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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

Published by Pacific Islands Fisheries Science Center | National Oceanic and Atmospheric Administration, Department of Commerce | Catalog Last Checked: August 02, 2026 at 11:23 PM | Dataset Last Updated: April 20, 2022 at 12:00 AM
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.

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EARTH SCIENCE > BIOSPHERE > ECOSYSTEMS > MARINE ECOSYSTEMS > BENTHIC EARTH SCIENCE > BIOSPHERE > ECOSYSTEMS > MARINE ECOSYSTEMS > REEF > CORAL REEF EARTH SCIENCE > OCEANS > MARINE ENVIRONMENT MONITORING > MARINE SUBMERGED DEBRIS CONTINENT > NORTH AMERICA > UNITED STATES OF AMERICA > HAWAII OCEAN > PACIFIC OCEAN > CENTRAL PACIFIC OCEAN > HAWAIIAN ISLANDS Numeric Data Sets > Benthic EARTH SCIENCE > Biosphere > Aquatic Habitat > Benthic Habitat EARTH SCIENCE > Biosphere > Aquatic Habitat > Reef Habitat

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accessLevel public
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describedByType application/octet-steam
description 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 
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identifier https://data.noaa.gov/waf/NOAA/nmfs/pifsc/iso/xml/59172.xml
issued 2020-03-30T00:00:00.000+00:00
keyword 
[
  "EARTH SCIENCE > BIOSPHERE > ECOSYSTEMS > MARINE ECOSYSTEMS > BENTHIC",
  "EARTH SCIENCE > BIOSPHERE > ECOSYSTEMS > MARINE ECOSYSTEMS > REEF > CORAL REEF",
  "EARTH SCIENCE > OCEANS > MARINE ENVIRONMENT MONITORING > MARINE SUBMERGED DEBRIS",
  "CONTINENT > NORTH AMERICA > UNITED STATES OF AMERICA > HAWAII",
  "OCEAN > PACIFIC OCEAN > CENTRAL PACIFIC OCEAN > HAWAIIAN ISLANDS",
  "Numeric Data Sets > Benthic",
  "EARTH SCIENCE > Biosphere > Aquatic Habitat > Benthic Habitat",
  "EARTH SCIENCE > Biosphere > Aquatic Habitat > Reef Habitat",
  "EARTH SCIENCE > Biosphere > Vegetation > Algae > Algal Cover",
  "EARTH SCIENCE > Biosphere > Vegetation > Algae > Crustose Coralline Algae",
  "EARTH SCIENCE > Biosphere > Vegetation > Algae > Fleshy Macroalgae",
  "EARTH SCIENCE > Biosphere > Vegetation > Algae > Turf Algae",
  "EARTH SCIENCE > Biosphere > Zoology > Corals",
  "EARTH SCIENCE > Biosphere > Zoology > Corals > Reef Damage Assessment > Marine Debris",
  "EARTH SCIENCE > Biosphere > Zoology > Corals > Reef Monitoring and Assessment > Photographic Analysis",
  "EARTH SCIENCE > Biosphere > Zoology > Sponges",
  "EARTH SCIENCE > Oceans > Bathymetry/Seafloor Topography > Hard Seafloor Substrate",
  "EARTH SCIENCE > Oceans > Coastal Processes > Coral Reefs",
  "EARTH SCIENCE > Oceans > Coastal Processes > Coral Reefs > Coral Reef Ecology",
  "EARTH SCIENCE > Oceans > Coastal Processes > Coral Reefs > Coral Reef Ecology > Coral Cover",
  "EARTH SCIENCE > Oceans > Marine Biology > Coral",
  "DEBRIS",
  "REEF AND/OR BOTTOM REGIME - PERCENT COVER",
  "derived products",
  "in situ",
  "CORAL REEF STUDIES",
  "US DOC; NOAA; NMFS; Pacific Islands Fisheries Science Center; Ecosystem Sciences Division",
  "COUNTRY/TERRITORY > United States of America > Hawaii > Honolulu > Northwestern Hawaiian Islands (28N178W0000)",
  "COUNTRY/TERRITORY > United States of America > Hawaii > Honolulu > Pearl and Hermes Reef (27N176W0001)",
  "OCEAN BASIN > Pacific Ocean > Central Pacific Ocean > Northwestern Hawaiian Islands (28N178W0000)",
  "OCEAN BASIN > Pacific Ocean > Central Pacific Ocean > Northwestern Hawaiian Islands > Pearl and Hermes Reef (27N176W0001)",
  "North Pacific Ocean",
  "Papahanaumokuakea Marine National Monument",
  "photograph",
  "scale",
  "M/V IMUA",
  "OSCAR ELTON SETTE",
  "CRED",
  "CREP",
  "Coral Reef Ecosystem Division",
  "Coral Reef Ecosystem Program",
  "ESD",
  "Ecosystem Sciences Division",
  "Marine Debris Program",
  "PIFSC",
  "Pacific Islands Fisheries Science Center",
  "SfM",
  "Structure from Motion",
  "benthic cover",
  "derelict fishing gear",
  "fishing nets",
  "marine debris",
  "NWHI",
  "PHR",
  "PMNM",
  "Pearl and Hermes",
  "DOC/NOAA/NMFS/PIFSC > Pacific Islands Fisheries Science Center, National Marine Fisheries Service, NOAA, U.S. Department of Commerce",
  "Marine Debris"
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language 
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license https://creativecommons.org/publicdomain/zero/1.0/
modified 2022-04-20T00:00:00.000+00:00
publisher 
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  "@type": "org:Organization"
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spatial -175.7880926,27.82745706,-175.8211335,27.89404863
temporal 2018-09-24T00:00:00+00:00/2018-10-03T00:00:00+00:00
theme 
[
  "geospatial"
]
title 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

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