No abstract

No abstract

For the first time, a spontaneous spawning of hake was recorded in Spain in April 2009. The spawn was obtained from broodstock kept in captivity for two years at the facilities of the Spanish Institute of Oceanography in Vigo (NW Spain). Eggs were transparent, spherical and had an average diameter of 1.067 ± 0.024 mm; yolk occupied the majority of egg volume. The oil droplet had a diameter of 0.27 ± 0.03 mm. The incubation period of the eggs lasted for 4 days at 14°C and the duration from hatching to the total absorption of the yolk sac was between 5–7 days after hatching, at the same temperature. Newly hatched larvae had an average total length of 3.20 ± 0.13 mm and began feeding 6 days after hatching; a daily growth rate of 0.158 mm day‐1 was observed from hatching to yolk sac consumption. This paper describes the daily evolution of biometric and morphological characteristics of the different stages of embryos and larvae of European hake up to the age of 19 days.

The survival, growth, gonadal development and sex ratios of gynogenetic diploid turbot Scophthalmus maximus between 9 and 36 months of age were investigated. Gynogenesis was induced by activation of freshly collected eggs with diluted (1 : 10 with Ringer) and UVirradiated (30000 erg mm À2 ) sperm, followed by a cold shock at À1 to 0 C for 25 min, starting at 6Á5 min after fertilization. The exclusive maternal inheritance of the resulting gynogenetic diploids was confirmed in all individuals used in the experiment by microsatellite markers. Mean total length and mass throughout the experiment was higher in the controls than in the gynogenetics. The gonadal development in gynogenetic males proceeded normally, and in gynogenetic females it was delayed during the first sexual maturation but was normal during the second one. The sex ratio was 1 male (M) : 1 female (F) in the controls, as expected, but 1 M : 3 F in the gynogenetics. In a second, independent experiment, carried out with fish originating from different broodstock, however, the sex ratio was 1 M : 1 F in the controls and 0 M : 1 F (i.e. 100% females) in the gynogenetics. Together, these results suggested that the main sex-determining genetic component in turbot fits well to female homogamety, in accordance with data from other flatfishes. These results indicate that it will be possible to obtain near or all-female turbot stocks through induced gynogenesis or by crosses involving hormonally sex-reversed fish.

No abstract

The effect of the adherence of the lipid droplet in the yolk-sac on the growth and survival of the European hake (Merluccius merluccius) larvae was studied under starved and feeding conditions. Recently hatched hake larvae with adhered and non-adhered lipid droplet (ALD and non-ALD) were maintained during 8 days under starvation conditions. The adherence of the lipid droplet positively affected larval survival during starvation. At the end of the yolk consumption period (7-8 days after hatching), 90% of the surviving larvae had an ALD, while 10% of the survivors had a non-ALD and showed a higher mortality rate. In a month feeding experiment, results show that the presence of non-ALD in newly hatched hake larvae negatively affected their growth and survival. Dry weight and length (TL) of 20-days-old larvae with ALD were significantly higher than those with non-ALD. Furthermore, lifespan of those larvae with non-adhered lipid droplet was shorter, with most of them dying during the first 15-20 days of culture. As conclusion, the percentage of the lipid droplet adherence at hatching could be used as an indicator of 'quality' for European hake larvae: the greater the number of larvae with adhered lipid droplet, the better larval growth and survival.

Four different wreckfish (Polyprion americanus) broodstock batches were maintained in research facilities under different photo and thermo-period conditions, one in Greece, the Helenic Center for Marine Research (HCMR, n = 3) and three in Spain: Instituto Español de Oceanografía (IEO, n = 13) in Vigo, Aquarium Finisterrae (MC2, n = 21) in A Coruña and Consellería do Mar (CMRM, n = 11). The CMRM includes two centers that work together: Instituto Galego de Formación en Acuicultura (IGAFA) and Centro de Investigacións Mariñas (CIMA), both in Pontevedra. During the five years of the project DIVERSIFY (Exploring the biological and socio-economic potential of new-emerging candidate fish species for the expansion of the European aquaculture industry, 2013–2018) works focused on the reproductive biology of the species, broodstock, and larvae nutrition and development of incubation and larval rearing protocols have been carried out. In terms of reproduction, catch methods of new wild animals, the reproductive cycle, sperm characteristics evaluation, and spontaneous and induced spawning methods have been described for wreckfish. Regarding nutrition, the positive effect of two types of enrichment on the fatty acid profiles of Artemia and rotifer has been verified. The relationship between the fatty acid profile of the diets supplied to the broodstock and the fatty acid profile obtained in the oocytes and eggs of the females fed with different diets, has also been demonstrated. Finally, early larval ontogeny has been described and incubation and larval rearing protocols have been proposed based on the results obtained in the different experiments of temperature, growth, survival, and larval feeding that were carried out.