CRED Marine Debris Survey and Removal Efforts within the Northwestern Hawaiian Islands during 1999-2012

Supported by the Papahanaumokuakea Marine National Monument, NOAA's Marine Debris Program (MDP),NOAA's Damage Assessment Remediation and Restoration Program (DARRP), and NOAA's Coral Reef Conservation Program (CRCP), the marine debris team of Coral Reef Ecosystem Division (CRED) at the Pacific Islands Fisheries Science Center (PIFSC) conducts cruises to the NWHI for the purpose of surveying and removing DFG. Exploratory and opportunistic efforts began in 1996 that eventually evolved into dedicated cruises deployed for up to 4 months at a time with a team of up to 16 divers. To date, the marine debris team of CRED has removed approximately 753 metric tons of derelict fishing gear from the NWHI, including the atolls and islets of Pearl and Hermes Atoll (PHR), Midway Atoll (MID), Kure Atoll (KUR), Lisianski Island (LIS), Laysan Island (LAY), Maro Reef (MAR), and French Frigate Shoals (FFS).

Surveys are conducted by divers based on small boats launched from a ship. Two survey methods are used to search for marine debris; tow survey and swim survey. Tow surveys are used in the relatively even-depth (usually less than 10 meters deep), contiguous backreef habitats, while swim surveys are used in the comparatively high-relief and patchy lagoonal reef habitats. Survey areas are chosen based on regional reef morphology and past accumulation records.

In a tow survey, two freediving divers are towed behind a small boat at an average of 1-2 knots. Each diver has a board with which they maneuver through the water column in a vertical and horizontal serpentine pattern. The small boat coxswain drives the boat in parallel tracks to cover the planned survey area. Tow tracks are recorded on a GPS unit that is set to record at 15 second intervals. Tow track survey lines are downloaded and converted to polygon features in ArcGIS using a 15 meter buffer (7.5 meters on each side) to represent area surveyed by the towed divers. The swim survey method, first used for NWHI marine debris detection in 2002, was developed as a necessary alternative to towed diver surveys in lagoonal, reticulated reef areas that were either too shallow or too irregular to be surveyed effectively with the tow survey technique. The divers are directed by personnel in small boats to follow pre-planned routes. When a distinguishable reef has been surveyed, the small boat coxswain drives a GPS-recorded track around that particular reef. These areas are digitized into polygon features in ArcGIS using a combination of the recorded tracks and IKONOS satellite imagery in which reef edges are visible in 4 meter resolution.

When a diver encounters a piece of DFG during either type of survey, the diver notifies the coxswain to stop the boat and take a waypoint over the DFG. Descriptive data about the piece of DFG such as DFG type, DFG color, estimated depth, length/width/height (layout of DFG in the water as found by divers), foul level, presence/absence of coral growth on DFG (including growth type and coral genera), substrate composition/color and volume are recorded and maintained in a Microsoft Access database. Waypoints are recorded for locations of DFG and are downloaded as shapefiles with attributes that include waypoint name, UTC date and time collected, Hawaii standard time collected, small boat label, GPS unit label, survey type (swim or tow), survey zone (high entanglement risk zone or standard), source (water or land) and an Item designation. Waypoint data for DFG is maintained in an Access database table that is linked to descriptive data about each point of DFG via a common waypoint name, date, and GPS unit label.

Cruises target one or more of the atolls of the NWHI and vary in duration from one to four months. The following table displays the names of vessels that participated in research cruises each year and the atolls they visited.

CALENDAR YEAR VESSEL NAME ATOLLS VISITED 1999 NOAA Ship Townsend Cromwell LIS, PHR 2000 NOAA Ship Townsend Cromwell FFS, KUR, LIS, PHR 2001 American Islander, Ocean Fury, Katmai, Townsend Cromwell FFS, KUR, LIS, PHR 2002 American Islander, Ocean Fury FFS, KUR, LAY, LIS, MID, PHR 2003 American Islandr, Ocean Fury FFS, KUR, LAY, LIS, MAR, MID, PHR 2004 Casitas FFS, KUR, LAY, LIS, MAR, PHR 2005 Casitas, Freebird, USCG Ship Walnut, USCG Ship Kukui FFS, KUR, LAY, LIS, MAR, MID, PHR 2006 NOAA Ship Oscar Elton Sette, Land Based Midway Effort FFS, KUR, LAY, LIS, MID, PHR 2007 NOAA Ship Oscar Elton Sette FFS, KUR, LAY, LIS, PHR 2008 USCG Ship Walnut MAR, MID 2009 NOAA Ship Oscar Elton Sette, USCG Ship Walnut FFS, KUR, LAY, LIS, MAR, MID, PHR 2011 NOAA Ship Oscar Elton Sette FFS, KUR, LAY, LIS, MID, PHR 2012 NOAA Ship Oscar Elton Sette FFS, KUR, LAY, LIS, MID, PHR

A high turnover rate of staff has led to various data management styles over the history of the program, thus, the marine debris team has undertaken an effort to error-check and centralize all marine debris data into a Microsoft Access database, which was completed in December 2010. For more detailed information regarding specific cruises and the data collection process, contact the Coral Reef Ecosystem Division.