CRED Towed-Diver Fish Biomass Surveys at Laysan Island, NW Hawaiian Islands in 2004

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. 5 towboard surveys (7.9074 km in length), were conducted at Laysan Island in the NW Hawaiian Islands from 13 September - 17 October 2004 as part of RAMP Cruise HI0401. 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.

Tags: 1221, algae) - rapid ecological assessments at all u.s. pacific islands, benthic habitats, biology, biosphere, central pacific ocean, coastal processes, coral reef, coral reef ecology, coral reefs, corals, coris_metadata, country/territory, earth science, hawaii, hi0401, honolulu, laysan island, laysan island (25n171w0001), long-term monitoring of benthos (coral, marine ecosystem, northwestern hawaiian islands, numeric data sets, nw hawaiian islands, nwhi, ocean basin, oceans, other invertebrates, pacific ocean, reef assessment and monitoring program (ramp), reef fish census, reef fishes, reef monitoring and assessment, the united states, towed diver surveys, united states of america, zoology
Organization: National Oceanic and Atmospheric Administration, Department of Commerce