Penelitian terkait reproduksi ikan khususnya tentang ukuran pertama kali matang gonad (lm) dan ukuran pertama kali tertangkap (lc) pada ikan senangin (eleutheronema tetradactylum) yang didaratkan di tangkahan cv. mentari pagi sebatik perlu dilakukan pengkajian, guna menjaga kelestarian dan keberadaan populasi ikan yang ada di perairan. tujuan penelitian untuk menerangkan sex ratio atau nisbah kelamin, tingkat kematangan gonad ikan dan ukuran pertama kali matang gonad serta ukuran pertama kali tertangkap pada ikan senangin yang didaratkan di tangkahan cv. mentari pagi sebatik. metode penelitian ini menggunakan metode deskriptif kuantitatif dengan pendekatan observasi dengan pengamatan dan pengukuran ikan senangin. metode yang digunakan dalam pengambilan sampel menggunakan metode random sampling. penelitian ini dilaksanakan pada bulan desember – februari 2024. total sampel penelitian sebanyak 300 ekor yang terdiri dari 294 ekor jantan dan 6 ekor betina. sampel diukur panjangnya menggunakan penggaris. pengamatan jenis kelamin dilakukan secara anatomi dengan melihat gonad ikan. sex ratio sampel ikan senangin selama penelitian yaitu 1 : 0,02. tingkat kematangan gonad ikan senangin jantan dan betina dominan tkg iii. hasil pengukuran lm dan lc sampel ikan senangin diperoleh nilai lc > lm (lm = 28,920 cm; lc = 48,695 cm), artinya sebagian besar ikan yang tertangkap di perairan sebatik memiliki peluang untuk melakukan pemijahan dan ikan yang tertangkap sudah layak untuk ditangkap sehingga hal tersebut dapat menambah populasi ikan. kata kunci: ikan senangin, matang gonad, perairan sebatik, rasio kelamin

The research related to fish reproduction, especially about the size of the first mature gonad (lm) and the size of the first time caught (lc) in fourfinger threadfin (eleutheronema tetradactylum) landed at the cv. mentari pagi sebatik catchment needs to be studied, in order to maintain the sustainability and existence of fish populations in the waters. the purpose of the study was to explain the sex ratio, the level of maturity of fish gonads and the size of the first time mature gonads and the size of the first time caught in fourfinger threadfin landed at the cv. mentari pagi sebatik catchment. this research method used a descriptive quantitative method with an observation approach by observing and measuring the fourfinger threadfin. the method used in sampling was a random sampling method. this research was conducted in december february 2024. the total research sample was 300 fish consisting of 294 males and 6 females. samples were measured in length using a ruler. sex observation was done anatomically by looking at the fish gonads. sex ratio of the fourfinger threadfin samples during the study was 1:0.02. the maturity level of male and female fourfinger threadfin gonads was dominantly in tkg iii. the results of measuring lm and le of the fourfinger threadfin samples obtained the value of lc lm (lm28.920 cm; lc 48.695 cm), meaning that most of the fish caught in sebatik waters have the opportunity to spawn and the fish caught are suitable for catching so that it can increase the fish population. keywords: eleutheronema tetradactylum, gonad mature, sebatik waters, sex ratio