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Daverat F.,IRSTEA | Morais P.,FARO | Morais P.,University of Porto | Dias E.,University of Porto | And 8 more authors.
Marine Ecology Progress Series | Year: 2012

European flounder Platichthys flesus life history patterns were investigated in 3 basins along a latitudinal gradient (Minho, N Portugal; Gironde, SW France; Seine, N France). We used coupled Sr:Ca and Ba:Ca otolith signatures and microstructure to retrospectively determine habitats occupied by flounder during their life, including early larval ontogeny. Flounder exhibited high life history plasticity among and even within basins, apparent by the diversity of habitats used during larval ontogeny and throughout their lives, and by the age at which flounder migrated to freshwater. Egg signatures probably had a strong maternal influence, and our interpretation suggests that flounder spawned and/or hatched predominantly in brackish waters in the Minho, while in the Gironde and Seine, flounder spawned and/or hatched either in coastal, brackish or freshwater environments. The freshwater egg signature was most frequent in the Seine. These interpretations contradict the current general assumption that flounder spawn exclusively in coastal waters. During pre-metamorphosis and metamorphosis, flounder were predominantly in brackish waters in the Minho, while in the Gironde and Seine, they were mainly in coastal and freshwater environments, respectively. The diversity of flounder life histories (LH) (i.e. sequence of habitat residence: freshwater, brackish or coastal) after metamorphosis was similar between the Minho (LH = 13), Gironde (LH = 13) and Seine (LH = 14) basins. The age at which flounder migrated to freshwater also varied among sites, at an earlier age in the Minho and Gironde (<0.5 yr old) than in the Seine, where flounder migrating from the coast into freshwater reached maximum frequencies at age 1.3 yr old. Thus, catadromy in European flounder may be facultative, and the factors influencing flounder high LH plasticity deserve thorough research. © 2012 Inter-Research and Fisheries and Oceans Canada. Source

Ilarri M.I.,The Interdisciplinary Center | Ilarri M.I.,Abel Salazar Biomedical Sciences Institute | Souza A.T.,The Interdisciplinary Center | Antunes C.,The Interdisciplinary Center | And 6 more authors.
Estuarine, Coastal and Shelf Science | Year: 2014

One of the most widespread invasive alien species (IAS) in aquatic ecosystems is the Asian clam Corbicula fluminea. Several studies have shown that C.fluminea can cause large-scale changes in macrozoobenthic assemblages; however, very few attempted to investigate the effects of this IAS on mobile epibenthic species, such as fishes and crustaceans. In this context, the influence of C.fluminea on epibenthic species was investigated during one year by comparing the associated epibenthic fauna in three nearby sites of the Minho estuary (NW of the Iberian Peninsula), wherein the abiotic conditions are similar but the density of the Asian clam is highly different. From a total of 13 species, six were significantly influenced by C.fluminea; five responded positively, namely the brown shrimp Crangon crangon, the European eel Anguilla anguilla, the common goby Pomatoschistus microps, the brown trout Salmo trutta fario and the great pipefish Syngnathus acus, whereas the shore crab Carcinus maenas was negatively influenced. However, stomach contents analysis revealed that fish and crustacean species do not feed on C.fluminea, suggesting that this IAS is still not a large component of the diet of higher trophic levels in this estuarine ecosystem. Our results suggest that the structure provided by C.fluminea shells is likely to be one of the main factors responsible for the differences observed. C.fluminea physical structure seems to influence the epibenthic associated fauna, when found in densities higher than 1000ind./m2, with sedentary small-bodied crustaceans and fishes being mainly attracted by the increasing in habitat complexity and consequent enhancement of heterogeneity and shelter availability. © 2014 Elsevier Ltd. Source

Dias E.,Abel Salazar Biomedical Sciences Institute | Dias E.,University of Porto | Morais P.,University of Porto | Morais P.,University of Algarve | And 3 more authors.
Biological Invasions | Year: 2014

The Asian clam, Corbicula fluminea, is among the most pervasive invasive species in freshwater ecosystems worldwide. Our objective was to study C. fluminea’s functional response in terms of feeding behavior and food selectivity, using the natural variation in organic matter (OM) sources that occur in estuarine environments. Using C and N stable isotopes, we identified and quantified the contribution of different OM sources supporting the production of C. fluminea along the salinity gradient occupied in the Minho River estuary (NW-Iberian Peninsula, Europe), where this species presently dominates the benthic macrofauna biomass. We observed a pronounced shift in the quality of OM available for C. fluminea along the estuarine mixing zone. Stable isotope analysis, POM C/N, and phytoplankton contribution estimates based on C:Chl a revealed that POM was largely comprised of terrestrial-derived OM in tidal freshwater stations (TFW) and was increasingly comprised of phytoplankton, a more palatable food source, towards the polyhaline estuary. A similar shift in the isotopic composition along the estuarine mixing zone was observed in C. fluminea, suggesting a shift in food resources. Accordingly, based on a Bayesian stable isotope mixing model, there was an upstream–downstream counter gradient in the contribution to C. fluminea biomass from terrestrial-derived OM (41–64 % in TFW) and phytoplankton (29–55 % in the brackish estuary). Although the majority of the food sources identified were filtered from the water column (70–80 %), reliance on sediment OM and microphytobenthos provided evidence for deposit feeding by C. fluminea. We conclude that C. fluminea has the ability to adapt to environments with low food quality because it can consume terrestrial-derived OM. This can be a competitive adaptation in systems with perennial low food quality such as the Minho River estuary. Moreover, its ability to couple benthic and pelagic environments and terrestrial ecosystems demonstrates a strong potential to alter food web flows in aquatic ecosystems. © 2014, Springer International Publishing Switzerland. Source

Ilarri M.I.,University of Porto | Freitas F.,University of Porto | Costa-Dias S.,University of Porto | Antunes C.,University of Porto | And 5 more authors.
Journal of Sea Research | Year: 2012

The Asian clam Corbicula fluminea is one of the most invasive species in brackish and freshwater ecosystems. In the Minho estuary (NW of the Iberian Peninsula) this invasive species can reach densities up to 4000ind m-2, occurring over large areas. C. fluminea can significantly alter the physical structure of the benthic environment, and the structure and functioning of this estuarine community. In this context, this work aimed to evaluate the correlation of different densities of C. fluminea on the macrozoobenthos across five sites in the Minho estuary during three distinct periods of 2009 (winter, spring and summer). The comparative analysis indicate that macrozoobenthic density, biomass and diversity positively respond to increasing density of C. fluminea, with abiotic conditions also playing an important role in the observed patterns, both in brackish and freshwater settings. Crustacea, Insecta and Gastropoda are the main faunal groups responding positively to C. fluminea increasing density. The mechanisms responsible for these positive trends still needs to be established although engineering activities and the increase in waste products may play essential roles. Nevertheless, despite such positive effects, earlier studies have showed that the density, biomass and spatial distribution of some species, especially native bivalves dramatically decreased after C. fluminea introduction. © 2011 Elsevier B.V. Source

Dias E.,University of Porto | Morais P.,University of Porto | Morais P.,FARO | Leopold M.,IMARES Wageningen UR | And 3 more authors.
Journal of Sea Research | Year: 2012

The ecological traits of piscivorous marine birds have been acknowledged to reflect ecosystem changes. We used the great cormorant as our indicator species in the Minho estuary (NW-Iberian Peninsula, Europe) to assess the temporal variation of their diet and the factors that could influence that variation. Pellets were collected in a night roost, located centrally in the estuary, during two consecutive wintering periods (2005-2006 and 2006-2007). The great cormorant population showed a high degree of feeding plasticity and most of the variation in cormorants' diet was attributed to river discharge fluctuations. Overall, during periods of increased river discharge, marine and marine opportunistic species disappeared from diet, whereas freshwater species increased. The cormorants in this study were using a roost in the middle of the estuary, so they were facing a changing food base over time, in accordance to variation in river discharges. The birds did not keep their diet constant but rather took what became locally available, notwithstanding their broad foraging range. Therefore, we suggest that great cormorants may be considered good samplers of local ichthyofauna and thus, temporal variation in the local prey can be followed by analyzing cormorants' diet. © 2012 Elsevier B.V. Source

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