Does the flatfish community of the Mondego estuary (Portugal) reflect environmental changes?

Abstract

Temporal and spatial patterns of abundance of the flatfish community in the Mondego estuary were investigated from 2003 to 2007, based on monthly beam trawl samples. During the study period there was a severe drought, with consequential reductions in river runoff. A total of eight flatfish species occurred within the estuary, with seasonal specific richness and abundance varying considerably. It was possible to identify three main groups: one composed of species present throughout the study period and in high densities: Platichthys flesus and Solea solea (maximum densities 3.7 and 4.1 Ind 1000 m )2 , respectively); a second group of less abundant but regularly present species: Scophthalmus rhombus and Solea senegalensis (maximum densities 0.2 and 0.3 Ind 1000 m )2 , respectively); and a third group of occasional species that occurred only during the drought period: Arnoglossus laterna, Buglossidium luteum, Dicologlossa hexophthalma and Pegusa lascaris. Flatfish distribution patterns varied according to the estuarine use guild: marine-estuarine dependent fish occurred mainly in the upper reaches, while marine stragglers and marine-estuarine opportunists occurred mostly in the downstream areas. Species with more northern latitudinal affinities were the most affected by the drought, related with a lesser extent of river plumes to the coastal area, resulting in a reduction in half of the abundance levels. However, flatfish species with more southern affinities increased in abundance during the drought, benefiting also from an increase in estuarine water temperature. Early summer salinity and precipitation values were good proxies for estimating abundance levels of P. flesus and S. solea, respectively, emphasizing the importance of hydrodynamics for the recruitment and abundance of these commercially important species.

Environmental forcing on jellyfish communities in a small temperate estuary

“…Marques et al, 2007;Dolbeth et al, 2010;Primo et al, 2011) leading to the appearance of invasive species or to an increase in density of subtropical species (e.g. Chícharo et al, 2009;Martinho et al, 2010). Thus, this study aims to investigate jellyfish community of the Mondego estuary, by assessing the impact of biological, hydrodynamic and large scale climatic variables on species abundance.…”

Organochlorine contaminants in different tissues from Platichthys flesus (Pisces, Pleuronectidea)

“…P. flesus economical value and human intake P. flesus is a commercial species, with great economic importance being consumed in many countries such as United Kingdom, France, Spain, Greece or Portugal. P. flesus reproduce in offshore waters and use estuaries as nursery areas or temporary habitats (alternative to coastal areas), because it increases their chances of survival (Martinho et al, 2010). According to FAO fishery statistics, in 2010 around 20 000 tons of fish were captured.…”

“…The European flounder (Platichthys flesus; Pisces, Pleuronectidea) is a demersal fish, with a wide distribution (from Norway to Portugal, Mediterranean, Baltic, North White and Black seas) (Morais et al, 2011), being present in both coastal waters and estuarine ecosystems (Vasconcelos et al, 2008). This species is among the most important components of estuarine fish assemblages in temperate latitudes (Franco et al, 2008;Martinho et al, 2010). P. flesus was chosen for this study due to its easy sampling and high ecological and economic relevance.…”

Effects of local and large-scale climate patterns on estuarine resident fishes: The example of Pomatoschistus microps and Pomatoschistus minutus

“…Contrary to P. microps, this species is less tolerant to the interrelated environmental variations that were relatively strong during the study period, mainly precipitation, freshwater flow and salinity. On the other hand, the lowest production values in 2005/06 could be attributed to predation, as during this extreme drought period some piscivorous species appeared inside the estuary, exploiting the temporarily available suitable habitat created by a higher salinity incursion, which might have caused a higher predation pressure on the resident species Martinho et al, 2010). Both species provided different responses to the selected environmental variables, suggesting different tolerance thresholds and adaptation strategies to the surrounding environment.…”