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2 results

  • 5 - Sampling Mixing and Its Environment

  • Michael C. Gregg, University of Washington
  • Book:
    Ocean Mixing
    Published online:
    10 March 2021
    Print publication:
    04 February 2021, pp 156-196

  • Summary

    This chapter explores how mixing is measured, focusing on what can be measured and how accurately. It begins with probes measuring dissipation scales, i.e. thermistors and airfoils, but also includes other devices not used routinely, such as pitot tubes. Finescale sensors are also examined, with an emphasis on absolute accuracy and salinity spiking. Then the vehicles carrying the probes are described, i.e. profilers, tows, AUVs, and submersibles. Moorings and fixed platforms are also briefly examined. Finally, remote sensing, principally using backscatter from high-frequency acoustics, is reviewed, along with tracer releases for measuring net diffusivity.

  • Sperm whale distribution and diving behaviour in relation to presence of jumbo squid in Guaymas Basin, Mexico

  • Juan-Pablo Gallo-Reynoso, Janitzio Égido-Villarreal, Elsa-María Coria-Galindo
  • Journal:
    Marine Biodiversity Records / Volume 2 / January 2009
    Published online by Cambridge University Press:
    20 August 2009, e139
    Print publication:
    January 2009

  • Sperm whale, Physeter macrocephalus, distribution was compared to acoustic backscatter observations in the Gulf of California. Forty-three sperm whale groups, totalling 813 individuals, were encountered during 28 observation days. Sperm whales occurred over deep waters (mean depth = 659 m, range: 300–1800 m). A significant correlation was found between the whales' maximum depth of dive and depth of the acoustic scattering layer (N = 36, r2 = 0.944, P = 0.000). We observed sperm whales dive to the scattering layer and then surface with prey in their jaws: jumbo squid, Dosidicus gigas (10 events) and unidentified fish (one event). The average depth of sperm whale foraging dives to the scattering layer was 342 m, the average diving time was 23 minutes, and the average surface interval between foraging dives was 6 minutes. Sperm whales spent 75% of their time diving and 25% on the surface. Swimming speed at the surface was slower when whales reached scattering layers during a dive (2.4 km/h) compared to dives when no scattering layer was reached (8.9 km/h). Our results establish a direct link between sperm whale distribution and presence of its prey in the Gulf of California.