys conducted at Pearl and Hermes Atoll.

Time Frame 1
2021-09-13 - 2021-09-14

Time frame of marine debris Structure from Motion (SfM) surveys at Pearl and Hermes Atoll during the 2021 mission.

Time Frame 2
2018-09-24 - 2018-10-03

Time frame of marine debris structure from motion surveys conducted at Pearl and Hermes Atoll during the 2018 mission.