Aspects of fish conservation in the upper Patos Lagoon basin

Abstract

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).

How Far Upstream: A Review of Estuary-Fresh Water Fish Movements in a Large Neotropical Basin

“…The artisanal fishery, organic pollution and other widespread environmental impacts of a large metropolitan area (over 4 million inhabitants) are the main pressures on the fish populations. A general overview and assessment of the conservation status of the Patos Lagoon system were provided by Fontoura et al (2016).…”

Defining the reproductive period of freshwater fish species using the Gonadosomatic Index: a proposed protocol applied to ten species of the Patos Lagoon basin

“…During the 2002 sampling program, rainfall increased during a moderate El Niño phenomenon, with an Oceanic El Niño Index above 1.0 (CPC, 2017). Summer has a mean temperature of 25°C in January; in winter the mean temperature is 14°C in July (see Fontoura et al, 2016, for a general characterization of the area). Data analysis.…”

“…To understand those reproductive strategies in relation to the size at maturity, reproductive period and spawning grounds is essential to management of both fisheries and aquatic ecosystems. Although the freshwater fish species of the Patos Lagoon basin are relatively well known taxonomically, with more than 200 recorded limnetic species (Malabarba, 1989;Reis et al, 2003;Bertaco et al, 2016;Fontoura et al, 2016), information concerning reproductive aspects of these species is still needed. Although recent reviews have treated aspects of the conservation and fishery (Ceni et al, 2016) of the Patos basin, the only general overview of the reproductive biology of fish species was by Marques et al (2007), who estimated the size at first maturity for some dominant species.…”

Coastal zone use and migratory behaviour of the southern population of Mugil liza in Brazil

“…The southern population reproduces in the coastal zone and most juveniles use estuaries, freshwater or coastal regions as nurseries (Fontoura et al ., ; Fortunato et al ., ; Vieira & Scalabrin, ). The southern population forms a spawning aggregation along the southern Brazilian coast that may extend from Santa Catarina to southern Paraná, depending on the intensity of the cold front (Lemos et al ., , ).…”