The development of adapted marmorated medaka Oryzias marmoratus (Aurich, 1935) at ex-situ habitat

Abstract

Marmorated Medaka (Oryzias marmoratus) is a small endemic fish species of Malili Lakes, South Sulawesi, Indonesia. The fish is a valuable commodity as an ornamental fish. However, their population in wild is threatened with extinction and has been categorized as vulnerable by IUCN. An effort to conserve O. marmoratus by ex-situ breeding is necessary for its sustainability. Research Center for Limnology-LIPI has succeeded to take the fish from Lake Towuti and adapted them in an ex-situ habitat (laboratory) (2017–2018). Research on the development to adapt O. marmoratus outside their natural habitat has been conducted in 2019-2020. The sex ratio of male: female was 1:2 (1:2.223±0.638). During mass spawning, the fish was able to reproduce seven times in 37 days which the dark moon phase. Egg diameter (mm) was 1.193±0.017. Reproduction viability was very good. Fertilization and hatching rates were 100% and 98.149±3.347%, respectively. Length of Incubation Period (LIP) (days) was 7.286±1.329, and the larva size (mm) was 3.3±0.483. Survival Rate on seven days (SR7) was 97.02112±5.510 % with larva size of 5.5±0.707. Juvenile size (mm) at 16 weeks was 33.6±5.661 (26–42). Oryzias marmoratus can be developed in ex-situ habitats and still needs further research.