Spatio-temporal distribution and acoustic characterization of haddock (Melanogrammus aeglefinus, Gadidae) calls in the Arctic fjord Kongsfjorden (Svalbard Islands).

In this study we analysed the acoustic properties and presence of haddock calls in the Arctic fjord Kongsfjorden (79° N-12° E, Svalbard Islands, Norway) in one year. Data were collected with three autonomous acoustic recorders located in the inner, middle, and outer parts of the fjord. The fjord is characterized by a gradient of oceanographic conditions from the inner to the outer part, reflecting changes from Arctic to Atlantic waters. Haddock sounds were more abundant in the outer fjord than in the middle fjord, whereas they were absent at the inner site. Mainly at the open-water site, the call abundance exhibited strong periodicity and a correlation with the cycles of neap tide (15 days) in August, with a clear diel cycle (24 h) in September and October. This result suggests that in this extreme environment with 24 h of light during summer, haddock regulate their acoustic activity according to the main available oscillating external physical driver, such as tide during the polar summer, while when the alternation of light/dark starts, they shift the periodicity of their calls to a diel cycle. Calls were recorded outside the spawning period (from July to October), and their characteristics indicated non-reproductive communicative contests. By using a detailed sound analysis based on previous laboratory studies for the first time, we suggest that the monitored population contains mainly juveniles (44% compared to 41% females and only approximately 15% mature males), showing the predominance of females in the middle fjord and juveniles at the open-water site.

Using passive acoustics to assess habitat selection by the brown meagre Sciaena umbra in a northern Adriatic Sea mussel farm.

Passive acoustic monitoring (PAM) of the brown meagre Sciaena umbra was conducted in a northern Adriatic Sea mussel farm. The level of acoustic activity was found to be constantly high from June to August before declining sharply in September and there was significantly higher acoustic activity in the structured habitats within the mussel farm than in the bare sandy bottom outside the farm. Results are discussed in the context of the use of this species as an indicator species of artificial rocky habitats along the Mediterranean coastal environments.

Behaviour of Arctic charr Salvelinus alpinus during an induced mating season in captivity: how male relative size influences male behavioural investment and female preference over time.

The behaviour of sexually mature Arctic charr Salvelinus alpinus specimens (fifth farm generation) was observed in captivity for four consecutive days. Only agonistic interactions between males of different size were facilitated on the first 2 days, while both agonistic and courtship interactions were possible from the third day up to the end of the experiment. The reliability of behavioural analysis was assessed in order to reduce the possibility of observer errors within the generated datasets. The behavioural investment of big males, small males and females was analysed using general linear models (two-way repeated measures ANOVAs with time and male size as factors). A peak in the agonistic interactions between males occurred during the first day of interactions, where the agonistic investment of big males was significantly higher than that of small males. This resulted in an increased investment in submissive behaviour by the small males, who consistently performed submissive behaviours from the second day of interactions up to the end of the trial. Big males were found to invest significantly more than small males in courtship behaviours for the duration of the trial. Even though females performed inter-sexual behaviours towards both big and small males for the entire observation period, female interaction rate towards big males was higher than towards small males. This study suggests that both male investment in mating behaviour and female preference might be related to male characteristics such as body length and that S. alpinus behavioural patterns and mate choice cues might be strongly context-related and characterized by high levels of behavioural plasticity (i.e. presence-absence of certain behavioural units or potential reversal of a mate choice cue) within the same species. Finally, in light of this, some conservation measures are discussed. In particular, effective management plans should take into account the high level of behavioural plasticity likely to be occurring in this species.

Sound production by the Shi drum Umbrina cirrosa and comparison with the brown meagre Sciaena umbra: a passive acoustic monitoring perspective.

Sounds produced by the Shi drum Umbrina cirrosa were short trains of pulses with an average pulse period of 180 ms, pulse duration of c. 40 ms and an average peak frequency of 400 Hz; average values of acoustical properties differed from those recorded from the brown meagre Sciaena umbra in previous studies. The present study provides a preliminary tool for discriminating between these two species while conducting passive acoustic monitoring. The potential effects of ontogeny on sound production in both species are discussed and recommendations are made for further research.

Seasonal patterns and individual differences in the calls of male haddock Melanogrammus aeglefinus.

Haddock Melanogrammus aeglefinus males observed in captivity proved to be vocally active throughout the whole year, although the highest levels of vocal activity were reached in the spawning season between February and April. During this season, the most common type of sound consisted of sequences of regularly repeated, almost identical, double-pulsed knocks (KN). These sequences were mostly associated with a particular behaviour pattern, the patrolling display, which has previously been shown to play a key role in territoriality and spawning. Differences in the double-pulsed KNs produced by three individual males were demonstrated by two different statistical methods and it is suggested that these differences may allow individual males to be discriminated by other fish, perhaps conveying fitness-related information on the sender. Some aspects of the calls changed seasonally, perhaps reflecting observed variations in the mass of the drumming muscles. When using passive listening to locate M. aeglefinus spawning grounds, the physical characteristics of the sounds may indicate how close the individual males are to spawning.