830 research outputs found
Algunas consideraciones sobre la acuicultura
El crecimiento de la acuicultura en las últimas décadas en España y en el mundo, ha
convertido esta actividad en el sector de la producción primaria de más rápido crecimiento.
Sin embargo este crecimiento ha ido acompañado de una considerable evolución en los
mercados y de importantes cambios que han sido dirigidos fundamentalmente a la mejora del
producto y al aumento de la diversidad de especies, para ofrecer al consumidor un alimento de
confianza, variado y sano desde el punto de vista económico, nutricional y sanitario. Esto
también ha llevado a la regulación de zonas consideradas protegidas en algunos casos, o de
dominio público en otros, para su utilización en acuicultura de forma racional. De la misma
manera, no podemos olvidar el papel fundamental que esa desarrollando la acuicultura en los
paÃses en vÃas de desarrollo, como un elemento indispensable para erradicar el hambre, ni los
efectos drásticos que pueda tener el cambio climático en el futuro de la acuiculturaDuring the last decades, aquaculture has become the activity with the fastest growth in the
primary sector in Spain. Nevertheless, this growth has been accompanied by a remarkable
evolution of the market and important changes towards mainly to the improvement of quality
product and species diversification, in order to deliver a trust worthy, healthy, nutritional and
reliable product for the consumer. This has also contributed to new regulations, regarding
protected areas in some cases, or of public domain in others, allowing their utilization in
aquaculture in a rational and responsible manner. Furthermore, we can not forget the
important role that aquaculture has in developing countries, as a vital element to eradicate
hunger, nor the drastic effect that climate change could have in the future of aquaculture
Effect of light and temperature on the development of turbot eggs
Different experiments were done to determine the effeets of light
and temperature on the embryonie development of turbot eggs (Seophthalmus
maximus L.) obtained in eaptivity.
No signifieant differen~es have
from fertilization to hC'tehing in the
been found between time elapsed
trials earried out wi th 24 hours
of light and those done in dark eonditions,therefore light is not a
determining faetor in the embryonie development of turbot eggs.
The relation between temperature and time needed to reaeh eaeh
embryonie stage, shows a elear inverse relationship. The exponential-potential
equation whieh relates temperature and the age of the eggs, defined
as the time in hours elapsed sinee fertilization, is:
Y = 27.64 . e -0.11 T + 0.05 i . 1.21
1 r = 0.9904
paper also provides
for eaeh experimental
From the applieation of this equation, this
th~ development eurves for eaeh embryonie stage
temperature (in the range 10 QC to 20 QC)
Individual spawning control in different turbot (Scophthalmus maximus L.) broodstock under artificial and natural photoperiod
As fry output depends highly on management and control of the spawners, this paper examines the results with spawn obtained under a natural and artificial light cycle over a one-year period. The broodstock consisted of 55 females and 69 males, distributed with the same age and sex ratio in 5 tanks. Two of tanks were subjected to controlled photoperiod (group A) and the other three to natural conditions (group B). The spawning period of group A lasted from March until June, and that of group B from May to October. During this period, the spawning sequences of females were monitored individually. The total production of larvae was 2,233,254 larvae, of which 71.72 % were from the tanks with controlled photoperiod. In the fifth tank, fema1es which had not spawned in the previous years were tested, and no 1arvae were produced. This confirmed that the criterion for se1ection was adequate. A mean of 260,933 eggs per Kg of females were obtained, of which 45.56% were of good qua1ity. The mean ferti1ization and hatching indices were 71.40% for group A and 21.99% for group B (not inc1uding tank T-5).0,000
Crossover in the nature of the metallic phases in the perovskite-type RNiO_3
We have measured the photoemission spectra of NdSmNiO,
where the metal-insulator transition and the N\'{e}el ordering occur at the
same temperature for and the metal-insulator transition
temperature () is higher than the N\'{e}el temperature for . For , the spectral intensity at the Fermi level is high in the
metallic phase above and gradually decreases with cooling in the
insulating phase below while for it shows a pseudogap-like
behavior above and further diminishes below . The results
clearly establish that there is a sharp change in the nature of the electronic
correlations in the middle () of the metallic phase of the
NiO system.Comment: 4 pages, 4 figure, submitted to Phys. Rev.
Relationship between egg quality and fatty acid content of various turbot broodstocks (Scophthalmus maximus L.)
Versión del editor0,000
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