Anthropogenic disturbance on nursery function of estuarine areas for marine species

Abstract

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.

Fish under influence: A macroecological analysis of relations between fish species richness and environmental gradients among European tidal estuaries

“…The present approach provides a standardized method to compare estuarine systems and estimate the variability in fish species richness due to environmental features. By taking this standardization into account, studying the effects of additional factors such as anthropogenic disturbances will lead to the selection of relevant fish assemblage indicators that will make it possible to assess the ecological status of estuaries (Courrat et al, 2009). Coastal and Shelf Science, n°86.…”

A zone-specific fish-based biotic index as a management tool for the Zeeschelde estuary (Belgium)

“…Thirdly, metrics should assess a particular ecological function of the different parts of the estuary. Different authors have described estuarine functions and how fish use the estuarine ecosystem (e.g., Courrat et al, 2009;Franco et al, 2008;Martinho et al, 2008b). Fourthly, metrics must be able to evaluate ecological goals.…”

Marinas as habitats for nearshore fish assemblages: comparative analysis of underwater visual census, baited cameras and fish traps

“…One of the major threats associated with coastal development is the loss of natural habitats through the construction of artificial structures, such as marinas and breakwaters (Airoldi andBeck 2007, Halpern et al 2008). Habitat conversions may result in profound changes in the composition and structure of natural communities, which in turn have effects on biodiversity, altering underlying ecosystem functions and services (Courrat et al 2009, Seitz et al 2014. Thus, it is becoming increasingly important to understand the extent to which artificial structures might fulfil the ecological roles provided by natural habitats.…”