Survival Rate and Early Development of Giant Gourami Padang Strain Osphronemus gouramy (Perciformes: Osphronemidae)

Abstract

Aquaculture of gourami in Indonesia is still carried out traditionally with a simple touch of technology that makes the mortality rate of larvae is still very high. This study aimed to determine the survival rate and development of giant gourami Padang strain larvae Osphronemus gouramy reared in a traditional way and to gain insight into the cause of mass death during the larval period. The larvae were obtained from six pairs of broodstocks that consisted of three categories, which is the grey broodstocks that spawned the previous month, the grey broodstocks that did not spawn the previous month, and the pink broodstocks that did not spawn the previous month, and were named after the body colour of their respective parents. The study was conducted in duplicate and the larvae were sampled for photography every day and the larvae development was described from Day 1 to Day 10. The eggs began to hatch on Day 2, and all eggs hatched on Day 3 that marked the end of the embryonic stage. Pale melanophores became more intense on Day 6 and the yolk sac was still visible on Day 10. The mass deaths during embryogenesis are thought to be influenced by factors such as broodstock quality, while the ones occurring in the late larval period are more likely related to water quality and stocking density. Ammonia excretion subsequently oxidized into more toxic nitrite was the only possible pollutant to be present in the rearing water. In the Grey II.1 and Grey II.2 basins where the mass death occurred on Day 10, the mean of survival rates declined significantly from 83.45% on Day 9 to 32.15% on Day 10. Thus, this study confirmed that the basins with larvae density of above 30 individuals per litre can support the larvae rearing for eight days and on Day 9 the larvae must be transferred to another tank. The success of larval production depends not only on the welfare and the feed quality of the broodstocks but also on the optimal environment in larval rearing. In addition, the nomenclature for the larval stage of gourami was also discussed and determined.