Résumé
The objectives of this paper are (1) to present VideoSolo, a new autonomous video system; and (2) to show its relevance through the analysis of temporal variability of fish populations at different temporal scales of years, days and hours. The underwater video system VideoSolo, designed for use in remote places, combines advantages in comparison to older systems necessitating the presence of a ship and whose autonomy is generally limited in time due to biofouling. All these issues have been resolved in VideoSolo, a fully autonomous long-term system, programmable, easy to set up and deploy (the housing weighs only 3 kg). It has sufficient energy storage and an anti-biofouling system in the form of its hydro-wiper, enabling continuous operation for up to one month. The experiment was conducted in a remote place (Glorioso Island, SW Indian Ocean) where the system was installed in front of the same coral colony (1 m(2)) at a depth of 8 m. Data was recorded in May for two subsequent years and six times per day (between 6 am and 4 pm). The analysis of the video sequences enabled the recording of 6224 individuals of 75 species belonging to 16 families over 41 days of experiment. At a small spatial scale, fish assemblages were variable over time at the three temporal scales studied. The number of individuals and species observed was variable between years whilst the number of individuals observed per day remained relatively stable through time. When occurrences were considered, less variation was observed between years. Analyses of temporal fish variability on the most abundant families revealed that the abundances of Acanthuridae, Labridae, Scaridae and resident Pomacentridae were significantly different between years and inversely so for the non-resident Pomacentridae. When the diurnal variations of fish assemblages were considered, the abundances differed significantly over time for Acanthuridae, higher in the morning (6 am and 9 am), and for Scaridae, higher at sunrise (6 am) and sunset (4 pm). The abundances of Pomacentridae and Labridae were stable from sunrise to sunset. The variability between years could be linked to events such as recruitment whilst daily variations could be more related to the effects of tidal cycles whose effects may have created periodic feeding opportunities. VideoSolo has demonstrated its efficiency and has remarkable potential in the field of aquatic biology in any location, as no human presence is required for it to work. (C) 2012 Elsevier B.V. All rights reserved.