Finding rockpool fishes: a quantitative comparison of non-invasive and invasive methods for assessing abundance, species richness and assemblage structure
Rocky intertidal shores are diverse ecosystems that have been extensively studied, yet there is a surprising lack of knowledge on the methods best suited to quantifying species abundance, diversity and assemblages. We compared visual census, unbaited remote underwater video (mini-RUV), baited remote underwater video (mini-BRUV) and draining/collection methods, with the goal of quantifying the effectiveness of non-invasive methods over more typical invasive methods for quantifying rockpool fish assemblages. In addition, we assessed the optimal set time of video deployment for mini-RUV and mini-BRUV. Fieldwork was undertaken from May–June 2016 using 20 rockpools at seven locations on the SE coast of NSW, Australia. Following standardisation of methods, visual census detected the lowest abundance of fishes whereas hand collection detected the highest out of any method. Increasing sampling time of mini-RUV and mini-BRUV from 10 to 25 min improved their effectiveness, with mini-BRUV detecting comparable abundances to invasive hand collection. The methods did not differ with respect to species richness however. Further, 25 min of mini-BRUV yielded greater detection of common species than hand collection. All together, these results suggest that mini-BRUV is the best method if the goal is to provide accurate estimates of overall abundance, richness and assemblages with minimal disturbance to rockpools, with a preferred set time of 25 min (and at least 15 min). The ability to conduct rapid and non-invasive species surveys of natural rockpool fish communities is an important conservation and management tool given that these habitats can be home to a variety of commercially important and rare species.
KeywordsRockpool Intertidal Fish Assemblage Abundance Bathygobius Mini-BRUV
We thank Pearl Ible, Daniel Colella, Daniel Swadling, Sarah Brady, Bridget Potts, Tom Horsley and Keira Leahey for assistance with fieldwork. We thank Andy Davis and David Ayre for comments on early manuscripts. This work was funded by the Centre for Sustainable Ecosystems Solutions in the School of Biological Sciences based at the University of Wollongong, NSW.
Compliance with ethical standards
All protocols complied with animal ethics regulations and approvals from the University of Wollongong, ethics approval number 14/05.
Conflict of interest
There are no conflicts of interest.
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