Development of endangered endemic fish Oryzias woworae Parenty & Hadiaty, 2010 at ex-situ habitat for conservation purposes

¹ Research Center for Limnology and Water Resources, National Research and Innovation Agency, 10340 Jakarta, Indonesia.
² Department of Fisheries Science, Faculty of Agriculture, University of Sultan Ageng Tirtayasa, 42121 Serang, Indonesia
³ Research Center for Biosystematics and Evolution, National Research and Innovation Agency, 10340 Jakarta, Indonesia

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Oryzias woworae Parenty & Hadiaty, 2010, is an endemic freshwater fish native to Muna Island, Southeast Sulawesi, Indonesia, valued for its vibrant coloration and potential as an ornamental species. However, it has been classified as Endangered by the IUCN, and there is limited information available on its biology. This study examines key reproductive parameters to support the ex-situ conservation and domestication of the species. Observations were conducted on F2 individuals aged 5–7 months from January to March 2022 at the Aquatic Laboratory of the Research Center for Limnology and Water Resources - BRIN. The fish, measuring 28–37 mm, exhibited fecundity of 11–49 eggs, with mature eggs averaging 1.1 ± 0.1 mm (ranged 0.9–1.2 mm) and immature eggs averaging 0.74 ± 0.14 mm (ranged 0.5–0.9 mm) in diameter. Spawning occurred 9–15 times, producing 59–120 eggs in total. Fertilization and hatching rates were high, ranging from 98.4% to 99.2% and 85.3% to 90.0%, respectively, with incubation lasting approximately 8 days. Larvae reached an average length of 20.41 ± 3.6 mm at 12 weeks, growing at a rate of 0.238 mm/day. These findings suggest that O. woworae can be successfully developed in ex-situ environments to support future conservation efforts.