Assessing the effectiveness of marine management is increasingly important to evaluate whether management goals are met. Baited Remote Underwater stereo-Video (stereo-BRUV) systems are one of many methods used to monitor marine communities and habitats, yet little is known about how spatial sampling design affects conclusions drawn about Marine Protected Area (MPAs) and No-Take Zones (NTZs).
In this study, we first compare the fish assemblage observed from two spatial sampling designs in two sites of southwestern Australia (Waatern Wagyl/Geographe Bay and Waatu Wagyl/Capes Region) to understand the effects of sampling design choice on the detection of assemblage-level NTZ effects. We then simulate 18 scenarios (six spatial sampling designs, three modelled species distributions, two sites) 1000 times each, to understand the influence of spatial sampling design choice on the detection of changes in species abundance in NTZs.
The two sampling designs observed significantly different assemblages, and the effect of NTZs on assemblage was consistent between the two. The performance of simulated spatial sampling designs (mean bias, RMSE, interval coverage, effect size and significance) differed across species and sites, with stratified spatially balanced sampling performing best and most consistently overall. Preferential designs performed well in Waatern Wagyl/Geographe Bay, while clustered and random spatially balanced sampling designs performed the poorest across all species and sites.
We recommend the use of stratified spatially balanced sampling designs in MPA assessments, as they present advantages in performance at a local scale, as well as interoperability and reusability of data across regions and research questions.