New insights into giant gourami (Osphronemus goramy) reproductive biology and egg production control

Reliable production of giant gourami Osphronemus goramy Lacepede (1801) fry is one of the main impediments hindering the aquaculture development of this species. The main objective of the present study was to experimentally assess the influence of various biotic or abiotic factors on the egg production of giant gourami. Egg production (egg-laying frequency, quantity and quality of the eggs produced) was compared across several strategies including different pond settings (open vs. compartmentalized ponds, number of nest supports, size of compartments), as well as broodfish management (sex ratio, duration of egg production period). A total of 705 spawns and > 2.2 million eggs were collected from the 533 broodfish of giant gourami monitored throughout this study. The dissection of fully sexually mature broodfish showed that giant gourami males are oligospermic with a GSI < 0.1%. In mature females, the GSI was < 5%, and the absolute fecundity (number of post-vitellogenic oocytes present in the ovaries) varied between 7800 and 15,200 eggs (mean relative fecundity of 4011 +/- 287 eggs per female kg). The best egg production was found in the production system consisting of a pond divided into compartments of 8 m(2) with one nest support provided and in which the broodfish were maintained at a sex ratio of 1:1 during egg production periods of 6-7 months separated by resting/reconditioning periods of 1 month. The results showed that a same male can fertilize eggs at 2-4 day-intervals and, in females, the minimum lapse of time found between two successive spawns is 20 days. At best, the number of eggs found in nests averaged 1410 +/- 101 eggs per female kg, which, compared with the potential fecundity of the species, indicates that egg losses at the time of spawning generally remain high. Based on these findings, recommendations are made for optimizing giant gourami egg production in aquaculture conditions