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Target strength measurements of Hawaiian mesopelagic boundary community animals Pubblico Deposited

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Abstract
  • A 200-kHz echosounder modified to digitize the envelope of the received echoes directly into a computer was used to measure the ex situ target strength (TS) of live animals from the Hawaiian mesopelagic boundary community as a function of animal size, tilt and roll angle, and biological classification. Dorsal aspect TS (in dB//1 m) at 200 kHz was related to the animal's length: myctophid fish TS = 20 log (standard length in cm)–58.8, r2 = 0.91, squid TS = 18.8 log (mantle length in cm)–61.7, r2 = 0.81, shrimp TS = 19.4 log (length in cm)–74.1, r2 = 0.83. Tilting the fish 5° and 10° changed the measured TS by up to 3.0 dB, decreasing TS as the fish was tilted forward and increasing TS as the fish was tilted backwards. In shrimp, forward tilt increased TS while backward tilt decreased TS by up to 3.3 dB. No consistent trend in squid TS change was observed with tilt angle. Roll angles of 5° and 10° increased the TS of all groups by up to 3.0 dB. Myctophid lateral aspect TS was consistently about 6 dB higher than the dorsal TS. Physiological analysis of the fishes' swimbladders revealed that the swimbladder is not the dominant scattering mechanism in the myctophid fishes studied.
  • Keywords: bioacoustics, underwater sound, acoustic wave scattering, oceanographic regions
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Citation
  • J. Acoust. Soc. Am. 110:812-819 (2001), DOI: 10.1121/1.1382620
Journal Title
Journal Volume
  • 110
Journal Issue/Number
  • 2
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Funding Statement (additional comments about funding)
  • National Marine Fisheries Service’s Honolulu Laboratory, for ship time aboard the Townsend Cromwell and free-standing tank.
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ISSN
  • 0001-4966

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