fish

In this study a detailed analysis of acoustical parameters of sounds produced by male Trichopsis vittatus, T. schalleri and T. pumilus during agonistic behaviour is reported. The calls consist of croaks which are composed of double pulses generated by modified pectoral fins. Calls of the three species are different in main frequency, number of double pulses within a croak and double pulse period. Croaks are uttered in series only in T. vittatus. Sound pressure levels are highest in T. pumilus, the smallest species. Amplitude of individual pulses of a double pulse are similar in T. pumilus and T. schalleri. Main frequency is negatively correlated with body mass in all species, but there is no correlation between sound pressure level and body mass. Differences in the calls of the three species suggest that T. schalleri is a distinct species. Furthermore, results indicate spectral characteristics and sound intensity could be of biological importance in fish.

In this paper a detailed analysis of the physical structure of sounds produced by male Padogobius martensi is reported. Sound production occurs during courtship and inter-male agonistic encounters. Both aggressive and courtship calls are made up of rapidly repeated pulses, with a pulse repetition rate decreasing through the course of the emission. By means of computerized analysis, the pulse repetition rate, its modulation and sound duration were determined. The water temperature was found to exert a marked and significant effect on the above parameters. In particular, the temperature directly affects the pulse rate and its decrease through the course of the emission (i.e. frequency modulation) and inversely affects sound duration. By contrast, size of the calling animal does not significantly influence the sound parameters considered. Aggressive sounds last longer and have a lower pulse repetition rate than the courtship sounds. Moreover, aggressive sounds appear more variable than the courtship ones as far as pulse rate and duration are concerned.

This is the first description of vocalisations produced by the mormyrid species Petrocephalus catostoma from the Upper Zambezi River whilst defending a territory. Agonistic behavioural displays of a dominant male towards a conspecific, such as mutual circling or short attacks, were accompanied by characteristic tonal sounds, termed hoots. The mean hoot duration (43 ± SD 1.8 ms) was longer, and the fundamental frequency (H1, 180 ± SD 4.7 Hz) lower, than in the closely related species Petrocephalus ballayi. P. catostoma vocalised hoots only during intraspecific agonistic interactions, especially those accompanying territorial conflict.

Several studies on fishes have shown that behaviour and auditory sensitivity are often affected by underwater noise. The current investigation concentrates on noise encountered by fish kept for leisure in aquaria and ponds. Noise spectra showed that all aquarium filters measured created a high amount of low-frequency noise, while the water outflow above the surface created additional high-frequency noise components. Audiograms of the Goldfish Carassius auratus, a species possessing hearing specializations, were determined between 0.1 and 4kHz using the noninvasive
auditory evoked potential (AEP) recording technique. The amount of masking was determined in the presence of four different noise-types: aquaria with external filter with outflow above the water surface (119dB re 1 µPa), external filter with outflow below the water surface (115dB), internal filter with outflow below the water surface (114dB broadband LLeq, 1min), and an unfiltered pond (95dB). The goldfish’s hearing was masked by all filter noise types and most affected at 0.1 and 0.3kHz by the external filter noise (threshold shifts of 15-19dB). Pond noise had no effect on the hearing threshold. The results indicate that fish with hearing specializations are considerably masked under common holding conditions found in aquaria but probably not in ponds. Thus, using a quieter filter setup with a quiet outflow might help to improve holding conditions in aquaria without compromising aeration of the water.