The MacKinnon Lists Technique: An efficient new method for rapidly assessing biodiversity and species abundance ranks in the marine environment

variation in fish assemblage composition more reliably, a key aim of many rapid assessment surveys and for conservation monitoring. It is worth also noting that because it collects multiple samples per video the MLT technique may sample solitary fish species to a greater extent than MaxN, which only focuses on the max- imum group size seen per video. This would make MLT a useful tool for assessing changes in relative abundance of solitary and numerically less common species, which would be consis- tent with data generated from terrestrial surveys [37]. In contrast, it is likely that the focus on maximum group size will mean the MaxN technique will more readily detect changes in rela- tive abundance of fish species that frequently move in large groups. For this reason, we suggest that, where sufficient funds are available, an effective approach to marine biodiversity assess- ments might be to use both the MLT and MaxN methods together to analyse videos, diver or other surveys and report the results of both so that the strengths of each complement each other and make the most of the data available. An important aspect of the MLT is that as a sampling with replacement methodology, it does not require all redetections of the same fish to be eliminated from the analysis. Most methods of assessing biodiversity patterns can be used with sampling with replacement meth- odologies that are not invalidated if some individuals are redetected. Here, we used a set of rules to reduce redetections (i.e. a species had to have been out of the field of view for > three

minutes before the same species was added to a new list). Although a useful time-saving step during processing of the videos this is not essential to the method. As with all methods, MLT has some limitations. As such, it should be taken in consider- ation that MLT tends to weight regularly spaced territorial species as more abundant than schooling species, which can affect the calculation of diversity indices and may result in the distribution of relative abundances to appear more even than using other methods such as MaxN (which is likely to estimate solitary species and species abundance and makes it chal- lenging to quantify sampling area in particular when bait is used). Moreover, Pourson (1997) noted that while MLT is a useful tool to determine sampling effort and species richness, differ- ences in species detectability mean that relative abundances can only be compared within spe- cies across habitats or sites. The importance of considering similar habitats when making comparisons has been noted by others previously [16,35,36]. There are currently a number of useful methods available to monitor and compare fish assemblage composition, including MaxN. The results of our study suggest that MLT is also likely to be a useful technique for the assessment of fish assemblages, enabling rapid assess- ment of spatial and temporal variation in species relative abundance, and one that may com- plement existing methods. The MLT method is a promising tool to collect biodiversity survey data or analyse video footage in aquatic environments where there is a limited budget, staff

time, available technology and conditions might be too challenging to maintain some other types of standardized sampling approach. In particular, we suggest MLT could be considered for difficult to standardize conditions such as transects in coral reef and other marine applica- tions such as diver and un-baited video or camera surveys. In this study, as well as providing the first test of the MLT for marine sampling, we also car- ried out the most comprehensive comparison to date between MLT and an existing biodiver- sity sampling methodology. By showing that species richness estimates, diversity indices, relative abundance and assemblage composition results were all consistent across methods our results are likely to be useful not just in the marine context but also for biodiversity surveys in general. We therefore suggest that the MLT methodology is likely to be effective not just for coral reef fish, for bird communities and amphibian communities (49), but also in other spe- cies-rich communities where biodiversity needs to be sampled cheaply, quickly and efficiently for conservation monitoring or other purposes. PLOS ONE A new method for monitoring marine biodiversity PLOS ONE | https://doi.org/10.1371/journal.pone.0231820 April 22, 2020 12 / 15