Hydrobiologia

https://doi.org/10.1007/s10750-023-05172-z

EFFECTS OF CHANGES IN SALINITY

Composition and distribution of fish assemblages

in a tropical river–estuarine continuum
Ana Caroline Batista da Silva · Matheus Souza Ferreira de Barros ·
Victor Emmanuel Lopes da Silva · Cícero Diogo Lins de Oliveira ·
Myrna Elis Ferreira Santos · Nidia Noemi Fabré

Received: 12 September 2022 / Revised: 3 February 2023 / Accepted: 11 February 2023

© The Author(s), under exclusive licence to Springer Nature Switzerland AG 2023

Abstract The damming in a watershed alters all its composition of the fish community in three distinct
fluvial dynamics, affecting the patterns of occurrence regions along the river–estuarine continuum of the
and distribution of the fish community. Despite being São Francisco River, raising the hypothesis that the
an important refuge for fish communities in tropi- seasonal effect does not interfere in the structuring of
cal Brazil, the river–estuarine continuum is strongly the fish assemblage. Our results demonstrate that sea-
affected by human activities that have considerably sonality does not influence the composition and dis-
disturbed the natural dynamics. In this study, our tribution of fish species in the lower São Francisco,
objective was to evaluate the spatial and seasonal this differentiation is due to the spatial effect of the
regions studied. These findings add to the available
knowledge about the absence of the seasonal effect in
Guest editors: Erik Jeppesen, Miguel Cañedo-Argüelles, highly dammed environments.
Sally Entrekin, Judit Padisák & S.S.S. Sarma / Effects of
induced changes in salinity on inland and coastal water Keywords River-estuary · Occurrence of species ·
ecosystems
São Francisco River · Dam · Salinity
Supplementary Information The online version
contains supplementary material available at https://​doi.​
org/​10.​1007/​s10750-​023-​05172-z. Introduction
A. C. B. da Silva (*) · V. E. L. da Silva · M. E. F. Santos ·
N. N. Fabré River–estuarine continuums are among the most
Laboratório de Ecologia de Peixes e Pesca (LaEPP), da productive ecosystems on earth, having a distinct
Universidade Federal de Alagoas (UFAL), Instituto de dynamic that is extremely important for biological
Ciências Biológicas e da Saúde (ICBS), Maceió, Brazil
communities and adjacent areas (Sin et al., 2015). For
e-mail: aninhacarolainebs@gmail.com
instance, the constant fluctuations in environmental
M. S. F. de Barros conditions that results from the mixing of fresh and
Dauphin Island Sea Lab, School of Marine saltwater (Pramanik, 2019; Nashima et al., 2021),
and Environmental Sciences, University of South
creates a challenging and stratified environment that
Alabama, Dauphin Island, AL 36528, USA
filters and determines species occurrence throughout
C. D. L. de Oliveira its extension. Fish assemblages, for example, often
Laboratório de Conservação e Manejo de Recursos follow an existing salinity gradient, where freshwa-
Naturais Renováveis (LACOM), , da Universidade Federal
ter species usually dominate upstream habitats, while
de Alagoas (UFAL), Instituto de Ciências Biológicas e da
Saúde (ICBS), Maceió, Brazil marine and estuarine fish mostly occupy downstream

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regions (Pramanik, 2019; Nashima et al., 2021; et al., 2011; Pereira et al., 2016; Arantes et al., 2019;
Roshni et al., 2021). Nascimento do Vasco et al., 2019; Pelicice et al.,
Nevertheless, natural rearrangements of this occu- 2021).
pancy pattern may occur due to seasonal changes in São Francisco river is the longest river that runs
abiotic parameters and freshwater discharge, which entirely in Brazilian territory, but this system is regu-
allow interchanges of species between different areas lated by seven dams, known to control approximately
within the same ecosystem (Passos et al., 2016; 98% of its drainage area, altering its hydrological
Polansky et al., 2018; da Silva et al., 2022). In tropi- regime and natural dynamics (Loures & Pompeu,
cal regions, for instance, rainfall regimes often con- 2012; Cavalcante et al., 2020; Melo et al., 2020;
trol the freshwater inputs throughout the continuum, D’avilla et al., 2021). From 1979 until 2012, dras-
causing changes in habitat structures and features, tic reductions occurred in the amount of freshwater
such as their salinity profile and productivity levels, being discharged downstream (up to 35%) (Nasci-
which facilitate the migration of species between dif- mento do Vasco et al., 2019), which caused a severe
ferent regions. However, those complex patterns can retraction of the estuarine plume, and a widespread
be easily modified by anthropogenic processes, with intrusion of saltwater upstream (Assis et al., 2017;
river damming being one of the most harmful activi- Cavalcante et al., 2020; D’avilla et al., 2021; Paiva &
ties to this dynamic (Agostinho et al., 2008; Nasci- Schettini, 2021). Following those events, unpredict-
mento do Vasco et al., 2019; D’avilla et al., 2021; able patterns of river discharge created a spatial and
Nashima et al., 2021). temporal homogenization of the system, especially
In general, the damming of rivers causes a large in its lower portion, which currently presents dis-
accumulation of sediments in the upstream portion tinct features in relation to its salinity profile, with no
of the dam and modifies the river natural flow, trans- clear pattern of differentiation along its extension (do
forming the lotic system into a lentic environment Vasco et al., 2019; Cavalcante et al., 2020). Moreover,
(Agostinho et al., 2008; Barletta et al., 2010; Wang notable changes in the productive chain of the Lower
et al., 2011; Petesse & Petrere, 2012; Grant et al., São Francisco also resulted from the alterations in
2013; Freedman et al., 2014; Pereira et al., 2016; natural abiotic conditions (dos Santos et al., 2018;
Arantes et al., 2019; Nascimento do Vasco et al., Affe et al., 2021). Different works have shown a sig-
2019; Cavalcante et al., 2020; Pelicice et al., 2021). nificant decrease in diversity and changes in species
Moreover, seasonal cycles are also affected, with con- composition within cascade reservoirs (Agostinho
siderable changes in environmental conditions, that, et al., 2016; Ganassin et al., 2021), however, there is
in some cases, may present a new distribution pat- no current knowledge available on how fish commu-
tern along the river extension (Agostinho et al., 2008; nities responded to these changes in the river–estua-
Barletta et al., 2010; Grant et al., 2013; Arantes et al., rine continuum.
2019; Cavalcante et al., 2020; Pelicice et al., 2021). The comprehension of how the damming process
The salinity profile, for example, is one of the first and its alteration in river dynamics affect the pat-
parameters to respond to the damming process, with terns of occurrence and distribution of fishes along
some ecosystems showing an extension of the estua- the continuum is extremely important for the con-
rine plume inside the system, or even a complete versation of species and the whole ecosystem. Fish
homogenization within the whole area (Agostinho species are among the most diverse and dynamic
et al., 2008; Barletta et al., 2010; Wang et al., 2011; groups within the river–estuarine continuum, with
Hossain et al., 2012; Petesse & Petrere, 2012; Freed- assemblages comprised of marine, freshwater, and
man et al., 2014; Pereira et al., 2016; Arantes et al., brackish fishes that use these areas throughout their
2019; Cavalcante et al., 2020; Pelicice et al., 2021). life cycle. The species may inhabit different habitats
These changes are strongly associated with the struc- due to their differences in physiological limitations
turing of biological community, leading to several and migratory patterns, being one of the main compo-
changes in the composition and abundance of species, nents in the functioning and resilience of ecosystems
favoring the occurrence of marine species in freshwa- and performing key functions related to the transport
ter habitats and the establishment of invasive species of organic matter between different regions (Arantes
(Agostinho et al., 2008; Barletta et al., 2010; Wang et al., 2019). Given this information, we aimed to

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assess the spatial and seasonal composition of fish 12 h in the water. Trawl nets were dragged for approx-
communities along the river–estuarine continuum of imately 30 min with 3 replicates for sample. Cast nets
the Lower São Francisco River. We hypothesized that were deployed 15 times in each station, while sieves
seasonality does not influence the composition and were used to sample small individuals found in the
distribution of the fish assemblages in the lower São marginal vegetation (20 replicates for sample).
Francisco, because we expected that the damming In each station, the following abiotic parameters
processes and their subsequent impacts on river flow were measured in the field with a YSI multiparameter
altered the expected outcome of seasonal changes. recorder sonde before fish sampling: conductivity (in
µS/cm), concentration of chlorophyll-a (in mSPU),
turbidity (in NTU), pH, temperature (in Celsius),
Materials and methods dissolved oxygen saturation (in %), and depth (in
meters). In addition, data on rainfall (in mm) for each
Study area region and sampled month were retrieved from the
Brazilian National Institute of Meteorology (INMET)
The São Francisco River is one of the largest rivers website. Sampling was previously authorized by the
in South America, being divided into four segments Brazilian Institute of Environment and Renewable
along its length: high, medium, sub-medium, and Natural Resources (IBAMA), under the license num-
low. Its lower portion, which runs for 265 km before ber (ABIO) 1124/2019 (5311925).
emptying into the Atlantic Ocean, has a dry sea- In the laboratory, collected fish were identified to
son between October and March and a rainy season species level according to dichotomous identification
between April and September, and has three major keys and specialized catalogs (Britski et al., 1988;
regions based on their respective geomorphological Godinho & Godinho, 2003; Reis et al., 2003; Araújo
characteristics. The first region is located in higher et al., 2004). Then, individuals had their standard
altitudes, having a diverse rocky substrate that forms length measured to the nearest millimeter and were
geomorphological depressions with freshwater domi- weighted in grams with a precision scale (Godinho
nance. The second is a transitional region where the & Godinho, 2003; Pompeu & Godinho, 2003; Reis
estuarine plume ends, comprising a coastal table- et al., 2003). Fish were subsequently classified into
land with an extensive network of river channels and guilds of habitat use, following Elliott et al., (2007)
intermediate altitude. The last region comprises the grouping species into freshwater fishes, estuarine res-
São Francisco River delta, a lowland characterized idents, marine migrants, and marine stragglers, based
by very low and plain altitudes, with brackish waters on biological information regarding physiological
throughout its whole extension. adaptations and migratory patterns.

Sampling and laboratory procedures Data analysis

For the present study, we established two sampling In order to better understand the river–estuarine con-
stations in each one of the three regions of the Lower tinuum of the Lower São Francisco River, we carried
São Francisco River, resulting in a total of six areas several analyses using the environmental and fish
(Fig. 1 and Table 1) that were bimonthly sampled data. First, significant differences in environmental
from August 2019 to June 2021 for fish individuals conditions between regions and seasons were tested
and environmental conditions. Four different fishing by a two-way permutation analysis of variance (PER-
gears were used to ensure a representative sample of MANOVA), performed using the Bray–Curtis dis-
studied assemblies: bottom and surface gillnets (20 m similarity index in the program statistic R, package
long, 1.6 m high, with mesh sizes of 12, 15, 20, 25, Vegan (adonis2) (Anderson, 2017).
30, 35, 40, 50 60, 70, 80, and 90 mm), trawl nets For fish sampling, which was carried out with
(12 mm mesh size), cast nets (radius of 1.5 m and different fishing gears, catches were standardized
25 mm mesh size), and sieves (5 mm mesh size). In before further analysis to account for bias towards
each station, the gillnets were deployed at nighttime applied methods (Gibson-Reinemer et al., 2017).
and removed during the morning after a period of Thus, we assumed a linear relationship between the

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Fig. 1  Sampling points at

each three regions in the
Lower São Francisco River.
“UHE Xingo” shows the
location of the dam

four used gears and the catch per unit effort esti- as covariables to avoid possible temporal and spa-
mated of samples (defined herein as the biomass tial effects in fish abundance. The normality of
of each sample divided by the fishing effort— residuals of the fitted model were then tested by
CPUE). Gears were ordered according to their the Shapiro–Wilk test, and since significant effects
degree of catchability (sieves—1, casting net—2, on CPUE values were only found for fishing gears
trawl—3, gillnets—4), and a generalized linear (P < 0.001, see supplementary materials for the
model (GLM) using the Gaussian family was car- whole output, Table S1 and Fig. S1), CPUE val-
ried out, with seasonality (dry and wet seasons) ues were standardized for each sample from the
and regions (depression, tableland, lowland) acting predicted values retrieved from the fitted model

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Table 1  Geographical coordinates of sampling points for each Results

region in the Lower São Francisco River
Region Coordinates Environmental conditions showed significant vari-
ation between locations and in different seasons
Lowland 10° 24′ 5.30″ S 36° 26′ 28.80″ W
(P < 0.05), showing significant seasonal changes
Lowland 10° 25′ 17.90″ S 36° 26′ 19.40″ W
between the three regions (Table 2).
Tableland 10° 17′ 31.60″ S 36° 35′ 14.30″ W
Overall, 3,282 fishes, belonging to 102 species
Tableland 10° 18′ 11.60″ S 36° 34′ 43.70″ W
and 38 families, were collected during the sampling
Depression 9° 58′ 36.30″ S 37° 0′ 57.70″ W
period (Supplementary Table S2). CPUE values var-
Depression 9° 58′ 24.10″ S 36° 59′ 52.00″ W
ied greatly among guilds (Table 3) and between the
three studied regions of low São Francisco (Table 3),
with a significant interaction between these two fac-
(Venables and Dichmont 2004; Mourato et al. tors (Table 3). In the depression zone, 62 species
2008; Hoyle et al. 2014; Souza et al. 2019). were caught, with freshwater and estuarine resident
To describe spatial and temporal patterns in the species being dominant in both seasons, and only a
composition and distribution of fish assemblages, small number of marine straggler fish occasionally
three different sets of analyses were performed. occurring during the rainy months (Fig. 2). Fifty-four
First, a three-way analysis of variance (ANOVA) species were registered in the tableland, where repre-
was performed to test for significant differences in sentatives of all guilds were found, but freshwater and
corrected CPUE values among guilds, regions, and marine straggler species were more common (Fig. 2).
seasons. CPUE data were Box-Cox transformed For the lowland area 62 species were caught, and
using the equation Y′ = (Y0.03–1)/0.03 to increase CPUE values were evenly distributed among guilds,
normality and meet the test assumptions. The Box- with a small decrease in the number of marine strag-
Cox transformation was chosen because it produces gler fish during the rainy season (Fig. 2).
the best transformation among the power family,
not only looking for a transformation that justifies Table 2  Results of the bidirectional Permutation Analysis of
assumptions, but a data set that can be expressed Variance (PERMANOVA) for the comparison of environmen-
succinctly (Box & Cox, 1964; Atkinson et al.., tal variables among the regions and seasons of the Lower São
2021). Second, a Bray–Curtis similarity matrix Francisco
was constructed from the corrected CPUE data and Factor Sum of squares DF F P value
used to test for significant differences in species
Season 0.797 1 66.219 0.001
composition between regions (lowland, tableland,
Region 0.344 2 14.281 0.001
and depression) and seasons (wet and dry) by an
Season × Region 0.054 2 2.256 0.053
analysis, two-way permutation of variance (two-
Residuals 1.171 102
way PERMANOVA) (Anderson, 2017).
Moreover, significant relationships between the
abiotic variables and fish assemblages were ana- Table 3  Results for the three-way ANOVA test applied in the
lyzed through the “envfit” function in the “vegan” Box-Cox transformed CPUE of fish among guilds, regions, and
R package (Oksanen, 2016). This function carries seasons of the Lower São Francisco River
an overlap between vectors that represent envi- Factor Sum of squares DF F P value
ronmental variables and nMDS ordination plots
(based on their first two dimensions), while search- Guild 55.02 3 15.56 < 0.001
ing for the best combination of variables that could Region 7.820 2 3.320 0.041
be related to the assemblages’ data (Smith et al., Season 0.360 1 0.304 0.582
2017). All statistical analyses were carried out in Guild × Region 65.07 6 9.202 < 0.001
the R statistics software using the vegan package Guild × Season 4.720 3 1.334 0.269
at a significance level of P < 0.05 (R Core Team, Region × Season 0.470 2 0.199 0.821
2013). Guild × Region × Sea- 5.480 4 1.163 0.332
son

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◂Fig. 2  Spatial and temporal variation of the number of indi- composition during its natural dynamics, with sea-
viduals (in log [N + 1]) (0–10) of fish species classified into sonal variations in environmental conditions leading
habitat use guilds according to Elliott et al. (2007) for each
geomorphological region of the São Francisco River and sea-
to changes in the distribution and occurrence of many
son. The silhouette for the most abundant species of each guild fishes (Agostinho et al., 2016). In tropical regions, for
was used. This schematic representation expresses a seasonal example, rainfall regimes often control the inputs of
shift in the fish assemblages between regions of the Lower São freshwater and sediments along rivers and estuarine
Francisco River
systems, which cause significant changes in the pro-
ductivity, salinity, and dissolved oxygen levels, result-
Although environmental variables changed accord- ing in the spatial rearrangement of species (da Silva
ing to regions and seasonality, the assemblage com- et al., 2018, 2021). This natural dynamic is credited
position differed only among regions (Tables 2, 4), as a key mechanism of ecosystem’s resilience that
and no significant pattern of correlation between allows the movement of species among different habi-
environmental conditions and fish species could tats and areas found in the ecosystem (da Silva et al.,
be found for the entire river–estuarine continuum 2021, 2022), being one of the main components of
(Table 5). Rather, each region had a different set of the estuarine and neritic zone connectivity (Passos
environmental variables associated to the structuring et al., 2016; Macedo et al., 2021, 2023).
of assemblages, with distinct strengths and signifi- However, dammed environments are often char-
cances (Table 5). For depression region no significant acterized by the loss of this temporal effect, due
correlation was found, while fish composition in the to severe changes in their natural flow, which can
tableland was related to fluctuations in the depth and affect different areas of the system and their respec-
salinity of the region (Table 5). The lowland’s fish tive fish assemblages (Agostinho et al., 2016; Santos
assemblages were better explained by the interaction et al., 2022). As identified in our study, the lower São
of depth, pH, and turbidity (Table 5). Francisco river–estuarine continuum appears to be
highly impacted by upstream dams, showing a sig-
nificant loss of seasonal effects on the structuring of
Discussion fish assemblages between the studied regions, prob-
ably due to impacts reported since its damming, such
To the best of our knowledge, this is the first study to as the substantial extent of upstream estuarine condi-
analyze, in detail, the fish community structure of the tions, which decreased the pattern of differentiation in
São Francisco river–estuarine continuum, one of the its salinity profile along its extension (Li et al., 2013;
longest and most important rivers in South America. Nascimento do Vasco et al., 2019; Cavalcante et al.,
Although a clear spatial configuration in the distribu- 2020).
tion of species can be observed along the whole sys- Furthermore, despite the absence of a seasonal
tem, our results indicate that despite the differences effects on the assembling of species, the three regions
in environmental conditions between regions and sea- studied in the Lower São Francisco showed differen-
sons, seasonality does not have significant effects on tiation in their structures, with a clear spatial pattern
the structuring of fish assemblages. One of the possi- of occupation. These significant differences between
ble mitigating factors for this pattern is the damming regions are probably due to their geomorphological
process, which may have altered the natural dynam- diversity, as well as the changes they underwent after
ics of the river–estuarine continuum, modifying the the damming (Agostinho et al., 2016; Nascimento do
natural hydrological regime by increasing or reducing Vasco et al., 2019; Paiva & Schettini, 2021; Santos
flood peaks due to the controlled flow (Godinho & et al., 2022). For example, in the depression region,
Godinho, 2003; Petesse & Petrere, 2012; Agostinho our results showed a dominance of freshwater spe-
et al., 2016). cies, which can be explained by the abiotic conditions
in the area. The control of the natural flow and the
Species composition and spatial distribution direct discharge of freshwater in this pediplain region
allows the abiotic conditions to remain stable, with
Overall, river–estuarine continuums are expected to low salinity and little depth in relation to the other
have temporal and spatial fluctuations in assemblages’ regions (Franzen, 2020).

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Table 4  Results of the two-way Permutational Analysis of features reflect estuarine conditions, which are
Variance (PERMANOVA) for the comparison of fish assem- highly diverse and productive places (Sin et al.,
blages’ composition among regions and seasons in the Lower
São Francisco River
2015; Nashima et al., 2021). However, we observed
that this region did not behave as expected, having
Factor Sum of squares DF F P value the same number of species found in the depres-
Region 4.408 2 5.324 0.001 sion region and presenting the same guilds of the
Season 0.501 1 1.212 0.193 other regions. This result might also be linked to the
Region × Season 0.964 2 1.165 0.176 presence of dams in the systems that alter the river
Residuals 41.216 102 flow and impact biogeochemical and physical pro-
cesses, mainly affecting productivity, which directly
interfere in the fish community structure (Hossain
Table 5  Multivariate correlations between the environmental et al., 2012; Montagna et al., 2013; Agostinho et al.,
variables and fish species found for the Lower São Francisco 2016).
River (LSFR) and its regions, displaying the top model from
the BEST output, as well as its strength (ρ) and significance (P
value)
Current concerns and implications for conservation
Region Best model Correlation (ρ) P value

LSFR Depth + turbidity 0.074 0.118 Natural river ecosystems depend on the frequency
Depression Depth + pH 0.059 0.421 and duration of floods for the exchange of energy,
Tableland Depth + salinity 0.168 0.027 nutrients, sediments, and organisms (McCartney
Lowland Depth + pH + turbidity 0.201 0.011 et al., 2001; Arantes et al., 2019), but when this eco-
system is dammed, there are changes in the biotic
structure and in their seasonal patterns, as identified
The tableland region is in a pre-coastal position, in our study. These changes often result from a vari-
being a transition area between the domain of high- ety of factors, such as the extent of estuarine condi-
lands and the coastal plain, influenced by estuaries tions (Nascimento do Vasco et al., 2019; Cavalcante
and sea level fluctuations (Franzen, 2020). For this et al., 2020; Paiva & Schettini, 2021), changes in the
region, our results showed that salinity and depth natural characteristics of habitats and the alteration of
significantly affect species composition, with the the river flow (Li et al., 2013; Freedman et al., 2014).
absence of a dominance pattern among the guilds These impacts have already been recorded in different
found within. Even though it is a region that has river–estuarine continuums around the world, includ-
marine interference, this influence was probably ing in the Lower São Francisco River (Mourato et al.,
increased by the control of the natural flow of the 2008; Wang et al., 2011; Li et al., 2013, 2016; Cooper
river as discussed in the work of Brito & Magalhães et al., 2017; Gubiani et al., 2018).
(2017), where authors show that seawater entered Moreover, a dammed system in cascade can cumu-
upstream and altered salinity values, modifying latively cause the fragmentation of river landscapes,
chemical parameters in this region of the lower São negatively impacting the distribution of fish species
Francisco River. However, it is important to highlight (Arantes et al., 2019). In our study, we demonstrate
that although not significant for species distribution, that, although there are seasonal variations in envi-
seasonal periods can result in an intrusion or decrease ronmental conditions between the regions studied,
of salt water upstream (Cavalcante et al., 2020), as they do not impact the structuring of fish assem-
shown in our results, where environmental vari- blages, which can be an indicator of spatial segrega-
ables between regions were different in each seasonal tion between regions. Since the movement of species
period. between the whole continuum is often linked to key
The lowland region of the lower São Francisco ecological and ecosystem processes, for the conser-
River is directly influenced by eustatic changes vation and management of fish species in this region,
in sea level, being the transition part between we propose that the results found herein should be
fresh water from rivers and salt water from the taken into account for the effective planning and man-
sea (Franzen, 2020). These important unique agement of the Lower São Francisco River.

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Acknowledgements The authors would like to thank all fel- Box, G. E. P. & D. R. Cox, 1964. An analysis of transforma-
lows from the Management and Conservation of Renewable tions. Journal of the Royal Statistical Society. Series B
Resources Laboratory and Laboratory of Ecology, Fish and (Methodological) 26(211–252): 371.
Fisheries, that continuously contributed to the data. The São Brito, M. F. G. & A. L. B. Magalhães, 2017. Brazil’s develop-
Francisco Hydroelectric Company (CHESF) and Water and ment turns river into sea. Science 358(6360): 179.
Land laboratory for the availability of data from the monitoring Britski, H. A., Y. Sato, & A. B. S. Rosa, 1988. Manual de iden-
of the São Francisco River. We thank the Coordination for the tificação de peixes da região de Três Marias.
Improvement of Higher Education Personnel CAPES-Brazil Cavalcante, G., F. Vieira, E. Campos, N. Brandini & P. R. P.
CAPES (#23038.000452/2017-16). Medeiros, 2020. Temporal streamflow reduction and
impact on the salt dynamics of the São Francisco River
Funding Funding was provided by Coordenação de Aper- Estuary and adjacent coastal zone (NE/Brazil). Regional
feiçoamento de Pessoal de Nível Superior (Grant no. 001). Studies in Marine Science 38: 101363.
Cooper, A. R., D. M. Infante, W. M. Daniel, K. E. Wehrly, L.
Data availability Not applicable. Wang & T. O. Brenden, 2017. Assessment of dam effects
on streams and fish assemblages of the conterminous
Declarations USA. Science of the Total Environment 586: 879–889.
D’avilla, T., E. M. Costa-neto & M. F. G. Brito, 2021. Impacts
Conflict of interest The authors have no relevant financial or on fisheries assessed by local ecological knowledge in a
non-financial interests to disclose. reservoir cascade in the lower São Francisco River, north-
eastern Brazil. Neotropical Ichthyology 19: e200156.
da Silva, V. E. L., E. C. Teixeira, V. S. Batista & N. N. Fabré,
2018. Spatial distribution of juvenile fish species in nurs-
ery grounds of a tropical coastal area of the south-western
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Effects of dams in river networks on fish assemblages in
and applicable law.
non-impoundment sections of rivers in Michigan and

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