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REVIEW PAPER
Conservation threats and future prospects for the freshwater
fishes of Ecuador: A hotspot of Neotropical fish diversity
Windsor E. Aguirre
1,2,3
| Gabriela Alvarez-Mieles
4
|
Fernando Anaguano-Yancha
5
| Ricardo Burgos Morán
6
| Roberto V. Cucal
on
1
|
Daniel Escobar-Camacho
7
| Iván Jácome-Negrete
8
| Pedro Jiménez Prado
9,10
|
Enrique Laaz
11
| Katherin Miranda-Troya
12
| Ronald Navarrete-Amaya
13
|
Fredy Nugra Salazar
14,15
| Willan Revelo
16
| Juan F. Rivadeneira
12
|
Jonathan Valdiviezo Rivera
2
| Edwin Zárate Hugo
15
1
Department of Biological Sciences, DePaul University, Chicago, Illinois, USA
2
Instituto Nacional de Biodiversidad, Quito, Ecuador
3
Field Museum of Natural History, Chicago, Illinois, USA
4
Facultad de Ciencias Naturales, Universidad de Guayaquil, Guayaquil, Ecuador
5
Wildlife Conservation Society –Programa Ecuador, Quito, Ecuador
6
Departamento de Ciencias de la Tierra, Universidad Estatal Amaz
onica, Puyo, Ecuador
7
Instituto BIOSFERA, Universidad San Francisco de Quito, Quito, Ecuador
8
Facultad de Ciencias Biol
ogicas, Instituto de Estudios Amaz
onicos e Insulares, Universidad Central del Ecuador, Quito, Ecuador
9
Pontificia Universidad Cat
olica del Ecuador Sede Esmeraldas, Esmeraldas, Ecuador
10
Area de Ecología, Departamento de Ciencias Agrarias y del Medio Natural, Escuela Politécnica Superior de Huesca, Universidad de Zaragoza, Huesca, Spain
11
Instituto Público de Investigaci
on de Acuicultura y Pesca, Guayaquil, Ecuador
12
Facultad de Ciencias Biol
ogicas, Universidad Central del Ecuador, Quito, Ecuador
13
Urb. Paraíso del Río 1, Guayaquil, Ecuador
14
ONG Bosque Medicinal, ONG Forest.ink, Gualaquiza, Ecuador
15
Laboratorio de Limnología de la Universidad del Azuay, Cuenca, Ecuador
16
Unidad de Recursos Demersales Bent
onicos de Agua Dulce y Embalses, Instituto Público de Investigaci
on de Acuicultura y Pesca, Guayaquil, Ecuador
Correspondence
Windsor E. Aguirre, Department of Biological
Sciences, DePaul University, 2325 North
Clifton Ave., Chicago, IL 60614, USA.
Email: waguirre@depaul.edu
Present address
Roberto V. Cucal
on, Program in Ecology,
Evolution, and Conservation Biology,
University of Illinois at Urbana-Champaign,
Champaign, Illinois, USA
Funding information
Wildlife Conservation Society
ABSTRACT
Freshwater fish communities in Ecuador exhibit some of the highest levels of diver-
sity and endemism in the Neotropics. Unfortunately, aquatic ecosystems in the coun-
try are under serious threat and conditions are deteriorating. In 2018–19, the
government of Ecuador sponsored a series of workshops to examine the conserva-
tion status of Ecuador's freshwater fishes. Concerns were identified for 35 species,
most of which are native to the Amazon region, and overfishing of Amazonian pim-
elodid catfishes emerged as a major issue. However, much of the information needed
to make decisions across fish groups and regions was not available, hindering the pro-
cess and highlighting the need for a review of the conservation threats to Ecuador's
Received: 21 March 2021 Accepted: 4 July 2021
DOI: 10.1111/jfb.14844
FISH
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any
medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
© 2021 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.
1158 J Fish Biol. 2021;99:1158–1189.wileyonlinelibrary.com/journal/jfb
freshwater fishes. Here, we review how the physical alteration of rivers, deforesta-
tion, wetland and floodplain degradation, agricultural and urban water pollution, min-
ing, oil extraction, dams, overfishing, introduced species and climate change are
affecting freshwater fishes in Ecuador. Although many of these factors affect fishes
throughout the Neotropics, the lack of data on Ecuadorian fish communities is stag-
gering and highlights the urgent need for more research. We also make recommenda-
tions, including the need for proper enforcement of existing environmental laws,
restoration of degraded aquatic ecosystems, establishment of a national monitoring
system for freshwater ecosystems, investment in research to fill gaps in knowledge,
and encouragement of public engagement in citizen science and conservation efforts.
Freshwater fishes are an important component of the cultural and biological legacy of
the Ecuadorian people. Conserving them for future generations is critical.
KEYWORDS
biodiversity, conservation, Ecuador, endemism, freshwater fishes, Neotropics
1|INTRODUCTION
Neotropical ecosystems are among the most biodiverse and ecologically
important in the world. Few groups highlight the importance of the Neo-
tropics more than the freshwater fishes. There are likely over 7000 spe-
cies of freshwater fishes in South and Central America, which
corresponds to approximately one in five fishes in the world or one in
10 vertebrates (Albert & Reis, 2011b). Freshwater fishes play crucial roles
in their ecosystems, constitute important components of the historical
and evolutionary legacy of the Neotropics, and are important sources of
food and livelihoods for people (Albert & Reis, 2011a; Lo et al., 2020;
Toussaint et al., 2016; van der Sleen & Albert, 2018). Unfortunately, Neo-
tropical ecosystems are under serious threat, and knowledge of freshwa-
ter fishes and their conservation status lags behind that of other
vertebrates (Anderson & Maldonado-Ocampo, 2011; Myers et al., 2000).
Since freshwater fisheries typically generate only one tenth of the fisher-
ies revenue compared to marine fishes, there is little economic incentive
for governments to enforce conservation laws aimed at protecting them
(FAO, 2018; Jiménez-Segura et al., 2016). The decline of Neotropical
fishes disproportionally affects human populations in rural areas and
indigenous people, which also makes it a social justice issue (Jiménez-
Segura et al., 2016; Lo et al., 2020).
The threats that Neotropical fishes face have been increasingly rec-
ognized by ichthyologists and conservation biologists, resulting in several
publications summarizing the vulnerable state of Neotropical fishes in dif-
ferent areas (Anderson & Maldonado-Ocampo, 2011; Jiménez-Segura
et al., 2016; Lasso et al., 2015; Mojica et al., 2012; Pelicice et al., 2017;
Reis et al., 2016). In 2018–19, via Acuerdo Ministerial 069, the govern-
ment of Ecuador organized a series of workshops to generate national
red lists of endangered species (Ministerio del Ambiente, 2019). The
Freshwater Fishes Working Group reviewed 163 species and identified
35 species that were vulnerable, near threatened, endangered or critically
endangered (Aguirre et al., 2019b). Although an important step forward,
the work was greatly complicated by the lack of information because
many species were deemed data deficient, highlighting the need for more
research on the freshwater fishes of Ecuador. As the group discussed the
conservation challenges for the freshwater fishes of Ecuador over several
meetings, it became clear that their state was alarming and deteriorating
across the country, much of the information needed to make decisions
on the status of many species was not available, and the existing relevant
literature was scattered and often difficult to access. Critically, with some
exceptions (Jiménez-Prado et al., 2020; Jiménez-Prado & Vásquez, 2021;
Loomis, 2017; Vélez Espino, 2003, 2006), there are few studies docu-
menting how freshwater fish abundances, fisheries catches or geographic
ranges have been affected by the environmental problems that aquatic
ecosystems are experiencing. Available quantitative data on fish abun-
dance and fisheries catches are typically based on short-term studies with
a limited geographic scope that employ different methodologies, making
trends difficult to decipher (Burgos-Morán et al., 2018; Jácome-Negrete
et al., 2018; Revelo, 2010; Utreras, 2010).
In this review, we summarize current knowledge of the major
conservation threats and prospects of the freshwater fishes of Ecua-
dor. First, we present an overview of the geography of the major
drainage basins in continental Ecuador. Second, we characterize the
taxonomic and geographic distribution of the fish species for which
concerns could be identified by the Freshwater Fishes Working
Group. Third, we review the major factors causing the decline of
freshwater fishes in Ecuador. Finally, we conclude by making recom-
mendations for needed conservation actions.
2|FISH DIVERSITY AND THE MAJOR
DRIANAGE BASINS OF ECUADOR
Freshwater fishes constitute an important component of the biodiver-
sity of Ecuador (Figure 1). In the most recent national list of the
AGUIRRE ET AL.1159
FISH
freshwater fishes of Ecuador, Barriga (2012) included 951 species,
most of which are in the Amazon region and the Amazon slopes of
the Andes (Table 1). Since the publication of this list, new freshwater
fish species have been described while others have been synonymized
(e.g., Arbour et al., 2014; Crampton et al., 2016; Lujan et al., 2015b;
Provenzano & Barriga-Salazar, 2018; Tobes et al., 2020). Jimenez-
Prado et al. (2015) updated the list for Western Ecuador, removing
over 100 species listed in Barriga (2012) that are primarily estuarine.
This resulted in a decline in the total number of primarily freshwater
fish species to 836 (Table 1). Although the number of species will
likely continue to change as new species are described and taxonomic
revisions synonymize species, the general patterns are clear. The
Ostariophysii dominate, as is the case in freshwaters throughout the
world, with the Siluriformes (catfishes) and Characiformes (tetras and
relatives) adding up to 694 species or about 83% of all Ecuadorian
freshwater fishes. Within these orders, the most diverse families both
on the western and Amazonian slopes of the Andes are the Char-
acidae (tetras) and Loricariidae (suckermouth catfishes), with approxi-
mately 184 (22%) and 107 (12.8%) species respectively, representing
over one-third of all freshwater fish in Ecuador (Table 1).
FIGURE 1 Representative
Ecuadorian freshwater fish.
(a) Creagrutus kunturus, (b) Rhoadsia
minor, (c) Gasteropelecus maculatus,
(d) Hoplias malabaricus,
(e) Eretmobrycon sp., (f) Pygocentrus
nattereri, (g) Brycon sp., (h)
Tetragonopterus argenteus, (i) Ancistrus
clementinae, (j) Hypostomus
cf. niceforoi, (k) Rhamdia cinerascens,
(l) Sturisomatichthys frenatus, (m)
Astroblepus sp., (n) Brachyplatystoma
juruense, (o) Pseudopimelodus bufonius,
(p) Brachyhypopomus palenque, (q)
Potamotrygon motoro, (r) Andinoacara
rivulatus, (s) Astronotus ocellatus, (t)
Sicydium sp., (u) Arapaima gigas, (v)
Synbranchus marmoratus
1160 AGUIRRE ET AL.
FISH
TABLE 1 Number of freshwater fish species by taxonomic family in Ecuador distributed along the western and Amazon slopes
Order Family Western slope Amazon slope
Myliobatiformes Potamotrygonidae 0 (0%) 6 (0.8%)
Osteoglossiformes Osteoglossidae 0 (0%) 1 (0.1%)
Osteoglossiformes Arapaimidae 0 (0%) 1 (0.1%)
Clupeiformes Engraulidae 0 (0%) 3 (0.4%)
Clupeiformes Pristigasteridae 0 (0%) 2 (0.3%)
Characiformes Anostomidae 1 (0.9%) 24 (3.3%)
Characiformes Bryconidae 5 (4.4%) 7 (1%)
Characiformes Characidae 19 (16.8%) 165 (22.8%)
Characiformes Curimatidae 5 (4.4%) 30 (4.1%)
Characiformes Erythrinidae 2 (1.8%) 2 (0.3%)
Characiformes Gasteropelecidae 1 (0.9%) 7 (1%)
Characiformes Lebiasinidae 3 (2.7%) 15 (2.1%)
Characiformes Parodontidae 2 (1.8%) 3 (0.4%)
Characiformes Prochilodontidae 1 (0.9%) 2 (0.3%)
Characiformes Chilodontidae 0 (0%) 2 (0.3%)
Characiformes Crenuchidae 0 (0%) 12 (1.7%)
Characiformes Hemiodontidae 0 (0%) 6 (0.8%)
Characiformes Alestiidae 0 (0%) 1 (0.1%)
Characiformes Serrasalmidae 0 (0%) 17 (2.3%)
Characiformes Acestrorhynchidae 0 (0%) 6 (0.8%)
Characiformes Cynodontidae 0 (0%) 4 (0.6%)
Characiformes Ctenoluciidae 0 (0%) 3 (0.4%)
Gymnotiformes Apteronotidae 1 (0.9%) 17 (2.3%)
Gymnotiformes Gymnotidae 1 (0.9%) 7 (1%)
Gymnotiformes Hypopomidae 1 (0.9%) 5 (0.7%)
Gymnotiformes Sternopygidae 2 (1.8%) 8 (1.1%)
Gymnotiformes Rhamphichthyidae 0 (0%) 4 (0.6%)
Siluriformes Astroblepidae 14 (12.4%) 8 (1.1%)
Siluriformes Cetopsidae 4 (3.5%) 8 (1.1%)
Siluriformes Heptapteridae 4 (3.5%) 22 (3%)
Siluriformes Loricariidae 12 (10.6%) 95 (13.1%)
Siluriformes Pseudopimelodidae 3 (2.7%) 5 (0.7%)
Siluriformes Trichomycteridae 4 (3.5%) 28 (3.9%)
Siluriformes Aspredinidae 0 (0%) 14 (1.9%)
Siluriformes Callichthyidae 0 (0%) 32 (4.4%)
Siluriformes Pimelodidae 0 (0%) 43 (5.9%)
Siluriformes Doradidae 0 (0%) 31 (4.3%)
Siluriformes Auchenipteridae 0 (0%) 22 (3%)
Cyprinodontiformes Poeciliidae 2 (1.8%) 0 (0%)
Cyprinodontiformes Rivulidae 0 (0%) 7 (1%)
Beloniformes Belonidae 1 (0.9%) 4 (0.6%)
Mugiliformes Mugilidae 1 (0.9%) 0 (0%)
Cichliformes Cichlidae 5 (4.4%) 34 (4.7%)
Perciformes Haemulidae 1 (0.9%) 0 (0%)
Perciformes Sciaenidae 1 (0.9%) 2 (0.3%)
Perciformes Polycentridae 0 (0%) 1 (0.1%)
(Continues)
AGUIRRE ET AL.1161
FISH
Geographically, continental Ecuador is typically divided into three
regions: (1) western Ecuador also known as the coastal region (Costa)
included within the North Andean Pacific Slopes-Rio Atrato region, (2)
the Andes Mountains region (Sierra), and (3) the Amazonian region (Ori-
ente), which includes both the Amazonian lowlands and the western Ama-
zon Piedmont (Abell et al., 2008; Jimenez-Prado et al., 2015) (Figure 2).
These three regions are extremely different in their geological history,
environmental characteristics and biotic communities (Barriga, 2012).
2.1 |Western Ecuador
Western Ecuador is characterized by its isolation, high levels of ende-
mism and relatively low diversity (Figure 3a–d) (Jimenez-Prado
et al., 2015). The rise of the Andes Mountains drastically altered the
aquatic landscape in the region, greatly influencing the climatic, geolog-
ical and hydrological conditions (Jimenez-Prado et al., 2015;
Wolf, 1892). Other mountains, such as the Cordillera Chong
on-Colonche,
TABLE 1 (Continued)
Order Family Western slope Amazon slope
Gobiiformes Eleotridae 4 (3.5%) 0 (0%)
Gobiiformes Gobiidae 7 (6.2%) 0 (0%)
Pleuronectiformes Achiridae 4 (3.5%) 5 (0.7%)
Synbranchiformes Synbranchidae 1 (0.9%) 2 (0.3%)
Syngnathiformes Syngnathidae 1 (0.9%) 0 (0%)
Batrachoidiformes Batrachoididae 0 (0%) 1 (0.1%)
Tetraodontiformes Teraodontidae 0 (0%) 1 (0.1%)
Total=113 725
Note: Percentages are the percentage of the total species richness for each family by slope. Data for the Western slope is from Jimenez-Prado et al. (2015)
updated for new and synonymized species and data from the Amazon slope is from Barriga (2012).
FIGURE 2 Map of Ecuador
showing the major drainage basins.
1, Santiago-Cayapas Drainage;
2, Esmeraldas River; 3, Chone River;
4, Portoviejo River; 5, Daule River;
6, Babahoyo River; 7, Zapotal River;
8, Guayas River; 9, Taura River;
10, Cañar River; 11, Balao River;
12, Jubones River; 13, Aguarico River;
14, Napo River; 15, Curaray River;
16, Pastaza River; 17, Morona River;
18, Santiago River
1162 AGUIRRE ET AL.
FISH
also play an important role in generating environmental variation and
determining water flow patterns in the region. Western Ecuador has a
pronounced humidity gradient going from extremely wet rainforest in
the southern reaches of the Choc
o in northwestern Ecuador, becoming
seasonally dry forest southward until it transitions into near desert in
northern Peru. This topographic and environmental complexity has
resulted in high levels of endemism across taxonomic groups at micro-
geographical scales, such that some plant species are known from sin-
gle hill tops (Bonifaz & Cornejo, 2004; Dodson et al., 1985; Dodson &
Gentry, 1978, 1991). Approximately 38% of freshwater fishes (43 of
112) are endemic (Jimenez-Prado et al., 2015), which is a high rate even
for Neotropical ecosystems (Albert et al., 2011; Maldonado-Ocampo
et al., 2012). The region includes a subset of the families present in the
Amazon region, with estuarine groups being overrepresented (Table 1).
Unfortunately, western Ecuador is the region of the country that has
been most severely impacted by human development (Dodson & Gen-
try, 1991; Cuesta et al., 2017). It has the largest human populations and
most of the land has been transformed to agricultural fields (Dodson &
Gentry, 1991). The major drainage systems in Western Ecuador are
listed below.
FIGURE 3 Representative
Ecuadorian rivers. (a) Mindo
(Esmeraldas drainage), (b) Rio Palenque
Reserve (Guayas drainage), (c) Abras de
Mantequilla wetland (Guayas
drainage), (d) Jubones River, (e) San
Pedro River (high Andes near Quito),
(f) Napo River, (g) Laguna de
Limoncocha, (h) Curaray River
AGUIRRE ET AL.1163
FISH
2.1.1 | The Santiago-Cayapas drainage system
This is the northernmost major drainage basin in western Ecuador and
includes the Santiago and Cayapas Rivers and their tributaries in
Esmeraldas Province (Table A). It is the region in western Ecuador with
the greatest precipitation and includes the last remaining large tracts of
primary rainforest in coastal Ecuador. There is an important transition in
the ichthyofauna in the Santiago-Cayapas system, which includes diver-
gent species not seen southward, such as the freshwater hatchet fish
Gasteropelecus maculatus (Steindachner, 1879) (Figure 1c) and the
characid Roeboides occidentalis Meek & Hildebrand 1916 (Jimenez-Prado
et al., 2015). Jimenez-Prado et al. (2015) report 62 species of freshwater
fishes from this drainage of which 15 (24.2%) are endemic.
2.1.2 | The Esmeraldas drainage system
This drainage is south of the Santiago-Cayapas and Mira drainages
flowing from high in the Andes in a north-west direction and draining
into the Pacific at the city of Esmeraldas. It receives a good deal of
precipitation and includes some rainforest as well, although the forest
and rivers have been greatly impacted by human development. Quito,
the capital of Ecuador, and several small towns that cover a popula-
tion of approximately 2 million inhabitants are located in the inter-
Andean valley. Bodies of water in the highlands are severely affected
by urban expansion and the lack of wastewater treatment from
populations settled in the valley. The Esmeraldas basin is the second
largest drainage in western Ecuador in terms of both area and water
volume drained, and harbours an important freshwater fish fauna
that varies substantially with elevation. The fish fauna is composed
of some species that occur in the Guayas drainage (see below) and
other rivers combined with some species that are unique to this
drainage, such as the newly described pseudopimelodid Microglanis
berbixae Tobes et al. (2020), or shared with the Santiago-Cayapas
drainage. Jimenez-Prado et al. (2015) report 65 species of freshwa-
ter fishes from this drainage of which 17 (26.2%) are endemic to
the drainage.
2.1.3 | Rivers of the northern coastal area
In the area between the mouths of the Esmeraldas and Guayas Rivers,
there are small rivers running between the Coastal Mountain Range and
the Pacific Ocean. The transition between humid and dry coastal forest
appears to occur just north of the Chone River near Bahía de Caráquez
(Wolf, 1892). However, there is an important pocket of humid forest
south of the Chone River in the area between Puerto Cayo and Ol
on,
where the coastal mountain chain lies in close proximity to the ocean. In
this area, the Ayampe River holds water year round and is surrounded
by lush forest (Fundaci
on Jocotoco, 2020). South of Ol
on conditions get
dry with the Peninsula of Santa Elena, including some of the driest habi-
tats in Ecuador. Important rivers in this region include the Atacames,
Muisne, Chone, Portoviejo, Ayampe and Zapotal. Reliable lists of the
freshwater fishes in the region are not available although they are likely
related to those in the Esmeraldas and Guayas basins, with low species
diversity and an overrepresentation of estuarine species.
2.1.4 | The Guayas drainage system
The Guayas drainage basin is the largest drainage system in western
Ecuador spanning an area of approximately 32,674 km
2
between the
Cordillera Chongon-Colonche and the Andes Mountains in the prov-
inces of Guayas and Los Rios (G
omez, 1989). The Cordillera Chongon-
Colonche plays a key role in separating the Guayas drainage system
from rivers along the coast and in funnelling the rivers south over a
larger area towards the Gulf of Guayaquil. The Guayas River is formed
by the union of its two major rivers near its mouth: the Daule and
Babahoyo. The native vegetation in the lowlands of the Guayas basin
has largely been replaced with agricultural fields (Dodson &
Gentry, 1991). Because of its size and isolation, the Guayas drainage
has both the highest number of freshwater fish species in western
Ecuador (70 species) and the greatest percentage of endemic species
(34.3%), including commercially important species like Ichthyoelephas
humeralis (Günther, 1860) and Leporinus ecuadorensis Eigenmann and
Henn, 1916 (Jimenez-Prado et al., 2015). Major rivers include the
Guayas, Babahoyo, Daule, Vinces, Quevedo and Yaguachi.
2.1.5 | The southern coastal system
South of the Guayas River along the coast there is a series of small rivers
with steep slopes that run short distances between the Andes Mountains
and the Pacific Ocean (Valdiviezo-Rivera et al., 2018b). The freshwater
fishes in this region seem to be mostly a subcomponent of those present
in the Guayas drainage system, enriched for species adapted to mountain
streams. However, Barriga (2012) recognized a distinct biogeographic
zone for freshwater fishes in the southern portion of this region, the
Catamayo zone, spanning from the Jubones River just north of the city of
Machala southward to northern Peru. This region is recognized as an
important hotspot of endemism for other groups, suggesting that there
has been significant historical isolation (Aguirre et al., 2016; Cucal
on
Tamayo, 2019; Tapia-Armijos et al., 2015). Major rivers in this system
include the Taura, Cañar, Bulubulu, Balao, Jubones and Santa Rosa.
2.2 |The Andes region
The Andes have played a fundamental role in shaping the ecology and
evolution of Ecuador's flora and fauna. They divide the lowlands into
western and Amazonian regions that harbour largely distinct fish
faunas (Barriga, 2012). Rivers along the western slopes of the Andes
drain relatively short distances to the Pacific while those on the east-
ern slopes constitute tributaries that eventually drain into the Atlantic
Ocean through the Amazon River. Andean rivers are characterized by
fast-flowing water and very rapid habitat transitions due to the steep
1164 AGUIRRE ET AL.
FISH
slopes, resulting in high levels of biological diversity and endemism
(Anderson & Maldonado-Ocampo, 2011). Fish diversity tends to be
highest at mid and low elevations in Andean streams, and the fish
communities transition with elevation (Aguirre et al., 2016; Jimenez-
Prado et al., 2015). The Andean catfish genus Astroblepus (Figure 1m) pre-
dominates at high elevations, together with introduced species like the
rainbow trout Onchorhynchus mykiss (Walbaum, 1792) and brown trout
Salmo trutta Linnaeus, 1758 (Anderson & Maldonado-Ocampo, 2011;
Maldonado et al., 2011). The Andes region has been severely impacted
by anthropogenic factors for hundreds of years with much of the natural
forest having been substituted for agricultural fields, non-native timber
plantations and pastures (Sierra, 2013). Many large cities lacking proper
wastewater treatment are located in the Andes, and introduced trout are
highly detrimental to native species (Vimos et al., 2015). There has also
been an increase in dam constructioninrecentyears(Anderson
et al., 2018). The major rivers of the Ecuadorian Andes are discussed in
the sections on Western Ecuador and the Amazon region (see above and
below). The Andes are also peppered by stunning natural lakes, lagoons
and ponds of tectonic, glacial and volcanic origins, such as Laguna San
Pablo, Yaguarcocha, Yanacocha, Papallacta, Quilotoa, Tambo and Colta
(Le
on Velasco, 2010; Nieto, 2008). Some of these are or were inhabited
by native species like Astroblepus spp., but many have been stocked with
introduced species such as rainbow trout, carp, goldfish and largemouth
bass, threatening the native fishes and possibly driving some to local
extinction (Casallas & Gunkel, 2001; Terneus Jácome, 2014; Vélez
Espino, 2003).
2.3 |The Amazon region
The largest remaining forests and greatest number of freshwater fish
species in Ecuador are found in the Amazon region. Although it rains
throughout the year, precipitation increases between March and July,
resulting in seasonal flooding and a hydrological cycle with highly vari-
able water levels (Galacatos et al., 1996, 2004; Junk et al., 2007; Silva &
Stewart, 2017). The lowlands harbour the characteristic fish diversity
of the Amazon basin, including large pimelodid catfishes, a great diver-
sity of characiforms, suckermouth catfishes, cichlids, osteoglossiforms
and myliobatiforms, among many others. The Amazon Piedmont region
is characterized by rapid turnover of habitats and fishes. Despite a
number of recent studies on the diversity of the ichthyofauna in the
region (Barriga, 2012; Barriga, 1986; Barriga et al., 2016; Galacatos
et al., 1996; Hidalgo & Rivadeneira-R, 2008; Nugra-Salazar et al., 2016;
Rivadeneira et al., 2010; Rodríguez-Galarza et al., 2017; Stewart
et al., 1987; Valdiviezo-Rivera, 2012), there have been no systematic
reviews of the entire fauna and much remains to be learned about the
ecology of most species. Much of the region lacks roads but road con-
struction is accelerating (Articulaci
on Regional Amaz
onica, 2011; Char-
ity et al., 2016), and there is a growing number of threats, including oil
and mineral exploitation, deforestation and growing human
populations (Lessmann et al., 2016; L
opez et al., 2013; Sierra, 2000).
Barriga (2012) divided rivers in the Amazonian region into biogeo-
graphic zones for freshwater fishes. Above 600 m, he identified the
High Napo, High Pastaza, Upano-Zamora and Chinchipe zones, while
for the lowlands he recognized the Napo-Pastaza and Morona-
Santiago zones. The major drainages in this region are listed below.
2.3.1 | The Aguarico River
The Aguarico River is a tributary of the Napo River and is the north-
ernmost major drainage in the Amazonian region, draining an area of
approximately 12,000 km
2
(Le
on Velasco, 2010). It originates in the
Cordillera Oriental of the Andes and is formed by the confluence of
the Cofanes, Azuela and San Miguel Rivers. The Aguarico proper is a
turbid whitewater river with a high load of suspended solids that
winds through the Amazonian lowlands forming an abundance of
oxbow lakes and floodplain pools (Saul, 1975). Although a complete
species list is not available, fish diversity appears substantial (Borman
et al., 2007; Ibarra & Stewart, 1989; Saul, 1975; Vriesendorp
et al., 2009). In August 2017, the Cuyabeno Wildlife Production
Reserve, which forms part of the Aguarico River drainage, was
included in the Ramsar Convention (Ramsar 2018).
2.3.2 | The Napo River
The Napo drainage is the largest and most important drainage in the
Ecuadorian Amazonian region, draining an area approximately of
30,600 km
2
, and is a main tributary of the upper Amazon (Nieto, 2008).
Although there is much to be learned about the freshwater fishes in this
drainage, it is one of the better studied drainages of the Ecuadorian
Amazon because of the classic studies by Stewart et al. (1987, 2002)
and Ibarra and Stewart (1989), who collected 222 fish community sam-
ples between 200 and 2500 m in elevation. More recent studies
include Valdiviezo-Rivera (2012) and Valdiviezo-Rivera et al.(2018a),
who created a field guide of the fishes of the Limoncocha Lagoon. The
diversity of freshwater fishes in the Napo is by far the highest in Ecua-
dor (Galacatos et al., 1996; Ibarra & Stewart, 1989; Saul, 1975; Stewart
et al., 2002; Valdiviezo-Rivera et al., 2018a), with Barriga (2012)
reporting 680 fish species for the drainage.
2.3.3 | The Curaray River
This river drains an area approximately of 18,000 km
2
(Le
on
Velasco, 2010) and is a tributary of the Napo drainage, sharing part of
its ichthyofauna and habitat characteristics in lowlands and flooded
forest areas (Jácome-Negrete, 2013). Studies of the fishes in this
region have focused on the use of fishes by native people and have
documented species richness and occurrence in the middle and low
parts of the drainage (Guarderas et al., 2013; Jácome-Negrete, 2013).
2.3.4 | The Pastaza River
The Pastaza River is formed by the union of the Patate and Chambo
Rivers and is a tributary of the Marañon drainage in Peru (Rivadeneira
AGUIRRE ET AL.1165
FISH
et al., 2010). It drains an area of approximately 40,000 km
2
. Other
important rivers in the drainage include the Topo, Palora and
Bobonaza. Rivadeneira et al. (2010) compiled information on the
fishes of the Pastaza drainage and reported 142 species occurring
between 300 and 2840 m in elevation. They also indicated that
31 new species have been described from this basin, a little under half
of which (14) appear to be endemic. Very little is known otherwise
about the ecology of most species. Unfortunately, the upper Pastaza
drainage has been significantly impacted by dam construction and the
lowlands by oil extraction. At the border with Peru, the Pastaza is a
Ramsar protected site (Articulaci
on Regional Amaz
onica, 2011; Mac-
edo & Castello, 2015).
2.3.5 | The Morona River
The Morona River originates on the eastern side of the Kutukú
protected forest area, one of the largest protected areas in Ecuador
(CARE et al., 2012). It is a tributary of the Marañon River. There is
very little published about the freshwater fishes in this river since it
is relatively far from large human populations and oil extraction activi-
ties. However, this drainage is likely threatened by illegal mining activ-
ities (Fierro, 2015).
2.3.6 | The Santiago River
The southernmost major drainage in the Ecuadorian Amazon is the
Santiago River drainage, which drains an area of approximately
15,400 km
2
(Le
on Velasco, 2010). This drainage is structurally com-
plex because of its proximity to rivers running along the foothills such
as the Upano and Paute Rivers in the central Ecuadorian Amazon and
the Zamora River in the south. These rivers merge in an important bio-
diversity hot spot known as the Kutukú-C
ondor corridor (CARE
et al., 2012), which includes some remarkably diverse ecosystems
harbouring many undescribed terrestrial and aquatic species
(Schulenberg & Awbrey, 1997). This has also been a region of histori-
cal conflict over land disputes between Ecuador and Peru
(Schulenberg & Awbrey, 1997). Recent years have seen the develop-
ment of new mining operations and dam construction, which have
stimulated efforts to study the fishes in the region (Barriga, 1997;
Nugra et al., 2018).
3|THE THREATENED FRESHWATER
FISHES OF ECUADOR
It is clear that the freshwater fishes of Ecuador are under grave threat
(Barriga, 2012; Celi & Villamarín, 2020; Jimenez-Prado et al., 2015). At
least one marine species that enters freshwater, the critically endan-
gered largetooth sawfish Pristis pristis (Linnaeus, 1758), seems to have
gone functionally extinct in Ecuador and is now extremely rare or
locally extinct (Dulvy et al., 2016; Mendoza et al., 2017). The Andean
catfish Astroblepus ubidiai, the only native fish in the high Andes of
Imbabura Province in northern Ecuador, is considered critically endan-
gered after having gone through a severe range contraction driven by
multiple anthropogenic factors. It is now known only from a few iso-
lated localities (Arguello & Jimenez-Prado, 2016; Vélez Espino, 2003,
2006). In north-western Ecuador, Astyanax ruberrimus seems to have
been locally extirpated from the Atacames basin after the construc-
tion of a dam (Jiménez-Prado et al., 2020), while the native poeciliid
Pseudopoecilia fria seems to have been displaced to the upper reaches
of the Atacames basin after the introduction of the exotic poeciliid
Poecilia gilli (Jiménez-Prado & Vásquez, 2021). In the Puyango drain-
age in southern Ecuador, an unidentified loricariid previously con-
sumed by people in the area was reported to have gone locally extinct
by Tarras-Wahlberg et al. (2001), possibly due to mining pollution.
Given the lack of historical data and systematic research, the cases
described above may be just the tip of the iceberg. It is possible that
many other fishes have gone locally extinct or that undescribed spe-
cies have been lost.
The Endangered Freshwater Fishes Working Group evaluated the
status of 163 freshwater fish species in Ecuador (Aguirre et al., 2019b).
Unfortunately, a lack of information resulted in 66 of these 163 species
(40.5%) being deemed data deficient (DD). Additionally, many of the spe-
cies that were not evaluated lacked sufficient data to even be considered
for evaluation so the real number of species in the DD category is likely
much greater. Of the remaining species, 62 were categorized as least con-
cern (LC), 15 as vulnerable (VU), 13 were categorized as near threatened
(NT), six as endangered (EN) and one as critically endangered
(CR) (Table 2). Geographically, the greatest number of species, 22, was
from the Amazon region, where unregulated fisheries pressures and habi-
tat degradation resulted in concerns being identified for 16 pimelodid
catfishes. The threats were deemed severe enough that five of these
were categorized as endangered in Ecuador. From the Andes region, con-
cerns were only identified for four species, although the only species cat-
egorized as critically endangered, Astroblepus ubidiai (Pellegrin,
1931), is from this region (Arguello & Jimenez-Prado, 2016; Mena-
Valenzuela & Valdiviezo-Rivera, 2016; Vélez Espino, 2003, 2006).
The remaining nine species for which concerns could be identified
were from Western Ecuador. Only one species from this region,
the characid Pseudochalceus bohlkei Orcés, 1967 from Esmeraldas
province (Orcés, 1967), was categorized as endangered in Ecuador.
Given the lack of data, it is likely that more species may be threat-
ened, although it is also possible that some of the species listed in
Aguirre et al. (2019b) are in better condition than currently recog-
nized. Directed studies are urgently needed to improve our under-
standing of the threats to Ecuador's freshwater fishes.
4|THE FACTORS CAUSING THE DECLINE
OF ECUADOR'S FRESHWATER FISHES
As human populations have grown and technology has made it easier
to exploit natural resources, the pressure on Ecuadorian aquatic eco-
systems has increased, resulting in a variety of threats for the
1166 AGUIRRE ET AL.
FISH
freshwater fishes that vary regionally. Below, we review some of the
major threats.
4.1 |Habitat loss through physical alteration of
rivers
Habitat loss in aquatic ecosystems in Ecuador is caused by many fac-
tors, among which the physical alteration of the river bottom and
banks is one of the most severe (Figure 4). Freshwater fishes have
evolved over geological time scales to inhabit portions of rivers with
certain sets of environmental and physical characteristics. Logs,
woody debris, rocks, fallen leaves, macrophytes, natural caves, etc.,
are often required for routine activities such as procuring food and for
reproduction (Angermeier & Karr, 1984; Grenouillet et al., 2002; Lo
et al., 2020; Wright & Flecker, 2004; Zeni & Casatti, 2014). When the
physical substrate of the river is altered, the affected portion of
TABLE 2 Critically endangered (CR), endangered (EN), near threatened (NT) and vulnerable (VU) freshwater fishes of Ecuador identified by
the national endangered freshwater fishes working group (Aguirre et al., 2019b)
Order Family Species Nat. cat. Eval. crit. Glob. Cat. Region
Myliobatiformes Potamotrygonidae Potamotrygon motoro NT NA DD AMZ
Osteoglossiformes Osteoglossidae Osteoglossum bicirrhosum NT NA NE AMZ
Osteoglossiforme Arapaimidae Arapaima gigas VU B2ab(iii) DD AMZ
Characiformes Curimatidae Potamorhina altamazonica NT NA NE AMZ
Characiformes Curimatidae Pseudocurimata boehlkei VU B1b(iii)c(i) DD WE
Characiformes Curimatidae Pseudocurimata boulengeri NT NA NE WE
Characiformes Prochilodontidae Ichthyoelephas humeralis NT NA NE WE
Characiformes Prochilodontidae Prochilodus nigricans VU A2ad +4ad NE AMZ
Characiformes Anostomatidae Leporinus ecuadorensis NT NA NE WE
Characiformes Serrasalmidae Mylossoma duriventre NT NA NE AMZ
Characiformes Characidae Grundulus quitoensis VU D2 NE AND
Characiformes Characidae Pseudochalceus bohlkei EN B2b(iv)c(i) NE WE
Characiformes Characidae Pseudochalceus longianalis VU NA NE WE
Siluriformes Cetopsidae Paracetopsis esmeraldas NT NA NT WE
Siluriformes Pimelodidae Brachyplatystoma filamentosum VU A2a,d +A4a,d NE AMZ
Siluriformes Pimelodidae Brachyplatystoma juruense VU A2d +4d NE AMZ
Siluriformes Pimelodidae Brachyplatystoma platynemum EN A2d +A4d NE AMZ
Siluriformes Pimelodidae Brachyplatystoma rousseauxii EN A2d +4d LC AMZ
Siluriformes Pimelodidae Brachyplatystoma tigrinum VU A2d +A4d NE AMZ
Siluriformes Pimelodidae Brachyplatystoma vaillantii EN A2d +A4d NE AMZ
Siluriformes Pimelodidae Calophysus macropterus VU A2d +A4d NE AMZ
Siluriformes Pimelodidae Leiarius marmoratus VU A2d +A4d NE AMZ
Siluriformes Pimelodidae Phractocephalus hemioliopterus VU A2d +4d NE AMZ
Siluriformes Pimelodidae Pinirampus pirinampu EN A2d +A4d NE AMZ
Siluriformes Pimelodidae Platynematichthys notatus NT NA NE AMZ
Siluriformes Pimelodidae Pseudoplatystoma punctifer EN A2d +A4d NE AMZ
Siluriformes Pimelodidae Pseudoplatystoma tigrinum VU A2d +A4d NE AMZ
Siluriformes Pimelodidae Sorubimichthys planiceps NT NA NE AMZ
Siluriformes Pimelodidae Zungaro zungaro VU A2d +A4d NE AMZ
Siluriformes Pimelodidae Batrochoglanis transmontanus VU B1ab(iii)c(ii) LC AMZ
Siluriformes Astroblepidae Astroblepus mindoensis NT NA NT AND
Siluriformes Astroblepidae Astroblepus ubidiai CR NA CR AND
Siluriformes Astroblepidae Astroblepus vaillanti NT NA DD AND
Cichliformes Cichlidae Andinoacara sapayensis VU A3c +B1b(iii)c(i) DD WE
Gobiiformes Gobiidae Sicydium rosenbergii NT NA NT WE
Note: Nat. cat. is the national category assigned by the working group, Eval. crit. are the IUCN criteria used to assign the national category, Glob. cat. is the
IUCN global category for the species (DD, data deficient; NE, near endangered), and Region is the region of Ecuador in which the species occurs (AMZ,
Amazon region; AND, Andean region; WE, Western Ecuador).
AGUIRRE ET AL.1167
FISH
the river often becomes a very poor or unusable habitat for native
species. The loss of required habitat for reproduction can be particu-
larly severe and result in the local extinction of sensitive species
(Aarts et al., 2004). River alteration can also facilitate colonization by
invasive species, which are often more tolerant of poor environmental
conditions (Bates et al., 2013; Casatti et al., 2009). The movement of
bottom materials can affect downstream portions of the river, increas-
ing turbidity and burying fish habitat in silt (Berkman & Rabeni, 1987;
Lo et al., 2020). Importantly, the damage is often not obvious when
seen from land.
The use of heavy machinery for the removal of river gravel for
construction is common throughout Ecuador (Le
on-Ortiz, 2017;
Matamoros-Ramírez, 2013) and is poorly controlled. Removal of
gravel and rocks by heavy machinery can results in a total loss of natu-
ral habitat conditions. Artisanal miners can also take advantage of the
movement of the substrate to illegally mine the impacted river
stretches, resulting in further contamination of the river (Matamoros-
Ramírez, 2013). There are also concerns about possible unforeseen
impacts of large megaprojects on rivers. For example, Ecuador lost
one of its iconic waterfalls, Cascada de San Rafael, in February 2020,
just a few years after the completion of the nearby massive Coca-
Codo-Sinclair hydroelectric project. Evidence indicates that the hydro-
electric project substantially increased erosion rates in the Coca River
(Escuela Politecnica Nacional, 2020), and concerns have been raised
about the project's potential influence on the waterfall collapse
(Cobo, 2020). No studies to date have examined the impact of the
physical alteration of river substrates on Ecuadorian freshwater fishes.
4.2 |Deforestation
Deforestation impacts aquatic ecosystems in a number of ways. It
increases soil erosion, which increases turbidity and sedimentation,
and causes contaminants to enter streams (Jones et al., 1999; Webb
et al., 2004; Wood & Armitage, 1997). In the Ecuadorian Amazon, ero-
sion in deforested areas is causing the release of natural mercury,
which is biomagnified in food webs and accumulates in large fish that
are consumed by indigenous people (Mainville et al., 2006; Moreno
Vallejo, 2017; Webb et al., 2004; WHO, 2011). Deforestation also
changes water temperature and light conditions (Castelle et al., 1994;
Ilha et al., 2018; Macedo et al., 2013; Pusey & Arthington, 2003),
reduces levels of litter detritus and increases periphyton (Bojsen &
Jacobsen, 2003; Lorion & Kennedy, 2009), reduces habitat complexity
(Lo et al., 2020), affects hydrological processes (Iñiguez-Armijos
et al., 2014), is associated with the increase of introduced species in
streams (Jones et al., 1999; Pusey & Arthington, 2003), and affects
alpha and beta diversity, community composition, and ecosystem
function (Bojsen & Jacobsen, 2003; Iñiguez-Armijos et al., 2014; Lo
et al., 2020; Lorion & Kennedy, 2009; Pusey & Arthington, 2003; Zeni
et al., 2019). Deforestation has even been associated with morpholog-
ical changes in fish (Ilha et al., 2018).
Deforestation in Ecuador has been severe (Dodson &
Gentry, 1991; Mosandl et al., 2008; Sierra, 2000; Tapia-Armijos
et al., 2015). Although the proportion of the deforested area and
timing of deforestation varies substantially by region (Ministerio del
Ambiente, 2017; Sierra, 2013), Ecuador had the highest average
annual rate of deforestation in Latin America between 1990 and 2012
(Armenteras & Rodríguez Eraso, 2014). Using satellite imagery,
González-Jaramillo et al. (2016) reported that forests covered
11,871,700 ha or 48.1% of the surface area of continental Ecuador in
1986, declining to 10,368,500 ha or 36.8% by 2008. Data from
Ecuador's Ministerio del Ambiente are more optimistic. They report
that 50.7% of the area of continental Ecuador or 12,631.198 ha
remained covered by native forests in 2016 and that deforestation
rates show a declining trend from 129.943 ha/year of native forest
lost between 1990–2000 to 94.353 ha/year in 2014–16 (Ministerio
del Ambiente, 2017). High rates of population growth in Ecuador have
been one of the main factors. Population size more than quadrupled
from an estimated 4 million people in 1957 (Dodson & Gentry, 1991)
to over 17 million by 2018 (The World Bank, 2020).
Regionally, deforestation has been most severe in Western Ecua-
dor, where as much as 70% of the original forest has been lost
FIGURE 4 Physical destruction of river banks and bottom caused
by the removal of gravel for construction. Pictures from the Guayas
River basin in western Ecuador
1168 AGUIRRE ET AL.
FISH
(Cuesta et al., 2017). Patches of primary forest remain in the very
north-western region of Ecuador close to the Colombian border,
scattered along the steep slopes of hills and in small reserves. The
construction of an elaborate road system in the mid-twentieth cen-
tury made the rapid deforestation of the region possible. Deforesta-
tion was exacerbated by the implementation of land reform laws in
the 1960s that allowed the confiscation of “unproductive”land for
redistribution to landless peasants, encouraging deforestation on pri-
vately owned land to avoid seizure (Dodson & Gentry, 1991). The
very high levels of endemism in the region make the loss all the worse
(Barriga, 2012; Bonifaz & Cornejo, 2004; Dodson & Gentry, 1991;
Jimenez-Prado et al., 2015). The Andes region has also suffered
severe deforestation such that approximately 40% of the original veg-
etation has been lost (Cuesta et al., 2017). Much of the remaining pri-
mary forest in the region occurs in areas with extremely steep slopes
that are inappropriate for agriculture or harvesting timber or in small
preserves (Marian et al., 2020; Mosandl et al., 2008; Tapia-Armijos
et al., 2015; Wunder, 1996). Villages, towns and cities in the region
are often packed in small valleys, exacerbating demands on nearby
natural resources. Large indigenous populations predominate in this
region and have modified the Andean landscape for centuries
(Mosandl et al., 2008). Native forest and páramo habitat have largely
been replaced with non-native tree monocultures of Pinus,Eucalyptus,
Cupressus,etc., increasing habitat homogeneity and changing the envi-
ronmental conditions (Buytaert et al., 2007; Hofstede et al., 2002;
Marian et al., 2020; Wunder, 1996). The rapid habitat transitions that
occur with elevation make the Andes extraordinary centers of biologi-
cal diversity (Anderson & Maldonado-Ocampo, 2011; Hamilton, 1995;
Homeier et al., 2010; Myers et al., 2000). Fish species adapted to a
narrow range of environmental conditions in mountain streams may
be particularly susceptible to local extinction when habitat conditions
degrade. The Amazon region has the most remaining original vegeta-
tion and the most diverse freshwater fish communities (Barriga, 2012).
However, it is experiencing some of the highest rates of deforestation
(Lessmann et al., 2016; Myers, 1993; Sierra, 2000; Southgate
et al., 1991). Deforestation has been worst in the northern Amazon
region where oil deposits are largest. Myers (1993) identified the
Napo region as one of 14 global deforestation fronts. As is the case in
the coastal region, government land reform initiatives encouraged
deforestation by colonists (Sierra, 2000; Wunder, 1996). Road con-
struction for oil extraction and a population growth rate that is double
the national average are aggravating the problem (L
opez et al., 2013).
Only two studies have directly examined the effects of deforesta-
tion on Ecuadorian fish communities and both were conducted in the
Amazonian region. Bojsen and Barriga (2002) studied fishes in 12 sites
in headwater streams of the upper Napo River catchment that were in
relatively good condition. Half of these sites were in forested areas
and half were in deforested areas. They did not find a significant
effect of deforestation on species richness, but beta diversity was
higher among forested than deforested sites, indicating that defores-
tation may homogenize fish diversity across communities. The per-
centage of rare species was also positively associated with canopy
cover. Total fish density was actually higher in deforested sites but
the communities changed from being dominated by omnivorous and
insectivorous characiforms in forested sites to periphyton-feeding
loricariids in deforested sites. Bojsen (2005) further examined the
effect of deforestation on the diet and condition of three characids in
small streams of the Napo basin. The impact of deforestation
depended on the ecology of the species, with species depending on
terrestrial invertebrates and exhibiting less diet flexibility being most
severely impacted. Thus, even in streams that are still in relatively
good condition, deforestation may change the composition of fish
communities and their ecosystem functions, as well as impact the via-
bility of vulnerable rare species with narrow habitat preferences
(Bojsen, 2005; Lo et al., 2020). When deforestation is accompanied by
severe stream habitat degradation, the impact on fish communities
can be catastrophic. Studies conducted on macroinvertebrate commu-
nities in Ecuador have been more common and have similarly demon-
strated the importance of native forest cover on water quality,
species diversity, community structure and the presence of sensitive
taxa (Arroyo & Encalada, 2009; Bücker et al., 2010; Damanik-Ambarita
et al., 2016; Guerrero Chuez et al., 2017; Iñiguez-Armijos et al., 2014,
2016, 2018; Urdanigo et al., 2019). Much more work is needed on the
effects of deforestation on Ecuadorian freshwater fish communities.
4.3 |Wetland and flood plain degradation
Neotropical wetlands constitute a critical habitat for many freshwater
fish species. Seasonal rains often result in the formation of highly pro-
ductive floodplains that many fish species have evolved to use as
nursery habitat or feeding grounds during portions of their life cycle
(Davies & Walker, 2013; King et al., 2003; Winemiller, 2004;
Winemiller & Jepsen, 2004). These floodplains can contribute to
maintaining the biodiversity of the whole river ecosystem, provided
that connectivity is maintained (Aarts et al., 2004). Despite all the eco-
systems services floodplains provide, dams, water transfers and
abstractions, and conversion of land to agricultural fields have modi-
fied the natural flood regimes of rivers and their associated flood-
plains, resulting in a loss of crucial fish habitat and, subsequently, a
reduction in fish production and diversity (Welcomme & Halls, 2004;
Winemiller & Jepsen, 1998).
In Ecuador, floodplains and wetlands cover an area of approxi-
mately 15,000 km
2
at elevations below 500 m in elevation, of which
61% is in the Amazon region (DINAREN, 2002). Seasonally flooded
forests cover an area of over 8600 km
2
in the Amazon and another
363 km
2
are covered by grasslands and farmlands. Fortunately, much
of the natural flooded forest in Ecuador's Amazonian region is still
standing. However in the coastal region there are approximately
5800 km
2
of seasonally flooded land, of which only 7.4% still harbours
native vegetation. Most flood plains in the coastal region have been
converted to rice fields, banana plantations, grassland for cattle, sugar
cane plantations and maize fields. To stop cultivated areas from get-
ting flooded in the rainy season, dams, dikes and canal systems have
been constructed throughout the region, which has resulted in a loss
of approximately 82.6% of the floodplain habitat (DINAREN, 2002).
AGUIRRE ET AL.1169
FISH
Abras de Mantequilla (AdM, Figure 3c) is one of the most impor-
tant wetlands remaining in Western Ecuador (Alvarez-Mieles, 2019)
and provides insight into the consequences of the degradation of
Ecuador's floodplains. AdM is located at the center of the Guayas
River basin in the lowlands-coastal area of Western Ecuador and is
a river-wetland system that experiences marked predictable sea-
sonality. During the wet season (January–April), the system floods
and expands before decreasing dramatically in the dry season, with
water remaining only in the main channels (Alvarez-Mieles, 2019).
The wetland was declared a Ramsar site in March 2000 and is a
valuable site for freshwater fishes, supporting at least 22 species,
including commercially important species (Alvarez-Mieles, 2019;
Ochoa Ubilla et al., 2016; Ramsar, ). Macrophytes, which provide
shelter from predators, food, and spawning and nursery grounds
(Agostinho et al., 2007; Alvarez-Mieles, 2019; Meerhoff
et al., 2007; Meschiatti et al., 2000), are abundant at AdM, with
the floating macrophyte Eichornia crassipes (Pontederiaceae), com-
monly known as ‘water hyacinth’, representing around 80% of the
total macrophytes biomass in the wetland, and Salvinia auriculata
Aubl. 1775, Pistia stratiotes Linnaeus 1753, Ludwigia peploides
(Kunth) P. H. Raven, Lemna aequinoctialis Welwitsch 1859, Pas-
palum repens P. J. Bergius and Panicum frondescens G. Mey, also
being relatively common (Alvarez-Mieles, 2019). Characids like
Eretmobrycon festae (Boulenger 1898), Rhoadsia altipinna Fowler
1911 and Landonia latidens Eigenmann and Henn 1914 are the
most abundant fishes representing between 87% and 89% of the
total littoral fish abundance, and are an important source of food
for commercially important fish species. Other important endemic
characids like Phenacobrycon henni (Eigenmann 1914), Iotabrycon
praecox Roberts 1973 and Hyphessobrycon ecuadoriensis
Eigenmann and Henn 1914 occur in the area, albeit at lower densi-
ties, as do fisheries species like Andinoacara rivulatus (Günther
1860), Mesoheros festae (Boulenger 1899), Pseudocurimata
boulengeri (Eigenmann 1889), Brycon dentex Günter 1860 and
Ichthyoelephas humeralis (Günther 1860) (Alvarez-Mieles
et al., 2019). Ochoa Ubilla et al. (2016) specifically studied the
community composition and size structure of commercially impor-
tant native fishes in AdM and reported that I. humeralis and
Pseudocurimata spp. were the most abundant fisheries species. The
abundance of I. humeralis, a migratory and ecologically important
species that is highly valued as a food fish in rural areas of the
Guayas basin (Prado España, 2012), highlights the importance of
wetlands like AdM. In addition, Revelo (2010) reported that 70%
of fish collected in the region between January and March (peak
wet season) are in an advanced stage of sexual maturity. Although
fishing is prohibited during 2 months in the peak spawning period
(Revelo, 2010), this is very difficult to enforce and the movement
and congregation of fishes makes them extremely vulnerable to
overfishing during this period.
With the loss of most of the natural floodplain area in Western
Ecuador, it is likely that many native freshwater fishes have been
greatly affected and some species may not be able to recover even
if other problems are resolved. Finding ways to restore floodplain
habitat will be an important challenge for future conservation
efforts.
4.4 |Agricultural and urban water pollution
In Ecuador, high population growth rates and economic need have led
to rapid increases in agricultural production and urban expansion,
often resulting in the uncontrolled influx of pollutants to freshwater
ecosystems (Borbor-Cordova et al., 2006; Donoso & Rios-
Touma, 2020) (Figure 5). Plantations and cities often border rivers,
facilitating the influx of agrochemicals, sediments and untreated waste
water (Donoso & Rios-Touma, 2020; Universidad Agraria del
Ecuador, 2011). Solid waste is sometimes dumped directly into
streams. Some pollutants are poorly soluble in water and adhere to
sediments, allowing them to persist at contaminated sites for long
periods (Abellán, 2006). Others are fat soluble and can be
biomagnified as they rise through the food web, reaching very high
concentrations in apex predators (Abellán, 2006). No studies have
directly examined the effects of agricultural or urban pollutants on
freshwater fishes in Ecuador, but water quality and macroinvertebrate
data provide evidence that this is likely a serious problem.
The Guayas River basin in western Ecuador illustrates the poten-
tial magnitude of the problem. It constitutes the most important agri-
cultural center in Ecuador, with approximately 68% of national crops
grown there, and harbours some of the largest human populations,
including Guayaquil, the largest city in the country (Borbor-Cordova
et al., 2006). Fertilizers and pesticides are applied in great quantities
and leach into rivers, and untreated waste water flows into rivers
throughout the basin (Borbor-Cordova et al., 2006; Deknock
et al., 2019; Ribeiro et al., 2017; Universidad Agraria del
Ecuador, 2011). As a consequence, the Guayas basin includes some of
the most degraded aquatic ecosystems in the country (Dodson &
Gentry, 1991), threatening freshwater fish communities with high
rates of endemism (Jimenez-Prado et al., 2015). High levels of bacte-
rial coliforms surpassing permitted limits have been commonly
reported close to cities (Robinson Vera, 2015; Valencia Díaz, 2018).
Damanik-Ambarita et al. (2016) examined water quality at 120 sites
throughout the basin using macroinvertebrate indices and found com-
promised water quality at sites on arable land and bad water quality at
sites in residential areas. Low oxygen levels (<5 mg/l) have been
reported in the Daule River and may be a product of releases of
anoxic water from the Daule-Peripa impoundment combined with
eutrophication from fertilizer leaching and the influx of untreated
waste water (Universidad Agraria del Ecuador, 2011). Deknock
et al. (2019) examined pesticides from water samples taken at
181 sites throughout the Guayas basin and found detectable levels
at 60% of sites, with cudusafos, butachlor and pendimethalin being
the most common detectable pesticides. Banana and rice plantations
were implicated as the likely sources. Banned pesticides like lindane,
endrin and heptachlor have also been detected (Universidad Agraria
del Ecuador, 2011). Mero et al. (2019) found levels of cadmium
exceeding recommended limits (>0.67 mg/kg) in sediment, as well as
1170 AGUIRRE ET AL.
FISH
in the water hyacinth Eichhornia crassipes and the snail Pomacea can-
aliculata, in the Guayas, Babahoyo and Daule Rivers, and Carpio
Rivera (2016) reported cadmium contamination in the Chimbo River,
south-eastern Guayas basin.
Similar problems are affecting rivers throughout the country. In
the upper Napo basin of the Amazon region, Vellosa Capparelli
et al. (2020) found concentrations of several metals, including Hg, Cd,
Cu and Pb, above permissible limits, and associated these with the
presence of nearby gold-mining operations, nonfunctional municipal
landfills, urban centers and fish-farming operations. The Teaone River,
a highly impacted tributary to the Esmeraldas River with about 50%
of its watershed area converted to agricultural land, exhibits excesses
of phosphates in its main channel that are likely associated with
human activity (Molinero et al., 2019). Lack of wastewater treatment
is a common problem in Ecuador, such that even the capital Quito
treats less than 10% of the waste water that it generates (Castillo
Pazmiño, 2012; Donoso & Rios-Touma, 2020). Studies of the San
Pedro–Guayllabamba–Esmeraldas Rivers, which receive waste waters
from Quito, found persistence of pollutants like carbamazepine
and acesulfame throughout the watershed, while other emerging
organic pollutants, such as caffeine, sulfamethoxazole, venlafaxine,
O-desmethylvenlafaxine and steroidal estrogens, were detectable but
degraded as they moved downstream (Voloshenko-Rossin
et al., 2014). Similarly, Donoso and Rios-Touma (2020) found some of
the highest concentrations reported for suspended microplastics, as
well as significant concentrations in sediment of the Guayllabamba
River. With all the reported problems, studies on the effects of agri-
cultural and urban pollutants on freshwater fishes throughout Ecuador
are urgently needed.
4.5 |Mining
Artisanal mining, which is common in Ecuador, is typically poorly regu-
lated and can cause severe environmental damage due to the poor
safety practices employed. New policies and changes in existing min-
ing laws in Ecuador have resulted in the development of large-scale
industrial mining that is also causing serious problems (Adler
Miserendino et al., 2013; L
opez et al., 2013; Wildlife Conservation
Society, 2020). In addition, the government of Ecuador increased min-
ing concessions from about 3% to 13% of Ecuador's land area in
2016–17, threatening the roughly 30% of the total land area protec-
ted by Bosques Protectores included in these new concessions (Roy
et al., 2018).
The southern Andes of Ecuador are rich in gold deposits along both
their western and eastern slopes (Appleton et al., 2001; Ramírez
Requelme et al., 2003; Tarras-Wahlberg et al., 2001). On the western
side, large gold deposits near the populations of Portovelo-Zaruma,
Ponce Enriquez and Puyango have been exploited for hundreds of years
and constitute some of the most important mining lands in the country
(Adler Miserendino et al., 2013; Betancourt et al., 2005; Tarras-
Wahlberg et al., 2001). They are also significant sources of contamina-
tion, especially of mercury. Much of the mining in the area is artisanal
and performed with poor environmental safety practices including illegal
dumping of waste directly into rivers (Adler Miserendino et al., 2013).
As a consequence, water turbidity typically increases close to mining
operations, and mercury is relatively common in suspended particulate
matter and bottom sediments in the region (Appleton et al., 2001;
Tarras-Wahlberg et al., 2001). Levels of cyanide, mercury and other
metals in rivers often exceed environmental quality criteria (Appleton
et al., 2001; Betancourt et al., 2005; Mora et al., 2016; Tarras-Wahlberg
et al., 2001), strongly affecting fishes, which sometimes disappear
completely close to mining operations and decline in abundance farther
downstream. In the only published study reporting mercury concentra-
tions in freshwater fishes from the region, Tarras-Wahlberg et al. (2001)
documented the disappearance of an unidentified loricariid
(suckermouth catfish) previously consumed by locals in the Puyango
catchment, and found mercury levels above recommended limits in
native cichlids and characiform fishes. Nonetheless, mercury levels in
inhabitants of the region appear to be relatively low, possibly because
FIGURE 5 Pollution is a serious problem affecting rivers
throughout Ecuador. (a) Many cities and towns are on the shores of
rivers, resulting in a constant flow of waste into rivers. View of the
city of Vinces on the Vinces River. (b) Small contaminated stream in
Portovelo
AGUIRRE ET AL.1171
FISH
the transformation of elemental mercury into toxic methyl-mercury
appears to be low (Betancourt et al., 2005).
Mineral exploitation is widespread in the Amazon region (L
opez
et al., 2013). Exploitation of large gold deposits on the eastern side
of the Andes in Zamora Chinchipe province, southern Ecuador, espe-
cially in Nambija and Chinapintza, has caused significant environ-
mental problems. Although Amazonian river sediments can have
naturally elevated levels of mercury (Mora et al., 2019; Webb
et al., 2004), several studies have documented mercury concentra-
tions in rivers close to mining operations that are several times back-
ground levels, including the Congüime, Nangaritza, Nambija, Zamora
and Yacuambi Rivers (González-Merizalde et al., 2016; L
opez-Blanco
et al., 2015; Mora et al., 2018, 2019; Ramírez Requelme et al., 2003).
Elevated concentrations of other metals like lead and manganese have
also been documented (González-Merizalde et al., 2016; Mora
et al., 2018, 2019), as have elevated concentrations of metals in people
in the area (González-Merizalde et al., 2016). In the Cordillera del
C
ondor, Santiago River basin, several large-scale mines are clearing large
tracts of rainforest and displacing indigenous people (Federaci
on Inter-
nacional por los Derechos Humanos, 2017; Pérez, 2019). Studies
directly examining the impacts on freshwater fishes are urgently
needed.
The negative effects of mining have also been reported for many
years in Esmeraldas Province in north-western Ecuador (Figure 6)
(Rebolledo & Jiménez-Prado, 2013). Illegal mining in the region has
increased substantially since 2008 and largely occurs in the proximity of
rivers, causing severe habitat degradation and conflict between miners
and residents. It is estimated that approximately 57% of the original forest
in the area has been affected (Lapierre Robles & Aguasanta
Macías, 2019). By 2012, the mined area included 5709 ha directly sub-
jected to mining activity and an area of 224,284 ha affected indirectly
(Rebolledo & Jiménez-Prado, 2013). In a study carried out between 2015
and 2017 involving 32 sample sites along the Santiago-Cayapas River
basin, all streams and estuaries sampled showed very high concentrations
of aluminium and iron throughout the study period (Lapierre Robles &
Aguasanta Macías, 2019). An estimated 4800 mining pools containing
contaminated water have been left open in Esmeraldas Province
(Moreno-Parra, 2019). Besides the serious damage to the physical struc-
ture of river banks, the high turbidity resulting from mining limits the
entry of light into the water, severely affecting the growth of filamentous
algae and phytoplankton. As a consequence, herbivorous bottom-feeding
fishes like the loricariids Chaetostoma marginatum Regan 1904 (guañas),
Sturisomatichthys frenatus (Boulenger 1902) (palo secos)andRineloricaria
jubata (Boulenger 1902) (mantequeros), and the freshwater gobies
Awaous transandeanus (Günther 1861) (babosos) and Sicydium
sp. (ñemes), are forced to consume detritus, ingesting metals present in
high proportions in sediments as well. Elevated concentrations of metals
have been detected in C. marginatum, an important food fish for local
people in the upper Bogotá, Santiago basin (Rebolledo & Jiménez-
Prado, 2013). Arsenic (0.5 mg kg
–1
)wasalsodetectedinGobiomorus mac-
ulatus (Günther 1859) (Cagua de Concepci
on)andmercury(0.2mgkg
–1
)in
Strongylura fluviatilis (Regan 1903) (Cherre) (Rebolledo & Jiménez-
Prado, 2013), both of which are also consumed locally.
4.6 |Oil extraction
Large oil deposits were discovered in the Amazon region of Ecuador
in the 1970s, and oil production became the main export for
Ecuador by 2011 (Lessmann et al., 2016). Unfortunately, these oil
deposits are under some of the most biodiverse Neotropical rainforest
in the world and in territories inhabited by indigenous people (L
opez
et al., 2013). Oil extraction has a long history of causing accidental oil
spills, leaching or improper dumping of waste products, loss of wildlife
and health issues for local people (Anderson et al., 2019; Bass
et al., 2010; Lessmann et al., 2016). Past oil-related environmental
problems in Ecuador have resulted in large international lawsuits
against oil companies and significant conflicts between oil interests
and indigenous people (Cely, 2014; Moreno Vallejo, 2017). Indirect
problems associated with oil extraction, like road construction, can
also cause severe problems (Espinosa et al., 2018; Suárez et al., 2013).
In the 2010s, the government of Ecuador launched a significant
expansion of oil extraction activities, reviewed in Lessmann
et al. (2016). Although the government initially sought international
support to leave oil in the earth in environmentally sensitive areas like
the Ishpingo-Tambococha-Tiputini (ITT) oil field in a remote section of
Yasuní National Park, lack of international support made this inviable.
Instead, many new blocks in Ecuador's southern Amazon region have
been opened for oil concessions. Consequently, approximately 68% of
the Amazon rainforest region now consists of oil extraction blocks.
What is worse, the oil blocks occur within biologically rich reserves
like Yasuní National Park, Cuyabeno Wildlife Reserve, Limoncocha
Biological Reserve and Cofán Bermeo Ecological Reserve. Only about
16% of the Ecuadorian Amazon is now protected in nature reserves
free of oil blocks (Lessmann et al., 2016).
There is surprisingly little research directly examining the impacts
of oil extraction on fishes of the Ecuadorian Amazon. Moreno Val-
lejo (2017) examined contaminants associated with oil extraction in
tissues from detritivorous loricariids and the predator Hoplias
FIGURE 6 Damage from mining operations. Santiago-Cayapas
River drainage, Esmeraldas province, northwestern Ecuador
1172 AGUIRRE ET AL.
FISH
malabaricus (Bloch 1794) in rivers of the northern Amazon impacted
by oil extraction and rivers of the southern Amazon where oil is not
extracted. He did not find significant differences between regions but
did find significant differences among sites, including in metals like
Co, Ba, Cd and Hg, which he associated with oil spills. This is consis-
tent with elevated Hg levels found in H. malabaricus collected near an
oil spill site in the Corrientes River, Peruvian Amazon (Webb
et al., 2015). In Moreno Vallejo's (2017) study, Hg levels were higher
in H. malabaricus than in the loricariids, likely due to bioaccumulation
in the predator vs. the primary consumer, and As and Hg concentra-
tions were above permitted levels, indicating significant risks for
human populations. Levels of Ba, Cd and Pb were particularly high in
the Conde and Payacu Rivers. Mena Olmedo (2016) used a similar
approach to examine contaminants in tissues of the freshwater prawn
Macrobrachium brasiliense (Heller 1862), and also found elevated
values at some sites.
4.7 |Dams
One of the most serious threats to Neotropical rivers is the continued
construction of dams that impede the movement of fishes and sedi-
ments, and alter the abiotic and biotic conditions of rivers (Agostinho
et al., 2008; Anderson et al., 2018; Baxter, 1977; Carvajal-Quintero
et al., 2017; Sanz Ronda et al., 2009; Timpe & Kaplan, 2017;
Winemiller et al., 2016; Zarfl et al., 2015). While some industrialized
countries are removing their dams to restore natural ecosystem func-
tions (O'Connor et al., 2015), hundreds of new dams are under con-
struction or planned in some of the most biodiverse tropical countries
(Anderson et al., 2018; Winemiller et al., 2016; Zarfl et al., 2015). Dam
construction throughout Ecuador has accelerated in the last few
decades as increasing hydroelectric power became a major govern-
ment objective (Anderson et al., 2018; L
opez et al., 2013) (Figure 7).
Problems associated with dams have been reported throughout
Ecuador. In the Santiago River basin in the Ecuadorian southern Ama-
zon region, the Paute Integral Hydroelectric Complex has been oper-
ating for more than 30 years (CELEC EP HIDROPAUTE, 2013). As
occurs in other artificial reservoirs, the Centrales Molino and Mazar
impoundments provide habitat for introduced species, accumulate
sediment and have anoxic bottom water, which may affect species
downstream when it is periodically released (El Comercio, 2009).
Alteration of natural water flow patterns can also be severe
(Figure 7d). In northern Ecuador, a hydroelectric power plant located
in Manduriacu (border of Imbabura and Pichincha provinces) has been
implicated in environmental problems downstream. The plant became
operational in March 2015 (La Hora, 2016) and is supplied by the
Guayllabamba River, which collects sewage from the entire city of
Quito and its surroundings, and drains into the Blanco River,
Esmeraldas basin. Since May 2016, there have been at least three
massive fish kills linked to the release of water and accumulated sedi-
ments from the impoundment (La Hora, 2016). In the Atacames River
drainage, a small coastal drainage basin in coastal Esmeraldas
Province, two dams were built in the 2000s to collect water for irriga-
tion. Unfortunately, the dams have become barriers for some species.
In 2012, large numbers of Astyanax ruberrimus Eigenmann 1913, a
characid known locally as tacuana, were documented attempting to
migrate upstream, presumably for reproductive purposes, but could
not pass the dam (Jiménez-Prado, 2012). Although other factors
could be at play, by 2016 A. ruberrimus was no longer found in the
Atacames basin and is possibly locally extinct there (Jiménez-Prado &
Vásquez, 2021).
The Guayas basin in Western Ecuador harbours the largest artifi-
cial impoundment in the country, the Daule-Peripa multipurpose pro-
ject, located 10 km upstream of the town of Pichincha at the
confluence of the Daule and Peripa Rivers. The Daule-Peripa dam and
associated structures were built in the 1980s to store water for agri-
cultural use, for the transfer of water to water-deficient areas and for
the generation of hydroelectric power (CELEC EP, 2013). It has a
water storage capacity of 6000 m
3
and covers approximately
27,000 ha at capacity (CELEC EP, 2013). Despite its size, there has
been very little published research on its impacts on fish communities
in its area of influence. As is often the case for artificial impound-
ments, the Daule-Peripa impoundment harbours relatively large
populations of edible fishes that are exploited by local fishermen
(Aguirre et al., 2013; Baxter, 1977). However, much of the deep
waters are anoxic and their release has been associated with low oxy-
gen levels detected in the Daule River (Universidad Agraria del
Ecuador, 2011). It is also an important component of a canal system
for transferring water throughout much of the central portion of
Western Ecuador, from Daule-Peripa west to the Peninsula of Santa
Elena, south to the Chong
on impoundment close to Guayaquil and
east to the Baba River (CELEC EP, 2013), which has the potential to
allow gene flow between previously unconnected fish populations in
western Ecuador. Another more recent dam has been constructed in
the eastern side of the Guayas basin on the Baba River (Cruz, 2013).
Monitoring by the Instituto Público de Investigaci
on de Acuicultura y
Pesca suggests that species exhibiting migratory behaviours, such as
bocachico (I. humeralis), dama de montaña,dama blanca, and sábalo
(Brycon spp.), dica (Pseudocurimata spp.), etc., appear to be declining
there (Willan Revelo, pers. obs.). The plight of the prochilodontid
I. humeralis, a migratory species that is endemic to the Guayas basin
and is one of the commercially most important freshwater fishes in
Western Ecuador, is particularly concerning. At the start of the rainy
season in Western Ecuador (November–December), I. humeralis forms
large schools to begin its upstream migration, making it vulnerable to
over exploitation. Monitoring data indicate that it has declined sub-
stantially upstream of the impoundment since the dam was con-
structed and fishing activities have largely ceased (Willan Revelo, pers.
obs.). General environmental degradation in the area may also be
playing a role.
The impacts of dams may not be limited to ecological processes.
The transformation of a river into an artificial impoundment is a major
form of habitat transformation resulting in substantial change in selec-
tive regimes. Several studies have documented significant
AGUIRRE ET AL.1173
FISH
morphological changes associated with adaptation to conditions in arti-
ficial impoundments in other areas (Haas et al., 2010; Palkovacs
et al., 2007; Svozil et al., 2020), including genetic changes
(Franssen, 2011, 2012). Significant divergence in body shape between
river and artificial impoundment populations has been reported in the
predatory fish Hoplias microlepis (Günther 1864), with impoundment
populations generally being more robust and differing in fin placement
and size (Aguirre et al., 2013; Granda Pardo & Montero Loayza, 2015).
Even greater changes in body shape may be occurring in the more
active predatory fish Brycon alburnus Günther 1859 (Windsor Aguirre,
unpublished data). Although phenotypic plasticity is likely at play, some
genetic adaptation may also be occurring as has been observed in other
populations subjected to strong selection (Bell & Aguirre, 2013;
Hendry & Kinnison, 1999). If so, the flow of alleles favoured in artificial
impoundments into river populations would be of concern given the
potential for these alleles to be maladaptive in river habitats given the
ecological differences between these habitats.
4.8 |Overfishing
Freshwater fisheries are widespread throughout Ecuador, and fishes
are an important and often inexpensive source of protein for people
in rural areas (Barnhill Les et al., 1974; Revelo & Laaz, 2012;
Utreras, 2010) (Figure 8). Unfortunately, freshwater fisheries in Ecua-
dor are often difficult to regulate, making overexploitation a constant
threat. There are also few published data on long-term trends in fresh-
water fisheries catches, making it extremely difficult to assess the
magnitude of the problem. However, it is broadly recognized that fish-
eries catches for commercially important species, like large Amazonian
catfishes, have declined (Jácome-Negrete et al., 2018; Utreras, 2010).
In Western Ecuador, freshwater fisheries have been most impor-
tant in the Guayas River basin, where catches are largely locally con-
sumed (Barnhill Les et al., 1974; Revelo, 2010; Revelo & Laaz, 2012).
The most important fisheries species in the Guayas basin include
Ichthyoelephas humeralis,Pseudocurimata spp. and Brycon spp.
FIGURE 7 Dams have been constructed in rivers throughout Ecuador and more dams are planned. (a) View of impoundment formed by
Daule-Peripa Dam, upper Guayas basin (western Ecuador). (b) Dam in the Baba River, Guayas drainage basin (western Ecuador). (c) Impoundment
formed by the Chongon Dam outside of the city of Guayaquil (western Ecuador). (d) Daniel Palacios Dam (Paute Integral Hydroelectric Complex)
showing river without water (Andes)
1174 AGUIRRE ET AL.
FISH
(Figure 1g), Hoplias microlepis (guanchiche), Dormitator latifrons
(Richardson, 1844) (chame), Leporinus ecuadorensis (rat
on), Mesoheros
and Andinoacara (Figure 1r) (viejas), Rhamdia (Figure 1k) (barbudo), and
introduced tilapia (Barnhill Les et al., 1974; Revelo, 2010). Although
monitoring of the fisheries has been sporadic, fishermen universally
indicate that major fisheries species have declined. The lack of
long-term data makes the magnitude of the problem unclear. Fisheries
in Los Ríos province have been followed most closely and show clear
evidence of decline (Instituto Nacional de Pesca, 2012; Prado
et al., 2012; Revelo, 2010; Revelo & Laaz, 2012). Use of illegal fishing
gear like gill nets or illegal mesh sizes likely exacerbates the problem
(Revelo, unpublished data).
Fisheries in the Amazon region are important as a critical