Growth and condition of 0-group European flounder, Platichthys flesus as indicator of estuarine habitat quality

Abstract

The purpose of this present study was to use the growth rates, RNA-DNA ratio and morphometric (Fulton's K) condition indices measured on 0-group juveniles European flounder, as a means of comparing the quality of estuarine nursery habitats. The Seine estuary, heavily impacted by manmade modifications and one of the most contaminated in Europe, was compared to two smaller estuaries considered as clean (low domestic, agricultural and industrial effluents). Indicators of human disturbance (sediment chemical contaminants) as well as biotic data (macrobenthos abundances) were used to establish between-site differences in environmental quality. The abundance of macrobenthos (potential preys for juvenile) was high and not significantly different among the three estuaries confirming the important role played by estuaries as feeding grounds. Sediment metal concentrations (Cd, Cr, Cu, Pb, Zn) were significantly higher in the Seine than in the Canche and Authie estuaries. Otolith growth was closely related to somatic fish growth, and we used daily otolith increments from the previous 10 days before capture as an indicator of 0-group flounder recent growth (RG). RG did not vary significantly among flounders from the Canche and Authie estuaries and individuals from the Seine had slower RG. RNA-DNA ratio and K values were also significantly lower in individuals from the Seine compared to those of the Authie or the Canche. Pollution (e.g. metal contaminants) is the most likely cause of growth and condition differences among estuaries. The results of this study suggest that habitat-specific fish growth and condition are useful proxies for habitat quality since they integrate the effect of multiple environmental factors.

Spatial and seasonal variations of trace elements concentrations in liver and muscle of round Sardinelle (Sardinella aurita) and Senegalese sole (Solea senegalensis) along the Senegalese coast

“…S. aurita feed mainly on phytoplankton and migrate between Senegal and Morocco to reproduce. S. senegalensis is a coastal fish species particularly sensitive to the effects of pollution since they feed on benthic organisms and live in close association with the bottom sediments where many contaminants accumulate (Amara et al, 2009).…”

Plasticity of European flounder life history patterns discloses alternatives to catadromy

“…comm. ), and also in other estuaries such as the Canche and Otie (both in France) (Amara et al 2009). Further, the assignment of both the pre-metamorphic and metamorphic stages is supported by previous work that has documented flounder in estuarine ichthyoplankton (Ramos et al 2010).…”

“…data), allowing juveniles to attain faster growth rates (Fonds et al 1992). Other factors than temperature, such as juvenile density and habitat contamination, may also interact (Gilliers et al 2006, Amara et al 2009) and influence flounder life history.…”

Juvenile nursery colonization patterns for the European flounder (Platichthys flesus): A latitudinal approach

“…the first ring that forms a complete circle after the outermost accessory primordia) and the edge of the otolith. The total increment counts provided an estimate of the total age in days, in accordance with Bos (1999) and Amara et al (2009). Otolith increments were counted twice, and the duration of each stage (days) was regarded as the average of the two counts.…”