Brown meagre vocalization rate increases during repetitive boat noise exposures: A possible case of vocal compensation

Abstract

This study investigated whether or not boat noise causes variations in brown meagre (Sciaena umbra) vocalizations recorded in a nearshore Mediterranean marine reserve. Six nocturnal experimental sessions were carried out from June to September 2009. In each of them, a recreational boat passed over vocalizing fish 6 times with 1 boat passage every 10 min. For this purpose three different boats were used in random order: an 8.5-m cabin-cruiser (CC), a 5-m fiberglass boat (FB), and a 7-m inflatable boat (INF). In situ continuous acoustic recordings were collected using a self-standing sonobuoy. Because boat noise levels largely exceeded both background noise and S. umbra vocalizations in the species' hearing frequency range, masking of acoustic communication was assumed. Although no immediate effect was observed during a single boat passage, the S. umbra mean pulse rate increased over multiple boat passages in the experimental condition but not in the control condition, excluding that the observed effect was due to a natural rise in fish vocalizations. The observed vocal enhancement may result either from an increased density of callers or from an increased number of pulses/sounds produced by already acoustically active individuals, as a form of vocal compensation. These two explanations are discussed.

The Importance of Ambient Sound Level to Characterise Anuran Habitat

“…In this context, the impact of anthropogenic noise on wildlife has drawn an increasing interest among bioacousticians in the past years, notably with studies on city noise pollution effects on birds [22–27], road noise effects on frogs [28,29] and marine noise effects on fishes and marine mammals [30–32]. Despite these studies, the effect of natural noise on the ecology and evolution of animal species is rarely investigated [33,34], and ambient noise level remains an underused variable in ecological studies [35–39].…”

Ecology of sound communication in fishes

“…This information, however, requires support from additional studies that include visual observations. A short‐term increase in calling activity was recorded when different boat types passed over vocalizing brown meagre in a nearshore Mediterranean marine reserve (Table ) (Picciulin et al., ). The fish's mean pulse rate increased after several boats passed in an experiment (Figure ).…”

“…Picciulin et al. () argued that this behavioural change may be a case of vocal compensation for impaired intraspecific communication.…”

“…To date, however, no effects on populations have been demonstrated in any study, in contrast to the damage done by overfishing (Jackson et al., ; Allan et al., ; http://www.greenpeace.org). A few contradictory observations are available regarding the effects of ship noise on calling behaviour (Correa et al., ; Luczkovich, Krahforst, & Sprague, ; Picciulin, Sebastianutto, Codarin, Calcagno, & Ferrero, ). The present review does not focus on anthropogenic noise as such, but on potential modifications of sound communication under varying noise conditions.…”

Anthropogenic noise is associated with changes in acoustic but not visual signals in red-winged blackbirds

“…The association between noise and rattle rate was more robust. Some studies have found different repetition rates of acoustic elements (e.g., songs, elements, pulses) associated with different noise levels: in birds (e.g., Slabbekoorn and Smith 2002;Slabbekoorn and den Boer-Visser 2006), fishes (Picciulin et al 2012), whales (Lesage et al 1999), and frogs (Kaiser and Hammers 2009). It remains to be investigated whether different rattle rates convey a detection advantage in noisy conditions.…”