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Estuaries serve as nursery grounds for many marine fish species. However increasing human activities within estuaries and surrounding areas lead to significant habitat loss for the juveniles and decrease the quality of the remaining habitats. This study is based on the data of 470 beam trawls from surveys that were conducted in 13 French estuaries for the purpose of the European Water Framework Directive. It aimed at testing the effects of anthropogenic disturbances on the nursery function of estuaries. With a multispecific approach based on ecological guilds, two fish metrics, abundance and species richness of Marine juvenile migrant fishes, were used as proxies for the estuarine nursery function. Indices of heavy metal and organic contaminations were used to estimate anthropogenic disturbances impacting these estuaries. Fish metrics were described with statistical models that took into account: (a) sampling protocol, (b) estuarine features and (c) contamination. The results of these models showed that the fish metrics highly depend on the sampling protocol, and especially type of gear, depth and salinity, which highlights the necessity of considering such metrics at the sampling (trawl haul) scale. Densities and species richness of Marine juvenile fishes appeared to be strongly and negatively correlated to contamination indices. These results are consistent with the hypothesis that human disturbances impact the nursery function of estuaries. Finally, the densities of Marine juvenile migrant species appeared as a potential robust and useful fish indicator for the assessment of the ecological status of estuaries within the Water Framework Directive. (C) 2008 Elsevier Ltd. All rights reserved.

Estuaries serve as nursery grounds for many marine fish species. However increasing human activities within estuaries and surrounding areas lead to significant habitat loss for the juveniles and decrease the quality of the remaining habitats. This study is based on the data of 470 beam trawls from surveys that were conducted in 13 French estuaries for the purpose of the European Water Framework Directive. It aimed at testing the effects of anthropogenic disturbances on the nursery function of estuaries. With a multispecific approach based on ecological guilds, two fish metrics, abundance and species richness of Marine juvenile migrant fishes, were used as proxies for the estuarine nursery function. Indices of heavy metal and organic contaminations were used to estimate anthropogenic disturbances impacting these estuaries. Fish metrics were described with statistical models that took into account: (a) sampling protocol, (b) estuarine features and (c) contamination. The results of these models showed that the fish metrics highly depend on the sampling protocol, and especially type of gear, depth and salinity, which highlights the necessity of considering such metrics at the sampling (trawl haul) scale. Densities and species richness of Marine juvenile fishes appeared to be strongly and negatively correlated to contamination indices. These results are consistent with the hypothesis that human disturbances impact the nursery function of estuaries. Finally, the densities of Marine juvenile migrant species appeared as a potential robust and useful fish indicator for the assessment of the ecological status of estuaries within the Water Framework Directive. (C) 2008 Elsevier Ltd. All rights reserved.

Estuaries serve as nursery grounds for many marine fish species. However increasing human activities within estuaries and surrounding areas lead to significant habitat loss for the juveniles and decrease the quality of the remaining habitats. This study is based on the data of 470 beam trawls from surveys that were conducted in 13 French estuaries for the purpose of the European Water Framework Directive. It aimed at testing the effects of anthropogenic disturbances on the nursery function of estuaries. With a multispecific approach based on ecological guilds, two fish metrics, abundance and species richness of Marine juvenile migrant fishes, were used as proxies for the estuarine nursery function. Indices of heavy metal and organic contaminations were used to estimate anthropogenic disturbances impacting these estuaries. Fish metrics were described with statistical models that took into account: (a) sampling protocol, (b) estuarine features and (c) contamination. The results of these models showed that the fish metrics highly depend on the sampling protocol, and especially type of gear, depth and salinity, which highlights the necessity of considering such metrics at the sampling (trawl haul) scale. Densities and species richness of Marine juvenile fishes appeared to be strongly and negatively correlated to contamination indices. These results are consistent with the hypothesis that human disturbances impact the nursery function of estuaries. Finally, the densities of Marine juvenile migrant species appeared as a potential robust and useful fish indicator for the assessment of the ecological status of estuaries within the Water Framework Directive. (C) 2008 Elsevier Ltd. All rights reserved.

Restructuring coastal fish nursery habitats by extensive shellfish fanning in the French part of the Bay of Biscay could influence fish physiology and behaviour and affect the ecological performance of the species. The influence of oyster-trestle cultivation installations on sole (Solea solea) swimming behaviour was investigated using an experimental pond mesocosm. A pen was constructed with three interconnected zones (two with bags of live oysters or oyster shells on trestles, and one free zone). Water renewal depended on the tide. Environmental variables were recorded continuously (temperature, oxygen, pH, meteorological data), every 3-5 days (salinity, samples taken for water analysis and estimation of sedimentation rate) or intermittently (illumination). Sediment cores were taken in each zone before and after the experiment, for sediment redox and water content, plus an evaluation of potential prey. Fish movements (nine sole collected in the wild and tagged with electronic transmitters) were registered during three fortnight-long sessions in spring 2002. In addition to shading from the oyster trestles, water and sediment properties changed significantly in the live oyster zone. Environmental changes and sole swimming behaviour were linked by direct or indirect effects: swimming activity for eight of nine sole followed a diel cycle, with greater travelling distance by night. All the environmental variables modulated swimming activity, but temperature increase, water renewal, and climatic events were associated with key changes between sessions or individual sole. A multilinear regression analysis suggested strongest links with oxygen, atmospheric pressure, light level, water column height, and pH. All sole moved around the enclosure at night, probably to forage. By day, except during gale-force wind, sole returned to the same resting zones. Under the oyster-rearing structures appeared to be the most attractive resting sites. Sole seemingly can occupy an entire nu

Restructuring coastal fish nursery habitats by extensive shellfish fanning in the French part of the Bay of Biscay could influence fish physiology and behaviour and affect the ecological performance of the species. The influence of oyster-trestle cultivation installations on sole (Solea solea) swimming behaviour was investigated using an experimental pond mesocosm. A pen was constructed with three interconnected zones (two with bags of live oysters or oyster shells on trestles, and one free zone). Water renewal depended on the tide. Environmental variables were recorded continuously (temperature, oxygen, pH, meteorological data), every 3-5 days (salinity, samples taken for water analysis and estimation of sedimentation rate) or intermittently (illumination). Sediment cores were taken in each zone before and after the experiment, for sediment redox and water content, plus an evaluation of potential prey. Fish movements (nine sole collected in the wild and tagged with electronic transmitters) were registered during three fortnight-long sessions in spring 2002. In addition to shading from the oyster trestles, water and sediment properties changed significantly in the live oyster zone. Environmental changes and sole swimming behaviour were linked by direct or indirect effects: swimming activity for eight of nine sole followed a diel cycle, with greater travelling distance by night. All the environmental variables modulated swimming activity, but temperature increase, water renewal, and climatic events were associated with key changes between sessions or individual sole. A multilinear regression analysis suggested strongest links with oxygen, atmospheric pressure, light level, water column height, and pH. All sole moved around the enclosure at night, probably to forage. By day, except during gale-force wind, sole returned to the same resting zones. Under the oyster-rearing structures appeared to be the most attractive resting sites. Sole seemingly can occupy an entire nu

Restructuring coastal fish nursery habitats by extensive shellfish fanning in the French part of the Bay of Biscay could influence fish physiology and behaviour and affect the ecological performance of the species. The influence of oyster-trestle cultivation installations on sole (Solea solea) swimming behaviour was investigated using an experimental pond mesocosm. A pen was constructed with three interconnected zones (two with bags of live oysters or oyster shells on trestles, and one free zone). Water renewal depended on the tide. Environmental variables were recorded continuously (temperature, oxygen, pH, meteorological data), every 3-5 days (salinity, samples taken for water analysis and estimation of sedimentation rate) or intermittently (illumination). Sediment cores were taken in each zone before and after the experiment, for sediment redox and water content, plus an evaluation of potential prey. Fish movements (nine sole collected in the wild and tagged with electronic transmitters) were registered during three fortnight-long sessions in spring 2002. In addition to shading from the oyster trestles, water and sediment properties changed significantly in the live oyster zone. Environmental changes and sole swimming behaviour were linked by direct or indirect effects: swimming activity for eight of nine sole followed a diel cycle, with greater travelling distance by night. All the environmental variables modulated swimming activity, but temperature increase, water renewal, and climatic events were associated with key changes between sessions or individual sole. A multilinear regression analysis suggested strongest links with oxygen, atmospheric pressure, light level, water column height, and pH. All sole moved around the enclosure at night, probably to forage. By day, except during gale-force wind, sole returned to the same resting zones. Under the oyster-rearing structures appeared to be the most attractive resting sites. Sole seemingly can occupy an entire nu

The effects of tagging with acoustic transmitters on the growth of juvenile seabass, Dicentrarchus labrax (L.) (initial mean mass +/- SD, 173 g +/- 23.4) in a 47 d tank experiment, and sole. Solea solea (L.) ( 103.2 g +/- 14.8) in a 72 d tank experiment and (104.0 g +/- 18.4) in a 58 d salt marsh mesocosm experiment were examined. Twenty externally tagged seabass grew more slowly than the 20 with surgically implanted tags, which reached the same mass as nine control fish. Movements of the external transmitter's harness caused abrasions of the skin and loss of the tag in 60% of the cases. We thus recommend implanting transmitters for telemetry studies of juvenile seabass weighing between 120 and 214 g and carrying a tag that represents 2.2-2.5% of body mass. Both tank and mesocosm experiments conducted on juvenile sole concluded that the externally attached tag retention rate was good, but at the expense of the fish growth rate.

The effects of tagging with acoustic transmitters on the growth of juvenile seabass, Dicentrarchus labrax (L.) (initial mean mass +/- SD, 173 g +/- 23.4) in a 47 d tank experiment, and sole. Solea solea (L.) ( 103.2 g +/- 14.8) in a 72 d tank experiment and (104.0 g +/- 18.4) in a 58 d salt marsh mesocosm experiment were examined. Twenty externally tagged seabass grew more slowly than the 20 with surgically implanted tags, which reached the same mass as nine control fish. Movements of the external transmitter's harness caused abrasions of the skin and loss of the tag in 60% of the cases. We thus recommend implanting transmitters for telemetry studies of juvenile seabass weighing between 120 and 214 g and carrying a tag that represents 2.2-2.5% of body mass. Both tank and mesocosm experiments conducted on juvenile sole concluded that the externally attached tag retention rate was good, but at the expense of the fish growth rate.

The effects of tagging with acoustic transmitters on the growth of juvenile seabass, Dicentrarchus labrax (L.) (initial mean mass +/- SD, 173 g +/- 23.4) in a 47 d tank experiment, and sole. Solea solea (L.) ( 103.2 g +/- 14.8) in a 72 d tank experiment and (104.0 g +/- 18.4) in a 58 d salt marsh mesocosm experiment were examined. Twenty externally tagged seabass grew more slowly than the 20 with surgically implanted tags, which reached the same mass as nine control fish. Movements of the external transmitter's harness caused abrasions of the skin and loss of the tag in 60% of the cases. We thus recommend implanting transmitters for telemetry studies of juvenile seabass weighing between 120 and 214 g and carrying a tag that represents 2.2-2.5% of body mass. Both tank and mesocosm experiments conducted on juvenile sole concluded that the externally attached tag retention rate was good, but at the expense of the fish growth rate.