634
as well as providing limitations on use of resources in these areas through the implementation of protected areas (UNCED 1992).
Coastal ecosystems are especially important for being temporary grounds for
commercial and subsistence species that use these spaces and their resources as
settlement, feeding and nursery (Whitfield 1999; Kjerfve 1994; Able 2005; Dantas
et al. 2010; Ramos et al. 2016; Lima and Barletta 2016; Potter et al. 2013). Many
fish species spawn in estuaries at times that ensure protection and food availability
for their eggs and larvae (North and Houde 2003; Martino and Houde 2010; Lima
et al. 2015). Seasonal variations on environmental variables (e.g. salinity, temperature, dissolved oxygen, turbidity and food availability) are the main factors influencing the spatio-temporal distribution of fishes in estuaries around the world
(Blaber 1997; Barletta-Bergan et al. 2002a, b; Barletta et al. 2005; Hoffmeyer et al.
2009; Ooi and Chong 2011; Williams et al. 2012).
Estuaries support a high biological production and also have high recovering
capacity. However, ecological services, including fisheries, can be reduced by
human interventions (Barletta et al. 2016; Dyke and Weaver 2013; Elliott and
Quintino 2007), especially unplanned or unpredicted ones. In the last 500 years, the
majority of tropical estuaries underwent human colonization and exploitation of
their natural resources and services based on the European model. This colonial
model has no regard to nature and/or resources conservation. In addition, the high
diversity and performance of ecological services provided by estuarine areas
favoured poorly planned urban and industrial settlements. Face the large scale of
occupation of coastal ecosystems as these, problems of basic sanitation became one
of the most important concerns regarding modification of water quality (Costa and
Barletta 2016) in the twenty-first century since effluents, solid wastes and port facilities have surpassed all carrying capacity of the local-regional environment. Urban
settlements tends to be more widely spread along the coasts, meaning that coastal
habitats are likely to be altered or polluted, sometimes to the point of impairing its
services and resources maintenance. Therefore, tropical estuaries were often
severely abused and are now in a precarious state of natural conservation, overexploited or heavily polluted by sewage, agricultural run-off, industrial effluents
and solid wastes (Blaber 2000; Lima et al. 2014; Costa and Barletta 2016), not to
mention that often they are encircled by settlements of sub-human conditions that
also include traditional fishers populations.
South American estuaries are among those that have been altered by direct and
indirect human actions such as dredging, aggradation, damming, road building, pollution by wastewater and solid wastes, and their potential for producing sustained
fish harvests has been reduced or permanently impaired (Barletta et al. 2010, 2016;
Blaber and Barletta 2016; Costa and Barletta 2016; Reis et al. 2016). One of the
most urgent challenges in managing coastal fisheries is to stop and revert the loss of
coastal wetlands. These wetlands provide habitat for many adult fish, shellfish and
crabs, and are essential breeding and rearing areas, and provide a number of geochemical services essential to water quality. Therefore, efforts are arising to protect
these ecosystems.
M. Barletta et al.
as well as providing limitations on use of resources in these areas through the implementation of protected areas (UNCED 1992).
Coastal ecosystems are especially important for being temporary grounds for
commercial and subsistence species that use these spaces and their resources as
settlement, feeding and nursery (Whitfield 1999; Kjerfve 1994; Able 2005; Dantas
et al. 2010; Ramos et al. 2016; Lima and Barletta 2016; Potter et al. 2013). Many
fish species spawn in estuaries at times that ensure protection and food availability
for their eggs and larvae (North and Houde 2003; Martino and Houde 2010; Lima
et al. 2015). Seasonal variations on environmental variables (e.g. salinity, temperature, dissolved oxygen, turbidity and food availability) are the main factors influencing the spatio-temporal distribution of fishes in estuaries around the world
(Blaber 1997; Barletta-Bergan et al. 2002a, b; Barletta et al. 2005; Hoffmeyer et al.
2009; Ooi and Chong 2011; Williams et al. 2012).
Estuaries support a high biological production and also have high recovering
capacity. However, ecological services, including fisheries, can be reduced by
human interventions (Barletta et al. 2016; Dyke and Weaver 2013; Elliott and
Quintino 2007), especially unplanned or unpredicted ones. In the last 500 years, the
majority of tropical estuaries underwent human colonization and exploitation of
their natural resources and services based on the European model. This colonial
model has no regard to nature and/or resources conservation. In addition, the high
diversity and performance of ecological services provided by estuarine areas
favoured poorly planned urban and industrial settlements. Face the large scale of
occupation of coastal ecosystems as these, problems of basic sanitation became one
of the most important concerns regarding modification of water quality (Costa and
Barletta 2016) in the twenty-first century since effluents, solid wastes and port facilities have surpassed all carrying capacity of the local-regional environment. Urban
settlements tends to be more widely spread along the coasts, meaning that coastal
habitats are likely to be altered or polluted, sometimes to the point of impairing its
services and resources maintenance. Therefore, tropical estuaries were often
severely abused and are now in a precarious state of natural conservation, overexploited or heavily polluted by sewage, agricultural run-off, industrial effluents
and solid wastes (Blaber 2000; Lima et al. 2014; Costa and Barletta 2016), not to
mention that often they are encircled by settlements of sub-human conditions that
also include traditional fishers populations.
South American estuaries are among those that have been altered by direct and
indirect human actions such as dredging, aggradation, damming, road building, pollution by wastewater and solid wastes, and their potential for producing sustained
fish harvests has been reduced or permanently impaired (Barletta et al. 2010, 2016;
Blaber and Barletta 2016; Costa and Barletta 2016; Reis et al. 2016). One of the
most urgent challenges in managing coastal fisheries is to stop and revert the loss of
coastal wetlands. These wetlands provide habitat for many adult fish, shellfish and
crabs, and are essential breeding and rearing areas, and provide a number of geochemical services essential to water quality. Therefore, efforts are arising to protect
these ecosystems.
M. Barletta et al.