Flexible Methods for Rapid Mapping of Marine and Estuarine Habitats and Fish Presence Using Towed Underwater Video

Faced with the need to efficiently and safely map nearshore benthic habitat for baseline studies in support of an environmental impact statement in SE Alaska, we developed a method using GIS interpolation of coded data from subsampled towed underwater video transects. Supplemented by remote sensing techniques and standard intertidal quadrat transects, this method resulted in detailed maps of several habitat variables. Different interpolation methods were combined to form separate component surfaces (bedrock, gravel, sand, mud, shell, kelp and algae), which were mapped individually and then merged into maps of dominant substrates and biological components using conditional statements.

In contrast to SCUBA transect methods, the use of continuous geolocated digital video allowed for increases in subsample size and independent error assessment without further field effort. This allowed us to stratify our sample sizes according to project needs: We selected evenly-spaced samples in areas needing general characterization and increased sample density in areas where direct project impacts were expected and higher resolution/larger scale maps were needed.

The flexibility of this method allows it to be used at a variety of scales and depths. Habitat coding methods can accommodate diverse classification schemes such as NOAA’s Coastal and Marine Ecological Classification Standard (CMECS). Spatially concurrent trawling and incidental faunal sightings also indicate that species/habitat associations could be integrated with increased field effort.