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Despite the long Mediterranean tradition in fishery investigations, studies on the influence of the environment on the population dynamics of exploited species are scarce, especially for deep-sea fishes. The aim of this contribution is to assess the link between body condition of nekto-benthic fishes and environmental features in two areas of the western Mediterranean, located in the Balearic (BsB) and the Algerian (AsB) sub-basins, with different geo-morphological and hydrodynamic characteristics. Two multidisciplinary surveys were carried out in December 2009 and July 2010: (i) one on board a commercial fishing boat to sample nekto- and epi-benthic communities; (ii) and (ii) another on board an oceanographic research vessel to collect hydrographic data and to sample zooplankton along the water column, as well as the meso-pelagic species of the deep scattering layers, which were detected by acoustic methods. Depths in the survey ranged from 200 and to 1000 m. Differences in community structure, fish condition of 15 exploited deep-sea fish species and environmental parameters were compared between areas and seasons, by means of uni- and multi-variant analysis and Generalized Linear Models. To estimate fish condition Fulton¿s (K) and relative condition (Kn) indices, as well as standardized residuals from the weight- length relationship, were used. Results showed a better fish condition in the BsB during in summer, despite differences among the three indices used. The oceanographic variables oxygen and fluorescence were significantly higher in the BsB during in summer season. , and sSimilar results were also obtained with respect to zooplankton, mesopelagic and epi-benthic communities, as potential preys for the nekto-benthic fish assemblages. These results show the importance of the environment on the condition of deep-sea fishes and suggest an important trophic coupling between the benthic and the pelagic domain in the Balearic Islands, one of the most oligotrophic

According to most specialists, the dearth of information on oceanic cephalopods reflects the inability of present day sampling equipments to catch them, since stomach content analyses of their predators suggest that they are very abundant along the water column. Stomach analyses, however, have an important inherent problem that should be taken into account when addressing this hypothesis. Cephalopod flesh digests more quickly than fish flesh and, in most cases, the identification of cephalopod remains is done from beaks, which are difficult to digest and may accumulate for long times in the stomachs. Such beak accumulations obviously bring forth an overestimation of the importance of cephalopods in the predator’s diet. With the expectation of determining if pelagic cephalopod abundances in the Mediterranean are in agreement with inferences from teutophagous predator’s diet, we analysed the structure and dynamics of cephalopod assemblages at different bathymetric strata from the surface to bottom grounds down to 900 m depth: 1) near surface (SUR); 2) in the benthic boundary layer (BBL); 3) in the deep scattering layer (DSL); and 4) on the bottom (BOT). Pelagic trawls were carried out in the strongest acoustic sound layers. Although bottom trawl samples were only available from daytime hours, mid-water trawl samples were taken both during the day and night, which allowed comparisons of day-night cephalopod abundances and nictemeral movements along the water column. A total of 26 cephalopod species belonging to 12 Families were caught. On the slope, diversity increased with depth from near the surface to the bottom; on the shelf, diversity was also highest at BOT. Total species richness did not show important differences at SUR, DSL and BBL levels, but increased at bottom levels both on shelf and slope. Mean species richness on the slope was higher at BBL and BOT than at SUR and DSL. On the shelf, mean species richness was markedly higher at the bottom strata than at S

Empirical and modelled data were used to examine the influence of the Leeuwin Current on larval fish assemblages along the Western Australian continental shelf and adjacent eastern Indian Ocean (22°S-34°S) during the late austral autumn. Larval fish assemblages, comprising >200 taxa from 114 neritic and oceanic teleost families, displayed significantly distinct latitudinal and cross-shelf variability, which was linked to meso-scale features of the Leeuwin Current, specifically anticyclonic eddies. Results of Lagrangian particle back-tracking showed good connection between the shelf and a developing eddy situated at 27°S; connectivity was highest in the 0-20 m depth stratum where >80% of the particles entering the eddy were derived from the shelf. This was supported by the high abundance (mean: 84 larvae m -2) of larval neritic taxa, especially small anchovy Engraulis australis larvae in the eddy. The lack of a significant difference in the size structure of these larvae between the shelf and eddy indicated continuous connection between these waters. In contrast, connectivity between the shelf and an older eddy further south was much lower (<40% of particles in the 0-20 m stratum) and the larval fish assemblage was dominated by meso-pelagic species. Further, the distribution of Myctophidae larvae (Diaphus spp.) highlighted areas of enhanced onshore transport in the south. The study has shown that, in the alongshore dominated Leeuwin Current system, cross-shelf transport can be similarly important in dispersal processes. © Inter-Research 2012

The mesopelagic fish community of the western Mediterranean was studied during two cruises carried out in December 2009 and July 2010 in the shelf and slope zones around the Balearic Islands. Much of what was previously known about this deep water group of fishes in the Mediterranean Sea came from studies performed using planktonic and small midwater nets. This study was the first attempt to use large pelagic trawls and small nets combined with information about the main sound scattering layers to analyse mesopelagic fish composition, diversity and species assemblages. This community is characterised by a relatively low diversity compared to other oceanic regions of the world, with Myctophiformes and Stomiiformes being the main contributors. Bathymetry and the level of the water column were the most important factors structuring the investigated fish assemblages, and similar vertical patterns were observed for the different species collected during the two study periods. A shelf assemblage composed of a few species of myctophids, with Notoscopelus elongatus being the main contributor, was distinguished. The slope assemblage included both Myctophiformes and Stomiiformes that showed differences in their day–night main location along the water column. In terms of species behaviour, two important groups were detected. The first was non-migrant or weakly migrant species, with the paradigmatic example being the gonostomatid Cyclothone braueri, which occurred at a depth of 400–600 m; this species is partly responsible for the permanent acoustic (38 kHz) response at this depth. The second group, near-surface migrants at night, was represented by most of the juvenile and adult myctophids, exemplified by Ceratoscopelus maderensis, with the exception of just a few of the largest size classes of some species, such as Lampanyctus crocodilus and N. elongatus that remain near the bottom

We have analysed the relationship of the ictioplankton community with its fisical and trophic environment in two hydrographical contrasting conditions (summer stratification versus autumn mixed column), and we have characterized the larval diet of five teleost species in the NW Mediterranean: the three clupeiform of the region [anchovy (Engraulis encrasicolus), sardine (Sardina pilchardus) and round sardinella (Sardinella aurita)], a small tuna [bullet tuna (Auxis rochei)] and the most important demersal species of the region [hake (Merluccius merluccius)]. These species have been chosen because they represent two different morphotypes, 1) that of the clupeiforms, which correspond to a stylized larvae with small mouth, long body and digestive tract linked to the tail, and 2) that of bullet tuna and hake, which correspond to a robust larvae with big mouth, robust body and compact digestive tract independent of the tail. Moreover, we have studied the diet variations i) along development, in relation to ii) prey availability and iii) morphology of the feeding-related structures like visual system, mouth and digestive tract. Feeding is an important aspect of the larval fish ecology that affects the population dynamics (through larval survival and subsequence recruitment fluctuations). The factors that affect the larvae in their prey selection and the feeding strategies have been scarcely studied for these species in the Catalan Sea. These factors can be different depending on the species and can change with ontogeny. The main objective of this Ph.D has been to understand the specific trophic strategies of the larvae of these five important species in Mediterranean fisheries. We can point out three types of strategies: 1) The hake’s one, which from the onset specializes feeding in a prey type (Clausocalanus spp.) and only increases the number of copepods to respond to the nutritional requirements of growth. 2) Anchovy and sardine’s type, which show low feeding incidence

Feeding ecology was analysed for the first time in the larvae of the European hake (Merluccius merluccius) to determine whether their diet and selectivity were constrained by environmental conditions and how these feeding characteristics were related to ontogeny, prey availability and visual capabilities. Larvae collected during both day and night were analysed, and it was found that feeding incidence was high, regardless of the time of day. Examination of the visual system corroborated the hypothesis that hake larvae should be able to cope with a wide range of photic conditions and to forage even at low light intensity. A clear preference for adult calanoid copepods and, especially, for Clausocalanus spp. was observed in all sizes analysed. Prey number increased with larval size, but prey size did not. This finding indicates that hake larvae behave as selective and specialist predators that consume an increasing number of prey rather than larger prey during larval growth

The feeding ecology of the larvae of the two most important small pelagic species in the western Mediterranean, anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus), is investigated. Samples were collected in early summer (anchovy) and autumn (sardine). Composition of the diet and prey selectivity were compared over the course of ontogeny in anchovy (2.7-14.5 mm standard length, SL) and sardine (5.5-15.8 mm SL) larvae. Anchovy larvae begin feeding on prey items >150 m at smaller sizes than sardine larvae, and the diets of both species are based mainly on copepod nauplii and postnauplii. Seasonal differences in the composition of the plankton influenced the contributions of prey types to the diets of the two species, e.g. the cladoceran Evadne spp. in anchovy and the tintinnid Codonellopsis sp. in sardine. Although copepod eggs are generally present in the diets of larval clupeoids, they were not major components of the diets of the species considered here. Despite morphological similarity, selection patterns were different between the species and changed through ontogeny. © 2009 International Council for the Exploration of the Sea

[EN] In some routine studies of larval condition based on RNA:DNA ratios, heads and/or guts are removed for further age and feeding analysis. Also, during capture larvae are often found with their eyes missing. In this work we analysed tissues effects (muscle, head, eye, gut and the whole larvae) on RNA:DNA ratios from different species (Sardina pilchardus, Engraulis encrasicolus, Atherina presbyter and Paralichthys orbignyanus) in different developmental stages and from different locations. For all species and development phases, it was shown that RNA:DNA ratios in the head were significantly lower than in muscle or gut. The comparison of RNA:DNA ratios of head with or without eyes did not show significant differences. In a comparison of results from muscle from two tail sections, RNA:DNA ratios were higher for the anterior section in Sardina pilchardus and Engraulis encrasicolus larvae. Caution is needed when RNA:DNA ratios are compared with other studies employing different dissection protocols. For the species studied we propose conversion factors to be applied to RNA:DNA ratio data when different body sections are analysed. We discuss the most appropriate tissues for assessing nutritional condition in fish larvae, based on trends in concentrations of nucleic acids and ratios during starvation experiments, [ES] Efecto del tipo de tejido sobre los cocientes ARN:ADN en larvas de peces marinos. – En estudios de condición nutricional larvaria basados en la relación ARN:ADN, las cabezas y/o tubos digestivos suelen diseccionarse para posteriores estudios de edad o alimentación. Además, durante la captura algunas larvas pierden los ojos. En este trabajo analizamos el efecto de diferentes tejidos (músculo, cabeza, ojos y tubo digestivo) sobre la relación ARN:ADN en Sardina pilchardus, Engraulis encrasicolus, Atherina presbyter y Paralichthys orbignyanus, en diferentes estadios de desarrollo y en diversas regiones. En todas las especies la relación ARN:ADN en la cabeza fue significativamente menor que para el músculo o el tubo digestivo. La comparación de la relación ARN:ADN de la cabeza con o sin ojos no mostró diferencias significativas. Al comparar dos secciones de músculo de la cola en Sardina pilchardus y Engraulis encrasicolus se observó mayor ARN:ADN en la parte anterior que en la posterior. Es necesaria precaución cuando se comparan ARN:ADN entre estudios que emplean diferentes protocolos de disección. Proponemos factores de conversión para ser aplicados a las relaciones ARN:ADN cuando se analizan diferentes secciones del cuerpo. Se discute cuales son los tejidos más apropiados para determinar la condición nutricional de larvas de peces, basados en las concentraciones de ácidos nucleicos y sus cocientes obtenidos en experimentos de inanición

For the first time, tuna spawning in a transport cage being towed from the western Mediterranean spawning ground to a fattening facility off the coast of northeastern Spain was examined during the 2008 fishing season. Daylight and night surface plankton samples were collected using bongo nets located in front of and behind the transport cage. The results for the different time intervals revealed clear and massive nocturnal spawning from 03:00 to 05:00, when the rear bongo was completely jammed with eggs (up to 250 000–300 000 eggs per 1000 m3). Egg size and morphology were consistent with the features of Thunnus thynnus eggs, and identification was confirmed by genetic analysis. Microscopic examination showed the eggs to be in the very early developmental stages. Spawning took place every night over the entire journey. The study showed that neither captivity nor handling/environmental changes along the route inhibited T. thynnus spawning to a very precise biological clock. The study also revealed the diel temporal concurrence of T. thynnus spawning and jellyfish larvae at the sea surface.

We analyse the spatial structure of early developmental stages of three ecologically important small pelagic schooling fish species in the northwestern Mediterranean Sea: the anchovy Engraulis encrasicolus, the round sardinella Sardinella aurita, and the sardine Sardina pilchardus. We used data on egg and larval abundance (arranged by development stage), hydrographic data and potential prey biomass collected during two cruises in summer and autumn 2005. Our analysis is based on the computation of Lloyd's patchiness index during the ontogeny of early developmental stages, as well as the computation of spatial auto-correlograms and cross-correlograms with environmental variables. The combined analysis allowed determination of the relative role of behavioural traits and the influence of hydrographic conditions in shaping the spatial structure of the three clupeiforms. We show that the spawning and developmental strategies of the two summer-spawning species (E. encrasicolus and S. aurita) are different. Engraulis encrasicolus has relatively low patchiness for all early developmental stages, while the importance of trophic variables in determining spatial structure increases during development. Sardinella aurita spawns in a trophically favourable environment and the patchiness of its early developmental stages increases for older larvae, becoming decoupled from environmental variables. The autumn spawned S. pilchardus eggs and larvae showed a development strategy similar to S. aurita, with limited importance of environmental variables in determining their patchiness

In the NW Mediterranean Sea, anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) are the most important small pelagic fish in terms of biomass and catch. Round sardinella (Sardinella aurita) and sprat (Sprattus sprattus) are also present in this region. A review of the information available on their biology and ecology has been done (Palomera et al., 2007) to point out the gaps in current knowledge necessary to understand the dynamics of small pelagic fish in the region and to progress towards a precautionary and adaptive management. The commercial exploitation of small pelagics in the NW Mediterranean has been significant since the early 1940s. Although sardine makes up the largest share, anchovy reaches a higher price in the market and is thus more important and subject to heavier fishing pressure

Larval fish assemblages within two meso-scale eddies, located off the coast of south-western Australia, were investigated as part of an interdisciplinary study examining the biophysical nature of the eddies. Larval fish were sampled using oblique and depth-stratified plankton tows, taken within the centre, body and perimeter of both a cold-core cyclonic eddy and a warm-core anti-cyclonic eddy. Larvae from the oceanic families Myctophidae, Phosichthyidae and Gonostomatidae were the most abundant within the larval fish assemblage, with larvae from the families Sternoptychidae, Paralepididae and Stomiidae also common. Larval fish assemblages from the warm-core eddy were significantly different to those from the cold-core eddy. Significant differences were found between assemblages from the centre and body, and the centre and perimeter of the warm-core eddy, but there were no significant differences across zones in the cold-core eddy. Assemblages were more strongly structured with depth in the cold-core eddy than in the warm-core eddy. The correlation of environmental data to larval fish assemblages showed that sea-surface temperature was the variable best correlated with larval fish assemblage structure between eddies. Depth of the mixed-layer was best correlated with assemblages in the warm-core eddy only, but no significant environmental correlations existed in the cold-core eddy assemblages. We hypothesise that this was a result of the differing oceanographic structure between the two eddies

Six condition indices based on RNA, total soluble protein and two metabolic enzymes [lactate dehydrogenase (LDH) and citrate synthase (CS)] were analysed in muscle tissue of individual larvae, post-flexion reared sea bass Dicentrarchus labrax using DNA and total soluble protein as standards for size. In addition, the effect of 2 days of food deprivation on the cell proliferation rates was assessed. The RNA:DNA best reflected short-term changes in feeding conditions. If standardized by DNA content, LDH activity was a better indicator of condition than any other index but RNA:DNA. Further, the analysis of cell proliferation rates in muscle from 26 day-old larvae proved useful in distinguishing continuously fed larvae from individuals subjected to 2 days of fast.

The Gulf of Lions is one of the main anchovy (Engraulis encrasicolus) spawning areas in the NW Mediterranean. During the spring, low-salinity surface water from the outflow of the Rhône is advected by the shelf-slope current along the continental slope off the Catalan coast. In June 2000, a Lagrangian experiment tracking these low-salinity surface waters was conducted to assess the importance of this transport mechanism for anchovy larvae and to determine the suitability of the tracked surface waters for survival of anchovy larvae. The experiment consisted of sampling the tracked water parcel for 10 days with three drifters launched at the core of the shelf-slope current where low-salinity surface waters were detected. The survey was completed by sampling the surrounding waters. Anchovy larvae from the spawning area in the Gulf of Lions were advected towards the south in the low-salinity waters. The size increase of anchovy larvae throughout the Lagrangian tracking closely followed the general growth rate calculated by otolith analysis (0.65 mm day−1). However, advection by the current was not the only mechanism of anchovy larval transport. A series of anticyclonic eddies, originated in the Gulf of Lions and advected southwards, seemed to play a complementary role in the transport of larvae from the spawning ground towards the nursery areas. These eddies not only contributed to larval transport but also prevented their dispersion. These transport and aggregation mechanisms may be important for anchovy populations along the Catalan coast and require further study

The Mediterranean is globally considered an oligotrophic sea. However, there are some places or certain seasons in which mechanisms that enhance fertility may occur. These mechanisms and related processes are especially relevant when they take place during the period of larval development. This study analyzes how environmental conditions occurring in the NW Mediterranean, at local and seasonal scales, contribute to determine the temporal and spatial patterns of fish reproductive activity in the region. The structure of the bathymetry, types of bottoms, diversity of adult fish habitats, as well as mechanisms conditioning the primary production of the region determine the location of spawning, whereas physical processes (e.g., shelf-slope density front and associated current, continental water inflows, winter mixing, stratification of the water column) determine the final distribution patterns of fish eggs and larvae. High larval concentrations occur over the edge of the continental shelf in relation to the presence of the shelf-slope front and its associated convergence. However, this pattern is subject to considerable spatio-temporal variability, due to frontal mesoscale activity. High larval abundance can also be observed near the coast in zones with topographic irregularities that can greatly modify circulation favouring penetration of slope waters into the shelf. Finally, larvae of large pelagic migratory species are mainly distributed in areas under the influence of recent Atlantic Water (AW) and near the frontal system between these inflowing AW and the more saline waters of the northern basin. A pronounced seasonal variability regarding both the number of species and the number of fish larvae in the plankton can be observed throughout the year. The two dominant species, sardine and anchovy, have non-overlapping spawning periods, autumn–winter and spring–summer, respectively. The diversity of feeding patterns as well as the fact that different fish species have

We estimated patchiness for different life stages (egg, larvae and juveniles) of European hake (Merluccius merluccius) from two ichthyoplankton surveys (September and November 1999) and four bottom-trawl surveys (November 1998, February, June and September 1999). Lloyd’s patchiness P=1+1/k, where k is the dispersion parameter of the negative binomial distribution, was calculated. Juveniles showed lower indices of patchiness than early ontogenetic stages. In juveniles, patchiness was highest for smaller size classes (3.5–5 cm TL) settling to their near-bottom habitat and was very low for those larger than 5 cm up to the 30–35 cm size class (approximately 3 yr of age, 50% mature individuals). Patchiness of settling juveniles was especially high in the June and September surveys, coinciding with peak recruitment to the bottom. Both eggs and yolk sac larvae showed patchiness values <10, increasing in flexion stage larvae from 12 to 20. This pattern is different to that observed in other studies for pelagic species, where patchiness of early-stage eggs is very high, but coincides with results obtained for other demersal species with pelagic eggs. Factors that may explain these patterns are discussed in light of oceanographic conditions, adult distribution and larval ontogenesis.

Relationships between environmental factors and the growth and condition of pilchard Sardina pilchardus (Walbaum) larvae were studied in November 1998 in the northwestern Mediterranean(NWM). Long-term growth of fish was assessed using otolith analysis and condition was assessed through histological and biochemical (RNA/DNA) indices. These measurements were conducted on larvae belonging to 2 station groups (A and B) previously defined through principal component analysis (PCA) on 7 environmental variables. Correlations between individual condition indices and environmental values at place of capture were also performed. Condition in environmental group A was significantly higher than in group B as assessed by both histological indices and RNA/DNA. Long-term growth, however, did not differ significantly between groups except for the otolith diameter vs. standard length (SL) relationship. The stations conforming to environmental group A were characterised by environmental ranges that would form a favorable habitat for larval success, including surface temperatures <19°C, relatively low stratification (maximum Brunt Väissälä, B-V, <0.8 cycles h-1) and mean potential food abundance >4500 nauplii(N) m-3 or >5500 of other microzooplankters (T-N) m–3. Apart from the good agreement found between histological and RNA/DNA results, each approach offered different information: histological indices detected the largest portion of unfit larvae at size-ranges ≤8 mm, whereas RNA/DNA best discriminated large larvae. The results from this study support the view that links exist between mesoscale anomalies, spawning intensity and growth or condition of pilchard larvae in the NWM.

[EN] Assay protocols for RNA and DNA in crude plankton extracts using the fluorochrome SYBR Green II are developed here. The method is based on the fluorescence in 3 aliquots: the first measures RNA after DNA digestion; the second measures DNA after RNA digestion; and the third measures residual fluorescence after digestion of both DNA and RNA. This residual fluorescence measurement is critical for accurate calculations of the nucleic acids. Optimisation of the assay conditions are described: fluorochrome concentration, buffer composition, fluorescence stability, temperature and duration of nuclease incubation. In the optimised procedure, the assays are performed in 5 mM Tris buffer (containing 0.9 mM CaCl2·2H2O and 0.9 mM MgCl2·6H2O, pH 8.0); DNase and RNase incubations are conducted at 37ºC for 20 min; the fluorochrome is added to all assays at a final concentration of 3.5x10-4 and readings are done within the 10-60 min period following the SYBR Green II addition. The study evidenced the importance of the residual fluorescence after nuclease digestion, which is especially taken into account in the calculation of the nucleic acid concentrations. Finally, the variability of the fluorescent response to different RNA and DNA standards is examined; from the performed tests, calculations are based on rRNA from calf liver and DNA from calf thymus standards. The accompanying paper (Berdalet et al., 2005) describes the development of the extraction protocol, as well as the application of both protocols in measuring RNA/DNA ratios in natural plankton samples, and a comparison with ethidium bromide based methods, [ES] En este trabajo se desarrollan los protocolos para la cuantificación de ARN y ADN en extractos no purificados de plancton utilizando SYBR Green II. El método se basa en la fluorescencia de 3 alícuotas: la primera mide el ARN tras la digestión del ADN; la segunda mide el ADN tras la digestión del ARN y la tercera mide la fluorescencia residual tras la digestión tanto del ARN como del ADN. La medida de esta fluorescencia residual es crítica para obtener una buena estimación de los ácidos nucleicos. Se describen las condiciones de optimización del ensayo: concentración de fluorocromo, composición del tampón, estabilidad de la fluorescencia, temperatura y duración de la incubación con nucleasas. En el procedimiento optimizado los ensayos se realizan en tampón Tris 5 mM (0.9 mM CaCl2·2H2O y 0.9 mM MgCl2·6H2O, pH 8); las incubaciones con nucleasas se llevan a cabo a 37°C durante 20 min; el fluorocromo se añade a todos los ensayos a una concentración final de 3.5X10-4 y las lecturas se realizan en los 10-60 min posteriores a la adición de SYBR Green II. Este estudio evidencia la importancia de la fluorescencia residual después de la digestión con nucleasas, la cual es especialmente incluída en el cálculo de las concentraciones de ácidos nucleicos. Finalmente, se examinó la variabilidad de la respuesta fluorescente a diferentes patrones de ARN y ADN (rARN de hígado de ternera y ADN de bazo de ternera). La segunda parte de este estudio describe el desarrollo del protocolo de extracción, así como la aplicación de ambos protocolos para medir los cocientes ARN/ADN en muestras de plancton naturales y una comparación con los métodos basados en bromuro de etidio

The purpose of the project is to find out the spatial structure of the distribution of planktonic organisms with a large spatial resolution. It is intended to study various biological aspects (abundance, growth, condition) and types (micro and mesoplankton, eggs, hake larvae, sardine and anchovy.Throughout the campaign a record of continuous data of surface temperature and salinity will be obtained and the currents will be measured by means of the ADCP Obtaining hydrographic profiles using a CTD probe equipped with fluorescence sensor (parameters obtained: conductivity, temperature, density and fluorescence) Obtaining meteorological data (speed and wind direction) Sampling of microzzoplankton by vertical fishing with a Calvet net along the water column Sampling of mezozooplankton and macrozooplankton (including eggs and fish larvae). Oblique type plankton catches with a Bongo net will be carried out during this phase of the campaign The samples to be used for the evaluation of abundances will be concentrated, fixed and stored for further analysis in the laboratory. Larvae from one of the network's sleeves will be selected on board and stored in formaldehyde or liquid nitrogen. for further analysis Sampling plankton through an LHPR net In the wet laboratory, a preliminary analysis of the mesozooplankton samples will be carried out to determine the maximum larval abundance strata In the most abundant strata, horizontal fishing will be carried out with the LHPR net in order to determine the horizontal structure with a finer resolution

The influence of environmental conditions on the spatial distribution patterns of the early stages of Sardina pilchardus off the Catalan coast (Northwestern Mediterranean) during November 1998, February 1999 and November 1999 was investigated. As a general rule, eggs were found on the continental shelf, while larvae displayed a wider cross-shelf distribution. The local circulation during autumn–winter 1998–1999 was dominated by an anticyclonic eddy of new Atlantic Water that remained stationary at the centre of the Catalan Sea from September 1998 to the end of February 1999. Such a situation is very infrequent and the influence of these waters extended to the continental shelf zone, modifying the slope current by diverting the flow and even reversing the direction of the flow. On the third cruise, carried out at the beginning of the spawning season of 1999 (November), the circulation and water mass distribution in the region was typical, with the old Atlantic Water occupying the whole region. Abundance of pilchard eggs and larvae during this last cruise was higher than in the previous surveys. In November 1998, the abundance of pilchard eggs and larvae was relatively low in the zones affected by the new Atlantic Water. The most interesting result of these surveys was the very low concentrations of eggs and larvae found in February 1999, possibly due to the anomalous situation created by the eddy, which had remained almost stationary during the 1998–1999 spawning season

[EN] This thesis is organised in four main chapters. The first chapter is devoted to a general introduction and objectives. Number two is devoted to all the work developed in the laboratory. Chapter three embraces all the work that was done with field data. Each of these two central chapters collects a mixture of published and row material. In the sake of clarity, all the thesis has been written in the same format, regardless the state of publication of the information. If the information of a particular section has been published, it is indicated at the beginning of the section. Information which is considered important but which was not included in a particular published section, has been inserted after authors’ approval. A brief introduction and extensive discussion is given in each of the sections conforming chapters two and three. In chapter four, the main conclusions from each part are summarised. Provided that the thesis is organised in a similar way that a compendium of publications, and as a guide to the reader, the repetition of some material at the introduction was unavoidable, [ES] Esta tesis se organiza en cuatro capítulos principales. El primer capítulo ofrece una introducción y objetivos generales. El segundo contiene la información obtenida de la experimentación en laboratorio. El tercer capítulo está dedicado a los estudios de campo. Cada uno de estos capítulos centrales se organiza en secciones. La información que contienen son una mezcla de material publicado e inédito. Todas las secciones se han escrito en un formato similar para facilitar la comprensión. Si una sección o parte de ella ha sido publicada, la referencia se señala al principio de la sección correspondiente. En los casos en que la información publicada ha sido ampliada, se ha obtenido el consentimiento de los autores de la publicación. En cada sección de los capítulos centrales se ha añadido una introducción y una discusión. En el capítulo cuarto se recogen las conclusiones generales de la tesis. Dado que la estructura de las seccciones es similar a la de un artículo, fue inevitable incluir, en algún caso, información redundante

Digital image analysis was applied to quantify the degradation of muscle in sea bass Dicentrarchus labrax (Pisces: Moronidae) larvae. The measure obtained was the percentage muscle fibre separation (MFS). This measurement was compared to that obtained through classical scoring. The percentage MFS classified correctly a larger number of larvae from different feeding treatments (Fed, Starved and Delayed treatments) and paralleled nutritional condition, both by age and by size. It also yielded a significant correlation with the survival of the Starved larvae. The onset of the mass mortality of Starved larvae was used to define a critical value (Mmax) of 6% MFS which would severely handicap survival. We regard MFS as a useful contribution to the determination of condition in fish larvae. It is a relatively fast quantitative method, and its use would reduce the bias caused by discrete grading (scores) and by differences in individual expertise

Anchovy and pilchard are the most abundant pelagic species in the NW Mediterranean Sea. They spawn in different seasons, subject to different environmental conditions: anchovy in summer, when the water column is stratified; pilchard in winter, when the water column is vertically homogeneous. The spatial distribution patterns of eggs and larvae of these 2 species are compared in relation to the main productive features in the region during their respective spawning seasons. The study was performed on the continental shelf off the Ebro River (NW Mediterranean) during June (for anchovy) and February (for pilchard). Sampling comprised a horizontal survey, designed to locate patches of eggs or larvae, followed by a Lagrangian experiment using stratified hauls to study the vertical distributions at different times of day in the water parcel tracked. While pelagic eggs and larvae of both species were present in the upper 70 m of the water column, we recorded differences in the preferential vertical distribution and migration patterns. Maximum concentrations of anchovy eggs and larvae were located in the upper 20 m; pilchard concentrations extended down to 10-40 m. Vertical displacements by the larger larvae at night occurred in both species, but with opposite patterns: anchovy larvae tended to aggregate in the upper 10 m, pilchard larvae exhibited greater dispersal at night, with a preference for levels below 30 m

This document is the final report of the research programme "Impact of fishery and environment on hake recruitment in Northwestern Mediterranean", LLUCET, funded by the Eurpoean programme FAIR, contract CT97-3522. The LLUCET project has been developed by 5 partners: ICM-CSIC - Institut de Ciències del Mar de Barcelona. Consejo Superior de Investigaciones Científicas IFREMER - Institut Français de Recherche pour l'Exploitation de la Mer CIBM - Centro Interuniversitario Biologia Marina Ecologia Applicata "G. Bacci" Livorno IZUG - Istituto di Zoologia. Università di Genova IMEDEA-CSIC - Institut Mediterrani d'Estudis Avançats. Consejo Superior de Investigaciones Científicas

The presence of a surface layer of a less saline water of continental influence (CIW) along the continental slope off the Catalan coast (NW Mediterranean) was observed in June 1995. This CIW was formed in the Gulf of Lions from Rhône runoff and carried by the current associated with the shelf-slope front. This study analyses the spatio-temporal behaviour of that water of continental influence in relation to the shelf-slope front, and its effect on the distribution of fish larvae, in particular the larvae of the anchovy, Engraulis encrasicolus. Displacements of the front are observed to follow an oscillation with a period of eight days and an amplitude of 10 km. Anchovy larvae were associated with the presence of CIW, whereas the oceanic species Hygophum benoiti appeared in the region of the slope when the front, and the associated CIW layer, moved close inshore during its oscillation. The size frequency distribution for the anchovy larvae trapped within the CIW suggests that the larvae had been spawned further north, near the Gulf of Lions. It is concluded not only that larvae were transported by the current but also that their development had taken place entirely inside the CIW. The possible benefit to the survival of anchovy larvae of being kept inside that water, though they have been carried far from their spawning areas, is discussed in the basis of fluorescence and microzooplankton data

[EN] This paper describes the suitability of a closed recirculation system to study the development of fish larvae in a strictly controlled environment, where only feeding was varied (fed, starved, delayed and late fast treatments). The system served both as an incubator and hatchery. The time variation of physical and chemical parameters together with survival and growth of reared sea bass larvae (Dicentrarchus labrax) were studied over the first month of life. The recirculation design allowed for the maintenance of levels of ammonia, nitrite and nitrate below those cited as responsible for mortality or decreased feeding ability in other marine fish larvae. Almost no larval mortality occurred in the fed larvae from day 9 after hatching. The starved group of larvae showed a sharp decline in survival after 16 days of food deprivation. Larvae for which feeding was delayed until day 13 ceased dying 4 days after food was supplied. Fast feeding on days 24 and 25 had no effect on larval survival. Growth in length was similar during the first 2 weeks of larval life regardless of feeding treatment. Two days of late fast had no effect on larval growth. Growth patterns of fed larvae in this study were similar to those reported for larvae reared in flow through systems. We believe that survival and growth of the reared larvae was a direct function of diet, and that the type of rearing system did not adversely affect these parameters. The rearing design and the results obtained suggest that future nutritional studies of field-collected larvae will benefit from this kind of rearing experiment. (C) 2000 Ifremer/Cnrs/Inra/Ird/Cemagref/Editions scientifiques et medicales Elsevier SAS, [FR] Cette étude décrit l'adaptation d'un système de circulation d'eau en circuit fermé pour analyser le développement de larves de poisson en milieu strictement contrôlé lorsque seule, l'alimentation varie (larves nourries, à jeun, alimentation différée, et alimentation accélérée mais tardive). Le sytème sert à la fois d'incubateur et d'écloserie. Les variations dans le temps des paramètres physiques et chimiques, associées au taux de survie, à la croissance des larves de bar (Dicentrarchus labrax) ont été étudiées au cours de leur première année. Le système de recirculation permet le maintien de niveaux d'ammoniaque, nitrite et nitrate inférieurs à ceux connus pour provoquer des mortalités ou d'une baisse des capacités nutritionnelles des larves. Presqu'aucune mortalité larvaire ne s'est produite chez les larves nourries à partir du 9e jour après l'éclosion. Le groupe de larves restées à jeun a montré une forte hausse de la mortalité après 16 jours de privation de nourriture. Les larves dont l'alimentation a été différée jusqu'au 13e jour, cessèrent de disparaître 4 jours après qu'elles soient alimentées. Les larves nourries plus rapidement le 24e et 25e jour n'ont pas eu un taux de survie modifié. La croissance en longueur était similaire durant les deux premières semaines de vie larvaire quel que soit le traitement. Deux jours d'alimentation différée mais rapide n'ont pas eu d'effet sur la croissance. Le modèle de croissance des larves nourries dans cette étude était similaire à celui de larves élevées en circuit ouvert. Nous pensons que la survie et la croissance de larves en élevage est une fonction directe de l'alimentation et que ce type de système d'élevage n'affecte pas ces paramètres. Le système d'élevage et les résultats obtenus montrent que des études nutritionnelles sur des larves collectées dans le milieu naturel bénéficieront de ce type d'expérimentation

The study focuses on the analysis of the physiological and developmental conditions of sardine larvae. It is intended to compare the physiological situation of larvae developed at various points (platform, slope) and in different periods

The study focuses on the analysis of the physiological and developmental conditions of sardine larvae. It is intended to compare the physiological situation of larvae developed at various points (platform, slope) and in different periods

Study on the distribution of hake eggs and larvae and their relationship to hydrographic conditions

The paper is based on larval distribution data from five lanternfish species outside the spawning grounds of the adult populations. Using hydrographic information collected with the larvae, the effect of surface currents on the observed patterns of distribution is discussed. In the South-East Atlantic, adjacent to the Benguela upwelling system, larvae of the pseudoceanic Lampanyctodes hectoris were found farther offshore (250 - 450 km) than usual. The general flow of the current is parallel to the coast, but upwelling filaments extend offshore. The size distributions of the L. hectoris larvae found, together with the rather low temperature at two of the oceanic stations sampled, indicate that they had been displaced by a filament. In the South-West Indian Ocean, the distribution of larvae of highly oceanic species of lanternfish over the shelf is related to onshore intrusions of the Agulhas Current. The size distributions of Hygophum hygomii and Scopelopsis multipunctatus indicate southward transport of larvae. The presence of larvae of Myctophum selenops and Benthosema pterotum, which have not been documented as adults in the region, indicates not only transport to the area, but also that spawning could be taking place closer to the area than previously reported

Se analiza la presencia de larvas de peces a lo largo de un ciclo anual en la zona litoral de la costa catalana sujeta a la influencia de los efectos hidrodinámicos del cañón de Blanes

This study examines the extent of the interaction between the short- time-scale variability in the location of the shelf-slope salinity front and the species composition and abundance of larval fish in the NW Mediterranean. Three extensive cruises were carried out during spring (May and June 1992), a season characterized by high mesoscale variability. Variations in the position of the shelf-slope front were correlated with large changes in the distribution and abundance of fish larvae. In the 3 surveys, offshore dispersal of fish larvae of shelf-dwelling species appeared to be limited by the geographical position of the front. When the frontal structure was detected over the shelf, the distribution of larvae of shell- dwelling species was confined to the coastal side of the front, while larvae of mesopelagic fish species were located on the oceanic side. When the front was detected over the slope, it did not act as a barrier separating the larval distributions of shelf and oceanic species but instead limited the offshore extent of the larval distribution of shelf species