The rhythmic behavior of marine species generates uncertainties in population and biodiversity assessments if the frequency of sampling is too low and irregular over time. Few attempts have been made to link community changes to the rhythmic behavior of individuals within populations. Cabled video observatories can be used to explore community changes over different temporal windows as a result of the activity rhythms of individuals within populations. In this study, we used, for the first time, a coastal cabled observatory (OBSEA) to video monitor activity rhythms of different fish species within an artificial reef area at a high frequency. During 1 mo, 30 min daily count patterns were continuously measured and compared with the corresponding solar irradiance. A significant (p < 0.05) day-night patterning was observed in the majority of recognized taxa by Chi-Square periodogram analysis. Three types of rhythms were identified in waveform plotting: (1) diurnal (Chromis chromis, Coris julis, Diplodus annularis, D. cervinus, D. sargus, D. vulgaris, Serranus cabrilla, Dentex dentex, Symphodus sp.); (2) nocturnal (Atherina sp. and Scorpaena sp.); and (3) crepuscular (Apogon imberbis, Oblada melanura, and Spicara maena). Diurnal species clustered around maximum averaged irradiance (computed from a cosinor analysis). The results were discussed evaluating whether visual count time series represent a reliable proxy for the swimming activity rhythms of individuals and whether the complex habitat use of coastal fishes would require the use of spatial networks of cameras.
KEY WORDS:OBSEA · Cabled video observatories · Swimming rhythms · Western Mediterranean · Coastal areas · Temperate fishes · Irradiance · Daily activity
Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 486: [223][224][225][226][227][228][229][230][231][232][233][234][235][236] 2013 seasons in coastal areas (Condal et al. 2012). The consideration of these aspects of activity and perceived community structure is critical in monitoring the effectiveness of marine protected areas, in improving survey designs for fisheries assessment, and in evaluating habitat use (Willis et al. 2000). To date, few attempts have been made to link temporal changes in communities to the behavioral rhythms of individuals within populations (Aguzzi et al. 2011a). Fish swimming/resting activity rhythms have traditionally been studied through laboratory experiments (re viewed by Reebs 2002, López-Olmeda & Sánchez-Vázquez 2010. Over the past few decades, however, the activity rhythms of a variety of species have also been the focus of increased study in the field based on a variety of sampling techniques subject to technical constraints on the repetition and duration of sampling. These techniques include the use of beach seines (Harmelin-Vivien & Francour 1992, Letourneur et al. 2001, Dul