Spontaneous spawning of Atlantic bluefin tuna Thunnus thynnus kept in captivity

Beginning 48-72 h after GnRHa treatment in 2009, massive spawning occurred for 17 days, with a daily maximum of 34 million eggs collected (SELFDOTT, 2010). On 17th June 2010 spontaneous spawning started in cage R2. From this day onwards and more or less daily viable eggs were obtained from both cages so no hormonal implants were used. Fish spawned intermittently for a period of 34 days in both cages, with a total of 58 million eggs collected. Cage R1 spawned for 26 days and produced 48 million eggs and cage R2 spawned for 28 days and produced 10 million eggs (Figure 1). As happened in 2009 (SELFDOTT, 2010), due to the almost non-existence of currents throughout the spawning period, almost all the eggs were collected at the surface, held by the plastic curtain. Only a small amount of eggs were captured by the egg collectors, which were designed to operate under current. Eggs were transported to the IEO facilities in Mazarrón (SE- Spain) where they were incubated. On average, the hatching rate was above 90%. No difference in hatching success was observed between 2009 (from hormonally treated cage) and 2010 (from spontaneously spawning fish).Commission of the European Communities, specific RTD program of Framework Program 7, SELFDOTT, “From capture based to self-sustained aquaculture and domestication of bluefin tuna, Thunnus thynnus” (GA 212797)

Obtención de puestas masivas de huevos de atún rojo (Thunnus thynnus) en cautividad, durante 3 años consecutivos

Within the framework of the SELFDOTT project, captive-reared bluefin tuna (Thunnus thynnus) maintained in captivity since 2007 in Cartagena (Spain) produced massive spawning during the natural period for this species in the Mediterranean Sea (June-July). The fish were induced with GnRHa implants in 2008 and 2009. In 2008 no spawnings were detected. From 2009, massive spawnings occurred being spontaneous (without hormone implants) in 2010 and 2011. The total egg collection was 140 million in 2009, 60 million in 2010 and 160 million in 2011.7º Programa Marco de la Unión Europea, “Food, Agriculture, Fisheries and Biotechnology" del Proyecto SELFDOTT (From capture based to SELF-sustained aquaculture and Domestication Of bluefin tuna, Thunnus thynnus)” GA 212797

Estudio preliminar sobre una posible inhibición dopaminérgia en la reproducción del lenguado senegalés (Solea senegalensis)

El objetivo del presente estudio fue evaluar el efecto del sistema dopaminérgico sobre la reproducción del lenguado senegalés (Solea senegalensis). Para ello, reproductores de lenguado senegalés nacidos y criados en cautividad (generación F1) fueron tratados con 1) GnRHa, 2) inhibidor dopaminérgico (pimozide) o 3) un tratamiento combinado (GnRHa + pimozide). El efecto de los tratamientos se evaluó a nivel de producción de huevos y esperma (cantidad y calidad); además se estudió el efecto sobre niveles plasmáticos de esteroides sexuales y desarrollo gonadal (histología). Las hembras no mostraron una estimulación en la ocurrencia de puestas por el tratamiento combinado GnRHa + pimozide respecto a aquellas tratadas solo con GnRHa. Sin embargo, los machos que recibieron el tratamiento combinado mostraron una mayor estimulación en la producción de esperma y en el grado de maduración testicular respecto a aquellos que recibieron solo GnRHa o pimozide. Los resultados indican que el sistema dopaminérgico no parece ejercer una acción fuerte sobre la ocurrencia de puestas en hembras, aunque podría estimular la espermiación en machos de lenguado senegalés.Preliminary study on dopaminergic inhibition in Senegalese sole reproduction (Solea senegalensis) The aim of the present study was to evaluate the effect of the dopaminergic system on Senegalese sole (Solea senegalensis) reproduction. For this purpose, Senegalese sole breeders hatched and raised in captivity (F1 generation) were treated with 1) GnRHa, 2) a well-known dopaminergic inhibitor (pimozide) or 3) a combined treatment (GnRHa + pimozide). The effect of each treatment was determined by studying spawning occurrence and sperm (quantity and quality); in addition, effects on sex steroids levels and on gonadal development (histology) were also considered. Females did not show any improvement of spawning occurrence by combining GnRHa and pimozide respect to those females treated only with GnRHa. However, males which received the combined treatment showed a greater stimulation of sperm production and testicular maturity than those males treated with a single GnRHa or pimozide treatment. Our results indicate that dopaminergic system do not seem to play a strong action on eggs spawning in females, but may stimulate spermiation in Senegalese sole males

Intra-pituitary relationship of follicle stimulating hormone and luteinizing hormone during pubertal development in Atlantic Bluefin tuna (Thunnus thynnus)

As part of the endeavor aiming at the domestication of Atlantic bluefin tuna (BFT; Thunnus thynnus), first sexual maturity in captivity was studied by documenting its occurrence and by characterizing the key hormones of the reproductive axis: follicle stimulating hormone (FSH) and luteinizing hormone (LH). The full length sequence encoding for the related hormone b-subunits, bftFSHb and bftLHb, were determined, revealing two bftFSHb mRNA variants, differing in their 50 untranslated region. A quantitative immuno-dot-blot assay to measure pituitary FSH content in BFT was developed and validated enabling, for the first time in this species, data sets for both LH and FSH to be compared. The expression and accumulation patterns of LH in the pituitary showed a steady increase of this hormone, concomitant with fish age, reaching higher levels in adult females compared to males of the same age class. Conversely, the pituitary FSH levels were elevated only in 2Y and adult fish. The pituitary FSH to LH ratio was consistently higher (>1) in immature than in maturing or pubertal fish, resembling the situation in mammals. Nevertheless, the results suggest that a rise in the LH storage level above a minimum threshold may be an indicator of the onset of puberty in BFT females. The higher pituitary LH levels in adult females over males may further support this notion. In contrast three year-old (3Y) males were pubertal while cognate females were still immature. However, it is not yet clear whether the advanced puberty in the 3Y males was a general feature typifying wild BFT populations or was induced by the culture conditions. Future studies testing the effects of captivity and hormonal treatments on precocious maturity may allow for improved handling of this species in a controlled environment which would lead to more cost-efficient farming.Versión del editor