Aspects of fish conservation in the upper Patos Lagoon basin.
The Patos Lagoon basin is a large (201 626 km(2) ) and complex drainage system in southern Brazil. The lagoon is 250 km long and 60 km wide, covering an area of 10 360 km(2) . The exchange of water with the Atlantic Ocean occurs through a 0·8 km wide and 15 m deep inlet, fixed by 4 km long jetties, at the southernmost part of the Patos Lagoon. The estuarine area is restricted to its southern portion (10%), although the upper limit of saline waters migrates seasonally and year to year, influenced by the wind regime and river discharge. The known number of recorded limnetic fish species is 200, but this number is expected to increase. A higher endemism is observed in fish species occurring in upper tributaries. The basin suffers from the direct impact of almost 7 million inhabitants, concentrated in small to large cities, most with untreated domestic effluents. There are at least 16 non-native species recorded in natural habitats of the Patos Lagoon basin, about half of these being from other South American river basins. Concerning the fishery, although sport and commercial fisheries are widespread throughout the Patos Lagoon basin, the lagoon itself and the estuarine area are the main fishing areas. Landing statistics are not available on a regular basis or for the whole basin. The fishery in the northern Patos Lagoon captures 31 different species, nine of which are responsible for most of the commercial catches, but only three species are actually sustaining the artisanal fishery: the viola Loricariichthys anus: 455 kg per 10 000 m(2) gillnet per day, the mullet Mugil liza: 123 kg per 10 000 m(2) gillnet per day and the marine catfish Genidens barbus: 50 kg per 10 000 m(2) gillnet per day. A decline of the fish stocks can be attributed to inadequate fishery surveillance, which leads to overfishing and mortality of juveniles, or to decreasing water quality because of urban and industrial activities and power production. Global climatic changes also represent a major threat to the Patos system by changing the frequency of El Niño-La Niña-Southern Oscillation (ENSO).
Pontifícia Universidade Católica do Rio Grande do Sul, Departamento de Biodiversidade e Ecologia, C. P. 1429, CEP 90619-900 Porto Alegre, RS, Brazil.
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Fontoura
Fundação Universidade Federal de Rio Grande, Instituto de Oceanografia, Laboratório de Ictiologia, C. P. 474, CEP 96201-900, Rio Grande, RS, Brazil.
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Vieira
Universidade Federal do Rio Grande do Sul, Instituto de Biociências, Departamento de Ecologia, Av. Bento Gonçalves 9500, 91501-970, Porto Alegre, RS, Brazil.
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Becker
Universidade Federal do Rio Grande do Sul, Instituto de Pesquisas Hidráulicas, Laboratório de Ecotecnologia e Limnologia, Av. Bento Gonçalves 9500, 91501-970, Porto Alegre, RS, Brazil.
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Rodrigues
Universidade Federal do Rio Grande do Sul, Instituto de Biociências, Departamento de Zoologia, Av. Bento Gonçalves 9500, 91501-970, Porto Alegre, RS, Brazil.
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Malabarba
Universidade do Vale do Rio dos Sinos, Laboratório de Ecologia de Peixes, Av. Unisinos, 950, CEP 93022-000, São Leopoldo, RS, Brazil.
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Schulz
Fundação Universidade Federal de Rio Grande, Instituto de Oceanografia, Laboratório de Oceanografia Costeira e Estuarina, CP. 474, CEP 96201-900, Rio Grande, RS, Brazil.
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Möller
Fundação Universidade Federal de Rio Grande, Instituto de Oceanografia, Laboratório de Ictiologia, C. P. 474, CEP 96201-900, Rio Grande, RS, Brazil.
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Garcia
Simbiota Consultoria Ambiental, Rua Emiliano de Macedo, 1425, CEP 95800-000, Venâncio Aires, RS, Brazil.
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Vilella
D000818:Animals; D001267:Atlantic Ocean; D001938:Brazil; D003247:Conservation of Natural Resources; D017753:Ecosystem; D059000:El Nino-Southern Oscillation; D005398:Fisheries; D005399:Fishes; D058865:Introduced Species; D045483:Rivers; D023701:Smegmamorpha
artisanal fishery; climate change; overfishing; southern Brazil