Nelayan Kota Tarakan menggunakan alat tangkap rawai (longline) dalam memanfaatkan sumberdaya perikanan, dengan hasil tangkapan utamanya ikan kakap merah (Lutjanus sp.) dan ikan arut (Pomadasys sp.). Data ilmiah terkait dengan rawai dan hasil tangkapannya, sangat penting sebagai dasar dalam pengelolaan sumberdaya perikanan lestari dan berkelanjutan, salah satunya data ilmiah terkait dengan aspek bio-ekologi perikanan. Tujuan penelitian menjelaskan tentang aspek biologi ikan yang mencakup rasio kelamin, tingkat kematangan gonad (TKG), indeks kematangan gonad (IKG), fekunditas, dan kebiasaan makan. Penelitian telah dilaksanakan dari Januari - Maret 2021 di perairan Tarakan, dengan metode penelitian secara observasi kuantitatif dan metode pengumpulan sampel secara purposive random sampling. Hasil penelitian menunjukkan bahwa pada nisbah kelamin Pomadasys sp. dan Lutjanus sp., sampel betina lebih dominan tertangkap. TKG arut jantan dominan TKG II dan sampel betina dominan TKG III. Ikan kakap merah jantan dominan TKG I dan sampel betina dominan TKG I. Nilai IKG ikan arut jantan 0.020 - 0,702 dan sampel betina 0.020 - 7,988. Nilai IKG ikan kakap merah jantan 0.010 - 0,209 dan sampel betina 0.010 - 1,587. Fekunditas tertinggi ikan arut 13.836 butir (TKG IV) dan ikan kakap merah, nilai fekunditas tertinggi 4.942 butir (TKG III). Pomadasys sp.dan Lutjanus sp. merupakan ikan karnivora dengan jenis makanan utamanya, yang secara kuantitatif hasil analisa IRP (Indeks Relatif Penting) yaitu makanan lumat atau hancur (94,61% dan 86,89%), yang terindikasi dari kelompok chordate dan crustacean, serta sebagai makanan tambahan adalah cumi-cumi (cephalopoda).
Kata kunci: Bioreproduksi; Kebiasaan Makan; Rawai Dasar; Ikan Arut; Ikan Kakap Merah

The Tarakan City fishermen used the bottom longline fish catcher by utilizing the water resources, with the main catch of red snapper (Lutjanus sp.) and arut fish (Pomadasys sp.). the scientific data related to bottom longline and catch, were greatly important as a base in managing the long-lasting and sustainable fishery resources, that is, scientific data related to the bio-ecological fishery aspects. This research aims at explaining fish biological aspects covering sex ratio, Gonal Maturity Level (GML), Gonad Maturity Index (GMI), fecundity, and eating habit. The research was conducted in January March 2021 in Tarakan waters, using an observational qualitative method. The samples were collected using a purposive random sampling technique. The research results show that the sex ratio of Pomadasys sp. and Lutjanus sp., in female samples was more dominantly captured. The male arut fish dominantly had GML II, while the females dominantly had GML III. The male red snapper dominantly had GML I while the female samples dominantly had GML I. The GMI value of male arut fish was 0.020 - 0.702, while that of the female samples was 0.020 - 7.988. The GMI value of male red snapper was 0.010-0.209, while that of the female samples was 0.010-1.587. The highest fecundity of arut fish was 13,836 items (GML IV) and that of red snapper was 4,942 items (GML III). Pomadasys sp.and Lutjanus sp. Are carnivorous fish with its main food qualitatively had the Relatively Important Index (RII) in which the food was perfectly crushed or damaged (94.61% and 86.89%), indicated from chordate and crustacean group, as well as food supplementation, that is, octopus (cephalopoda). Keywords: Bioreproduction; Eating Habit; Bottom Longline; Arut Fish; Red Snapper