Temporal and spatial variation in adult and juvenile mobile fauna associated with natural and artificial coastal habitats

Abstract

Coastal habitats are important for commercially exploited and protected species of fish and larger mobile invertebrates. The addition of artificial structures within the marine environment has the potential to alter the connectivity between habitats and to affect metapopulations of a region. Baited remote underwater videos (BRUV) were used to investigate the spatial and seasonal variation in abundance of adult and juvenile mobile species associated with subtidal natural and artificial habitats within Poole Bay on the south coast of England in 2019. Metrics included the relative maximum abundance (MaxN), number of species seen (S), assemblage structure and size range of fish. Higher values of MaxN and S were recorded on artificial structures in the spring and early summer; however, this pattern was reversed by mid-summer and early autumn when more fish were recorded on the natural reefs. Yet overall differences in MaxN and S between habitats were not significant. Differences in assemblage composition between habitats varied monthly, but this was mostly driven by particular sites. Although most fish observed were juveniles, there were some seasonal differences in the size of fish using natural and artificial sites, especially bib (Trisopterus luscus), black bream (Spondyliosoma cantharus), bass (Dicentrarchus labrax) and pollack (Pollachius pollachius). The artificial habitats in this region appeared to be important in certain months, so temporal studies of this type need to be incorporated within surveys, particularly those in proximity to protected areas.