Comparison of Sea Floor Character in Two Areas Mapped by the California Seafloor and Coastal Mapping Program.

Since the California Seafloor and Coastal Mapping Program (CSCMP) began in 2008 multibeam echo sounder (MBES) data have been acquired in all mainland State Waters (shoreline to 3 nautical miles). As of this writing a suite of map products derived from the data has been published for 22 of the network of 83 CSCMP map blocks along the mainland coast. These publications provide the first opportunity to contrast physical habitats in different areas; here we compare the seafloor character in a set of 6 blocks along the mainland coast of the Santa Barbara Channel (Hueneme Canyon to Refugio Beach), with that of a similarly sized subset of blocks along the more energetic coast of Northern California (Salt Point to Drakes Bay). Seafloor character, one of the products being produced for the CSCMP, is a raster with a small number of substrate classes (soft-flat, hard-flat, and hard-rugose) designed for inclusion in multi-variant analysis of fisheries data that include visual observations of substrate type. Seafloor character is derived with bottom-video supervised maximum likelihood classification of MBES backscatter intensity data and vector ruggedness derived from the MBES bathymetry data. Typically areas of fine-grained sand and mud with infauna occupy the soft-flat areas, hard-flat areas are a mix of low-relief coarse sediment and flat bedrock pavement with sparse epifauna, and hard-rugose areas are highly valued rocky reef habitat with a diverse assemblage of epifauna. In the Northern California area waters less than 100 m deep the percentage of hard-rugose habitat is 8% of the seafloor whereas in the Santa Barbara area it is 0.2%. In both areas Marine Protected Areas contain a higher percentage of hard-rugose habitat than is found in the larger surrounding region. The scarcity of hard-rugose habitat in the Santa Barbara area increases the value of protected habitat in the Channel Islands bounding the channel as well as artificial habitat created by offshore oil rigs.