Sound discrimination of two sympatric, threatened fish species allows for their in situ mapping

Abstract

1. Human impacts on marine ecosystems are increasing and the number of fish species listed in the Red List is constantly growing. In the Mediterranean Sea, seven of the 10 bony fishes defined as Threatened by the IUCN are known to be vocal, including the target species of this study: the shi drum (Umbrina cirrosa Linnaeus, 1758) and the brown meagre (Sciaena umbra Linnaeus, 1758). As a result, non-invasive passive acoustic monitoring (PAM) can be used to pinpoint their distribution at sea. However, for PAM to be effective, reliable acoustic discrimination is required because the sounds they emit during reproduction are remarkably similar (i.e. short broadband pulsed sounds).2. The shi drum and the brown meagre are closely related, elusive, vocal sciaenids, partially overlapping in their ecological niche. During summer 2019, three PAM surveys were conducted along the tidal inlets of the Venice lagoon (Italy). Here, the calls of both species have been recognized according to their temporal features: shi drum sounds were made up of a lower number of longer pulses with a different envelope, repeated at a lower rate than those of the brown meagre. Further, shi drum and brown meagre sounds of different origins (aquaculture and semi-natural conditions) were analysed and compared with those collected during the survey of the study area in order to validate the field collected data.3. Call discrimination allowed for a fine-scale species mapping, showing a partially overlapping distribution of the two species along the inlets. This is the first case in which two sciaenids have been documented to share their reproductive habitat in the Mediterranean Sea.4. This study demonstrates that it is feasible to acoustically monitor the target species even in those parts of the Mediterranean Sea where they co-exist. This, in its turn, could provide managers with the required data for effective conservation measures to be implemented.

Use of passive acoustic monitoring to fill knowledge gaps of fish global conservation status

“…from Vulnerable to Critically Endangered) bony fish species inhabiting the Mediterranean Sea are soniferous and could therefore be monitored remotely using PAM (besides gobies; Picciulin et al, 2021). In this basin, PAM has already been applied to monitor Epinephelus marginatus (Endangered; Bertucci et al, 2015; IUCN, 2022), Mycteroperca rubra (Least Concearn; Desiderà et al, 2022; IUCN, 2022), Sciaena umbra (Near Threatened; Picciulin et al, 2013; Parmentier et al, 2017; Bolgan et al, 2022; IUCN, 2022), Umbrina cirrosa (Vulnerable; Picciulin et al, 2021; IUCN, 2022) and Scorpaena sp. (Least Concern; Di Iorio et al, 2018; Bolgan et al, 2019; Bolgan et al, 2022; IUCN, 2022).…”

“…This would allow for discrimination between closely related species, as demonstrated in other fish taxa (e.g. Serrasalmidae, Pomacentridae, Sciaenidae; Monczak et al, 2017; Monczak et al, 2019; Raick et al, 2020; Picciulin et al, 2021; Parmentier & Lecchini, 2022). In particular, the temporal succession of pulses within O. rochei ’s sounds constitutes a species‐specific, easily measurable and reliable acoustic tag of this species’ presence at sea (Figure 1).…”

Rhythmic properties of Sciaena umbra calls across space and time in the Mediterranean Sea

“…Acoustic data collection relates to previous projects [ 16 , 17 , 24 , 27 , 30 , 50 ] carried out in four Mediterranean sites ( Fig 1 ), which differed for several environmental and anthropic conditions. Data were recorded in Palma Bay Marine Reserve (Mallorca, Spain) and the Underwater Biotechnological Park of Crete (Greece).…”

“…Furthermore, the richness of the fish acoustic community (i.e. acoustic richness: number of different fish sound types) was 8 in Crete, 4 in Mallorca [ 27 ] and 2 in Venice and Trieste [ 17 , 24 , 50 ]. No permits were needed to conduct this research.…”

“…In Venice (Italy), a pre-amplified GP1280 hydrophone (Colmar SRL, La Spezia, IT; sensitivity −170 dB re. 1 V Pa −1 ; frequency range, 5 Hz–90 kHz) connected to a Tascam Handy Recorder (Tascam, Montebello, CA) generating .wav files at 44.1 kHz and 16-bit depth was used; three single 10-h acoustic summer campaigns were conducted at 40 listening points along two summers [ 17 , 24 , 50 ]. In Trieste, recordings were collected (i) by using an acoustic data logger prototype provided with a pre-amplified TC 4013 hydrophone (Reson, A/S, Salangerup, Denmark; sensitivity −170 dB re 1 V μPa −1 ; frequency range 1 Hz to 170 kHz) connected to a Gemini iKey Plus Recording Device (10 min .wav files at 44.1 kHz and 16 bits) in 2009 (series of nocturnal 11-h recordings from June-September) and (ii) by using an underwater acoustic data logger SNAP settled for recording 1 min every 5 min (over the 24 h) for one week (unpublished data).…”