Distress sounds of thorny catfishes emitted underwater and in air:characteristics and potential significance

Abstract

Thorny catfishes produce stridulation (SR) sounds using their pectoral fins and drumming (DR) sounds via a swimbladder mechanism in distress situations when hand held in water and in air. It has been argued that SR and DR sounds are aimed at different receivers (predators) in different media. The aim of this study was to analyse and compare sounds emitted in both air and water in order to test different hypotheses on the functional significance of distress sounds. Five representatives of the family Doradidae were investigated. Fish were hand held and sounds emitted in air and underwater were recorded (number of sounds, sound duration, dominant and fundamental frequency, sound pressure level and peak-to-peak amplitudes). All species produced SR sounds in both media, but DR sounds could not be recorded in air for two species. Differences in sound characteristics between media were small and mainly limited to spectral differences in SR. The number of sounds emitted decreased over time, whereas the duration of SR sounds increased. The dominant frequency of SR and the fundamental frequency of DR decreased and sound pressure level of SR increased with body size across species. The hypothesis that catfish produce more SR sounds in air and more DR sounds in water as a result of different predation pressure (birds versus fish) could not be confirmed. It is assumed that SR sounds serve as distress sounds in both media, whereas DR sounds might primarily be used as intraspecific communication signals in water in species possessing both mechanisms.

Variation in swim bladder drumming sounds from three doradid catfish species with similar sonic morphologies

“…Similar sounds were reported from P. armatulus (formerly P. costatus) in an earlier study (Ladich, 1997). In a study of sounds from five doradid species including A. pectinifrons, Knight and Ladich (2014) observed continuous 'single drumming sounds' in all five species and 'series of short drumming pulses' that were separated by silent interpulse intervals in two of the five species, Megalodoras uranoscopus and Oxydoras niger. Sharply peaked pulses, similar to P. hancockii type I sounds were observed in Doras sp.…”

“…As sonic muscle lengths increase, contraction cycle duration is expected to increase (Wainwright and Richard, 1995), and the resulting sound frequency should decrease (Connaughton et al, 2000). Consistent with this prediction, Knight and Ladich (2014) observed a very modest inverse relationship between dominant frequency and body size among individuals of five doradid catfishes. In our study, muscle lengths probably varied somewhat among species because of the overall size differences among fish and as a result of species differences in relative sonic muscle length.…”

“…Because detailed life-history information is lacking for many catfishes with swim bladder sonic mechanisms, it is not yet known if changes occur in the condition of sonic muscle with reproductive season and sex. The intra-and interspecific diversity of disturbance sounds observed in the current and previous studies (Kaatz and Stewart, 2012;Knight and Ladich, 2014) indicates the potential for these sound types to signal different kinds of information in other behavioral contexts. Different context-dependent swim bladder sounds were observed in doradoid fishes by Kaatz (1999) in which agonistic sounds were continuous and reproductive sounds were pulsed.…”

“…Parmentier et al, 2008Parmentier et al, , 2010Kéver et al, 2012). Yet, drumming sounds from doradids can be quite complex and exhibit variation in pulse rate, temporal patterning, waveform shape, frequency modulation and amplitude modulation (Kastberger, 1977(Kastberger, , 1978Ladich, 1997;Papes and Ladich, 2011;Kaatz and Stewart, 2012;Knight and Ladich, 2014).…”

Acoustic signalling in female fish: factors influencing sound characteristics in croaking gouramis

“…This may be due to a different sonic mechanism in which resonance properties of air-filled cavities do not determine dominant frequencies of sounds. The fundamental frequency of sounds may be related to size in some fish species possessing drumming muscles such as sciaenids or doradid catfishes (Connaughton et al 2000;Tellechea et al 2010a;2010b;Knight and Ladich 2014). Connaughton et al (2000) argued that larger muscles with longer fibres would take longer to complete a contraction, resulting in a lower frequency in drumming muscles in larger sciaenids.…”