In situ source level and source position estimates of biological transient signals produced by snapping shrimp in an underwater environment

Abstract

Biological transient signals produced by snapping shrimp are sensed underwater by a wide aperture array. The instantaneous range and bearing of the source position of each snap is estimated along with a source level equal to the peak-to-peak amplitude of the pressure impulse generated by the snap at a standard distance of 1 m from its point of origin. For a sample of 1000 snaps recorded in Sydney Harbour, the distribution of peak-to-peak sound pressure levels has a mean value of 187 dB (re 1 microPa) and an interquartile range of 185-189 dB (re 1 microPa). Plotting the Cartesian coordinates of the source positions of the biological transient signals over a period of time maps the two-dimensional spatial distribution of the local snapping shrimp population. The principal habitat is found to be geocoincident with a 120-m-long wharf, the closest point of which is 60 m from the middle of the receiving array. The passive ranging performance of the wide aperture array is evaluated by generating mechanical transient signals at selected positions along the wharf. Precise estimates of the relative times-of-arrival of the acoustic wavefronts lead to source range and bearing estimates with standard deviations of only 0.1 m and 0.005 degrees (respectively), in agreement with theoretical predictions.

Rapidly obtained ecosystem indicators from coral reef soundscapes

“…Nondestructively determining whether there is any such relationship may be challenging as snapping shrimp are usually subterranean creatures and are rarely observed above the substrate. Directional acoustic re ceivers may be employed to determine the location of snaps in an area (Ferguson & Cleary 2001, Chitre et al 2012, Kaplan et al 2015, producing estimates of snapping shrimp distribution in a localized area. Re gardless of the process that connects high-frequency sound and the proportion of algal cover, the correlative findings shown here introduce the possibility of an acoustic indicator of algal dominance, and in some situations, of reef degradation.…”

Mapping the diversity of spectral shapes discriminates between adjacent benthic biophonies

“…The marine environment facilitates the propagation of acoustic waves (Urick 1967), and noise levels emitted by different sound sources such as bivalves, echinoderms or crustaceans can be very different (Ferguson & Cleary 2001, Coquereau et al 2016a. Describing a biophony at a sampling point based on its power or number of BIS per unit of time can mask low-power but ecologically relevant pulses.…”

“…We suggest defining it as the propagation distance of the most powerful biological sound source in the environment studied. For example, if it is the snapping shrimp, then the propagation radius may be more 3000 m (source level taken from Ferguson & Cleary 2001; propagation distances calculated as described in Coquereau et al 2016a). In this propagation area (3 km), it would be impossible to distinguish the acoustic presence of feeding sea urchins Echinus spp.…”

Acoustic behaviours of large crustaceans in NE Atlantic coastal habitats

“…It would be interesting to conduct species-specific behaviour studies to investigate the mechanism of sound production during Type 1 behaviour and during the other unidentified behaviours that produced well-structured sounds. Indeed, these well-structured sounds were among the loudest sounds recorded in this study (up to 142 dB re 1 μPa [pp]) and were as loud as the snapping sounds of A. nitescens, which belongs to a family (Alpheidae) that produces some of the louder sounds in the oceans (Au & Banks 1998, Ferguson & Cleary 2001, Schmitz 2002. This implies that when numerous, these sounds contribute substantially to natural coastal soundscapes and could be detected in field recordings.…”