Bioacoustics supports genus identification in piranhasa)

Stridulation sounds of the pacamã Lophiosilurus alexandri Steindachner, 1876 (Pseudopimelodidae), a threatened endemic Brazilian catfish

Pseudopimelodidae comprises 49 species of freshwater catfish endemic to South America, with limited research on their acoustic behaviour. This study focuses on the pacamã Lophiosilurus alexandri Steindachner, 1876, a vulnerable catfish species endemic to the São Francisco River basin, known for its ecological and economic importance. Sound production by this species was analysed for the first time. Three individuals were recorded while being held underwater revealing the production of two distinct sound types (type I and type II) associated with pectoral fin movements (abduction and adduction). Sounds were 85-135 ms long with a variable number of pulses or peaks. Type II sounds were longer and louder than type I sounds, with both types showing a similar peak frequency ranging between 200 and 500 Hz. The sounds were produced alternately by the pectoral fins, with occasional lateralization. More research is needed to determine whether these sounds can be used for monitoring or if they lack sufficient species-specific characteristics.

Sounds as taxonomic indicators in Holocentrid fishes

The species-specific character of sounds in the animal kingdom has been extensively documented, yet research on fishes has predominantly focused on a limited number of species, overlooking the potential of acoustic signals to reflect broader taxonomic ranks. In this study, we analyzed acoustic data of hand-held sounds from 388 specimens spanning 5 genera and 33 species within the family Holocentridae, with the objective of evaluating the use of sound characteristics for taxonomic discrimination across various levels (subfamily, genus, species). Sounds could be indicative of grouping. Taxa discriminability depends on taxonomic level; the higher the taxonomic level, the better the discrimination of taxa based on sounds. Analogous to the role of morphological traits in taxonomic delineation, this research corroborates the utility of acoustic features in identifying fish taxa across multiple hierarchical levels. Remarkably, certain holocentrid species have evolved complex sound patterns characterized by unique temporal arrangements where pulses are not continuous but emitted in blocks, facilitating the exploitation of the acoustic space.

Introduction to the special issue on fish bioacoustics: Hearing and sound communicationa)

Fish bioacoustics, or the study of fish hearing, sound production, and acoustic communication, was discussed as early as Aristotle. However, questions about how fishes hear were not really addressed until the early 20th century. Work on fish bioacoustics grew after World War II and considerably in the 21st century since investigators, regulators, and others realized that anthropogenic (human-generated sounds), which had primarily been of interest to workers on marine mammals, was likely to have a major impact on fishes (as well as on aquatic invertebrates). Moreover, passive acoustic monitoring of fishes, recording fish sounds in the field, has blossomed as a noninvasive technique for sampling abundance, distribution, and reproduction of various sonic fishes. The field is vital since fishes and aquatic invertebrates make up a major portion of the protein eaten by a signification portion of humans. To help better understand fish bioacoustics and engage it with issues of anthropogenic sound, this special issue of The Journal of the Acoustical Society of America (JASA) brings together papers that explore the breadth of the topic, from a historical perspective to the latest findings on the impact of anthropogenic sounds on fishes.