M/V Davidson on benthic mapping cruise.

A substantial amount of seafloor has been mapped in Alaska by various sources using modern multibeam sonar technology (~425,000 km²). Part of this mapping was completed under the auspices of the Alaska Fisheries Science Center (AFSC), generating high resolution bathymetry with backscatter data.

Example of high resolution bathymetry (left) and backscatter (center) combined to create a habitat map (right).

This data may be used in concert to generate habitat maps of the ocean floor, as shown in the above example. Backscatter, or the strength of the sound pulse, is used to classify the substrate (i.e., dark shades = steep slopes or hard boulders), while bathymetry may delineate the feature extent. Most of the mapping in the Gulf of Alaska is in the form of “postage stamps” ranging in size from 27 km² to 790 km². Some of this mapping was in cooperation with the Alaska Department of Fish and Game and the University of Alaska Fairbanks. Mapped sites in the GOA were generally selected in the areas of fisheries for rockfish (Sebastes spp.). In contrast, for the Aleutian Islands, a systematic design was used to select sites to map, enabling a larger area of seafloor to be characterized. In theory such a systematic design allows extrapolation to unmapped areas.

Location of AFSC multibeam mapped areas in Alaska. (Click to enlarge)

Contact:
Kalei Shotwell
Auke Bay Laboratories
Alaska Fisheries Science Center, NOAA Fisheries

Ted Stevens Marine Research Institute
17109 Pt Lena Loop Rd
Juneau AK 99801
Kalei.Shotwell@noaa.gov