Towed-diver surveys (aka. Towboard surveys) are conducted by the Coral Reef Ecosystem Division (CRED) of the NOAA Pacific Islands Fisheries Science Center (PIFSC) as part of biennial Pacific Reef Assessment and Monitoring Program (RAMP) Cruises. These cruises support NOAA Coral Reef Conservation Program (CRCP) long-term goals for sustainable management and conservation of coral reef ecosystems. 3 towboard surveys (6.8533 km in length), were conducted at Santa Rosa Bank in the Marianas Archipelago from 3 - 9 October 2005 as part of RAMP Cruise OES0512. Towboard surveys are a good method for obtaining a general description of large reef areas, assessing the status of low-density populations of large-bodied reef fish, large-scale disturbances (e.g., bleaching), general distribution and abundance patterns of macro-invertebrates (e.g., COT, giant clams), and for assessing trends in these populations and metrics. A pair of scuba divers (1 fish and 1 benthic diver) are towed 60 m behind a small survey launch at a speed of 1-2 knots and a depth of approximately 15m. Each survey is 50 min long, covers about 2 km of habitat, and is divided into ten 5-minute survey segments. The fish diver records, to the lowest possible taxon, all large-bodied reef fishes (>50cmTL) seen within 5m either side and 10m in front of the towboard. Length of each individual is estimated to the nearest cm. The fish towboard is also outfitted with a forward-facing digital video camera to record the survey swath. The benthic diver records percent cover of coral and macroalgae, estimates benthic habitat type and complexity, and censuses a suite of benthic macroinvertebrates including Crown of Thorns sea stars and sea urchins. The benthic towboard is equipped with a downward-facing digital still camera which images the benthos at 15 second intervals. These images are analyzed for percent cover of coral, algae, and other benthic components. Both towboards are equipped with SEABIRD SBE-39 temperature/depth sensors set to record at 5 second intervals. Latitude and longitude of each survey track is recorded at 15 second intervals using a Global Positioning System (GPS) receiver onboard the tow boat. A layback algorithm is applied to more accurately map the position of the divers with respect to the reef environment. This algorithm calculates the position of the divers based on the position of the tow boat taking into account the length of the tow rope, the depth of the divers, and the curvature of the survey track. This metadata applies to the fish biomass observations.
Part of a biennial long-term monitoring program to document status and trends in the coral reef ecosystems of the US Pacific Territories.
Data collected: Species level abundance and length information for coral reef fishes >50cm total length. Data is linked to geographic shapefile via DiveID or SegID. Abundance and/or biomass data can be provided at the species or family level.
Ground condition
Please cite CRED when using the data. Coral Reef Ecosystem Division, Pacific Islands Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration
NOAA IRC
NMFS/PIFSC/CRED
1845 WASP Blvd., Building 176
e-mail preferred
Craig Musburger and Ben Richards,Coral Reef Ecosystem Division (CRED), Pacific Islands Fisheries Sciences Center, National Marine Fisheries Service, NOAA
Observations were made by the divers who are trained in fish taxonomy. Divers may change from year to year and by location.
The same data collection protocols were used at each island/bank surveyed.
The towboard surveys are completed in forereef, backreef, and lagoon habitats. The minimum spatial resolution of the towboard survey is the 5 minute survey segment which covers approximately 200m. As such, these surveys are appropriate for broad estimates but can not be used for fine scale, site level data analysis.
Although resource grade GPS units were used and a layback model was applied to the survey tracks, the exact survey positions were not physically marked and effort was not made to revisit exact same tracks.
Instrument parameters
SeaBird SBE-39 temp/depth recorder
The towboard survey involves a pair of scuba divers who are towed 60 m behind a small boat at a constant speed (~1.5 knots). The towboard survey is typically 50 min long and covers about 2 km of habitat, depending on the depth profile of the divers. The survey is divided into 5 min segments. During the survey, the fish diver records, to the lowest possible taxon, large fishes observed within a survey swath 5 m to either side of the diver and 10 m in front the diver.
While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.
Contact CRED data management team for information
