Influence of loggerhead egg agregation on survival: why does single eggs buried into natural sand dye in few days?

[EN] The incubation is an essential life period for oviparous species that very often experiences a high mortality. In some reptile species the number of eggs that develop together in the incubation chamber affects survival and hatchling phenotype. Sea turtle eggs develop in underground locations on sandy beaches in large masses that usually have more than 80 eggs. Natural egg mortality seems to vary among species and for the sensitive leatherbacks, external eggs seems to survive better than internal ones within the nest.

Dose-dependent effect of a single GnRHa injection on the spawning of meagre ("Argyrosomus regius") broodstock reared in captivity

[EN]The present study aimed to determine the spawning efficacy, egg quality and quantity of captive breed meagre induced with a single gonadotrophin-releasing hormone agonist (GnRHa) injection of 0, 1, 5, 10, 15, 20, 25, 30, 40 or 50 μg kg–1 to determine a recommended optimum dose to induce spawning. The doses 10, 15 and 20 μg kg–1 gave eggs with the highest quality (measured as: percentage of viability, floating, fertilisation and hatch) and quantity (measured as: total number of eggs, number of viable eggs, number of floating eggs, number of hatched larvae and number of larvae that reabsorbed the yolk sac). All egg quantity parameters were described by Gaussian regression analysis with R2 = 0.89 or R2 = 0.88. The Gaussian regression analysis identified that the optimal dose used was 15 μg kg–1. The regression analysis highlighted that this comprehensive study examined doses that ranged from low doses insufficient to stimulate a high spawning response (significantly lower egg quantities, p < 0.05) compared to 15 μg kg–1 through to high doses that stimulated the spawning of significantly lower egg quantities and eggs with significantly lower quality (egg viability). In addition, the latency period (time from hormone application to spawning) decreased with increasing doses to give a regression (R2 = 0.93), which suggests that higher doses accelerated oocyte development that in turn reduced egg quality and quantity. The identification of an optimal dose for the spawning of meagre, which has high aquaculture potential, represents an important advance for the Mediterranean aquaculture industry.

Obtención en cautividad de puestas naturales del pez de limon(Seriola dumerili), en la isla de Gran Canaria (España).

[EN]In the present study, natural spawning of a broodstock group of greater amberjack (Seriola dumerili) is described with regards to: date, number of spawns, and total number of eggs produced per spawn. Fish werecaught in 2011 in the Canary Islands, Gran Canaria (Canary Islands, Spain), and kept in captivity. At the end of May 2014, the broodstock group was formed by two females with a weight 9.81±1.08 kg, size 90.0±2.82cm, with oovocites > 800μ, and five males 9.46±2.04 kg, 86.75±5.43 cm, all fluent with sperm. Between the 1stof June and 18thof October 2014, a total of 25.60 million eggs were obtained in 23 spawns.

Comparación entre puestas naturales e inducidas, mediante inyección e implante de GnRHa, en la producción de huevos del pez de limón (Seriola dumerili)

[EN]The number of eggs obtained in natural spawning (25.60 million) is higher than those obtained by injections (12.9 million) and implants (10.5 million). The number of eggs per female was 12.80 million, in natural spawning, and 4.30 and 3.51 million, in induced with injections and implants, respectively. In number of eggs per spawn, significant differences was observed, between natural spawns (1.11 million), and induced spawning’s (0.44 and 0.21 millions, injected and implants respectively). Significant differences was also found, in number of eggs per Kg female/spawn, between natural spawning’s (56,700 eggs), injection induced (37,200 eggs) and implants (25,200 eggs).

Efecto del tipo de hormona y del metodo de aplicación, en las producciones de reproductores de corvina (Argyrosomus regius).

[EN]In the present study, the effect of three different hormonal treatments were tested (GnRHA and hCG injected and GnRHa implanted), in meagre (Argyrosomus regius) broodstock born in captivity, and their production. The highest productions per kg of female and spawn: number of eggs, fertilized eggs, hatched larvae, and larvae 3 days old after hatching, corresponds to the treatment of GnRHa injected. The number of viable eggs, hatched eggs and larvae 3 days with GnRha injected was significantly different from those treated with hGC. No significant differences were observed in production per kg female and induction in the different hormonal treatments,