Temporal partitioning of diurnal behavioural patterns of Coris julis and Diplodus vulgaris (Actinopterygii: Perciformes) in Mediterranean coralligenous habitats

Abstract

Background. There is need for more information on behavioural rhythms of fi shes in relation to their habitat use in few or not previously monitored areas, such as coralligenous habitats. Some studies have compiled inventories of observable fi sh species in this habitat, but no studies have been performed on the temporal patterning of fi sh behaviour, especially at the scale of the day. The presently reported study aims at providing knowledge on fi nescale fl uctuations of abundances and behaviour of two fi sh species in coralligenous habitats throughout the diurnal period. Materials and methods. Fish fauna was fi lmed hourly, for several days, from dusk to dawn, with autonomous, programmable, and rotating video systems. Diurnal variations in abundances per count, considering size classes and behaviour, were studied for two diurnal fi sh species-the Mediterranean rainbow wrasse, Coris julis (Linnaeus, 1758) (Labridae), and the common two-banded seabream, Diplodus vulgaris (Geoffroy Saint-Hilaire, 1817) (Sparidae) in two study areas of coralligenous habitats on the French Riviera.Results. Signifi cant temporal variability at the scale of the hour was revealed for abundances of C. julis in one of the two study areas, with few individuals in crepuscular periods and highest abundances in the morning and in the afternoon. These differences were mainly due to signifi cant diurnal variations in abundances of small and medium C. julis, which were low in crepuscular periods, whereas large-sized individuals were equally abundant during the day. On the other hand, no discernible diurnal rhythmicity of mean abundances of D. vulgaris was observed, regardless of the study area. Crepuscular periods were associated with sudden changes of abundances and behaviour for both species, with a greater percentage of mobile and solitary individuals, and few feeding individuals compared to the rest of the day. Feeding occurred mainly in the morning for C. julis. In contrast, no dial-time preference for feeding was revealed for D. vulgaris. Conclusions. The study provided preliminary insights into fi ne-scale diurnal variations of abundances of different life stages and of fi sh behaviour. Variability in abundances of life stages and of fi sh behaviours at different times of day should be taken into account for population assessments and spatial comparisons. Moreover, our study confi rmed the use of video-imaging as an effi cient non-destructive tool for the study of fi sh fauna in structurally complex, highly valuable habitats.

Fish distribution and behaviour with regard to the time of day and the anthropogenic structural modification of the shallow littoral

“…This is especially important considering that the actual abundance of fish does not change with time but rather their distribution over the littoral zone and its microhabitats/the areas sampled resulting in the abundance fluctuations recorded. The various species of the families Sparidae and Labridae generally feed during the day, whereas at night‐time they show low mobility (de Pirro et al ., 1999; Witkowski et al ., 2016), in agreement with the findings concerning the behaviour of D. vulgaris , D. puntazzo and C. julis in the current study. Furthermore, the diel variation in fish distribution and community composition may be relevant to competition for food and habitat as well as predation avoidance (Kronfeld‐Schor & Danyan, 2003).…”

“…At noon, feeding and sauntering are higher, whereas in the afternoon more individuals are found cruising. Other works have documented increased feeding behaviour in the morning and a decrease in the afternoon (de Pirro et al ., 1999; Sala et al ., 2007; Witkowski et al ., 2016). Despite the behavioural differences documented here, no abundance trend was found with time of day in this species, confirming the findings of Dulčić et al .…”

“…This high dynamism is also evident in fish populations demonstrating diel fluctuations in their distribution in the littoral (Aguzzi et al ., 2013; Azzurro et al ., 2007; Guidetti, 2000). Specific taxa, like the families Sparidae and Labridae – that dominate the shallow littoral (Garcia‐Rubies & Macpherson, 1995; Planes et al ., 1999) – show both abundance fluctuations and a behaviour affected by the diel cycle (de Pirro et al ., 1999; Dulčić et al ., 2004; Witkowski et al ., 2016).…”

Diel Variability in the Bottom-Trawl Catch Rates of Sparid Fishes in İzmir Bay (Central-Eastern Aegean Sea)

“…In the present study, average catch rates of D. annularis during the night were slightly higher than in daylight and twilight, respectively. These results could be related to the variation in feeding sheltering behaviours and predator avoidance of individuals of different sizes (Azzuro et al, 2007).On the other hand, Witkowski et al 2016 pointed out that the diel activity rhythm of D.vulgaris is still under discussion. According to their visual observations by the video monitoring system, there is no discernible rhythmicity of the abundances of D. vulgaris due to highly variable detections.…”

“…Few studies in the Mediterranean Sea have considered the relationships between fish abundance/catch rate and light intensity (Cartes et al, 1993;Pipitone et al, 1997;Relini et al, 1997;Dulcic et al, 2004;Carpentieri et al, 2005;Witkowski et al 2016). These studies, furthermore, have focused their attention on a few commercial species (i.e., M. merluccius or Aristeus antennatus) or the structure and composition of nektobenthic assemblages.…”