Near resonance acoustic scattering from organized schools of juvenile Atlantic bluefin tuna (Thunnus thynnus).
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Citations
A Review of Oceanographic Applications of Water Column Data from Multibeam Echosounders
Aerial surveys to monitor bluefin tuna abundance and track efficiency of management measures
Detecting the presence-absence of bluefin tuna by automated analysis of medium-range sonars on fishing vessels
Sound extinction by fish schools: forward scattering theory and data analysis.
Attenuation of low-frequency underwater sound using an array of air-filled balloons and comparison to effective medium theory
References
Low‐frequency ocean surface noise sources
Low frequency sound scattering from spherical assemblages of bubbles using effective medium theory.
The feasibility of direct photographic assessment of giant bluefin tuna, Thunnus thynnus, in New England waters
Consecutive acoustic observations of an Atlantic herring school in the Northwest Atlantic
Effects of multiple scattering, attenuation and dispersion in waveguide sensing of fish
Related Papers (5)
Frequently Asked Questions (9)
Q2. How long did the distance between the vessel and the school decrease?
2. Between pings 8 and 135 (approximately 0.5 min), the distance between the vessel and the school (as imaged by MBES) decreased nearly linearly from 65 to 30 m.
Q3. How many beams did the MBES use?
This MBES uses a Mills cross array topology to form 256 beams between 664 with a nominal angular resolution of 1 0.5 (horizontal and vertical 3 dB beamwidths) and was oriented so that its center beam was pointed horizontally in the vertical plane and approximately 45 off the starboard bow.
Q4. What is the angular dependence in the modeled school target strength?
There is also a strong angular dependence in the modeled school target strength with increased backscatter when the school is ensonified along its short axis compared to the model outputs for ensonification along the long axis.
Q5. What is the depth dependence of the swimbladder?
This depth dependence is expected for fish that have adapted to depth, however, and if the tuna are rapidly changing depth within the school, the swimbladder resonance frequency is expected to vary more widely, following a (1þz/10)5/6 relationship with depth, z, or about a 75% variation for the ABFT observed here.
Q6. What is the acoustic response of the swimbladder of the tuna?
The resulting swimbladder resonance frequencies very between approximately 45 and 65 Hz with a standard deviation slightly greater than 3 Hz.
Q7. What is the acoustic amplitude of the swimbladder?
The complex scattering amplitude of the swimbladder is assumed to be the same for a gas bubble acting as a monopole radiator (Clay and Medwin, 1977)si ¼ a expð jkaÞx2o=x 2 1 jd ; (3)where a ¼ ð3vsb=4pÞ1=3 is assumed to be the effective swimbladder radius based on its volume vsb, xo is the resonance frequency of the fish in radians per second, and d is a3808 J. Acoust.
Q8. How many different school target strength models are considered?
For reference, the school target strength is also calculated assuming that the scattered contributions add incoherently at the receiverTSinc ¼ 10 log10X263 i¼1 jpj2A2 r4 : (7)In total, seven different school target strength models are considered.
Q9. What is the acoustic frequency of the swimbladder?
Both the resonance frequency and damping constant are calculated following the formulation given by Love (1978) assuming the swimbladder to be filled with air with a density of 1.3 kg/m3 and a sound speed of 340 m/s, sea water and fish flesh densities of 1000 kg/m3 and 1050 kg/ m3, respectively, a viscosity parameter of 50 Pa s, and a surface tension of 1000 N/m.