The seasonal timing of recurring biological processes is essential for organisms living in temperate regions. While ample knowledge of these processes exists for terrestrial environments, seasonal timing in the marine environment is relatively understudied. Here, we characterized the annual rhythm of habitat use in six fsh species belonging to the Sparidae family, highlighting the main environmental variables that correlate to such rhythms. The study was conducted at a coastal artifcial reef through a cabled observatory system, which allowed gathering underwater time-lapse images every 30minutes consecutively over 3 years. Rhythms of fsh counts had a signifcant annual periodicity in four out of the six studied species. Species-specifc temporal patterns were found, demonstrating a clear annual temporal niche partitioning within the studied family. Temperature was the most important environmental variable correlated with fsh counts in the proximity of the artifcial reef, while daily photoperiod and salinity were not important. In a scenario of human-induced rapid environmental change, tracking phenological shifts may provide key indications about the efects of climate change at both species and ecosystem level. Our study reinforces the efcacy of underwater cabled videoobservatories as a reliable tool for long-term monitoring of phenological events.

Peer Reviewed