Local knowledge-based study on the status of horseshoe crabs along the Indonesian coast

Abstract

There is a dearth of knowledge of the ecology and population status of horseshoe crabs in Indonesia. To avoid the high costs of sampling and monitoring horseshoe crabs, a questionnaire-based survey was designed and administered to local people to collect local knowledge on the population status, distribution, and potential threats that horseshoe crabs face at 35 sites in Indonesia. The results from 237 interviewees showed that horseshoe crabs were observed in 62 districts, including 114 local areas in Java, Sumatra, Kalimantan, and Sulawesi Island. Approximately 70.5% of interviewees suggested that populations of horseshoe crabs in these districts are declining. The two most cited reasons for the decline included the habit of discarding horseshoe crab bycatch in locations where horseshoe crabs are unable to survive, such as river banks and trash piles (27.7%) and beach litter (19.8%). gillnetting (48.3%) and bottom trawling (42.4%) were the main types of fishing gear responsible for the capture of horseshoe crabs. Due to the common practice of consuming adult crabs in these areas (90.0%), mass harvesting of adult horseshoe crabs was also mentioned by respondents (29.3%). Local knowledge obtained in this study has provided critical information on the distribution, threats, and causes of the decline in horseshoe crab populations. The results of this study therefore suggest that there is an urgent need for a sound management strategy to effectively aid in the conservation of horseshoe crabs.