Rare and cryptic fish species such as the cusk-eel Ophidion rochei, an endemic sand-dwelling Mediterranean fish, are likely to go undetected by traditional non-invasive monitoring techniques commonly used to survey biodiversity.

This study located for the first time O. rochei in the north-western Adriatic Sea (Miramare MPA, Italy) using passive acoustic monitoring (PAM).

Results by PAM revealed long trains of low-frequency pulses, showing the typical and unique pulse period alternation pattern of O. rochei adult male reproductive calls. The authors state, that the consistency of these peculiar call features indicates that O. rochei is present in the MPA, where it is likely to reproduce.

The authors highlight that this is the first reported case in which PAM enabled the identification of a cryptic fish species in an MPA where visual census surveys of the fish fauna, carried out periodically, failed to detect the presence of this species.

It is concluded that PAM is a powerful tool for both conservation and fishery science that should be coupled with visual surveys in order to improve the resolution of fish biodiversity assessments.

https://onlinelibrary.wiley.com/doi/abs/10.1002/aqc.2973?af=R

Picciulin M, Kéver L, Parmentier E, Bolgan M (2018) Listening to the unseen: Passive acoustic monitoring reveals the presence of a cryptic fish species. Aquatic Conservation: Marine and Freshwater Ecosystems DOI: 10.1002/aqc.2973