Resumo

RADONIC, M et al. Improvement in flounder Paralichthys orbignyanus controlled spawning in Argentina. Cienc. mar [online]. 2007, vol.33, n.2, pp.187-196. ISSN 0185-3880.

This study evaluates the effect of temperature on gonadal maturation, egg release and broodstock performance of the flounder Paralichthys orbignyanus (Valenciennes 1839) in captivity. The sex ratio (female:male) was kept at 1:2.2 in broodstock 1 (B1) and 1:2.5 in broodstock 2 (B2). Mean female body weight was 3461 ± 861 g in B1 and 1416 ± 435 g in B2. Final maturation of broodfish was achieved through the use of a photoperiod and water temperature regimen simulating natural seasonal changes over a 10-month period, reaching 19-20°C and 16 h L:08 h D by February and March. The photothermal conditions used in this study successfully induced egg release in P. orbignyanus. The spawning period was extended for more than four months, egg release occurring at a frequency of 1-3 days: B1 spawned for 133 days, yielding 31.9% buoyant eggs, a mean egg diameter of 882.5 ± 76.4 μm, a hatching rate of 76.9 ± 17.0%, a 3-day post-hatching (3dph) survival rate of 38.3 ± 25.7%, and a specific activity index (SAI) of 6.1 ± 6.6; B2 spawned for 90 days, yielding 67.1% buoyant eggs, a mean egg diameter of 866.4 ± 37.9 μm, a hatching rate of 66.4 ± 30%, a 3dph survival rate of 67.8 ± 26.9% and SAI of 10.5 ± 7.5. No significant differences (Kruskal-Wallis nonparametric test, P > 0.05) in total egg production, fertilization rate, fecundity, egg diameter, hatching rate, survival at 3dph and SAI were found between B1 and B2; however, there were significant differences (P < 0.01) in the percentage of buoyant eggs, which was higher for B2. Egg diameter, hatching rate and larval length are good criteria for determining the egg and larval quality of P. orbignyanus.

Palavras-chave : Paralichthys orbignyanus; natural spawning; photothermal conditioning; egg quality; controlled spawning.

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