Growth analysis and population size estimation of coconut crabs based on a large recapture dataset

Abstract

Growth analysis and population size estimation of the northernmost population of coconut crabs inhabiting Ocean Expo Park, Okinawa, southern Japan, was performed using the fishmethods package on R software. In this study, we used more than 500 datasets obtained from the mark-recapture surveys conducted during 2006–2019. We also obtained 126 datasets from our previous study, which was performed using the same field protocol and manual data calculation. The generated data of growth parameters in the GROTAG model were similar to those of a previous study that calculated parameters manually using smaller datasets, and the results obtained were more accurate. To our knowledge, this is the first time that mark-recapture data were used for estimating the population size of coconut crab. The results showed that 1045 individuals (93.3/ha) inhabited the park. This indicates that despite certain environmental disadvantages in the northernmost area, the population density of coconut crabs in this region is not low compare to that at other locations.