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- Vocal repertoire and consistency of call features in the meagre Argyrosomous regius (Asso, 1801)Publication . Bolgan, Marta; Pereira, Beatriz P.; Crucianelli, Aurora; Mylonas, Constantinos C; Pousão-Ferreira, Pedro; Parmentier, Eric; Fonseca, Paulo J.; Amorim, Maria Clara PPassive Acoustic Monitoring (PAM) is a non-intrusive and cost-effective method capable of providing high-resolution, long-term information on the status and health of vocal populations and communities. To successfully monitor the same species over wide geographical and temporal scales, it is necessary to characterise the range of sound variability, as well as the consistency of sound features between populations. The meagre (Argyrosomus regius, Asso 1801) is an interesting case study because recent investigations suggest a wider vocal repertoire than previously described. In this study, meagre vocalizations were recorded and analysed from a variety of settings, ranging from rearing facilities to wild populations to provide a comprehensive characterisation of its vocal repertoire, while investigating the consistency of spawning sound features between populations. All sounds presented a similar acoustic structure in their basic unit (i.e. the pulse), while an important variability was found in the number of pulses; the meagre can emit sounds made of one single pulse or many pulses (up to more than 100). High level of overlap in the Principal Component Analysis made difficult to differentiate sound type clusters. Despite this, two sound types were identifiable: knocks (sounds from 1 to 3 pulses) and long grunts (sounds with more than 29 pulses). Discriminant Analysis carried out on PCA residuals showed that knock had the highest proportion of correct placement (92% of the observations correctly placed) followed by long grunts (80%). All other previously described sound types (intermediate grunt, short grunt and disturbance sounds) could not be separated and presented low levels of correct placement, suggesting that care should be taken when defining these as independent sound types. Finally, acoustic features consistency was found in meagre grunts emitted by different populations during spawning nights; statistical differences could be explained by recording settings and fish conditions. The results of this study provide important information for fostering PAM programs of wild meagre populations, while contributing to the discussion around the definition of fish sound types in vocal fish communities. Studies of this kind, which evaluate both variability and consistency of sound features, are of fundamental importance for maximising PAM efforts in the wild, at both the specific and the community level.
- Calling activity and calls' temporal features inform about fish reproductive condition and spawning in three cultured Sciaenidae speciesPublication . Bolgan, Marta; Crucianelli, A.; Mylonas, C.C.; Henry, S.; Falguière, J.C.; Parmentier, E.; Mollo, ErnestoAlthough many fish species are vocal, the use of fish sounds for aquaculture management and wild population protection has not received much attention. In this study, sound production of three members of the Sciaenidae family was monitored before and during spawning in aquaculture facilities. The species examined include the meagre Argyrosomus regius, the shi dum Umbrina cirrosa and red drum Sciaenops ocellatus. Red drum reproduces spontaneously in captivity, whereas shi drum and meagre often require hormonal stimulation using gonadotropin releasing hormone agonist (GnRHa) for the induction of oocyte maturation, ovulation and spawning. In all three species, a clear increase in calling activity was detected during spawning nights, when longer sounds with a higher number of faster repeated pulses were emitted. Changes of call temporal features could be related to histological changes in the sonic muscles. After GnRHa treatment and during spawning, meagre sonic fibres were wider and the ratio of sarcoplasmic reticulum to myofibril cross-sectional area was higher. The correlation of calling activity with spawning events opens up the possibility of using the monitoring of calling activity and of call temporal features as tools for evaluating the reproductive state of different sciaenid species, both in the wild and captivity.
- Detection of invasive fish species with passive acoustics: Discriminating between native and non-indigenous sciaenidsPublication . Amorim, Maria Clara P; Wanjala, Joan A.; Vieira, Manuel; Bolgan, Marta; Connaughton, Martin A.; Pereira, Beatriz P.; Fonseca, Paulo J.; Ribeiro, FilipeInvasive alien species have been rising exponentially in the last decades impacting biodiversity and ecosystem functioning. The soniferous weakfish, Cynoscion regalis, is a recent invasive sciaenid species in the Iberian Peninsula and was first reported in the Tagus estuary in 2015. There is concern about its possible impacts on native species, namely the confamiliar meagre, Argyrosomus regius, as there is overlap in their feeding regime, habitat use, and breeding behaviour. Here, we characterised the sciaenid-like sounds recently recorded in the Tagus estuary and showed that they are made by weakfish as they have similar numbers of pulses and pulse periods to the sounds made by captive breeding weakfish. We further demonstrate that breeding grunts from weakfish and the native sciaenid, recorded either in captivity or Tagus estuary, differ markedly in sound duration, number of pulses and pulse period in the two species, but overlap in their spectral features. Importantly, these differences are easily detected through visual and aural inspections of the recordings, making acoustic recognition easy even for the non-trained person. We propose that passive acoustic monitoring can be a cost-effective tool for in situ mapping of weakfish outside its natural distribution and an invaluable tool for early detection and to monitor its expansion.