Site History and Resources
Overview
Located off the California coast, 42 miles (68 km) northwest of San Francisco (Figure 3), Cordell Bank sanctuary, like many of the nation's 13 marine sanctuaries and one marine national monument, has been recognized for its biodiversity and ecological integrity. Due to its unique combination of bathymetry and ocean conditions, the Cordell Bank sanctuary is an extremely productive marine environment. As a result of its national significance as an area of exceptional natural beauty and resources, Cordell Bank National Marine Sanctuary was designated in 1989; it is administered by the National Oceanic and Atmospheric Administration (NOAA), within the Department of Commerce.
Sharing Boundaries
Three of the 14 areas managed by the Office of National Marine Sanctuaries have contiguous boundaries. Cordell Bank, Gulf of the Farallones and Monterey Bay National Marine Sanctuaries all reside within a coastal marine ecosystem dominated by the California Current. While each has distinct features and settings, some resources are similar and move freely between the sanctuaries. Therefore, site management is not always determined by site boundaries. Staff of the three sanctuaries share responsibilities for research, monitoring, education, enforcement, management plan development and other activities required to protect the region's natural and cultural heritage resources.
Figure 3. Cordell Bank National Marine Sanctuary is one of three contiguous National Marine Sanctuaries located along California's northern and central coast. (Image created by Pam van der Leeden, CBNMS)
Discovery of the Bank
Cordell Bank was first discovered in 1853 by George Davidson, a hydrographer with the U.S. Coastal Survey, when his ship became lost in the fog while sailing for San Francisco Bay (Figure 4). When he lowered the lead line, a depth measuring device, Davidson expected a reading of approximately 400 feet (122 m), but was surprised to find it registered only 180 feet (55m). Sixteen years later, Edward Cordell, a surveyor with the U.S. Coastal Survey, conducted additional surveys when he was sent to relocate a "shoal west of Point Reyes." The numerous birds and marine mammals helped Cordell to locate the bank (Schmieder 1991).
Figure 4. A nautical chart from 1869 showing the feature of Cordell Bank offshore of Point Reyes. (Credit: NOAA)
Several years prior to his surveys on the West Coast, Cordell accompanied Henry Stellwagen on his surveying vessel to map Stellwagen Bank, which is in the Gulf of Maine and now also among the significant marine areas designated as a national marine sanctuary.
Figure 5. Through the efforts of Cordell Expeditions, images of the biological diversity of Cordell Bank were available to the public for the first time. (Credit: Cordell Expeditions)
Geology
The Cordell Bank sanctuary is situated on the Pacific Plate, with its eastern boundary 7.5 miles (12 km) west of the convergence zone of two of the Earth's major tectonic plates: the Pacific and North American Plates (Figure 6). The Pacific Plate is slowly moving northward relative to the North American Plate at an average rate of about two inches (five cm) per year. Most of this motion occurs in catastrophic bursts of movement-recognized as earthquakes-along the San Andreas Fault system, which is hundreds of miles long and in places many miles wide.
Figure 6. Cordell Bank continues to move a few centimeters per year. (Credit: CBNMS)
The topography of western California is strongly influenced by the San Andreas Fault, which has been active for millions of years. Although the majority of the plate motion is "strike-slip" resulting in hundreds of miles of lateral displacement of the earth's crust, a small percentage of the plate motion is "compressional", or displaying a shortening and wrinkling of the earth's crust that creates northwest-southeast mountain ranges.
Cordell Bank is the most prominent geological feature of the sanctuary. The Salinian bedrock of Cordell Bank formed about 100 million years ago as part of the Sierra Nevada range. When the San Andreas fault was created ~20-30 million years ago it sheared off part of the range, including the granitic feature of Cordell Bank, and carried it north to its present location (Figure 6). Cordell Bank and the Farallon Islands are part of the same Farallon Ridge structural high. Sediments surrounding the base of Cordell bank on the continental shelf are composed predominantly of younger silt and sand deposits that originated from rivers and coastal erosion. These sediments continue to be moved around and further broken down by energetic seafloor ocean currents.
Commerce
The history of California’s North Coast is predominantly a maritime one. From the days of the early coastal Miwok inhabitants to the present, coastal waterways remain a main route of travel and supply. Ocean-based commerce and industries (e.g., fisheries, export and import, and coastal shipping) are important to the maritime history, the modern economy, and the social character of this region.
By 1935, San Francisco was the home port of twenty large American steamship lines, with more than forty foreign lines maintaining offices and agents in the city. More than five hundred ships called to this port every month of the year, and a large majority of those ships purchased a major portion of their supplies from San Francisco merchants. The population around San Francisco Bay has grown rapidly and now exceeds 8 million people. The Bay Area's economy ranks as one of the largest in the world, larger than that of many countries. More than 10 million tourists are estimated to visit the San Francisco Bay Area region each year.
Hunting of marine mammals for meat and fur in the 1800s and early 1900s contributed to declines of many species, including northern elephant seals (Mirounga angustirostris, harbor seals (Phoca vitulina), California (Zalophus californianus) and Steller sea lions (Eumetopias jubatus), and northern fur seals (Callorhinus ursinus). Hunting of large whales during the last two centuries nearly extirpated several species, including gray (Eschrichtius robustus), blue (Balaenoptera musculus), humpback (Megaptera novaeangliae) and fin (Balaenoptera physalus) whales. One of the last active whaling stations in America operated in San Francisco Bay until 1971.
Cordell Bank is a productive area and has historically supported important commercial and recreational fisheries. The Pacific Fishery Management Council, working with NOAA Fisheries and the California Department of Fish and Game, regulates fishing activity. Commercial fisheries generally target rockfish (Sebastesspp.) and other groundfish species, Chinook salmon (Oncorhynchus tshawytscha), Dungeness crab (Cancer magister) and albacore tuna (Thunnus alalunga) (Scholz et al. 2005).
Figure 7. Cordell Bank sanctuary is entirely offshore and contains an abundance of marine life, including humpback whales. (Photo: Sophie Webb.)
Because of the abundance of food, the Cordell Bank area is a feeding ground for fishes, seabirds, turtles, and a variety of marine mammals, including blue and humpback whales (Figure 7). Beginning in early summer and continuing through fall, foraging wildlife frequent sanctuary waters. This coincides with the calmest weather of the year, and as a result, many charter vessels from Bodega Bay and San Francisco make regular wildlife viewing trips to the bank at this time. Recreational fishing charters originating from Bodega Bay also frequent the waters surrounding Cordell Bank, targeting salmon, lingcod (Ophiodon elongatus) and rockfish and more recently, jumbo squid (Dosidicus gigas).
Water: Ocean Seasons
The calendar year at Cordell Bank can be separated into three oceanographic seasons: upwelling season in the spring and early summer, relaxation or oceanic in the late summer and fall, and the storm season in winter.
Upwelling Season
The Cordell Bank National Marine Sanctuary is located in one of the world's four major coastal upwelling systems; the other three systems are located along the west coast of South America, southwest Africa, and northwest Africa. The upwelling of nutrient-rich, deep ocean water supports a food-rich environment and promotes the growth of organisms at all levels of the marine food web.
Figure 8. Spring/summer upwelling in Cordell Bank region. (Credit: CBNMS)
During the upwelling season (March-July), strong northwest winds and the south flowing California Current combine with the earth's rotation to drive surface waters away from the shore (Figure 8). These surface waters are replaced by an upwelling of nutrient-rich deeper water from offshore. Rising into the sunlit layer of the ocean, these nutrients become available for incorporation into living systems through photosynthesis by phytoplankton (microscopic marine algae). Phytoplankton form the foundation of this oceanic food web; the infusion of nutrients and increased sunlight in spring initiates a bloom of life that radiates through the food web. An abundance of phytoplankton, zooplankton, and young fish are food for animals at higher levels of the marine food web. Productivity within the nearshore region is a balance between upwelling which stimulates phytoplankton growth, and mixing and advection, which transport phytoplankton below surface-lit layers as well as offshore. Thus, higher productivity within this region results from a combination of upwelling and relaxation events (Figure 9).
Figure 9. Contrasting surface current (HF radar) patterns, oceanographic conditions, and chlorophyll-a levels during upwelling and relaxation events during the upwelling season (June 2003) within the California Current in the region of Cordell Bank National Marine Sanctuary (Largier et al. 2006). For sea surface temperature (SST), red indicates warmer waters and blue indicates cooler waters. For chlorophyll-a, blue indicates lower concentrations and red indicates higher concentrations. Black arrows show the direction and intensity of surface currents (notice the increase in surface current vectors during upwelling conditions). (Credit: Largier et al. 2006)
Relaxation (or Oceanic) Season
During the late summer and fall (August to early November), persistent coastal winds weaken and the sea surface becomes calmer. Surface currents during this time period are mostly northward and water temperatures increase. During this time, coastal waters are rich with the products of upwelling, and many migratory animals are in the area feeding on an abundance of prey.
Winter Storm (or Davidson Current) Season
The winter storm season (mid-November through February) is dominated by rough seas and greater mixing of ocean water. Strong winter storms originating in the Gulf of Alaska cause turbulent conditions that break down stratified ocean layers in the upper water column, homogenizing temperature, salinity, and the distribution of nutrients. The northward-flowing Davidson Current has a stronger influence on circulation during this time period.
Habitat
Figure 10. The pinnacles of Cordell Bank harbor an abundance of life and provide structure for schooling rockfishes. (Photo: Kip Evans.)
Cordell Bank National Marine Sanctuary encompasses an area of 529 square miles (1369 km2). The sanctuary can be partitioned into three benthic habitat types. The continental shelf covers 313 square miles (810 km2) and is primarily mud bottom ranging from 230-656 feet (70-200m) deep. The continental slope covers 190 square miles (492 km2) and is primarily mud bottom with some rock outcrops and ranges between 656 feet (200 m) at the shelf break down to 6,955 feet (2,120 m) at the western boundary of the sanctuary. The main feature of the sanctuary is an offshore rocky bank roughly 4.5 miles wide by 9.5 miles long (7.2 x 15.2 km) covering an area of approximately 26 square miles (68 km2). The bank emerges from the soft sediments of the continental shelf, with the upper pinnacles reaching to within 115 feet (35 m) of the ocean's surface (Figures 10 and 11). Shelf depths at the base of the bank are between 300 and 400 feet (91-122 m).
The bank has a diversity of benthic habitats that include high relief rock pinnacles, flat rock, boulders, cobble, sand, and mud. Distinct biological assemblages are associated with each habitat type. The rugosity of the bank and the diversity of habitats are important contributors to the diversity of fishes and benthic invertebrates observed in the sanctuary.
Figure 11. Bathymetry of Cordell Bank based on high resolution multibeam echosounder data. Red represents the shallowest depths (to 35 meters), blue represents the deepest depths. The 200 meter contour line illustrates the proximity of Cordell Bank to the continental shelf break. Data source: Seafloor Mapping Laboratory at California State University Monterey Bay. (Image created by Lisa Etherington, CBNMS.)
The vertical relief and hard substrate of the bank provide habitats with nearshore characteristics in an open ocean environment about 20 miles (32 km) offshore. The resident reef community associated with the bank is ecologically linked with the open ocean (pelagic) community, which includes animals that travel thousands of miles each year to feed around the bank. The result is an array of resident and transient animals and tremendous biological diversity in the vicinity of the Cordell Bank National Marine Sanctuary.
Isolated rock piles and rock outcroppings are an important habitat component within the sanctuary. These areas, while nominal in terms of area, typically concentrate high abundance and biomass of marine life, particularly fishes. Submersible observations have documented hundreds of rockfish of several species and several lingcod in close proximity to a relatively small rock pile on the mud slope west of Cordell Bank (Cordell Bank sanctuary, unpubl. data). Fish observations diminished with distance from the feature (Cordell Bank sanctuary, unpubl. data).
Isolated rock piles and rock outcroppings are an important habitat component within the sanctuary. These areas, while nominal in terms of area, typically concentrate high abundance and biomass of marine life, particularly fishes. Submersible observations have documented hundreds of rockfish of several species and several lingcod in close proximity to a relatively small rock pile on the mud slope west of Cordell Bank (Cordell Bank sanctuary, unpubl. data). Fish observations diminished with distance from the feature (Cordell Bank sanctuary, unpubl. data).
Figure 12. Long-nosed skates are commonly found in soft bottom habitats along the continental shelf and slope. (Photo: Linda Snook, CBNMS.)
Soft bottom habitat constitutes the remaining continental shelf and slope protected within the Cordell Bank sanctuary. The lack of hard substratum for attachment prevents algae and some invertebrates from colonizing these habitats. Soft-bottom associated species live either on the surface of, or buried in the sediments (Figure 12). Sand and mud are the two primary soft bottom habitat types within the sanctuary. The majority of sand habitat is located on the eastern edge of the bank on the continental shelf or in areas between the hard substrates on the bank. Mud bottom makes up most of the remaining habitat on the continental shelf and slope. The shallowest depth in the sanctuary, excluding Cordell Bank, is approximately 230 feet (70 m), and is on the continental shelf area in the eastern part of the sanctuary.
In addition to the benthic habitats of Cordell Bank sanctuary, the open ocean water column is another major habitat. The water column is subject to seasonal and annual variations in physical parameters like turbidity, temperature, and salinity, as well as stratification. Larger scale oceanographic events, combined with local conditions, make the water column a dynamic habitat.
Living Resources
Benthos
Figure 13. Dense invertebrate cover of hydrocorals, sponges, and anemones, carpet the shallow areas on Cordell Bank. (Photo: Rick Starr, CBNMS.)
A dense cover of benthic organisms carpets the shallower rock surfaces of Cordell Bank. The high light penetration in this offshore environment allows for algal photosynthesis in far deeper water than in similar habitats nearshore along the mainland coast. The abundant food supply drifting over the bank, combined with a hard substrate for larval settlement and attachment, provide ideal conditions that support a rich assemblage of benthic invertebrates (Figure 13). Ridges are thickly covered with sponges, anemones, hard hydrocorals, soft gorgonian corals, hydroids, tunicates, scattered crabs, holothurians, and gastropods.
Soft bottom habitats also support a thriving community of benthic invertebrates. Adapted to life in and on a shifting substrate, these animals are either buried in the sediment, like polychaete worms and clams, or are mobile on the surface, such as sea stars and Dungeness crabs (Figure 14).
Figure 14. Dungeness crabs occupy the soft sediment habitats on the continental shelf habitats and are an important commercial species in the region. (Photo: Rick Starr, CBNMS)
The sea whip (Halipteris sp) is one common soft bottom resident that extends into the water column providing structure and relief for fishes and other invertebrates on the flat, mostly featureless bottom of the continental shelf.
Zooplankton
A myriad of gelatinous zooplankters are a little known component of the open ocean ecosystem at Cordell Bank. In addition to the common jellyfish, moon jellies (Aurelia aurita) and sea nettles (Chrysaora fuscescens), as well as more obscure invertebrate creatures such as hydromedusae, ctenophores, siphonophores, pteropods, and heteropods eat and are eaten in the water column around the bank. The ocean sunfish (Mola mola) and leatherback sea turtle (Dermochelys coriacea), which visit the sanctuary in the late summer and fall, exclusively eat these gelatinous creatures and depend on them to survive. Other animals such as the blue rockfish (Sebastes mystinus) and the yellowtail rockfish (Sebastes flavidus) are opportunistic feeders, gorging themselves when gelatinous zooplankton are abundant. Fish and invertebrate larvae also comprise a large component of the plankton community in late winter and spring.
Krill
Two species of krill (Thysanoessa spinifera and Euphausia pacifica) are important trophic links in the Cordell Bank ecosystem (Figure 15). These small, shrimp-like crustaceans are referred to as "keystone" species because they are critical prey for so many other species on and around the bank. At Cordell Bank, the presence of krill is the primary reason why the area is a destination feeding ground for many migratory animals such as Chinook salmon , humpback whales and blue whales. In addition, krill are prey for resident species like yellowtail rockfish (Sebastesflavidus) and Cassin's Auklets (Ptychoramphus aleuticus), which nest on the nearby Farallon Islands.
Figure 15. Krill are often found in large, concentrated groups, including dense swarms with as many as 100,000 krill per cubic meter of water. (Photo credit: Benjamin Saenz.)
Each spring and summer, massive swarms of krill provide food for dominant species of the Cordell Bank ecosystem including seabirds, fishes and whales. Krill exhibit unique behaviors that play an important role in affecting the distribution and abundance of predators. With the onset of darkness each night, krillmigrate from near the ocean floor into the upper water column. Many species of fish migrate with the krill in order to feed on them. These vertical migrations from seafloor to surface layers can cover almost 600 feet (over 180 m) in the span of an hour. In addition, T. spinifera will periodically form dense swarms at the ocean surface during daylight hours. Fishes, seabirds and whales all feed actively on T. spiniferawhen this happens. Fishermen key in on flocks of feeding seabirds, knowing that salmon are often feeding on the underside of the same patch of krill.
Squid
The nominal range of the jumbo squid is from Southern California to Peru, but recently these large oceanic squid have become a regular occurrence in northern California (Zeidberg and Robison 2007), particularly in the region of Cordell Bank. The appearance of D. gigas in the region occurred after the strong 1997/98 El Niño event (Zeidberg and Robison 2007, Field et al. 2007). Stomach samples of squid collected in 2005-2006 from waters of the California Current have shown that jumbo squid in this region preyed on a wide variety of sizes and types of prey, particularly larger fishes (Field et al. 2007). Some of the most frequently occurring prey items were species of commercial importance, including: Pacific hake (Merluccius productus), northern anchovy (Engraulis mordax), Pacific sardine (Sardinops sagax), rockfishes, and market squid (Loligo opalescens) (Field et al. 2007). Jumbo squid were also found to feed on myctophids, mesopelagic fishes, and small crustaceans (Field et al. 2007). It is unknown what kind of changes the presence of these large predators will have on the ecosystem as their range expands and contracts with changing ocean temperature regimes.
Fishes
Figure 16. Groundfish density in the region of Cordell Bank as measured by Delta submersible transects to assess the benthic community and habitat affinities. Rockfish account for 95% of fishes observed, with their abundance decreasing markedly as you move off the bank. Size of circles indicates comparative abundance in different locations on the bank. (Image created by Tara Anderson.)
More than 180 species of fish have been documented in the Cordell Bank National Marine Sanctuary (Eldridge 1994, NOAA Fisheries, unpubl. data, Cordell Bank sanctuary, unpubl. data), with rockfish dominating the fish community in both numbers and biomass (Figure 16). Between 2002 and 2005, sanctuary staff and partners conducted quantitative visual surveys from the ‘Delta’ submersible, focusing on characterizing the bank’s fishes and their preferred habitats (Anderson et al. 2007). During the fall of 2002, 70 fish species or species-groups representing 21 families were enumerated. Rockfishes (Sebastes spp.) were the dominant group, accounting for 27 species and 95% of all individuals. Of these, young-of-year rockfishes were the most numerous, accounting for 64 percent of all rockfishes. Cordell Bank is a suitable and important site for the recruitment of juvenile rockfishes transitioning from a pelagic to benthic stage in their early life history. These young-of-year rockfish species are important prey for salmon, seabirds and adult rockfishes as they provide an important energetic link in the trophic ecology of this system. The distribution and abundance of fishes were related to habitat type, depth, and location. It also appears that the deep boulder habitat provides a natural refuge for some overfished species, such as bocaccio (Sebastes paucispinis), yelloweye rockfish (S. ruberrimus), cowcod (S. levis) and the canary rockfish (S. pinniger). Lingcod are conspicuous in the wintertime, when they move up onto the bank to lay their eggs.
Limited scientific study has been directly focused on the ichthyofauna of the sanctuary's soft-bottom habitat; however, considerable information has been gathered and analyzed on the fish assemblages that inhabit the continental shelf and slope habitats of the northeastern Pacific Ocean (Allen 2006). While soft-bottom areas are predominantly the domain of flatfishes, skates, rays and a number of fusiform (spindle-shaped) fishes such as croakers, rockfishes, sculpins and surfperches also thrive in this habitat. Ecologically significant fishes most commonly found in the middle shelf include: big skate (Raja binoculata), longspine combfish (Zaniolepis latipinnis), shortbelly rockfish (Sebastes jordani) and pacific sand dab (Citharichthys sordidus). On the outer shelf, fishes more commonly seen in research collections include the stripetail rockfish (Sebastes saxicola), greenstriped rockfish (Sebastes elongatus) and slender sole (Lyopsetta exilis). Beyond the shelf break in the upper slope region, fishes most commonly found include poachers, splitnose rockfish (Sebastes diploproa) and sablefish (Anoplopoma fimbria). Among the fishes that inhabit all three depth zones are lingcod (Figure 17), spotted cusk eel (Chilara taylori), plainfin midshipman (Porichthys notatus) and Dover sole (Microstomus pacificus).
Figure 17. Lingcod can be found in many different habitats on and around Cordell Bank. (Photo: Kip Evans)
Most of the water column habitat within Cordell Bank sanctuary overlies the continental shelf and comprises the coastal pelagic realm. Fishes which occupy the epipelagic zone (depth to 200m) are a mixed group of larger, slow growing, longer-lived species and active, fast growing shorter-lived fishes (Allen and Cross 2006). Fishes commonly placed in the former group include sharks (blue shark Prionace glauca, white shark Carcharodon carcharias, thresher shark Alopias vulpinus) jack mackerel (Trachurus symmetuicus), pacific mackerel (Scomber japonicus) and pacific hake (Merluccius productus). The latter group occupying the epipelagic zone is composed of early life history stages of many fishes (including lingcod, rockfishes and many flatfish species) as well as the commercially important northern anchovy (Engraulis mordax) and pacific sardine (Sardinops sagax). Anchovies and sardines, which are an important prey for many coastal predators and a critical link in the coastal food web, have alternated as the most abundant fishes of the coastal pelagic realm off California throughout recent history. Abundance of these short lived fishes is related to oceanographic cycles within the region. For example, the alternating 20 to 30 year periods of cool and then warm phases in the Pacific Ocean track fluctuations in the alternating abundances of anchovies (cool periods) and sardines (warm periods) (Chavez et al. 2003). Other fishes that inhabit the epipelagic zone include species that frequent the sanctuary on a seasonal basis, such as albacore tuna (Thunnus alalunga) and salmon (Oncorhynchus tshawytscha, O. kisutch). Mesopelagic fishes (those found below the epipelagic zone to depths of 1000 meters) are relatively small, slow-growing and long-lived. Representatives of this group include the lanternfishes, hatchetfishes and deep-sea smelts. Many mesopleagic fishes make nocturnal vertical migrations to feed.
Seabirds
Figure 18. Black-footed albatrosses travel thousands of miles from the northwestern Hawaiian Islands to feed in the waters of Cordell Bank sanctuary. (Photo: Sophie Webb)
The waters around Cordell Bank provide critical foraging habitat for many species of seabirds. During the upwelling season, the highest levels of seabird biomass in the central portion of the California Current are found at Cordell Bank, Monterey Bay and the Farallon Ridge (Ford et al. 2004). Over fifty seabird species have been identified feeding in or near the sanctuary. Like the fishes and marine mammals, the composition of seabirds found at Cordell Bank is a mix of local breeding birds and highly migratory open-ocean species. For example, it is possible to see a large percentage of the world’s population of Ashy Storm-Petrels (Oceanodroma homochroa), which nest on the Farallon Islands, on the waters around Cordell Bank simultaneously (Stallcup 2004). More than 20,000 Cassin’s Auklets, which are also local breeders, have been counted around the bank in a single day (Stallcup 2004). Local representative species use the nearby Farallon Islands and Point Reyes areas to nest, while some migrant birds nest thousands of miles away. A recent study using satellite tags documented that Black-footed Albatross (Diomedea nigripes) nesting in the northwestern Hawaiian Islands “commute” to Cordell Bank waters to gather food for their chicks before returning to their nests (Hyrenbach et al. 2006) (Figure 18). Other migratory species use the productive waters around the bank as a stopover on their annual migration route. For example, tens of thousands of Sooty Shearwaters (Puffinus griseus) pass through the sanctuary annually as part of their migration between the west coast of North America and New Zealand.
Marine Mammals
Figure 19. Pacific white-sided dolphins are one of the most abundant marine mammals in the Cordell Bank sanctuary. (Photo: Cornelia Oedekoven, NOAA)
Over twenty species resident and migratory marine mammal species have been observed within the sanctuary (NCCOS 2007). Monthly monitoring of the Cordell Bank pelagic environment indicates that Pacific white-sided dolphins (Lagenorhynchus obliquidens) are the most frequently sighted marine mammal in the sanctuary (Figure 19). Other common cetaceans include Dall’s porpoise (Phocoenoides dalli) and northern right-whale dolphins (Lissodelphis borealis). Humpback and blue whales are regularly seen in the summer and fall when they visit the sanctuary to feed. In addition, gray whales pass the bank on their annual migrations between Arctic feeding grounds and Mexican breeding areas. Other mammals seen around the bank include Risso’s dolphins (Grampus griseus), killer whales (Orcinus orca), California sea lions northern fur seals (Callorhinus ursinus), northern elephant seals (Mirounga angustirostris) and Steller sea lions.
Maritime Archaeological Resources
It is unknown if any shipwrecks rest on the seafloor in the Cordell Bank National Marine Sanctuary. Prehistoric use of the island, when the bank was exposed during the last ice age, may also have occurred but remains undocumented. Until recently, Cordell Bank and the surrounding seabed have been inaccessible due to location, depth, and currents. Advances in modern technology such as sonar, remotely operated vehicles, and manned submersibles, has reduced some constraints to exploration. High resolution multibeam echosounder surveys of the entire bank, as well as limited side-scan sonar surveys of the soft bottom continental shelf area, have not detected any maritime archaeological resources in the sanctuary. However, only 18% of the sanctuary seafloor has been mapped with these remote sensing techniques.