Evidence of habitat fragmentation affecting fish movement between the Patos and Mirim coastal lagoons in southern Brazil

Marcelo D M Burns,David M L Motta Marques,João P Vieira,Vinicius Condini,Marlise A Bemvenuti,Alexandre M Garcia

doi:10.1590/s1679-62252006000100006

Marcelo D M Burns, David M L Motta Marques + Show 4 more

Open Access

https://doi.org/10.1590/s1679-62252006000100006

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Abstract

The communication between the Patos and Mirim lagoon systems occurs via a natural channel called São Gonçalo. In 1977, a dam was built in this channel to prevent entrance of saline waters from Patos Lagoon estuary into the Mirim Lagoon. Our results showed an abrupt discontinuity in salinity and fish species distribution along the study sites. Sites below the dam showed salinity values higher than zero, whereas sites above had zero salinity values across all sampling periods. Marine and estuarine fishes (e.g., mullets Mugil platanus, M. curema, silversides Odontesthes argentinensis, Atherinella brasiliensis, sardine Brevoortia pectinata, and white croaker Micropogonias furnieri) were not captured above the dam. If these juvenile fishes could enter the Mirim lagoon in greater numbers, they probably would enhance catches in the artisanal fishery. We hypothesized that the São Gonçalo dam acts as a barrier hindering the entrance of salinity water and fishes inside the Mirim Lagoon.

Highlights

The Patos-Mirim lagoon complex has a diverse flora and fauna and has long supported fisheries, agriculture, industry, and municipalities. These lagoons are located in the coastal plain of Rio Grande do Sul state, part of the Mirim lagoon is located in Uruguay (Fig. 1a)
The most important of these was a dam built in the São Gonçalo Channel in 1977 to prevent the entrance of salinity waters inside the Mirim Lagoon (Fig. 1b) where freshwater is extracted for rice irrigation
Fishes were sampled at six stations (Fig. 1b) encompassing Patos Lagoon estuary (A1, A2), São Gonçalo Channel (B1, B2) and Mirim lagoon (C1, C2)

Summary

Introduction

The Patos-Mirim lagoon complex has a diverse flora and fauna and has long supported fisheries, agriculture, industry, and municipalities. These lagoons are located in the coastal plain of Rio Grande do Sul state (southern Brazil), part of the Mirim lagoon is located in Uruguay (Fig. 1a). Intrusion of salinity waters and occurrence of marine and estuarine fishes (e.g., whitemouth croaker Micropogonias furnieri, mullet Mugil platanus, flounder Paralichthys orbignyanus), were common inside the Mirim Lagoon (Cunha, 1953; FAO, 1972; Machado, 1976).The effects of this salinity barrier on fish assemblages within Patos and Mirim lagoons have not been investigated

Material and Methods

Results and Discussion

Literature Cited