Some Aspects of the Reproductive of Japanese Threadfin Bream (Nemipterus japonicus Bloch, 1791) Caught in the Area Around the Artificial Reef in the Pitu Sunggu Waters of the Makassar Strait ABSTRACT Japanese readfin Bream is a demersal fish commonly found around artificial reefs. Food availability in the artificial reef ecosystem is essential for the sustainability of this species. Hence, this research aimed to determine several aspects of bio-reproduction of Japanese readfin Bream caught in the artificial reef (bioreeſtek). Samples were taken using handline fishing, twice a month (April-July 2020) in Pitu Sunggu Waters, Makassar Strait. e samples were observed for its reproduction aspects. e result showed that the Japanese readfin Bream fish caught have a balanced sex ratio between males and females, 1:1.03. e analysis of the gonad maturity stage obtained was II-IV, and the gonado somatic index ranged from 0.541-0.940 for males and 1.156-2.358 for females. e first mature Japanese readfin Bream size was 18.29 cm for males and 16.99 cm for females. e Japanese readfin Bream fish fecundity ranged between 35.042-42.061 eggs. Keywords: Artificial reefs; Japanese readfin Bream; Makassar Strait; reproduction INTRODUCTION The Makassar Strait is one of the Indonesian Fisheries Management Area (FMA) 713, besides the Flores Sea, Bone Bay and the Bali Sea. FMA 713 have high potential, shown with a total production of 1.177.857 ton/year; which include 208.414 ton/year for small pelagic fish, 645.058 ton/year for big pelagic fish, 252.869 ton/year for demersal fish, 19.856 ton/year for reef fish, and 51.660 ton/year for Penaeid, Lobster, Crab, and Squid. The great potential of FMA 713, especially in the Makassar strait, is because the primer productivity is high, and the waters are connected directly to the Western part of the Pacific Ocean (Inaku, 2015). This condition caused the Makassar Strait to become a potential area with high productivity (Rasyid, 2011) as a nursery and growing area for many aquatic resources. However, in FMA 713, most fish categories, such as small and big pelagic fish, reef fish, lobster and squid, are already classified as overexploitation (exploitation number ≥1). The demersal fish has been exploited 242.754.24 tonnes/year (96%). This number is classified as full exploitation (MMF, 2017). The Japanese Threadfin Bream (Nemipterus japonicus) is a demersal fish (Amine, 2012; Oktaviyani, 2014) that could be caught in FMA 713. It also could be found in the Philippines and Japan (Russel, 1993), the Western part of Indo Pacific, Eastern Africa, Persia Cape, and the Red Sea (Kerdgari et al ., 2013; Nettely, 2016). This species has high economic value (Brojo & Rian, 2002; Valinassab et al., 2006; Sutjipto et al., 2013; El-Alfawy et al., 2014; Rao et al., 2017). Japanese Threadfin Bream swim is known as fish that schooling (Kerdgari et al., 2009). These reasons could cause high catch intensity (Ghosh et al., 2015). Further, it will lead to catching pressure and cause the resource stock to decrease, and it also could change the population structure of the Japanese Threadfin Bream. Many pieces of research have been conducted in the last decade related to the Threadfin Bream (Nemipterus sp.), including N. japonicus species. Some of the researches are age estimation and food habits of Japanese Threadfin Bream (Nemipterus japonicus) by Afshari et al. (2013), stock estimation and biological aspects by Amine (2012); ElHaweet (2013) and Sen et al . ( 2014), reproductive cycle, sexual maturity and fecundity of Nemipterus fuscosus (Rahman & Amira, 2021), relative abundance and population growth of male and female Nemipterus furcosus f (Amira et al., 2016), kidney accessories Nemipterus japonicus its relationship with gonadal maturation (El-Alfawy & Amal, 2014), potential sustainability of Nemipterus japonicus ( Widagdo et al ., 2019), population dynamics of the Japanese Threadfin Bream ( Nemipterus hexodon) (Sutjipto et al., 2013) , Length-weight relationship of the Threadfin Bream (Nemipterus sp.) (Rapita et al., 2020), reproduction of the Japanese Threadfin Bream (Nemipterus japonicus) (Nettely et al., 2016; Rao et al., 2017), histology and ovarian development of Nemipterus japonicus (Kerdgari et al., 2013); reproductive biology of Nemipterus randali (Burcu & Sercan, 2021). However, these researches were done in the natural littoral area. This research will focus on biology reproductive for Japanese Threadfin Bream catches around the bioreeftek Wayan Kantun* 1 & Wilma Moka 2 1 Aquatic Resource Management, Balik Diwa Institute of Technology and Maritime Business, Makassar City, South Sulawesi, Indonesia 2 Aquatic Resource Management, Faculty of Marine Science and Fisheries, Universitas Hasanuddin, Makassar City, South Sulawesi, Indonesia *Corresponding author, email: aryakantun@gmail.com Submitted: 17 March 2022; Revised: 15 May 2022; Accepted : 01 Juli 2022 ISSN: 2502-5066 (Online) ISSN: 0853-6384 (Print) JURNAL PERIKANAN UNIVERSITAS GADJAH MADA Terakreditasi Ristekdikti No: 158/E/KPT/2021 ©2022 Jurnal Universitas Gadjah Mada. This article is distributed under a Creative Commons Attribution-Share Alike 4.0 International license. Vol. 24 (2), 147-153 DOI 10.22146/jfs.73629