Remote autonomous ecological acoustic recorders (EARs) were deployed in deep waters at five locations around the island of Kauai and one in waters off Ni'ihau in the main Hawaiian island chain. The EARs were moored to the bottom at depths between 400 and 800 m. The data acquisition sampling rate...
The roles of nocturnal light and lunar phase in the diel migration of micronekton from a nearshore scattering layer were examined. Migration patterns were measured over six complete lunar cycles using moored upwardlooking echosounders while nocturnal surface irradiance was recorded. We hypothesized that animals would remain at a constant isolume...
The biosonar system of dolphins and porpoises has been studied for about 5 decades and much has
been learned [Au,W.W. L. )1993). The Sonar of Dolphins (Springer, New York)]. Most experiments
have involved human-made targets; little is known about odontocetes’ echolocation of prey. To
address this issue, acoustic backscatter from...
Groups of spinner dolphins have been shown to cooperatively herd small prey. It was hypothesized that the strong group coordination is maintained by acoustic communication, specifically by frequency-modulated whistles. Observations of groups of spinner dolphins foraging at night within a sound-scattering layer were made with a multibeam echosounder while the...
Broadband simulated dolphin echolocation signals were used to measure the ex situ backscatter properties of mesopelagic boundary community MBC in order to gain a better understanding of the echolocation process of spinner dolphins foraging on the MBC. Subjects were captured by trawling with a 2-m-opening Isaacs-Kidd Midwater Trawl. Backscatter measurements...
This study presents the first target strength measurements of Dosidicus gigas, a large squid that is a key predator, a significant prey, and the target of an important fishery. Target strength of live, tethered squid was related to mantle length with values standardized to the length squared of −62.0, −67.4,...
Sonar techniques were used to quantitatively observe foraging predators and their prey simultaneously in three dimensions. Spinner dolphins foraged at night in highly coordinated groups of 16–28 individuals using strict four-dimensional patterns to increase prey density by up to 200 times. Herding exploited the prey’s own avoidance behavior to achieve...
The target strength as a function of aspect angle were measured for four species of fish using dolphin-like and porpoise-like echolocation signals. The polar diagram of target strength values measured from an energy flux density perspective showed considerably less fluctuation with azimuth than would a pure tone pulse. Using detection...
The hypothesis that sounds produced by odontocetes can debilitate fish was examined. The effects of simulated odontocete pulsed signals on three species of fish commonly preyed on by odontocetes were examined, exposing three individuals of each species as well as groups of four fish to a high-frequency click of a...
An experiment was conducted to investigate the sound pressure patterns on the melon of odontocetes by using four broadband hydrophones embedded in suction cups to measure echolocation signals on the surface of the forehead of two harbor porpoises (Phocoena phocoena). It has long been hypothesized that the special lipids found...