<b>Feeding of the whitemouth croaker Micropogonias furnieri (Sciaenidae; Pisces) in the estuary of the rio de la Plata and adjacent Uruguayn coastal waters</b>

Abstract

We studied the diet of the whitemouth croaker (Micropogonias furnieri) (Pisces) in the Río de la Plata estuary and adjacent ruguayan coastal waters. Fish were caught at different salinity ranges and bottom types. We analyzed 258 gut contents of whitemouth croaker (6-67 cm total length, TL) and calculated an index of relative importance of prey (IA) based on frequency of occurrence and biomass. Multivariate analyses were used to detect diet differences between sampling sites (ANOSIM, MDS). Micropogonias furnieri showed a tendency to specialization towards one single taxonomic prey type, bivalves, but also including other benthic invertebrates like polychaetes or crustaceans. The diet varied according to the size and area analyzed. The bivalve Mactra isabelleana was the main prey of croakers > 10 cm TL (%IA = 96.68), while mysids where the main prey of croakers < 10 cm TL (%IA = 85.3). Multivariate analyses defined three main groups of croakers which mainly feed on: M. isabelleana (estuarine and marine muddy bottoms), mysids (estuarine muddy bottoms) and Artemesia longinaris (marine and estuarine waters, heterogeneous bottoms). These three groups also represented distinct feeding behavior of croakers: specialization, generalization and mixed feeding strategies respectively. This plasticity in the feeding behavior could be one of the factors that allows for the extensive geographical distribution of whitemouth croaker, throughout different prey exploitation patterns.