Rapid baseline assessment of crab abundance and species richness in mangroves using a video recording method

Abstract

Crabs are among the most dominant macrofauna in mangrove ecosystems. Crabs play vital roles in maintaining the ecological functions of mangroves. However, there are limitations in assessing crab populations accurately. In previous studies crabs are caught or visually observed by researchers to obtain data on crab abundance and diversity. However, difficulties and biases arise due to complications in sighting crabs accurately and minimizing damage caused by intrusive methods used when attempts are made to capture crabs in situ. Therefore, more accurate observations, and less intrusive method should be implemented to identify crab populations. Two less destructive methods to investigate crab abundance were used in this study and compared to ascertain the efficiency of obtaining mangrove crab population data. Findings show that video recording method was more accurate compared with hand catch method in providing crab abundance data as hand catch method resulted in the under-sampling of crab abundance. This video recording method may be used: (1) to identify the abundance of crabs in a quadrat, (2) to provide crab population data as the quadrat is replicated in multiple sampling sites, and (3) to observe crab behaviour.