Estuarine colonization, population structure and nursery functioning for 0-group sea bass (Dicentrarchus labrax), flounder (Platichthys flesus) and sole (Solea solea) in a mesotidal temperate estuary

Abstract

Estuarine colonization, population structure and nursery functioning for 0-group sea bass (Dicentrarchus labrax), flounder (Platichthys flesus) and sole (Solea solea) in a mesotidal temperate estuary SummaryThe function of the Mondego estuary as a fish nursery habitat was investigated from June 2003 to June 2004 by comparing the timing of estuarine colonization with juveniles of sea bass Dicentrarchus labrax, flounder Platichthys flesus, and sole Solea solea, while also analysing their population structure, growth and diet composition. Differences in the onset of estuarine colonization were observed, since sole juveniles were the first to enter the estuary (in January), followed by flounder in April and sea bass in June. The estuarine population of these species consisted of several age-groups, although the majority of individuals belonged to age-groups 0 and 1. The growth rates determined for 0-group fish were within the range of those reported for other European estuarine systems. Some differences were also recognized regarding the timing of estuarine colonization and the length of the growing season. Diet of 0-group sea bass consisted mainly of Crustacea, Polychaeta and Mollusca. Flounder juveniles fed chiefly on Amphipoda (especially Corophium spp.), with Polychaeta, Isopoda and Decapoda also being common prey. The diet of 0-group sole was dominated by Polychaeta, with Amphipoda, Mollusca and Decapoda ranking highest, with other important benthic organisms also being present. Dietary overlap among these species was relatively low.

Latitudinal trends in habitat quality of shallow‑water flatfish nurseries

“…The results for sole are particularly indicative of how this mechanism may act: in the beginning of the growing season, the RG of sole is higher in southern compared with northern areas; however, throughout the season this pattern inverses. In contrast to northern European areas where sole only occur after plaice and flounder have settled (Jager et al 1995, Amara et al 2001, Van der Veer et al 2001a, in southern European nurseries, sole juveniles are the first marine species to colonize these areas, appearing in April−May (Cabral 2003, Dolbeth et al 2010, and in some years, young-of-the-year can even be observed from late January onwards (Martinho et al 2008). This could confer an advantage to sole by occupying an empty niche with ample food resources, which, combined with high summer temperatures, would allow for fast growth.…”

Mesozooplankton biomass and copepod estimated production in a temperate estuary (Mondego estuary): effects of processes operating at different timescales

“…The food chain of the Mondego estuary supports an important fish community (Martinho et al 2007). Studies performed by Martinho et al (2008) and Dolbeth et al (2008), who analyzed the feeding ecology of the main fish community, concluded that copepods were an important component of the fish diet. As a result, DVM behavior could lead to important trophodynamic effects in the fish community.…”

Environmental effects on the recruitment variability of nursery species

“…Data on abundance of 0-group juveniles were plotted from the original trawl data matrix according to Dolbeth et al (2008) and Martinho et al (2008) who determined that only one cohort is produced each year. Fish abundance (individuals per 1000 m 2 ) was determined as the number of 0-group fish caught in the total sampled area.…”

“…From each yearly cohort, the abundance of the first three months when estuarine catches start were chosen, since they represented the onset of the 0-group settlement period; at this time, fish are approximately three months old. In general, Solea solea's recruitment to estuarine waters starts in the winter, whereas for Platichthys flesus and Dicentrarchus labrax the recruitment usually starts in early and late spring, respectively (Dolbeth et al, 2008;Martinho et al, 2008). The environmental parameters were obtained on the third month prior to the first estuarine catch, based on their expected influence on the colonization process.…”