Research Technical Report

2010 Report on Davidson Seamount Marine Mammal and Seabird Surveys

King, C. (December 2010)

MBNMS Technical Report, 21pp.

ABSTRACT

In 2010, the Monterey Bay National Marine Sanctuary (MBNMS) and its partners conducted two aerial surveys and one ship-based survey of the surface waters surrounding the Davidson Seamount, an area typically regarded as having a higher abundance and diversity of marine mammals and seabirds. Each aerial survey occurred over one day in January and April, and covered 542 km and 400 km, respectively, of linear "on-effort" transects. The ship-based survey occurred over a three day period in July and covered 615 km of linear "on-effort" transects. Additional oceanographic and prey data were collected during the ship-based survey, including sea surface temperature, conductivity, salinity, plankton net tows, and echosounding. Rough marine mammal encounter rates (marine mammals per linear km) were calculated for each survey as follows: January aerial survey: 0.042 per km, April aerial survey: 0.788 per km, and July ship-based survey: 1.086 per km. Many years of future surveys are required to associate factors with any differences in encounter rates. Numerous factors include survey methods, inter-seasonal, and inter-annual variables.