Observation of Marine Animals Using Underwater Acoustic Camera

Abstract

An underwater acoustic camera enclosed in a pressure-resistant case was constructed to observe underwater marine animals. This enabled the measurement of the size, shape, and behavior of living marine animals in the detection range up to 240 cm. The transducer array of the acoustic camera was driven by 3.5 MHz ultrasonic signals, and B-mode acoustic images were obtained. Observations were conducted for captive animals in a water tank and for natural animals in a field. The captive animals, including fish, squid and jellyfish, were observed, and a three-dimensional internal structure of animals was reconstructed using multiple acoustical images. The most important contributors of acoustic scattering were the swimbladder and vertebra of bladdered fish, and the liver and reproductive organs of invertebrate animals. In a field experiment, the shape, size, and swimming behavior of wild animals were observed. The possibilities and limitations of the underwater acoustic camera for fishery applications were discussed.

Use of the distorted wave Born approximation to predict scattering by inhomogeneous objects: Application to squid

“…Measurements of density and sound speed of squid suggest that these invertebrates are well suited to being modeled as weak scatterers ͑Mukai et al, 2000; Kang et al, 2006;Iida et al, 2006͒. Accordingly, previous models of squid use the exact liquid prolate spheroid model and the DWBA formulation, also using a prolate spheroidal geometry ͑Arnaya and Sano, 1990;Mukai et al, 2000͒. However, these models assume homogeneous material properties within the scattering volume of simple shape.…”

Acoustic scattering of broadband echolocation signals from prey of Blainville's beaked whales : modeling and analysis

“…The interior body of the squid includes a long thin pen, a parrot-like beak, statoliths (small, bony inner ear organs), a hard cartilaginous cranium, and hard lenses in the eye (Williams, 1909). Iida et al (2006), also identifies the liver, a low density organ surrounded by higher density tissue, as a likely scatterer of sound. In combination it seems likely that scattering from the variety of inhomogeneities within a squid's body could significantly contribute to scattering and even dominate the scattering from off-broadside orientations.…”

“…Mukai et al (2000) whole squid 1.025 - Kang et al (2004) whole squid 1.028 1.04 Iida et al (2006) mantle tissue 1.043 1.053…”

“…Density and sound speed measurements of squid suggest that these invertebrates are well suited to modeling as weak scatterers (Mukai et al, 2000;Kang et al, 2004;Iida et al, 2006). Accordingly, previous models of squid use the exact liquid prolate spher-oid model (LPSM) and the DWBA formulation, also using prolate spheroid geometry (Arnaya and Sano, 1990b;Mukai et al, 2000).…”

Orientation dependence of broadband acoustic backscattering from live squid

“…However, there are no measurements available for the material properties of L. pealeii. Therefore, the tissue material properties of the Japanese flying squid (Todarodes pacificus) (g ¼ 1.043, h ¼ 1.053, Iida et al, 2006;Jones, 2006) were used instead for both the analytical DWBA prolate spheroid model and the threedimensional DWBA numerical model in this study.…”