Growth and condition of juvenile sole (<em>Solea solea</em> L.) as indicators of habitat quality in coastal and estuarine nurseries in the Bay of Biscay with a focus on sites exposed to Erika oil spill

Abstract

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...

Effect of starvation on condition and growth of juvenile plaice Pleuronectes platessa: nursery habitat quality assessment during the settlement period

“…However, according to GLMs, density of juvenile plaice in the area showed no significant effect on RNA/DNA values. This agrees withGilliers et al (2006) who found no evidence for density-dependent effects on juvenile sole S. solea condition in the Bay of Biscay. Thus, other factors, which were not considered in the present study, are probably the cause of variability.…”

“…Mehner & Wieser (1994) reported that in response to the stress of starvation, animals may reduce their resting metabolic rate and direct energy reserves away from growth into the support of vital processes. As reported by Gilliers et al (2006), the different time of response of biological indices suggests that no single measure may give an adequate description of fish habitat's quality. Compared with results reported by other authors, the sensitivity of the biological indices measured on juvenile plaice is in accordance with the literature.…”

Growth performances of juvenile soleSolea soleaunder environmental constraints of embayed nursery areas

“…In contrast, after being released into the pond, the sole recovered a better condition and growth. Within 160 days, they reached the maximum K observed in the Bay of Biscay in late summer (∼1.3 g cm −3 in Gilliers et al 2006). Those high growth performances and condition level were achieved at high fish densities (300 sole 1000 m −2 ) as compared with commonly estimated densities on main nursery grounds (e.g.…”

“…In the Bay of Biscay, the main nursery grounds have been localised in estuaries and bays from yearly autumn surveys (Le Pape et al 2003a). Comparison of various biological indicators indicated quality differences between nurseries, depending on the particular estuary or bay location (Le Pape et al 2003b;Gilliers et al 2006). In embayed nursery areas, and especially in the Pertuis Breton (Fig.…”

The food limitation hypothesis for juvenile marine fish

“…Indeed, density is less variable, food limitation is more obvious (Duncan and Holland 2006), and growth is less biased due to size-dependent selection (Meng et al 2000;Le Pape et al 2003a;Gilliers et al 2006;Amara et al 2007Amara et al , 2009Selleslagh and Amara 2013). Indeed, density is less variable, food limitation is more obvious (Duncan and Holland 2006), and growth is less biased due to size-dependent selection (Meng et al 2000;Le Pape et al 2003a;Gilliers et al 2006;Amara et al 2007Amara et al , 2009Selleslagh and Amara 2013).…”