Showing papers by "Andone C. Lavery published in 2011"

Broadband active acoustic sensing of fish and zooplankton in the kilohertz to megahertz range: Pursuing Van Holliday's vision

Abstract: Van Holliday had a vision for sensing marine organisms with active acoustics over a very wide range of frequencies. This inspired us at the Woods Hole Oceanographic Institution, Woods Hole, MA, to conduct a series of measurements, both in the laboratory and in the ocean, and associated modeling, over the range of 1.5 kHz to 3 MHz over the past 23 years. The organisms were as small as millimeter-size copepods and as large as 20-cm herring and squid. Broadband acoustic scattering measurements were conducted in the laboratory as a function of frequency (24 kHz 3 MHz) and angle of orientation (0–360 deg) of many species. Instruments were developed to measure broadband acoustic scattering in the ocean over the range 1.5 kHz 1.2 MHz with some gaps. Scattering models, based on the laboratory data, were also developed for several major anatomical groups of organisms and spanned a range of complexity, from low-resolution models that account only for length, width, and general shape to high resolution models that account for shape of the body and heterogeneities within the body in three dimensional at fine scale as well as including roughness. In this presentation, we review the laboratory measurements and scattering models, as well as development of the broadband ocean instruments and their use at sea.

Field applications of broadband acoustic scattering techniques for quantifying zooplankton distribution, abundance, and size.

Abstract: Discriminating among sources of scattering remains a key problem in ecological applications of active acoustics. This is particularly true in studies of zooplankton, which are often found in communities of heterogeneous species composition, and in the deployment of acoustics on autonomous platforms, where independent sampling with nets to ground‐truth acoustic observations is often not feasible. Broadband measurements can provide substantial improvements in species discrimination by characterizing more fully the frequency spectrum of scatterers relative to traditional single‐ and multi‐frequency narrowband techniques. Here, we present findings from a series of three cruises to the margins of Georges Bank examining patchiness in the distribution of krill and other zooplankton, as well as interactions with predators (fish, seabirds, and marine mammals). A heavily modified commercially‐available broadband system spanning a frequency band of 30–600 kHz, with some gaps, was deployed in a towed body to depths of 200 m. Concurrent measurements made with a surface‐towed multi‐frequency system (43, 120, 200, and 420 kHz) along with ground‐truthing information from depth‐stratified net sampling and a video plankton recorder allow an assessment of the strengths and limitations of broadband methods for remotely discriminating among sources of scattering and for estimating the abundance and size of animals.

Field Demonstration of a Broadband Acoustical Backscattering System Mounted on a REMUS-100 for Inferences of Zooplankton Size and Abundance

Abstract: : The long term goal of this research is to develop high-frequency broadband acoustical scattering techniques to remotely and autonomously characterize zooplankton distribution, size, abundance, and community structure, on ecologically relevant spatial and temporal scales. In order to achieve this goal, an autonomous, compact, low-power, high-frequency, broadband acoustical backscattering system suitable for use from gliders and small powered AUVs has been developed and mounted on a REMUS-100.