Empirical refinements applicable to the recording of fish sounds in small tanks

Abstract

Many underwater bioacoustical recording experiments (e.g., fish sound production during courtship or agonistic encounters) are usually conducted in a controlled laboratory environment of small-sized tanks. The effects of reverberation, resonance, and tank size on the characteristics of sound recorded inside small tanks have never been fully addressed, although these factors are known to influence the recordings. In this work, 5-cycle tone bursts of 1-kHz sound were used as a test signal to investigate the sound recorded in a 170-l rectangular glass tank at various depths and distances from a transducer. The dominant frequency, sound-pressure level, and power spectrum recorded in small tanks were significantly distorted compared to the original tone bursts. Due to resonance, the dominant frequency varied with water depth, and power spectrum level of the projected frequency decreased exponentially with increased distance between the hydrophone and the sound source; however, the resonant component was nearly uniform throughout the tank. Based on the empirical findings and theoretical calculation, a working protocol is presented that minimizes distortion in fish sound recordings in small tanks. To validate this approach, sounds produced by the croaking gourami (Trichopsis vittata) during staged agonistic encounters were recorded according to the proposed protocol in an 1800-l circular tank and in a 37-l rectangular tank to compare differences in acoustic characteristics associated with tank size and recording position. The findings underscore pitfalls associated with recording fish sounds in small tanks. Herein, an empirical solution to correct these distortions is provided.

Identifying Sciaenid Critical Spawning Habitats by the Use of Passive Acoustics

“…Most collected fish emitted calls upon first capture; recordings were made immediately after capture in air or in seawater (in a portable floating net-pen or a cooler). We recognize that captive recordings in such conditions may not produce sounds that are characteristic of free-ranging individuals and that there may be tank echo effects (Parvulescu 1967;Akamatsu et al 2002), reduced amplitude, and altered patterns of calling (i.e., distress calls are made rather than spawning calls). Underwater recordings of captive weakfish and red drum were made using an InterOcean Acoustic Listening and Calibration System (Model 902; frequency range ¼ 20-10,000 Hz; sensitivity ¼ À100 dB referenced to [re] 1 V/lPa), consisting of an InterOcean hydrophone (Model T-902; sensitivity ¼ À195 dB re 1 V/lPa) connected to an amplifier (gain adjustable from 15 to 95 dB in 10-dB increments, plus vernier adjustment).…”

Sound production to electric discharge: sonic muscle evolution in progress inSynodontisspp. catfishes (Mochokidae)

“…Sounds and EODs were recorded in a small aquarium (60 Â 29 cm, water depth kept at approx. 20 cm) with an estimated minimum resonance of 4.6 kHz [18]. Sounds were recorded on a Tascam DR-05 digital recorder (44.1 kHz sampling rate) connected to an HTI-Min 96 hydrophone (2186.4 dB re: 1 V mPa 21 , frequency response 2 Hz-30 kHz) placed at the centre of the aquarium.…”

Rumbling in the benthos: acoustic ecology of the California mantis shrimp Hemisquilla californiensis

“…For example, in the tank experiment, individuals were approached by a hydrophone or a stick; these animals probably produced sounds in an antipredator context (Bradbury & Vehrencamp 1998, Patek & Caldwell 2006, Staaterman et al 2010. Furthermore, tank recordings typically distort the acoustic quality of animal sounds (Parvulescu 1967, Akamatsu et al 2002, Patek et al 2009). Fig.…”