Marine Protected Areas (MPAs) are a popular management strategy aimed at protecting the diversity of ocean flora and fauna. Robust sampling of fish populations is important in understanding the effects of MPAs. We compared the sampling efficiencies of three commonly used methods of sampling fish assemblages (underwater visual census (UVC), baited remote underwater stereo-video systems (stereo-BRUVs), and diver operated underwater stereo-video (stereo-DOV)) and one emerging method (remotely operated vehicle with stereo-video system (stereo-ROV)). We assessed the assemblage composition, the number of species and individuals, and the statistical power of each method to detect hypothetical changes in the population.
Stereo-BRUVs sampled a distinctive assemblage compared to all transect-based methods, with more individuals and species observed and more predatory species. Stereo-DOV and stereo-ROV sampled similar assemblages and numbers of species. UVC sampled a distinctive assemblage compared to stereo-ROV and stereo-BRUVs. UVC sampled more species and individuals than stereo-ROV and a few unique small bodied and cryptic species. Some small bodied site attached species were sampled more effectively by transect-based methods. To effectively sample MPAs a combination of stereo-BRUVs and a transect-based method is needed. We recommend the use of stereo-ROVs because of their logistical, health and safety, and field efficiency advantages.