Patterns of fish occupancy of artificial habitats in the eastern Mediterranean shallow littoral

Coastal ecosystems act as spawning grounds, settlement areas or nurseries for a diversity of fish species. Today, these ecosystems are under various anthropogenic stressors. One of these disturbances is the structural modification of the shallow littoral by coastal infrastructure such as ports, piers, marinas and roads. Here, we investigate whether there are differences between modified (artificial) and non-modified (natural) habitats in central Greece in terms of the fish assemblage structure, species diversity and richness, fish abundance and the proportion of juveniles. We carried out underwater visual census from September 2020 to August 2021 across two habitats (natural and artificial) in three locations of central Greece. The fish community and Shannon diversity index did not vary across habitat type; however, both species richness and total abundance were significantly higher in artificial habitats. The abundance of five (out of ten examined in total) taxa was significantly affected by habitat type. Higher abundance in the artificial habitat in the warmer or more productive months was found, possibly relevant to food availability. The significance of habitat interactions with location and the temporal component in community composition and species abundance models indicated intense heterogeneity in species-specific occupancy and may be linked to the type and characteristics of artificial habitats. Modeling of the percentage of small-sized individuals indicated patterns of juvenile occupancy requiring further investigation about the potential role of artificial habitats for some species. Future research should examine the impact of specific artificial habitat types on population dynamics and investigate the implications of artificial habitat construction for conserving fish diversity and maintaining coastal ecosystem functioning.