Abstract
Monitoring programs that aim to measure the diversity, abundance and biomass of fishes depend on accurate and reliable biological data to guide the development of robust management plans. It is important to implement an appropriate sampling technique that provides a comprehensive assessment, while reducing associated biases in the data collection process. We compared the sampling abilities of four different underwater stereo-video techniques; baited remote underwater stereo-video systems (BRUV), diver operated stereo-video (DOV), and two relatively new methodologies; slow towed stereo-video (STV) and remotely operated vehicle (ROV) fitted with a stereo-video. Comparisons were conducted in a temperate reef system along a single limestone ridge within Geographe Bay, Western Australia. More fish species and individuals were sampled by BRUVs, while transect based methods (DOV, STV, and ROV) were comparable. Combining BRUVs with a transect method resulted in a ~10% increase in observed diversity. BRUVs had a higher statistical power to detect change in comparison to the transect methods. This was due to the higher variability observed in transect methods that may sample greater habitat heterogeneity within a sample unit compared to BRUVs. Although differences did exist, data collected with the ROV was generally comparable to the other transect methods. We believe further research into ROV use is warranted as they provide a safer alternative to diver-based techniques and have the ability to extend into deeper-waters. We recommend that for fish diversity and abundance assessments a sampling strategy that combines BRUVs and a transect method should be adopted.