Population study of the mangrove horseshoe crab Carcinoscorpius rotundicauda (Lattreille 1802) in Kuala Tungkal, Tanjung Jabung Barat, Jambi, Indonesia

Population and morphological data of the mangrove horseshoe crab Carcinoscorpius rotundicauda was collected off the coast of Kuala Tungkal, Tanjung Jabung Barat, Jambi, Indonesia from November 2011 to January 2012. The study site was divided into two areas: Station I (Parit 10) and Station II (Boyar), where the water was 4–8 m and 15–25 m deep, respectively. Four belt transects (5 m × 1000 m), 100 m apart, were set parallel with the shoreline in each area. Shrimp nets (5 m × 20 m), towed along the seabed by a fishing boat were used to capture crabs. The crabs were enumerated and measurements were taken of their carapace size and body weight. Abiotic factors were also measured, including water temperature, salinity, depth, and visibility. The population density of the crabs was 0.62 ± 0.23 individuals/100 m², and their distribution pattern was random. We found correlations between depth, visibility, and crab density only at Station I.