Marta Picciulin

Effects of ambient and boat noise on hearing and communication in three fish species living in a marine protected area (Miramare, Italy)

The WWF-Natural Marine Reserve of Miramare (Trieste, Italy) is located in a major industrial and vacation area in the Adriatic Sea. Consequently, noise emanating from boating and shipping is an inevitable factor for local fishes. This study investigates the effects of ambient and ship noise on representatives of three vocal fish families with different hearing abilities. Ambient and ship noise were recorded, their sound pressure levels measured and played back in the lab. Auditory sensitivity was determined in Chromis chromis, Sciaena umbra and Gobius cruentatus, utilizing the auditory evoked potential recording technique. Compared to lab conditions, hearing thresholds determined during ambient noise playbacks were barely masked. Contrary, the noise emanating from a cabin-cruiser substantially reduced auditory sensitivity relative to thresholds in ambient noise. This masking effect was most pronounced in the frequency range where acoustic communication takes place. Boat noise potentially affects acoustic communication in fishes inhabiting the reserve.

Sound pressure and particle acceleration audiograms in three marine fish species from the Adriatic Sea

Fishes show great variability in hearing sensitivity, bandwidth, and the appropriate stimulus component for the inner ear (particle motion or pressure). Here, hearing sensitivities in three vocal marine species belonging to different families were described in terms of sound pressure and particle acceleration. In particular, hearing sensitivity to tone bursts of varying frequencies were measured in the red-mouthed goby Gobius cruentatus, the Mediterranean damselfish Chromis chromis, and the brown meagre Sciaena umbra using the non-invasive auditory evoked potential-recording technique. Hearing thresholds were measured in terms of sound pressure level and particle acceleration level in the three Cartesian directions using a newly developed miniature pressure-acceleration sensor. The brown meagre showed the broadest hearing range (up to 3000 Hz) and the best hearing sensitivity, both in terms of sound pressure and particle acceleration. The red-mouthed goby and the damselfish were less sensitive, with upper frequency limits of 700 and 600 Hz, respectively. The low auditory thresholds and the large hearing bandwidth of S. umbra indicate that sound pressure may play a role in S. umbras hearing, even though pronounced connections between the swim bladder and the inner ears are lacking.

Leisure boating noise as a trigger for the displacement of the bottlenose dolphins of the Cres–Lošinj archipelago (northern Adriatic Sea, Croatia)

The waters of the Cres-Lošinj archipelago are subject to intense boat traffic related to the high number of leisure boats frequenting this area during the summer tourist season. Boat noise dominates the acoustic environment of the local bottlenose dolphin (Tursiops truncatus) population. This study investigates the spatial and temporal change in the underwater noise levels due to intense boating, and its effect on the distribution of the bottlenose dolphins. In the period 2007-2009 sea ambient noise (SAN) was sampled across ten acoustic stations. During data collection the presence of leisure boats was recorded if they were within 2 km of the sampling station. Bottlenose dolphin spatial distribution was monitored in the same period. Results showed a strong positive correlation between high SAN levels and boat presence, particularly in the tourist season. Dolphin distribution indicated significant seasonal displacements from noisy areas characterized by the intense leisure boating.

How boat noise affects an ecologically crucial behaviour: the case of territoriality in Gobius cruentatus (Gobiidae)

Gobius cruentatus emit sounds during agonistic interactions. In order to evaluate the effect of boat noise exposure on G. cruentatus territorial behaviour, we played a field-recorded diesel engine boat noise during aggressive encounters between an intruder and a resident fish in a laboratory-controlled tank. We tested two factors: role (resident vs. intruder) and condition (noisy vs. silent); the test animals underwent all the treatments in a round-robin design. Agonistic behavior of the residents was modified by boat noise: during the playback residents were more submissive and won less encounters than in the control (silent) condition. We suggest that sound production is an effective tool for territorial defense, since the impairment of acoustic communication due to the recreational boat noise diminished the ability of the resident to maintain its territory.

Diagnostics of nocturnal calls of Sciaena umbra (L., fam. Sciaenidae) in a nearshore Mediterranean marine reserve

Calls emitted by the brown meagre Sciaena umbra (L., fam. Sciaenidae) were recorded at the Natural Marine Reserve of Miramare (Trieste, Italy) in seven nocturnal surveys (12-h continuous sampling) during the summer of 2009. Calls consist of pulses, with the main energy content below 2 kHz and mean peak frequency of c. 270 Hz. Pulses were short, with an average duration of 20 ms and a pulse period of 100 ms. Sounds lasted approximately 500 ms. Three types of sound patterns were recognized: irregular (I), regular (R) and the chorus (C). Their acoustic parameters are described showing that I, R and C differ in pulse duration, pulse peak frequency and pulse period. Occurrence of the three call types changes throughout the night: the R pattern occurred mainly at dawn and dusk, C predominated after nightfall, while I calls were produced sporadically during the whole nocturnal period. Our results indicate that S. umbra has a pronounced nocturnal rhythm in vocalizing behaviour and highlight how the diagnostic time–frequency pattern of S. umbra calls can be used to identify the species in the field. Considering that the abundance of S. umbra is currently declining, the information presented here will be relevant in developing non-invasive and low-cost monitoring acoustic systems for managing S. umbra conservation and fishery along the Mediterranean Sea.

PASSIVE HYDROPHONE CENSUS OF SCIAENA UMBRA (SCIAENIDAE) IN THE GULF OF TRIESTE (NORTHERN ADRIATIC SEA, ITALY)

Sciaena umbra belongs to Sciaenids, often called croakers because most of tropical Sciaenids produce sounds by compressing the swimbladder with sonic muscles (S0rensen 1984). S. umbra has been known to emit sounds since 1947, when Dijkgraaf observed and heard them in the Naples Aquarium. It is distributed along the coasts of Mediterranean Sea and Black Sea and along the Atlantic coast from Senegal to the English Channel. Since 1995, UNEP has included S. umbra in the annex 3 of RAC-SPA protocol, i.e. the list of the species of fish whose exploitation has to be regulated (AA. VV. 1995). In Miramare Marine Reserve, Trieste, where the species is very abundant from May to September, it has been monitored by visual census and acoustic recordings since 1999 (Bonacito 2000). Other sites along the coast of Trieste gulf were acoustically mapped to determine where the species can be found. This has enabled the real distribution of the species to be assessed.

LOCATING SPAWNING HADDOCK BY MEANS OF SOUND

The haddock Melanogrammus aeglefinus is an important food fish, which is widely distributed throughout the deeper shelf waters of the North Atlantic. Many haddock stocks are exploited close to their safe biological limits, requiring restrictions upon fishing. In some areas, low spawning stock biomass has prompted the closure of spawning grounds to fishing. However, the type of habitat where spawning occurs, and the factors which bring fish together to spawn are not well known. We used the distinctive characteristics of the sounds made by haddock to locate spawning concentrations in a Norwegian fjord.

Four type of sounds for one winner: vocalizations during territorial behavior in the red-mouthed goby Gobius cruentatus (Pisces Gobiidae)

During territorial encounters, the acoustic repertoire of Gobius cruentatus consists of four types of sound emissions: a tonal sound, a noisy tonal sound, a train of individual pulses, and a complex sound. The complex sound is made of two distinct elements, an initial tonal part followed by pulses. This is the largest acoustic repertoire described so far in gobiid fish during aggressive interaction. Sounds are emitted, mainly by the residents, when fish have already started the interaction but before the encounter is settled. Therefore, sounds seem to have a threatening function.

Monitoring the Miramare Marine Reserve: Assessment of protection efficiency

Abstract The Miramare Reserve, in the Gulf of Trieste (North Adriatic‐Italy), is a small marine protected area (121 hectares) for research, education and conservation and is managed by WWF Italy. Different techniques for taking a qualitative and quantitative census of the fish species, for mapping the nests of Gobius cruentatus, Tripterygion delaisi and Cbromis chromis, for studying the reproductive behaviour of C. cbromis and for measuring the sea ambient noise were used. Visual census techniques were applied in the comparison of two areas which were similar from a morphological point of view, but differed in human activity.

Changes in whistle structure of resident bottlenose dolphins in relation to underwater noise and boat traffic

The habitat of the resident bottlenose dolphins (Tursiops truncatus) of the Cres-Lošinj archipelago overlaps with routes of intense boat traffic. Within these waters, Sea Ambient Noise (SAN) was sampled across ten acoustic stations between 2007 and 2009. Data on boat presence was concurrently collected and when dolphins were sighted group behaviour was also recorded. Acoustic recordings were analysed for 1/3 octave bands. Samples containing dolphin whistles were analysed and compared with boat presence and SAN levels. Results indicate that dolphins whistle at higher frequencies in conditions of elevated low frequency noise. Conversely, they reduce maximum, delta and start frequencies and frequency modulations when noise levels increase significantly across higher frequencies. The study shows that high levels of SAN causes significant changes in the acoustic structure of dolphin whistles. Additionally, changes in whistle parameters, in the presence of boats, appear to be related to the behavioural state of the dolphin group.