Abstract :
[en] In the Mediterranean Sea, the fish Sarpa salpa (Sparidae) is the only vertebrate grazer of Posidonia oceanica meadows. In order to gain knowledge about the behaviour of S. salpa and a better understanding of the meadow's primary production recycling, an original study was designed using ultrasonic telemetry to investigate activity patterns and space utilisation in the field. During June-September 2000, we compared diel movements of, six adult S. salpa (249-317 nim FL and 313-633 g) in the Bay of Calvi. These fish were tagged by intraperitoneal insertion of ultrasonic transmitters. Their positions were recorded with a directional hydrophone from a small boat with an accuracy between 10 and 50 m, depending on the local environment. The tracking duration ranged from 3 to 22 days (average 11.8 +/- 7.3). Locations were performed from at least dawn to dusk or early night, and one fish was tracked during the entire 24-h cycle. Fish were more mobile during the twilight periods, but statistical analysis indicated individual differences for the precise period of mobility. Two major behavioural patterns were observed: first, the fish remained in close vicinity of the harbour during the day and moved away to the north or the south at dusk to access nocturnal sites, occupying a home range of about 4.3 ha. The second behavioural pattern involved persistent occupation of the same sites during day and night within a relatively restricted home range (about 0.8 ha). Great variation in mobility was found and the same individual fish could show both kinds of behaviour. (C) 2002 Ifremer/CNRS/Inra/IRD/Cemagref/Editions scientifiques et medicales Elsevier SAS. All rights reserved.
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