Baited remote underwater video sample less site attached fish species along a subsea pipeline compared to a remotely operated vehicle.

Context: Remotely operated vehicles (ROVs) are routinely used to inspect oil and gas infrastructure for industry's operational purposes and scientists utilise this video footage to understand how fish interact with these structures. Aim: This study aims to clarify how fish abundance data obtained from ROV video compares to that collected using baited remote underwater video (BRUV). Method: This study compares fish assemblages observed using an industry ROV and BRUVs along a pipeline located in 130-m water depth in north-west Australia. Key results: Both methods recorded 22 species of fish, however each method observed 15 unique species. The fish assemblage recorded by each method was statistically different at all sites. Differences in the fish assemblages correlated with the caudal fin aspect ratio of each species: the mean caudal fin aspect ratio of fish recorded using BRUVs was 2.81, compared to 1.87 for ROV observations. Conclusions: We interpret this to indicate differences in site attachment, with site-attached species having generally lower caudal fin aspect ratios that are associated with slower swimming speeds with a burst and glide pattern. Implications: Our results show that these remote video methods predominantly sample different fish assemblages and demonstrates how different sampling methods can provide different insights into fish interactions with subsea infrastructure. Understanding the ecosystem around subsea oil and gas infrastructure is imperative to decommissioning. Our study found differences in fish assemblage data derived from industry remotely operated vehicle (ROV) video and baited remote underwater video (BRUV) collected along a subsea pipeline. Both methods sampled the same number of species, but ROV sampled more site attached species compared to BRUV. [ABSTRACT FROM AUTHOR]