Most of the deep-sea areas of the sanctuary are likely made up of soft substrates. Nevertheless, it is possible that rocky outcropping habitats exist within this region. In other areas, these hard-bottom habitats, which provide more relief than the surrounding soft-bottom areas, have been found to be suitable seafloor features for unique and sensitive species, such as deep-water corals and sponges. These biogenic habitats, in turn, provide suitable habitat for various fish and invertebrate communities.

Rock outcrops on the shallow margins of the continental slope (depths of less than 300 meters) are infrequently encountered during submersible surveys. The relief and structure of these isolated features provide important habitat for a variety of groundfishes. Despite the small area and patchy nature of these rocky outcrops, high densities of canary rockfish, yelloweye rockfish, yellowtail rockfish, bocaccio and ling cod can be observed in close proximity to these features. The community rapidly changes back to a soft-bottom assemblage with distance from the rocky feature.

Although by volume the deep sea encompasses 98 percent of all living space on the planet, it is among the least understood ecosystems because of the challenges of accessing this remote environment. Marine scientists claim that we know more about space than we do about the deep sea.

To reach the deep sea, scientists require a platform from which to deploy sampling or observational gear. Today, in addition to net sampling, manned and unmanned research submersibles are deployed from research ships to collect remote data and make observations.

Little is known about the deep-sea region within this sanctuary; however, several submersible dives have been conducted on the upper slope between 200 and 300 meters. These dives have yielded some interesting observations, including a high diversity of fishes as well as the presence of Humboldt squid.

Fishes observed on the mud substrate of this habitat include spotted ratfish, poachers, English sole, slender sole, stripetail rockfish, splitnosed rockfish, long-spined combfish, hagfish grotto and six-gilled shark. Humboldt squid, which have previously occupied a range with a northern extent at southern California, were observed within the upper continental slope habitat (depths of 250 to 300 meters) of the sanctuary in 2005. Aggregations of the fragile pink sea urchin are commonly observed on the mud bottom of the upper slope.

Conservation and management issues affecting sanctuary resources in the deep sea include marine debris, seabed disturbance and non-sustainable fishing.

Anything that is discarded or washed into the sea may eventually end up in the deep sea. Marine debris is a worldwide problem, and deep-sea communities can be negatively impacted by what we do on shore.

Bottom trawling is widely believed to have negative impacts on benthic habitats; these include modification of the substrate, disturbance of soft-bottom communities and removal of non-target fish species. The structure of entire seafloor communities is at risk from repeated disturbance due to this fishing method. Currently we have an incomplete picture about the extent of these impacts in the sanctuary, but the use of trawl gear is an ongoing source of concern.

In June 2006, the Pacific Fishery Management Council and National Oceanic and Atmospheric Administration (NOAA) Fisheries closed large portions of the continental slope to trawling to protect essential fish habitat (EFH) for groundfishes. This included 212 square kilometers within the western-most portion of the sanctuary. In addition, trawl rockfish conservation areas (RCAs), which are depth-related closures, have been put in place to help rebuild depleted rockfish populations.

Monitoring

Benthic Community Characterization and Monitoring
The Cordell Bank National Marine Sanctuary, in partnership with the NOAA Fisheries Laboratory in Santa Cruz, the U.S. Geologic Survey, California Academy of Sciences and the California Department of Fish and Game, has initiated a long-term study to classify habitats and monitor fishes and macro-invertebrates on and around Cordell Bank. Benthic transects were monitored annually from 2002 to 2005. The sanctuary plans to continue the monitoring program in the future; however, this is dependent upon funding levels.

Underwater surveys of fishes, invertebrates and their habitats are conducted on and around Cordell Bank using direct observation and video-transect methods from an occupied research submersible (Delta). Transects are distributed over the bank to sample all bank habitats and associated biota.

Initially, the data will provide the sanctuary with a species inventory of fishes and benthic invertebrates. Long-term data will be used to identify habitat affinities for species complexes, develop habitat suitability models and provide a foundation to evaluate change over time. Regular visits to fixed transects allow the detection of changes in the distribution, number and size of animals over time.

West Coast Bottom-Trawl Survey
The NOAA Fisheries Northwest Fisheries Science Center (NWFSC) conducts annual bottom-trawl surveys of U.S. West Coast groundfish resources. These surveys are designed to provide resource managers with fishery-independent data about the distribution, abundance and biological characteristics of commercially important fish species, particularly Pacific hake, sablefish, and many of the shelf and slope rockfish species.

Survey methodology has changed somewhat since the initiation of studies by the NOAA Fisheries Alaska Fisheries Science Center (AFSC), which conducted studies triennially from 1977 until 2001. Currently, NWFSC conducts annual surveys from the Canadian border to the Mexican border, using chartered commercial fishing vessels towing standardized nets. Separate shelf (55 to 500 meters) and slope (183 to 1,280 meters) surveys are performed.