Fish sounds are an important biological component of the underwater soundscape. Understanding species-specific sounds and their associated behaviour is critical for determining how animals use the biological component of the soundscape. Using both field and laboratory experiments, we describe the sound production of a nocturnal planktivore, Pempheris adspersa (New Zealand bigeye), and provide calculations for the potential effective distance of the sound for intraspecific communication. Bigeye vocalisations recorded in the field were confirmed as such by tank recordings. They can be described as popping sounds, with individual pops of short duration (7.9±0.3 ms) and a peak frequency of 405±12 Hz. Sound production varied during a 24 h period, with peak vocalisation activity occurring during the night, when the fish are most active. The source level of the bigeye vocalisation was 115.8±0.2 dB re. 1 µPa at 1 m, which is relatively quiet compared with other soniferous fish. Effective calling range, or active space, depended on both season and lunar phase, with a maximum calling distance of 31.6 m and a minimum of 0.6 m. The bigeyes' nocturnal behaviour, characteristics of their vocalisation, source level and the spatial scale of its active space reported in the current study demonstrate the potential for fish vocalisations to function effectively as contact calls for maintaining school cohesion in darkness.

Fish vocalisation is often a major component of underwater soundscapes. Therefore, interpretation of these soundscapes requires an understanding of the vocalisation characteristics of common soniferous fish species. This study of captive female bluefin gurnard, Chelidonichthys kumu, aims to formally characterise their vocalisation sounds and daily pattern of sound production. Four types of sound were produced and characterised, twice as many as previously reported in this species. These sounds fit two aural categories; grunt and growl, the mean peak frequencies for which ranged between 129 to 215 Hz. This species vocalized throughout the 24 hour period at an average rate of (18.5 ± 2.0 sounds fish-1 h-1) with an increase in vocalization rate at dawn and dusk. Competitive feeding did not elevate vocalisation as has been found in other gurnard species. Bluefin gurnard are common in coastal waters of New Zealand, Australia and Japan and, given their vocalization rate, are likely to be significant contributors to ambient underwater soundscape in these areas.

Recently the bigeye, Pempheris adspersa, has been found to be one of the few sound producing fish found in the temperate marine waters of New Zealand. An initial crude morphological examination of this species found a special connection, analogous to that of the well-defined laterophysic connection, between the otic capsule and the lateral line recess. The aim of the present study was to characterize the hearing ability of the bigeye using auditory evoked potentials, understand the role of this special connection, and describe the morphology of the hearing structures using microCT and MRI techniques. The novel connection consists of a robust ligament directly connecting the otic capsule to the lateral recess, with the swim bladder running directly posterior to the ligament. Pempheris adspersa could hear in the frequency range 100–1000 Hz, with greatest sensitivity between 100–800 Hz. Cutting the connecting ligament resulted in a 15–20 dB threshold shift, with a further 5–10 dB shift after swim bladder puncture. This connection represents a completely novel hearing specialization and shows that the lateral line is directly connected to the otic capsule, enhancing the hearing ability of this species especially at low frequencies (100–200 Hz).