Temporal dynamics of a fish community in the lower portion of a tidal creek, Pando sub-estuarine system, Uruguay

Rodrigo Gurdek,Alicia Acuña-Plavan

doi:10.1590/1678-4766e2017003

Abstract

ABSTRACT Estuaries are highly dynamic ecosystems subjected to variability of their fish communities over different time scales. The nearshore fish community of the lower Pando estuary, a temperate sub-system of the Río de la Plata estuary, was sampled from May 2002 to June 2003. A total of 2,165 fishes, represented by 16 species were caught by seine netting. Captures were dominated by juveniles (>90%), as well as by the sciaenid Micropogonias furnieri (Desmarest, 1823) (82.8%). The fish community showed high seasonal variability, with the greatest diversity and biomass in summer and spring and the highest species richness during summer. Lowest values of all community parameters occurred in winter and autumn, seasons that presented the highest similarity in fish composition. Number of species was correlated with water temperature and salinity. The ichthyofaunal composition showed significant diel differences in summer and spring. Diel changes were observed in the density of M. furnieri and Odontesthes argentinensis (Valenciennes, 1835), occurring mainly during the day, and of Mugil liza Valenciennes, 1836, Parapimelodus valenciennis (Lütken, 1874) and Brevoortia aurea (Spix & Agassiz, 1829), caught mostly during the night. Temporal variability was attributed to environmental fluctuations, life cycle of species as well as to feeding patterns and small-scale displacements. Presented findings in the Pando sub-estuary denote similar juvenile use and seasonal patterns to those found in estuaries. Further studies in the nursery function and juvenile dynamics over the year are recommended in order to better understand the ecological role of sub-estuaries.

Highlights

Estuaries are highly dynamic ecosystems subjected to variability of their fish communities over different time scales
The purpose of the present study was to compliment the seasonal analysis undertaken by Acuña et al (2010), and to determine the diel variability of the fish community in the Pando sub-estuary
The Pando tidal creek system (34°47’S, 55°52’W) is a small temperate sub-estuary influenced by tidal waters of the Río de la Plata (RdlP) (Acha et al, 2008) (Fig. 1)

Summary

Introduction

Estuaries are highly dynamic ecosystems subjected to variability of their fish communities over different time scales. Biomass and number of species of the estuarine fish assemblages in temperate estuaries are often reported (Hagan & Able, 2003; Barletta et al, 2008). Environmental variability such as salinity and temperature fluctuations, and timing of both reproduction and life history characteristics, have been the most commonly invoked drivers of the observed patterns (Hagan & Able, 2003; Simier et al, 2006). Species can respond to diel variation by timing activity levels with the diel period (Clark et al, 2003)

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