Artificial reefs create distinct fish assemblages

We conducted a before-after-control-impact (BACI) experiment to evaluate the effects of deploying small-scale artificial patch reefs on fish assemblages in a temperate bay (Port Phillip Bay) in south-eastern Australia. Three replicate artificial reef treatments were placed on sandy substratum and the response of the fish assemblage was compared with 3 control sites with no reef, and 3 nearby natural reef comparison sites. All habitats were sampled using baited remote underwater video (BRUV) and underwater visual census (UVC) multiple times, 6 mo before and 22 mo after artificial reef deployment. Fish species rapidly colonised artificial reefs, with 30 new species detected in the first year post deployment and only 4 in the following year. Both sampling methods captured a shift in assemblage structure, albeit with different species compositions, as individual species numbers varied dependent upon method used. BRUV provided better estimates of the important recreational species snapper Chrysophrys auratus (family Sparidae), with more snapper recorded on artificial and natural reefs compared to sediment. The artificial reef assemblages were dominated by species that favour the reef/sediment interface. Several reef-associated species were detected in the juvenile stages; however, adults of obligate reef species were not observed on artificial reefs. Sediment-associated species present before artificial reef deployment persisted within the artificial patch reef area over the course of the study. Overall, the deployment of patchwork artificial reefs increased local species diversity and abundance of fish, and did not impact existing sediment fish assemblages.