The Relationship between the Abundance of Mole Crabs and Sediment Grain Size in West Lombok Regency and Mataram City

Abstract

Indonesia is a maritime country with abundant marine biological resources, including benthic organisms inhabiting sandy coastal ecosystems. Mole crabs are benthic organisms that inhabit sandy beaches in the intertidal zone and are strongly influenced by substrate characteristics, particularly sediment grain size. This study aimed to determine the relationship between mole crab abundance and sediment grain size in the coastal areas of West Lombok Regency and Mataram City. The research was conducted in October 2025 at three observation stations using the line transect method with 1 × 1 m quadrats for mole crab sampling. Sediment samples were collected using a shovel and analyzed through sieve analysis to determine sediment grain size fractions, including fine sand, medium sand, coarse sand, and very coarse sand. Data were analyzed using correlation tests to evaluate the relationship between mole crab abundance and sediment grain size fractions. The results showed a total of 123 mole crab individuals consisting of two genera, namely Emerita and Hippa, with two identified species Emerita emeritus and Hippa adactyla. Correlation analysis revealed that the abundance of mole crabs had a negative correlation with the medium sand fraction (r = -0,48330) and with the mixed medium-to-coarse sand fraction (r = -0,44835). In contrast, the abundance of mole crabs showed a positive correlation with the very coarse sand fraction (r = 0,39587). These findings indicate that sediment grain size significantly influences the abundance and distribution of mole crabs in intertidal coastal ecosystems. This study provides important ecological information regarding habitat preferences of mole  crabs and contributes to the understanding, management, and conservation of sandy beach ecosystems in Indonesia.