A method for sampling biodiversity

Posted on July 20, 2015

Which field sampling methods give the most accurate picture of aquatic biodiversity? Working out an effective sampling design for biodiversity can be a lot more complicated than deciding how to target single species. This is because the usefulness of a given style of net, trap or other sampling device depends on the behaviour and body size of the various species concerned, the habitats in which the gear is used, and the extent to which each type of gear is deployed. Therefore, biodiversity studies should ideally include an initial period when the sampling design is developed. A protocol for doing this has been proposed by researchers at the University of Massachusetts. Using stream fish sampling as an example, they outline a five-step process. First, the specific aims of the study are clarified. Second, relevant literature is surveyed to decide which types of sampling gear might be suitable for the system concerned. Third, gear types that can’t be used at all study sites are eliminated. Fourth, an experiment with a replicated, randomised block design is set up in a typical stream reach to identify which types and amounts of sampling gear adequately measure fish diversity. The best combination of gear is then found by comparing the catch composition of a given gear type with that for all the gear types combined. The amount of gear to be used is determined by the point where a species accumulation curve (i.e., a plot of the total number of species caught by increasing units of gear) levels off. And fifth, resampling simulations are used to work out the best trade-off between sampling effectiveness and time investment. The authors illustrate their approach with data from a fishing experiment using three types of gear (minnow traps, hoop nets and electrofishing) and three levels of effort.

Reference: Smith, J.M. et al. 2014. Fish biodiversity sampling in stream ecosystems: a process for evaluating the appropriate types and amount of gear. Aquatic Conservation: Marine and Freshwater Ecosystems 24, 338–350. http://onlinelibrary.wiley.com/doi/10.1002/aqc.2420/epdf