Broodstock management and induced spawning of flounder Paralichthys orbignyanus (Valenciennes, 1839)under a closed recirculated system

Abstract

The present study was conducted to determine the parameters regulating spawning performance of P. orbignyanus wild broodstock. The adaptation to captivity was successfully achieved with minimal stress levels. In three consecutive spawning seasons, the annual photothermal manipulation was not effective for the maturation and natural spawning of females although males were running. Females were HCG injected, releasing non fertilized eggs. Artificial fertilization was carried out after stripping the fish with a total production of 18,000 fertilized eggs in 2001 (egg diameter=800±10 µm), 55,300 in 2002 (egg diameter= 850±12 µm)and 1,635,000 fertilized eggs in 2003 (egg diameter 818.4 ±30.08 µm, oil drop 98.1 ±2.96 µm). For the study of the ovulationtime, females were hand-stripped every 48 h (female 1), 96 h (female 2)and 144 h (female 3), after being induced by hormones. No statistical differences were found for fertilization and hatching rates and SAI. This could be attributed to the small sample sizes, individual variation and/or stripping frequencies. Nevertheless, qualitative differences were evident. Although long-term studies are needed to confirm these observations, 96 h stripping frequency could be considered a good technique to obtain eggs and larvae experimentally. The estimated fecundity by this technique varied from 185,951 to 399,118 total eggs per kg of female