A review of estuarine fish research in South America: what has been achieved and what is the future for sustainability and conservation?

Abstract

Estuarine fish research in South America began in the early 20th Century, but it is only within the last 40 years that detailed studies have been undertaken. This review firstly summarizes research results from South American estuaries by geographic area, starting with the temperate south-east, then the temperate-sub-tropical transition zone in Brazil, then the semi-arid and tropical estuaries of north and north-east Brazil including the Amazon complex, then the north and Caribbean coasts and finally down the Pacific coast of the continent. They include almost all types of estuarine systems, from large open systems (e.g. the temperate Rio de La Plata and tropical Amazon) to extensive coastal lakes (e.g. the temperate Patos Lagoon and tropical Cienega Grande de Santa Marta). They encompass a broad range of climatic and vegetation types, from saltmarsh systems in the south-east and fjords in the south-west to both arid and humid tropical systems, dominated by mangroves in the north. Their tidal regimes range from microtidal (e.g. Mar Chiquita, Argentina) through mesotidal (e.g. Goiana, Brazil) to macrotidal in the Amazon complex where they can exceed 7 m. The review uses where possible the recent standardization of estuarine fish categories and guilds, but the ways that fishes use tropical South American systems may necessitate further refinements of the categories and guilds, particularly in relation to freshwater fishes, notably the Siluriformes, which dominate many north and north-east South American systems. The extent to which South American studies contribute to discussions and paradigms of connectivity and estuarine dependence is summarized, but work on these topics has only just begun. The anthropogenic issue of pollution, particularly in relation to heavy metals and fishes and fisheries in estuaries is more advanced, but the possible effects of climate change have barely been addressed. Studies around conservation and management are briefly reviewed and the extent to which key factors are being addressed is examined. Although there have been major advances in knowledge of estuarine fishes in South America, information is patchy, with most data from relatively few systems in Argentina and Brazil.

Seasonal and environmental influences on recruitment patterns and habitat usage among resident and transient fishes in a World Heritage Site subtropical estuary

“…Rainfall and salinity strongly influence the diversity and abundance of estuarine fishes, particularly in tropical areas (Barletta et al ., , ; Blaber & Barletta, ). During the wet season, primary production increases (Longhurst & Pauly, ; Brandini & Thamm, ; Kitheka et al ., ) and additionally influxes of exogenous nutrients and sediments occur, enhancing larval fish feeding and thus, growth and survival (Robins et al ., ).…”

“…Such habitats normally are characterized by strong temporal changes in physical, chemical and biological variables, including temperature, salinity and tides that evoke seasonal and daily changes in primary productivity and, consequently, in ichthyofaunal distributions and abundances (Flores‐Verdugo et al ., ; Kimirei et al ., ; Pasquaud et al ., ). Of particular importance are freshwater inflows from inland areas, determined by wet and dry seasons (Haedrich, ; Blaber & Barletta, ). Furthermore, in subtropical and temperate estuaries, temperature is also a key factor influencing the seasonal distribution of marine fauna, while salinity plays a major role in spatial distributions (Jaureguizar et al ., ).…”

Special challenges in the conservation of fishes and aquatic environments of South America

“…Consequently, managerial systems still have to deal with politically segmented and disconnected river basins, estuaries and coastal areas. A major question is how to elaborate, propose and apply universal models of conservation of aquatic ecoclines in a megadiverse continent, that spans equatorial and polar regions, and is encircled by six or seven different marine provinces (Barletta et al ., ; Blaber & Barletta, ). Discussion around the unification of the water conservation issues and solutions across the continent are important, but should not aim at the standardization of actions.…”

“…At present, Brazil (the largest economy and population of the continent) is undergoing power shutdowns, because of prolonged drought and historical dependence on poorly managed water resources, which are used for both water supply and power generation. Literature reviews covering issues for the whole region have become more frequent and diverse in their core subjects (Barletta et al ., , ; Costa et al ., ; Turra et al ., ; Scherer et al ., ; Blaber & Barletta, ). This body of literature urges governmental action for the most basic rights of the population: sanitation and integrated soil use for water ecosystems and habitat conservation.…”

Fish and aquatic habitat conservation in South America

“…() for Cyprinus carpio . An overview of estuarine fish research in South America is provided by Blaber & Barletta () and the situation in the La Plata Estuary is reviewed in detail by Jaureguizar et al . (), while Saint‐Paul & Schneider () describe the role of Brazilian‐German collaborative research in the mangrove areas of northern Brazil.…”