Systematic Review of Fish Ecology and Anthropogenic Impacts in South American Estuaries: Setting Priorities for Ecosystem Conservation

Abstract

Research on estuarine ecology in South America (SA) increased quali-quantitatively since the early 1980 in search of consistent recommendations for estuarine conservation. The most important ecological theory achieved is that the seasonal fluctuation of the salinity gradient creates an ecocline influenced by gradual changes between river-dominated to marine-like waters. Estuarine fish fauna adapts to these changeable abiotic characteristics, including the spatial, and seasonal bioavailability of dissolved oxygen and numerous pollutants. However, studies on the influence of the estuarine ecocline are still missing for key estuarine systems. This study provides an overview of fish ecology and anthropogenic impacts within estuarine systems of SA and discusses priorities for environmental conservation. Research on fish reached important conclusions regarding essential habitats and fish interaction with other biological and abiotic compartments over spatio-temporal settings, including conditions of severe anthropogenic impacts. These impacts are related to unplanned urban settlements, industrial estates, ports, damming of major rivers, dredging activities, and deforestation for extensive farming. Changes in estuarine morphology alter natural flows and lead to habitat losses, disrupting the ecocline and impairing fishes from moving among formerly connected habitats, especially earlier ontogenetic phases. In addition, industrial, urban, and farming activities often result in high loads of metals and persistent organic pollutants, organic enrichment and oxygen depletion. Moreover, plastic debris, a ubiquitous contaminant with sources on every human activity, including fishing, when fragmented into microplastics, become preferably concentrated in semi-enclosed environments, as estuaries. Metals, POPs and microplastics are actually asserted to be persistent. When in high concentrations, they become bioavailable to the estuarine trophic web through bioaccumulation, being biomagnified or biotransfered toward higher trophic level organisms, such as top predator fishes. Therefore, research on environmental quality and fish ecology must be based on robust sampling designs along the whole ecocline using long-term approaches. In addition, basic sanitation, co-management, an improved Barletta and Lima Ecology and Conservation of South American Estuaries licensing system and scientifically-based risk assessments/monitoring for all sorts of enterprise are also urgent. These conservation priorities need to be in place before human-driven changes surpass the ecosystem's capacity to produce resources and maintain services.

Ichthyofauna from Santos-São Vincente upper estuary: a study before and during fire at Santos port terminal

“…A similar dominance was reported by Santos et al (2015) in the same area but with different species; only D. rhombeus was common to both studies. Overall, the richness and abundance reported in the present study agree with the patterns observed in other Brazilian estuaries reported by Araújo et al (1998), Azevedo et al (1999), Schwarz Jr. et al (2006, Carvalho-Neto & Castro (2008), Schmidt et al (2008), Barletta et al (2010), Silveira et al (2010), Catelani et al (2014), Marceniuk et al (2017), Vilar & Joyeux (2018) and Barletta & Lima (2019).…”

“…Historically, coastal regions play a strategic role in a country's economic development and population growth, mainly as a result of the construction of ports and terminals in these regions (Barletta et al, 2010;Blaber & Barletta, 2016;Barletta & Lima, 2019). In Brazil, more than half of the metropolitan regions are in estuarine areas (CETESB, 2001).…”

“…Despite the undeniable importance of estuaries for fish species, there is a dearth of studies on their species composition in Brazil (Silveira et al, 2010), which can lead to underestimation of the biodiversity (Barletta et al, 2010) even in areas that can be easily reached, such as those in metropolitan regions (Vilar & Joyeux, 2018). In many cases, Brazilian estuaries underwent extensive modifications before they were studied (Barletta et al, 2010;Silveira et al, 2010;Catelani et al, 2014;Marceniuk et al, 2017;Vilar & Joyeux, 2018; Barletta & Lima, 2019), as did Brazilian coastal reef environments (Pinheiro et al, 2015).…”

More than meets the eye: syntopic and morphologically similar mangrove killifish species show different mating systems and patterns of genetic structure along the Brazilian coast

“…Mangrove forests along this ~900 km long coastal area is discontinuous and heavily fragmented by urbanisation (Barletta and Lima, 2019;Branoff, 2017). We collected the fish using hand nets in mangrove temporary pools and crab burrows ( Fig.…”

Penja fish (Genus: Sicyopterus) from Karama River, West Sulawesi, Indonesia: Growth Pattern and Habitat Characteristics

“…The larvae drift immediately downstream to the estuary (Iida et al 2015), and after 2 to 6 months, the post-larvae migrate back into the rivers (Bauer 2013;Shiao et al 2015;Olii et al 2017;Tran et al 2018). Besides hydro-ecological characteristics, highnutrient found in the estuary can cause a high abundance of phytoplankton that affects zooplankton and fish at the early life stage, including postlarvae, which acts as consumers (Bhaumik et al 2011;Taillebois et al 2012;Cloern 2018).…”