Aceh Journal of Animal Science (2021) 6 (1): 23-26 Aceh Journal of Animal Science Journal homepage: www.jurnal.unsyiah.ac.id/AJAS * Corresponding author. Email address: msalehnurdin@gmail.com Printed ISSN 2502-9568; Electronic ISSN 2622-8734 This is an open access article under the CC - BY 4.0 license (https://creativecommons.org/licenses/by/4.0/) Gonad maturity and gonadal somatic index of blue swimming crab Portunus pelagicus harvested from Spermonde Archipelago, South Sulawesi, Indonesia Muh. Saleh Nurdin 1* , Fauziah Azmi 2 , Teuku Fadlon Haser 2 1 Faculty of Animal Husbandry and Fisheries, Tadulako University, Palu, Indonesia. 2 Faculty of Agriculture, Samudra University, Aceh, Indonesia. ARTICLE INFO ABSTRACT Keywords: Biology Blue Swimming Crab Ecosystems Spermonde Archipelago Received: 28 December 2020 Accepted: 12 February 2021 Available online: 28 February 2021 DOI: 10.13170/ajas.5.2.19187 Reproductive biology is one of the biological aspects that needed to formulate responsible management of blue swimming crab (BSC). The crab is one of the commercial fisheries commodities in South Sulawesi, Indonesia. Presently no information on the reproductive biology of this crab from Spermonde Archipelago, Sout Sulawesi. Therefore, the study aimed to analyze and compare gonad maturity stage (GMS) and gonadal somatic index (GSI) of the BSC caught on three ecosystems namely coral reef, seagrass, and mangrove in Salemo Island, Spermonde Archipelago. GMS and GSI were analyzed descriptively for five months from March to July 2015. Results indicate there was a difference in GMS of the BSC caught in mangroves, seagrass, and coral reef. Generally, mangrove was dominated by immature BSC with GMS I and GMS II, while the BSC caught in the seagrass and coral reef BSC were dominantly mature and spawn GMS III, IV, and V. GSI BSC caught in mangrove ecosystem are smaller than GSI BSC caught in seagrass and coral reef ecosystems. Seagrass and coral reef ecosystems suitable for development no-take zone of the BSC. Introduction Spermonde archipelago is located in the center of the Coral Triangle of which marine biota is highly diverse (Máñez et al., 2012; Sawall et al., 2013). These islands sit on the Makassar strait (Timm et al., 2017). The highly valued commodity from this region is blue swimming crabs (Portunus pelagicus), which is mainly captured surrounding Salemo island, is an island in the archipelago (Nurdin et al., 2016; Nurdin et al., 2020). Blue swimming crab (BSC) is an important commodity due to its high value in the global market fishery (Sahoo et al., 2011; Mehanna et al., 2013; Sabrah et al., 2020). Increasing demand for BSC is mainly in the form of frozen and canned meats (Lai et al., 2010), and freshly captured (Yusfiandayani and Sobari, 2011). The market demand triggers continuous exploitation of BSC in Salemo Island (Nurdin et al., 2019a). Presently, the BSC population in Salemo Island is facing multiple stressors. Over-exploitation has caused changes in reproductive biology patterns indicated by the shorter duration of spawning peak season (Ali et al., 2004; Redjeki et al., 2020). Apart from being heavily harvested, habitat degradation due to destructive fishing also contributes to factors that affect the BSC population (Kurnia et al., 2014; Astuti et al., 2020; Johnston and Yeoh, 2020). Continuous and intensive exploitation without management intervention on BSC fishery in Salemo Island can lead to local extinction (Adam et al., 2006). To retain sustainable production of BSC to contribute to the local economy, conservation efforts must be imposed. Conservation and management efforts must be supported by information from science to make the implementation more effective. Therefore, the objective of the present study was to assess the reproductive biology of blue swimming