Sanctuary Integrated Monitoring Network
National Marine Sanctuaries

Marine Mammals

Marine Mammals map
Figure 1. Marine Mammal hotspots within the Monterey Bay, Greater Farallones, and Cordell Bank National Marine Sanctuaries. [View Larger]
The three northern California sanctuaries boast some of the most diverse and abundant marine mammal assemblages in the world. This is due to a number of factors, such as the region's location on a migration pathway between Arctic feeding grounds and warmer breeding areas, the waters' great productivity, and great habitat diversity.

The region's marine mammal community is a mix of permanent and seasonal residents as well as species that use these waters for shorter periods - either as a feeding destination or in transit during long-distance migratory journeys (such as gray whales).

These waters are also important to several marine mammal species that are considered of special concern because of their reduced or declining populations. Examples include the humpback whale, blue whale, gray whale, northern fur seal and Steller sea lion.


For more information on marine mammal populations specific to a particular sanctuary, please visit the individual pages for Cordell Bank, Greater Farallones and Monterey Bay. Below are examples of the species found in the northern California region:

The fluke of a Humpback whale (Megaptera novaeangliae) in Monterey Bay.

This 72 pound Olive ridley sea turtle (<em>Lepidochelys olivacea</em>), beached itself at Stanford University\'s Hopkins Marine Station in Pacific Grove on 10/6/11. Aquarium staff, led by veterinarian Dr. Mike Murray, received permission from federal wildlife authorities to capture the turtle and bring it to the aquarium for short-term care. It was later released. For more information about this event, please see

Pinnipeds Sea Otters

Conservation and Management Issues

Human impacts to marine mammal populations worldwide include competition for food with commercial and recreational fisheries, entanglement in fishing gear and other marine debris, disturbance and injury from ocean noise, injury or death from ship strikes, and, in some cases, residual effects from past harvesting or bycatch.

In addition to human impacts, changes in climate and oceanographic conditions affect marine mammals. The prevalence of these animals in sanctuary waters changes from year to year due to fluctuations in marine conditions such as El Niño.


Marine mammal-focused monitoring efforts in the northern California region are numerous and range from regional, multi-agency studies to more focused efforts. For a full list of each sanctuary's monitoring efforts, see the individual monitoring sections for the Cordell Bank, Greater Farallones and Monterey Bay sanctuaries. A sample of research efforts is provided below.

The three sanctuaries are all participating in two studies whose geographic range reaches well beyond the sanctuaries' own boundaries: The Cordell Bank and Greater Farallones sanctuaries are collaborating with scientists from other organizations in the region to investigate the spatial and temporal relationships among krill, krill predators and oceanographic processes: The Monterey Bay and Greater Farallones sanctuaries are working together on several research initiatives. These include:
Marine Mammals map
Figure 2. Cetacean species richness within the Monterey Bay, Greater Farallones, and Cordell Bank National Marine Sanctuaries. [View Larger]
The Monterey Bay sanctuary is involved in a number sea otter studies: