Seasonal Variation of Captive Meagre Acoustic Signalling: A Manual and Automatic Recognition Approach

Abstract

Many species rely on acoustic communication to fulfil several functions such as advertisement and mediation of social interactions (e.g., agonistic, mating). Therefore, fish calls can be an important source of information, e.g., to recognize reproductive periods or to assess fish welfare, and should be considered a potential non-intrusive tool in aquaculture management. Assessing fish acoustic activity, however, often requires long sound recordings. To analyse these long recordings automatic methods are invaluable tools to detect and extract the relevant biological information. Here we present a study to characterize meagre (Argyrosomus regius) acoustic activity during social contexts in captivity using an automatic pattern-recognition methodology based on the Hidden Markov Model. Calls produced by meagre during the breading season showed a richer repertoire than previously reported. Besides the dense choruses composed by grunts already known for this species, meagre emitted successive series of isolated pulses, audible as ‘knocks’. Grunts with a variable number of pulses were also registered. The overall acoustic activity was concurrent with the number of spawning events. A diel call rhythms exhibit peak of calling activity from 15:00 to midnight. In addition, grunt acoustic parameters varied significantly along the reproduction season. These results open the possibility to use the meagre vocal activity to predict breeding and approaching spawning periods in aquaculture management.

Vocal repertoire and consistency of call features in the meagre Argyrosomous regius (Asso, 1801)

“…To assess pulse period variability within each sound, pulse period was plotted against pulse succession. Mean and standard deviation were calculated for all acoustic features by categorising sounds on the basis of their number of pulses, following the classification proposed by [ 41 ]. In particular, knocks were sounds made of 1 to 3 pulses, short grunts were sounds ranging from 4 to 6 pulses, intermediate grunts were sounds made of 7 to 29 pulses and long grunts were sounds with more than 30 pulses.…”

“…croakers and drummers, clearly points to their vocal abilities, which have been known and exploited for centuries [33][34][35][36][37][38]. Several studies have monitored sciaenids and their spawning aggregations in the wild by using PAM [16][17][19][20][21][22]32,[39][40][41]. Despite this, sound production in this family has been documented in only about 8% of the extant species; furthermore, lack of consistency can be found in sound types definition and nomenclature, as well as in the type of features used for characterising sounds.…”

“…The meagre (Argyrosomus regius, Asso 1801) is an interesting case because recent studies [41][42][43] suggest a wider vocal repertoire than previously described [37]. This species is widely distributed along the Atlantic coast of Europe and of Africa, as well as in the Mediterranean Sea [44] and has a significant commercial value for recreational and small-scale commercial fisheries, as well as aquaculture [45]; this implies that knowledge about meagre sound feature variability and consistency is imperative for populations monitoring over wide geographical and temporal scales.…”

Peer Review #1 of "Sound production in the Meagre, Argyrosomus regius (Asso, 1801): intraspecific variability associated with size, sex and context (v0.1)"

“…355 Additionally, sounds produced by both adults and juveniles showed significant differences 356 between disturbance and voluntary contexts, with disturbance sounds being of shorter duration, 357 including fewer pulses, and having a shorter pulse period and a lower peak frequency than 358 voluntary sounds. Though grunts with less than 5 pulses are produced by this species in voluntary 359 contexts (Vieira et al, 2019), in this study, these short sounds were not registered, likely because 360 the sounds produced were connected with breeding in which sounds tend to be of long duration, 361 or due to the short sampling effort. Finally, advertisement sounds recorded in Tagus estuary were 362 similar to the ones registered in captivity although they differed in the pulse period, possibly 363 associated with disparities in the environment and fish, such as the existence of higher temperature 364 fluctuations in the field (Ladich, 2018) and different sizes or group composition of the sound 365 emitters.…”

“…The analysed juvenile sounds 228 were produced in May 15 around 14h while the sounds analysed for adults were produced in July 229 7 between 18h and 23h. In the case of adults, the chosen time window corresponds to the diel vocal 230 activity period exhibited by this species (Vieira et al, 2019). The selected sampling day was the 231 one in which water temperature was the most similar to disturbance recordings.…”