Environmental influences on fish assemblages in Port Phillip Bay using stereo baited remote underwater video systems (sBRUVS)

Fish assemblages are under increasing pressure from human alterations to marine environments causing major shifts in community structure. Biodiversity assessments are needed to understand changing fish communities throughout different marine areas. Fish are important part of marine systems providing ecosystem services vital in maintaining the balance in systems. We quantified fish assemblages in Port Phillip Bay using stereo baited remote underwater video systems (sBRUVS) across 127 sites. sBRUVS were also used to collect information on biogenic habitat and reef complexity, while hobo loggers affixed to the sBRUVS, and a hydrodynamic model was used to characterise variations in the water column. We applied a DISTLM modelling approach to assess which variables were driving variations across assemblages. We observed 5679 individuals from 93 species throughout all deployments. This study found habitat and depth variables to significantly influence fish assemblages across Port Phillip Bay. We found soft sediment habitats significantly differed to both infralittoral and circalittoral reef habitats. In particular, we found canopy forming macroalgae and relief explained the greatest variation in fish assemblages. Our results highlight the importance of habitat and depth as variables in influencing temperate fish assemblages. These findings further indicate the importance of canopy forming macroalgae in influencing abundance and species richness. This work is important by providing baseline knowledge that can be used in future biodiversity assessments and is the largest bay wide biodiversity assessment using sBRUVS in Port Phillip Bay.