Improvement in flounder Paralichthys orbignyanus controlled spawning in Argentina

Abstract

Se evaluó el efecto de la temperatura sobre la maduración gonadal, la liberación de huevos y el comportamiento reproductivo del lenguado Paralichthys orbignyanus (Valenciennes 1839) en cautiverio. La relación de sexos fue de 1:2.2 y 1:2.5 (hembra:macho) en los grupos de reproductores B1 y B2, respectivamente. La talla promedio de las hembras en B1 fue de 3461 ± 861 g y en B2 fue de 1416 ± 435 g. La maduración gonadal se logró con la aplicación de un esquema de fotoperiodo y temperatura simulando las condiciones del medio natural en un periodo de 10 meses, alcanzando en febrero y marzo 19|00E2|??20ºC y 16 h L:08 h O. Las condiciones fototermales usadas en este estudio indujeron la liberación de huevos en P. orbignyanus. La producción de huevos se extendió por un periodo mayor a 4 meses con una frecuencia de 1 a 3 días. El grupo B1 desovó durante 133 días, produciendo 31.9% de huevos viables con diámetro de 882.5 ± 76.4 ?m, una tasa de eclosión de 76.9 ± 17.0%, una supervivencia al tercer día posterior a la eclosión (S-3dpe) de 38.3 ± 25.7%, y un índice de actividad larval (IAE) de 6.1 ± 6.6. El grupo B2 desovó durante 90 días con una producción de huevos viables de 67.1%, diámetro de 866.4 ± 37.9 ?m, tasa de eclosión de 66.4 ± 30%, una S-3dpe de 67.8 ± 26.9% y un IAE de 10.5 ± 7.5. No se hallaron diferencias significativas en la producción total de huevos, tasa de fecundación, fecundidad, diámetro del huevo, tasa de eclosión, S-3dpe y IAE (test no paramétrico de Kruskal-Wallis, P > 0.05) entre B1 y B2, sin embargo, el porcentaje de huevos viables fue significativamente diferente (P < 0.01) siendo mayor para B2. Los parámetros diámetro del huevo, tasa de eclosión y longitud larval serían criterios apropiados para determinar la calidad de huevos y larvas en P. orbignyanus.
 
 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|00E2|??20ºC 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|00E2|??3 days: B1 spawned for 133 days, yielding 31.9% buoyant eggs, a mean egg diameter of 882.5 ± 76.4 ?m, 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 ?m, 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.

Larval culture technique and quality control in juveniles of flounder Paralichthys orbignyanus (Valenciennes, 1839) in Argentina

“…This author reported total lengths at hatching of P. orbignyanus larvae ranging from 1.98 to 2.09 mm, when females were hand-stripped. Furthermore, Radonic et al (2007) verified that larvae obtained from natural spawnings were significantly larger (2.34±0.10 mm) than those obtained from hand stripping (2.19±0.10 mm).…”

Sperm quality of Brazilian flounder Paralichthys orbignyanus throughout the reproductive season

“…These intervals were subjectively studied, considering progressive motility from the time of activation up to at least when 50% of the cells were in movement, vibratory motility from this time point until no more vibrating cells could be observed and total sperm motility duration was the sum of progressive and vibratory motility duration. The experiments were carried out in triplicate and room temperature was maintained at 20 °C, the temperature at which Radonic, Müller, López, Bambill, Spinedi and Boccanfuso (2007) obtained the best results for natural spawning. All evaluations were conducted by the same observer in order to reduce variability.…”

Gonadal Sex Differentiation in Cultured Juvenile Flounder, Paralichthys orbignyanus (Valenciennes, 1839)

“…Different egg batches were obtained by natural tank spawning from the same broodstock with no control of individual spawning pairs ( N = 39; sex ratio 1 female : 2.5 male). Spawning technique, larval culture, and grow‐out protocols used for juvenile mass production were described by Bambill et al (2003, 2006), Radonic et al (2005, 2007) and Müller et al (2006a, b). A total of 61 fish were histologically sampled at approximately 10‐mm total length (TL) size intervals following metamorphosis.…”