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

The 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.