Marine Mammal Observation Summary
CalCOFI 1108, R/V New Horizon, Chief Scientist Dave Walgast
By Katherine Whitaker and Dominique Camacho
Marine mammal observations were conducted simultaneously with passive acoustic monitoring during daylight hours throughout the CC1108 cruise. Within a 17day period we performed observations on the CalCOFI grid. The first portion of this cruise was met with great weather, allowing for easy sight ability. Unfortunately, the weather condition on the second portion of the cruise was consistently Beaufort 5, giving us more of a challenge during observations. Overall, we accrued over 148 cetacean sightings totaling 3930 individuals, comprised of 8 different species. Acoustic effort confirmed presence of and sperm whales (Physeter macrocephalus), in the study area; however no visual sightings were made.
Odontocetes were the most diverse and commonly observed suborder this cruise. 68 sightings were comprised of common dolphins (Delphinus delphis, Delphinus capensis, and Delphinus spp.), bottlenose dolphins (Tursiops truncates), Risso’s (Grampus griseus), and Dall’s porpoise (Phocoenoides dalli). Sightings were most abundant along the continental shelf and steadily decreased as we progressed offshore. Coinciding with past trends short-beaked common dolphins (Delphinus delphis) were seen offshore while the long-beaked common dolphins (Delphinus capensis) were found near shore.
An exceptional sighting of blue whales Balaenoptera musculus), occurred while transiting along the near shore Sccoos line from station 87/33 to station 87/35. This group was comprised of 19 individuals, which surfaced for intervals of lunge feeding and then terminally dove. These whales were in an amazing feeding aggregation with 2 fin whales (Balaenoptera physalus), 2 minke whales (Balaenoptera acutorostrata) cow calf pair, and over 100 common dolphins comprised of (Delphinus delphis, Delphinus capensis, and Delphinus spp.).
Fin whales (Balaenoptera physalus), were sighted in two more large aggregations over the edge of the continental shelf. They were spread out for miles, and observed continually for up to three hours that numbered over 20 fin whales with some blue whales associated. On line 77/70 going to station 77/60 the smaller aggregation of fin whales, comprising of 10 or more, was on transect line 90 between station 60 and station 53.
California sea lions (Zalophus californianus) were predominately encountered within 200 nm from shore, for which we performed cumulative day counts. We observed 84 individuals over the course of the cruise.
There were 9 confirmed fur seal sightings scattered through out the survey near shore and into the offshore waters.
We can’t leave out the special observation of a jumping blue striped marlin as we headed out to 93/120, our farthest offshore station. A basking shark was observed near shore of San Diego while transiting back to port on the final day of our cruise.