Weather and ocean conditions permitting, single-day monitoring cruises over Cordell Bank have been conducted once a month from 2004 to the present on R/V C. Magister or R/V Fulmar. Data on the distribution of seabirds, marine mammals, and other vertebrates are collected by trained observers along six 12 km long east-west transects centered around Cordell Bank. In addition, observers score abundance of Velella velella, three jellyfish species, kelp, various types of marine debris and vessels. Physical and biological characteristics of the pelagic system are measured, including: water temperature, salinity, chlorophyll-a fluorescence, photosynthetically active radiation, and zooplankton abundance. Oceanographic data are collected continuously along the transects using underway data collection systems, as well as at seven locations with a CTD.

Data are used to relate the spatial patterns of bird and mammal distribution with oceanographic patterns on a seasonal and annual basis. These data will also be integrated with other west coast sanctuary monitoring programs to understand changes in the central California ocean environment.

Preliminary examination of data suggests a shift in distribution and abundance of seabirds, with responses varying depending on foraging strategy. Cassin’s auklets (Ptychoramphus aleuticus) are one of the most abundant species found in the waters surrounding Cordell Bank; however, the abundance of this planktivorous specialist decreased in 2005-2006, likely due to a lack of krill prey. Abundance of blue whales, which feed almost exclusively on krill, also decreased during this time period. In contrast, abundances of some foraging generalist species (e.g., shearwaters, albatrosses) did not appear to have changed between years in the Cordell Bank region. In 2006, we observed a change in the distribution of some piscivorous species (Common murre, Uria aalge, Brown pelican, Pelecanus occidentalis) from nearshore to offshore environments. These observations suggest suites of species may be responding differently to changes in the pelagic prey community in these offshore waters. These results indicate that regional changes in atmospheric and oceanographic conditions are reflected in local changes in seabird distribution and abundance in the region of Cordell Bank, which can provide insight into the overall abundance and re-distribution patterns of seabirds within the CCS.

Work is in progress to examine patterns of seabird abundance on a finer spatial scale and to understand their distribution relative to oceanographic features. Similar analyses are needed to understand spatial and temporal patterns of marine mammals. Future work will also involve a detailed analysis of spatial and temporal variability in oceanographic conditions in the region of Cordell Bank and how these patterns relate to regional oceanographic conditions. This effort will also involve comparison of oceanographic patterns from the monthly data collected as part of the Cordell Bank Ocean Monitoring Program with the fine temporal resolution of data being collected by the Cordell Bank oceanographic buoy.