SUMMARY:The Alborán Sea is a hydrographically complex and variable area in which wind-driven coastal upwelling occurs. Its most abundant small pelagic resource is the sardine (Sardina pilchardus), which is subject to major interannual oscillations. Postflexion stages of sardine larvae were sampled in their main nursery grounds in the north Alborán Sea, and sardine juveniles were sampled periodically throughout the recruitment season. Daily growth analysis was used to identify periods favourable for larval survival and to assess the evolution of daily increment widths during the first months of life. The results showed that juveniles born later in the spawning season grew relatively faster than those born earlier. Two main growth phases were observed in juveniles: an initial one in which daily increment widths increased progressively, and a second one in which widths fluctuated, showing a decreasing trend. The beginning of the second phase was almost synchronous among different sub-cohorts, suggesting that it was triggered by environmental factors. The estimated mean daily growth rates during the larval phase were higher in surviving juveniles than in postflexion larvae born in the same month, supporting the "bigger is better" hypothesis in relation to larval survival. The influence of the environmental regime on growth was explored, and the evolution of a growth-related index, derived from otolith increment width variability, was compared with a single environmental descriptor, a "wind index" based on wind stress and direction. This analysis suggested that larval survival and larval and juvenile growth rates showed a positive correlation with NW component winds, associated with upwelling events on the continental shelf and calm sea weather conditions in the inshore nursery grounds. Conversely, Levantine and southern wind periods, which interrupt the upwelling and create rough seas in the inshore bays, lead to a decrease in growth rates in juveniles and low larval survival.Keywords: Sardina pilchardus, daily growth, wind stress, recruitment, Alborán Sea. RESUMEN: CRECIMIENTO DIARIO EN LARVAS EN POSTFLEXION Y JUEVENILES DE SARDINA (SARDINA PILCHARDUS WALB.) DEL MARDE ALBORÁN: INFLUENCIA DEL VIENTO. -El mar de Alborán es una zona hidrográficamente compleja y variable, en la que se producen fenómenos de afloramiento costero inducidos por vientos. Su recurso más abundante entre los pequeños pelágicos es la sardina (Sardina pilchardus), que está sujeto a importantes fluctuaciones interanuales. Se muestrearon estadios larvarios avanzados (larvas en estadio de postflexión del urostilo), en sus principales áreas de reclutamiento del norte del mar de Alborán. Los juveniles de sardina fueron muestreados periódicamente a lo largo de la temporada de reclutamiento. Estudios de crecimiento diario permitieron identificar periodos de alta supervivencia larvaria, así como analizar la evolución de la anchura de los microincrementos durante los primeros meses de vida, revelando que los juveniles nacidos más tarde en la época de pue...

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SUMMARY:The waters surrounding the Balearic archipelago are considered to be prime spawning habitats of the bluefin tuna (Thunnus thynnus) and other tuna species such as albacore (T. alalunga) in the Mediterranean. During the 2003 bluefin and albacore spawning season, a tuna larval survey (TUNIBAL 0703) was carried out to assess the distribution of bluefin larvae in relation to hydrographic mesoscale features. Tuna larvae were collected by means of surface plankton tows with a bongo gear with a quadrangular mouth measuring 1 m diagonally. The otolith microstructure of 157 and 71 field-captured larvae of Mediterranean bluefin and albacore, respectively, were analyzed to estimate the daily growth pattern. Furthermore, biochemical analysis to estimate DNA, RNA and protein content was done on another batch of 114 bluefin and 132 albacore larvae. The size range included pre-flexion to post-flexion larvae, from 2.8 to 8.6 mm in body length. bluefin and albacore larvae grew linearly in standard length (0.35 and 0.33 mm/day, respectively) and potentially with respect to dry weight. No significant differences between species were observed in the size-weight relationship, or in the allometric relationship of body size and weight to otolith radius. However, the relationship of DNA and RNA to body size and weight showed a significant difference between species. Bluefin tuna larvae showed a greater nucleic acid content than albacore larvae. Protein content showed no significant differences with respect to body length.Keywords: bluefin tuna, albacore tuna, larvae, Mediterranean, growth, RNA/DNA, proteins. RESUMEN: CRECIMIENTO Y CONTENIDO DE LARVAS DE ATÚN ROJO (THUNNUS THYNNUS) Y ATÚN BLANCO (THUNNUS ALALUNGA).-Las aguas de las Islas Baleares representan una de las zonas más importantes de puesta del atún rojo (Thunnus thynnus) y de otras especies asociadas, como el atún blanco albacore (T. alalunga). En julio del 2003, época de puesta del atún, se realizó la campaña TUNIBAL, con el fin de delimitar las zonas de puesta del atún rojo, así como su relación con el modelo de circulación en el área. Las larvas de atunes se muestrearon mediante arrastres superficiales con una red Bongo de boca cuadrangular (1 m en diagonal). Para el estudio del crecimiento diario, 157 larvas de atún rojo y 71 larvas de atún blanco fueron analizadas. Para el estudio de la condición larvaria (DNA, RNA y proteínas), 119 larvas de atún rojo y 138 larvas de atún blanco fueron analizadas. Se analizaron larvas desde estados de pre-flexión a post-flexión, desde 2.8 a 8.6 mm de longitud estándar. Las larvas de atún rojo y atún blanco crecen linealmente en longitud estándar (0.35 y 0.33 mm/día respectivamente) y potencialmente en peso seco. No se encontraron diferencias significativas en la relación talla-peso, o en la relación del radio del otolito con talla o peso. Sin embargo, la relación entre DNA y RNA con talla o peso mostró diferencias significativas entre especies, siendo el atún rojo el que mostró mayores contenidos en ácidos nucleicos. No obstante,...

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