Issues to consider when sampling the sandhopper Atlantorchestoidea brasiliensis (Dana, 1853) for impact assessments on sandy beaches

Pitfalls can trap mobile fauna during their peak surface activity, whereas sediment corer efficiently capture individuals buried in the substrate. Corer sampling is the most used method to capture the sandhopper Atlantorchestoidea brasiliensis, because of the assumption that bias related to surface activity during daylight can be controlled by a careful sampling. The objective of the present study was to evaluate the efficiency of pitfalls to sample the sandhopper A. brasiliensis on sandy beaches with distinct impact levels. We compared our results with a previous impact assessment on the same beach arc that used corer sampling. The sandhopper abundance was more than 10 times higher in the pitfalls compared to the corer samples, suggesting prevalent activity on the sediment surface during daylight and possible bias when using corer sampling to estimate population size. The conclusion of the previous impact assessment, however, was not strongly affected by sampling tools, because seasonal trampling seems to be negative for the number of buried and surface-active individuals. Our results showed that the choice of sampling tool is an important issue to be considered when using sandhoppers as indicator species on sandy beaches.