Documenting juveniles’ presence is a crucial criterion for ensuring that a protected area can support robust populations of horseshoe crabs. Yet, there are no studies on the juvenile of Asian horseshoe crab in Indonesia. As the first report on the juvenile of Asian horseshoe crabs in Indonesia, this study aims to analyze the population density of the juvenile Asian horseshoe crab and the characteristics of nursery habitats in Teritip Beach, East Kalimantan, Indonesia. The discovery of the juvenile of three species (Carcinoscorpious rotundicauda, Tachypleus tridentatus, and T. gigas) was consistent and supporting the existence of adult individuals. Their population density was mainly dominated by C. rotundicauda (1.56–12.50 Ind./100 m2), followed by T. gigas (1.56–3.13 Ind./100 m2) and T. tridentatus (1.56–3.13 Ind./100 m2). The distribution pattern of C. rotundicauda showed that the juveniles were near the mangrove habitat during August–September and relatively seaward during October. Meanwhile, T. gigas and T. tridentatus exhibited a shift in the distribution pattern from September to October. The above results were supported by the most influential habitat parameter, particularly for silt content from the sediment. Based on the population density and habitat characteristics, 0.4 km2 of the intertidal zone was identified as a nursery/spawning ground. These findings are essential drivers for future marine protected areas (MPAs) proposals for horseshoe crabs.
