From zooplankton to the great whales:
How acoustics can be used to quantify zooplankton and track the whales

Khosrow Lashkari, Ph.D.
Monterey Bay Aquarium Research Institute

Friday, January 23, 1998
12:00 Noon—Pacific Forum

The food chain in the ocean begins with nutrients which serve as "fertilizer" for phytoplankton, the oceanic equivalent of grassy vegetation. Small shrimp-like animals known as zooplankton feed on phytoplankton. Zooplankton itself is food for larger marine animals from small fish to the largest whales.

The first part of this talk describes acoustic methods for quantification of zooplankton fields in the ocean. Various factors such as frequency, acoustic backscatter properties of plankton species, size and orientation, and physical properties of the ocean environment that determine the efficacy of acoustic methods are discussed. Results are presented from data collected during the March ‘97 Western Flyer cruise using MBARI's Simrad EK-500 system. These results are in good agreement with data collected from concurrent net tows and suggest that EK-500 is an effective sampling tool for studying the large-scale spatial distribution of zooplankton.

The second part of the talk describes methods and experiments for passive acoustic tracking of larger marine animals, such as blue and sperm whales and harbor porpoises. MBARI's Ocean Acoustic Observatory system will be described and several applications will be presented. This is a general-purpose system for processing large quantities of data in real-time and can serve as the oceanic equivalent of a radio telescope, an infrared telescope, and an optical telescope combined into one system.

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