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

Rodrigo Gurdek Bas, Alicia Acuña-Plavan

Resumo


Estuaries are highly dynamic ecosystems subjected to variability of their fish communities over different time scales. Given this, the nearshore fish community of the lower Pando estuary, a temperate sub-system of the Río de la Plata estuary, was sampled on a monthly basis from May 2002 to June 2003, increasing sampling effort to 24 h during each season of the year. A total of 2,165 fish, represented by 16 species were caught by seine netting over the study period. Captures were largely dominated by juveniles (>90%), as well as by the sciaenid Micropogonias furnieri (Desmarest, 1823) (82.8%). In general terms, fish community showed seasonal and diel changes in terms of ichthyofaunal composition, abundance, species richness and diversity. Greatest average values of species richness (4/ 300m2) and diversity (0.72/ 300m2) occurred during summer, while highest average values of biomass (4,532.3g/ 1000m2) during spring. Diel variance was detected for the species M. furnieri, Mugil liza Valenciennes, 1836, Parapimelodus valenciennis (Lütken, 1874), Odontesthes argentinensis (Valenciennes, 1835) and Brevoortia aurea (Spix & Agassiz, 1829). Variability was attributed to life cycle, environmental interaction and feeding activity of fish species, as well as to photoperiod. Sub-estuarine systems deserve further attention as they are ecologically important, mainly as transitional and permanent fish habitats.




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