SUMMARY: Several works have demonstrated trends in the distribution of fish species relative to global warming. This study investigated whether similar trends have occurred for selected flatfish species on the continental shelf of the Bay of Biscay. These species were used as indicators and changes in their populations were studied in a coastal nursery ground where flatfish juveniles are concentrated as well as on the entire shelf. Previous studies analysing changes in sea surface temperature for the continental shelf indicate that winter warming occurred in the 1980s and 1990s. Sixteen autumn cruises conducted since 1981 in the Bay of Vilaine nursery area and 11 autumn cruises since 1987 over the entire shelf provided data on a nearly annual basis for the abundance of benthic fish. The four most common flatfish species were selected and their occurrence and yearly abundance were analysed with regard to specific biogeographic ranges and climate change. Similar results were obtained for juveniles on a nursery scale and for all age groups on the entire shelf. Although sole (Solea solea) showed irregular yearly variations, northern winter spawners such as plaice (Pleuronectes platessa) and dab (Limanda limanda) exhibited significantly high abundance during the 1980s, followed by a continuing low level and ultimately zero catches. On the other hand, the wedge sole (Dicologoglossa cuneata), a southern summer spawner, showed an increasing trend in the late 1990s. Diversos trabajos han demostrado tendencias en la distribución de especies de peces relacionadas con el calentamiento global. Este estudio se investigó si han ocurrido tendencias similares en especies seleccionadas de peces planos en la plataforma continental del Golfo de Vizcaya. Esas especies fueron usadas como indicadores y los cambios en sus poblaciones fueron analizados tanto en un área costera de concentración de juveniles como en toda la plataforma. Estudios previos de los cambios en la temperatura superficial del mar en la plataforma continental, indican la ocurrencia de periodos de calentamiento de invierno en los años 1980s y 1990s. 16 campañas de otoño realizadas desde 1981 en el área de crecimiento de la Bahía de Vilaine y 11 campañas de otoño efectuadas desde 1987 en toda la plataforma continental proporcionaron datos en una base casi anual de la abundancia de peces bentónicos. Se seleccionaron las cuatro especies de peces planos más comunes y su presencia y abundancia anual fueron analizadas con respecto a sus rangos biogeográficos específicos y al cambio climático. Se obtuvieron resultados similares para los juveniles en su área de crecimiento y para todos los grupos de edad a escala de toda la plataforma continental. Aunque el lenguado (Solea solea) mostró variaciones anuales irregulares, la solla (Pleuronectes platessa) y la limanda (Limanda limanda) que se reproducen en invierno mostraron una abundancia significativamente más alta durante los 1980s, seguida de una disminución continua y por último capturas nulas. Por el contrario, el lenguad...

SUMMARY: Indicators of growth and condition were used to compare the habitat quality of nurseries of juvenile sole (Solea solea L.) in the Bay of Biscay, based on one survey in 2000. The four biological indicators are poorly correlated with each other, suggesting that no single measure may give an adequate description of fish health and of its habitat's quality. Growth indicators showed significant differences between northern and southern areas. Juveniles from the two southernmost nurseries, the Gironde estuary and the Pertuis Antioche, displayed significant lower otolith increment widths and mean sizes. These differences were inversely related to water temperature and unrelated to genetic or age differences, and are unlikely to be due to limiting trophic conditions in the nurseries. Hence, they may be considered in terms of differences in habitat quality and potential anthropogenic impacts. Condition indices do not show this north-south pattern but highlight low condition values in the Pertuis Antioche. Shortterm and fluctuating biochemical indicators such as RNA/DNA ratios appeared to be unreliable over a long-term study, while morphometric indices seemed to be relevant, complementary indicators as they integrate the whole juvenile life-history of sole in the nurseries. The growth and condition indices of juveniles in September 2000 from nursery grounds exposed to the Erika oil spill in December 1999 were relatively high. These results lead us to suggest that there was no obvious impact of this event on the health of juvenile sole and on the quality of the exposed nursery grounds a few months after the event.Keywords: essential fish habitat, otolith daily increment width, RNA/DNA, Erika oil spill. -Se usaron indicadores de crecimiento y condición de lenguados juveniles (Solea solea L.) para comparar la calidad del hábi-tat de áreas de cría en el Golfo de Vizcaya basados en un muestreo de 2000. Los cuatro indicadores biológicos mostraron bajas correlaciones entre sí, lo que sugiere que no existe una medida única para describir adecuadamente el estado de los peces y la calidad de su hábitat. Los indicadores de crecimiento mostraron diferencias significativas entre las áreas septentrionales y meridionales. Los juveniles de las áreas situadas más al sur: el estuario del Garona y Pertuis Antioche mostraron incrementos de otolitos y tamaños medios significativamente inferiores. Estas diferencias están inversamente relacionadas con la temperatura del agua, pero no con diferencias genéticas o de edad, y no es probable que se deba a una condición trófica limitante en las áreas de cría. Por tanto, pueden considerarse en términos de calidad del hábitat y el potencial impacto antropogénico. Los índices de condición no muestras este patrón norte-sur sino que destacan los bajos valores de condición en Pertuis Antioche. Los indicadores bioquímicos variables de corto término como las relaciones RNA/DNA no parecieron fiables para estudios de mayor escala, mientras que los índices morfométricos parecen ser relevantes y complem...

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Juveniles of numerous commercial marine flatfish species use coastal and estuarine habitats as nurseries. Hence, they are likely to be exposed to a number of anthropogenic stressors such as accidental and chronic exposure to chemical contaminants. Little is known about their response to such pollutants at the individual level and about the consequences on their population dynamics. Mesocosm experiments were conducted to determine whether short (24 h) but high exposure to petroleum hydrocarbons (1/1000 v: v water: fuel), similar to what happened after an oil spill on coastal areas, affects survival and biological (growth, body condition and lipid reserve) performances of juvenile common sole, which live on near shore and estuarine nursery grounds. Results demonstrated that this type of exposure significantly reduce survival, growth (size, recent otolith increment and body condition), and especially energy storage (triacylglycerol to free sterol ratio) of the juvenile fish on the medium-term (three months after the exposure). These medium-term consequences affect future recruitment of this longlived species.