JUSTE Doi: Journal of Science and Technology Naskah diterima: 18 Februari 2023 Naskah disetujui: 22 Agustus 2023 Perkembangan Embrio dan Rasio Penetasan Telur Ikan Zebra Danio rerio (Hamilton, 1822) di Instalasi Perikanan Budidaya Punten Batu (Embryo Development and Hatching Ratio of Zebra Fish Danio rerio (Hamilton, 1822) at Punten Batu Fishing Installations) Nur Khosim 1,* , Husain Latuconsina 1 , Rahadian Adietya Suhada 2 1 Departemen Biologi, Fakultas MIPA Universitas Islam Malang 2 Instalasi Perikanan Budidaya Punten Batu * Email korespondensi: nurkhosim.212@gmail.com Abstract Indonesia is a producer of ornamental fish and one of the commodities that has its own charm for its consumers, such as zebrafish (Danio rerio). The zebrafish has a four-stage life cycle: embryo, larva, young fish and adult fish. Zebrafish have the advantage of producing 300-400 eggs/week, transparent embryos so that their organs can be observed clearly, and easy to maintain. Egg quality is a primary factor in the success of fish hatchery. Quality eggs have high fertilization and hatching rates. This study aims to analyze the factors that can affect the process of embryo development and hatching of zebrafish (Danio rerio) eggs. This research is a mixed type of descriptive experimental and quantitative explaining all stages of development and the ratio of egg hatching and embryo development. The results of the study found that natural feeding was able to accelerate growth, ward off disease germs, and accelerate gonadal maturation. The best time to release the broodstock is in the morning and evening because the water temperature tends to be low. The results of observing eggs under a microscope found an attack by the fungus Saprolegnia sp., this fungus tends to grow spread on the surface of the egg and forms hyphae. Larvae hatch from 48 hours to 72 hours after fertilization. The 2-3 dpf larvae are kept in the hatching medium until they become seeds. The safety rate for embryos is around 50%, while for larvae up to 21 dpf it is around 100%. This is caused by the fungus Saprolegnia sp., so that the index value of the hatching ratio is less than optimal due to retarded embryo growth and leads to death. However, the high survival rate is due to optimal management of larvae rearing by providing proper feeding of dancow milk powder and good water treatment. Keywords: Spawning, Larvae Care, Survival Abstrak Indonesia termasuk penghasil ikan hias dan salah satu komoditas yang memiliki daya tarik tersendiri bagi konsumennya seperti ikan zebra (Danio rerio). Ikan zebra memiliki siklus hidup empat tahap yaitu: embrio, larva, ikan muda, dan ikan dewasa. Ikan zebra memiliki keuntungan yaitu menghasilkan telur 300-400 butir/minggu, embrio transparan sehingga organnya dapat diamati dengan jelas, dan mudah pemeliharaannya. Kualitas telur merupakan faktor primer dalam keberhasilan pembenihan ikan. Telur yang berkualitas memiliki tingkat pembuahan dan penetasan yang tinggi. Penelitian ini bertujuan menganalisis faktor yang dapat mempengaruhi proses perkembangan embrio dan penetasan telur ikan zebra (Danio rerio). Penelitian berjenis campuran antara deskriptif eksperimental dengan kuantitatif menjelaskan semua tahapan perkembangbiakan dan rasio penetasan telur serta perkembangan embrio. Hasil penelitian mendapatkan bahwa pemberian pakan alami mampu mempercepat pertumbuhan, menangkal bibit penyakit, dan mempercepat pematangan gonad. Waktu pelepasan induk yang baik yaitu pada pagi dan sore karena suhu perairan cenderung rendah. Hasil pengamatan telur di mikroskop didapati