Laboratory investigation of daily food intake and gut evacuation in larvae of African catfish Clarias gariepinus under different feeding conditions

Abstract Temporary accumulation of ascorbic acid 2-sulfate (AAS) was measured to estimate food intake and gut evacuation in larvae of African catfish. Fish larvae were fed decapsulated cysts of Artemia containing AAS. In a first experiment it was found that no biosynthesis of AAS occurs in the larvae of this species. In a second experiment, the gut contents of the fish larvae fed were calculated as they changed during development. In a third experiment, the gut evacuation rate of fish larvae was determined during continuous and discontinuous feeding regimes in the first five days after the start of exogenous feeding. Food consumption by catfish larvae increased from 46.5% of their body dry weight (BDW) on day 1 after the start of exogenous feeding to 53.8% BDW on day 3. Thereafter, food consumption decreased to 27.8% BDW on day 5. A similar pattern was observed for gut evacuation, which increased during the first days of exogenous feeding and decreased as fish growth continued. The rate of gut evacuation in a continuous feeding regime was significantly higher (P <0.05) than that under discontinuous feeding. On day 1 post-hatch and 7 h after first food ingestion the fish larvae evacuated 87% of the food in continuous feeding compared with 43% under discontinuous feeding. It was found that gut emptying differs during larval development. Under continuous feeding, on days 1 and 3 post-hatch and 11 h after the first meal 90% of the food was evacuated compared with 71% evacuated on day 5. The advantages and limitations of the AAS method for estimation of food consumption by fish larvae are discussed

Integral Field Spectroscopy based H\alpha\ sizes of local Luminous and Ultraluminous Infrared Galaxies. A Direct Comparison with high-z Massive Star Forming Galaxies

Aims. We study the analogy between local U/LIRGs and high-z massive SFGs by comparing basic H{\alpha} structural characteristics, such as size, and luminosity (and SFR) surface density, in an homogeneous way (i.e. same tracer and size definition, similar physical scales). Methods. We use Integral Field Spectroscopy based H{\alpha} emission maps for a representative sample of 54 local U/LIRGs (66 galaxies). From this initial sample we select 26 objects with H{\alpha} luminosities (L(H{\alpha})) similar to those of massive (i.e. M\ast \sim 10^10 M\odot or larger) SFGs at z \sim 2, and observed on similar physical scales. Results. The sizes of the H{\alpha} emitting region in the sample of local U/LIRGs span a large range, with r1/2(H{\alpha}) from 0.2 to 7 kpc. However, about 2/3 of local U/LIRGs with Lir > 10^11.4 L\odot have compact H{\alpha} emission (i.e. r1/2 < 2 kpc). The comparison sample of local U/LIRGs also shows a higher fraction (59%) of objects with compact H{\alpha} emission than the high-z sample (25%). This gives further support to the idea that for this luminosity range the size of the star forming region is a distinctive factor between local and distant galaxies of similar SF rates. However, when using H{\alpha} as a tracer for both local and high-z samples, the differences are smaller than the ones recently reported using a variety of other tracers. Despite of the higher fraction of galaxies with compact H{\alpha} emission, a sizable group (\sim 1/3) of local U/LIRGs are large (i.e. r1/2 > 2 kpc). These are systems showing pre-coalescence merger activity and they are indistinguishable from the massive high-z SFGs galaxies in terms of their H{\alpha} sizes, and luminosity and SFR surface densities.Comment: Accepted for publication in A&A. (!5 pages, 7 figures, 2 tables

Reglas de dimensionamiento en trazas tardogóticas españolas. Las catedrales de Sevilla y Segovia

The design and dimensioning criteria of the Gothic structures are currently not well known. This is exacerbated in the Spanish case, by the lack of coeval treaties like the Central European ones. These compile many simple numerical and geometrical rules, which could be analogous to the Spanish ones. These will be studied based on the cathedral traces of Seville and Segovia, drawn to scale and with labelled dimensions, specifying the length and width of the different building parts, and the pillars and walls sections. These elements and the buttresses compose the vertical structure. They are the main purpose of this study, for which the Late Gothic treaties are considered as a reference. Different hypotheses about the Spanish structural rules have been formulated, which could have been used by the masters for an initial dimensioning, drawn in the trace. This was enough to start the building ensuring technical feasibility.Los criterios de diseño y dimensionamiento de las estructuras góticas aún nos son en gran medida desconocidos, y particularmente en España al carecer de una tratadística coetánea similar a la centroeuropea. Ésta evidencia un sencillo proceder a través de reglas numéricas o geométricas, y cuyo paralelo se pretende detectar en nuestro contexto. Para ello se recurre al análisis de las trazas catedralicias de Sevilla y Segovia, dibujadas a escala e incluso con algunas cotas dimensionales rotuladas, especificando luces y secciones de pilares y muros. Estos elementos, junto con los contrafuertes, constituían la estructura portante vertical, y son el objeto principal de estudio, tomando como referente la tratadística centroeuropea. Ello ha permitido formular hipótesis sobre las posibles reglas estructurales al uso en nuestro país, que se utilizarían establecer un primer dimensionamiento, plasmado en la traça general del edificio. Éste sería suficiente para comenzar la fábrica con razonables garantías de viabilidad

Eight years of research on bluefin tuna (Thunnus thynnus) culture at the Spanish Institute of Oceanography (IEO)

Since 2000 the Spanish Institute of Oceanography (IEO) is participating in several research projects on BFT culture with the aim of contributing of the Domestication of this species, for improving the productive process and reducing the pressure on the wild stock as it has already happened with other full cycle cultured species

Spain's Atlantic Bluefin Tuna Aquaculture

In this chapter, we outline the advantes in Spain's ABT aquaculture between 2011 and 2015 and conclude with the details of the new land-based facility designed to take us into the future.Versión del edito

Closing the life cycle of the Atlantic bluefin tuna Thunnus thynnus in captivity

This is the first time that closing the life cycle of ABFT in captivity is reported. Egg size, larval size and hatching rate were similar to those observed in wild broodstock in last five years. This milestone will enable faster development of integrated aquaculture of this species, consolidating the leadership that the IEO and Murcia Region have in the domestication of bluefin tuna, at European and global scale

Recruits from farmed ABFT in Murcia ?

It has been demonstrated at least in the Murcia area, that the captive ABFT (Thunnus thynnus) for fattening activities reproduce actively in the farming cages in the natural spawning season (early June – middle July). Tens of millions of fertilized eggs coming from these cages had been collected in the last years and cultured in the facilities of the Spanish Institute of Oceanography (IEO) in Mazarrón (Murcia, SE Spain) and grown up to juveniles, demonstrating as well their viability. Taking into account that an ABFT female could spawn roughly hundred thousands of eggs per kg during all the spawning season and thousands of tones of ABFT adults have been farmed in the Murcia coast during the last years, the total fertilized eggs could reach hundreds of billions every year. Obviously the conditions in the Murcia coast are different of the natural spawning areas not only regarding the feeding availability but also the massive presence of many egg and larvae predators. It would be recommendable to carry out prospecting surveys in the aim to shed some light on this possible effect of farmed ABFT on the recruitment at least in Murcia