Mapping marine habitats with high resolution sidescan sonar

The application of marine geophysics and GIS techniques to the characteriza tion of benthic habitats has increased the ability of fisheries managers to assess distribution and habitat types beyond common practices. We report u pon a 150 kHz sidescan sonar survey offshore of Kruzof Island, Alaska under taken to characterize rockfish (Sebastes) habitat. Using GIS, MapGrafix and Map*Factory we determined the percentage of seafloor cover that exists in our survey area. Bathymetry in the study area was determined with sidescan interferometry. All XYZ data were gridded using Surfer and plotted in shade d relief, bathymetric contour, and 3-dimensional formats. Contoured bathyme try was used as an overlay in MapGrafix. Small sub-areas were extracted fro m the bathymetric data or closer study, and gridded in Surfer. Areas of the mosaic where backscatter patterns were not distinct were verified with han d samples and video collected with the submersible Delta. The use of submer sibles for verification of interpreted lithologies and surface textures ena bles a high degree of accuracy for the interpretations. Lithotypes were lum ped into larger groups based on morphology and fish associations with diffe rent morphologies verified using the submersible. The accuracy of digital m aps from high-resolution sidescan sonar data allows a close quantification of the areal extents of these important features, directing the application of management strategies to critical areas. (C) 1999 Ifremer / CNRS / IRD / Editions scientifiques et medicales Elsevier SAS.