ORIGINAL RESEARCH
published: 20 April 2022
doi: 10.3389/fmars.2022.838988
Edited by:
Carolyn J. Lundquist,
National Institute of Water and
Atmospheric Research (NIWA),
New Zealand
Reviewed by:
Mario Barletta,
Federal University of Pernambuco,
Brazil
Emigdio Marı´n-Enrı´quez,
National Council of Science and
Technology (CONACYT), Mexico
*Correspondence:
Federico Mosquera-Guerra
[email protected]
Specialty section:
This article was submitted to
Marine Conservation and
Sustainability,
a section of the journal
Frontiers in Marine Science
Received: 19 December 2021
Accepted: 24 March 2022
Published: 20 April 2022
Citation:
Mosquera-Guerra F, Trujillo F,
Pérez-Torres J, Mantilla-Meluk H,
Franco-León N, Paschoalini M,
Valderrama MJ, Usma Oviedo JS,
Campbell E, Alfaro-Shigueto J,
Mena JL, Mangel JC, Gilleman C,
Zumba M, Briceño Y, Valencia KY,
Torres-Forero PA, Sánchez L, Ferrer A,
Barreto S, van Damme PA and
Armenteras-Pascual D (2022)
Strategy to Identify Areas of Use
of Amazon River dolphins.
Front. Mar. Sci. 9:838988.
doi: 10.3389/fmars.2022.838988
Strategy to Identify Areas of Use of
Amazon River dolphins
Federico Mosquera-Guerra 1,2,3*, Fernando Trujillo 2, Jairo Pérez-Torres 1,
Hugo Mantilla-Meluk 4,5, Nicole Franco-León 2, Mariana Paschoalini 6,7,8,
Marı́a J. Valderrama 2, José S. Usma Oviedo 9, Elizabeth Campbell 10,11,12,
Joanna Alfaro-Shigueto 10,11,12, José L. Mena 13, Jeffrey C. Mangel 10,11,
Cédric Gilleman 14, Moisés Zumba 14, Yurasi Briceño 15, Kelly Y. Valencia 16,
Paula A. Torres-Forero 2, Leonardo Sánchez 15, Arnaldo Ferrer 15, Sebastian Barreto 3,
Paul A. van Damme 17 and Dolors Armenteras-Pascual 3
1 Laboratorio de Ecologı´a Funcional (LEF), Unidad de Ecologı´a y Sistemática (UNESIS), Pontificia Universidad Javeriana,
Bogotá, Colombia, 2 Fundación Omacha, Bogotá, Colombia, 3 Departamento de Biologı´a, Grupo de Ecologı´a del Paisaje y
Modelación de Ecosistemas (ECOLMOD), Facultad de Ciencias, Universidad Nacional de Colombia, Bogotá, Colombia,
4 Programa de Biologı´a, Centro de Estudios de Alta Montaña (CEAM), Facultad de Ciencias Básicas y Tecnologı´as,
Universidad del Quindı´o, Armenia, Colombia, 5 Programa de Biologı´a, Grupo de Investigación en Desarrollo y Estudio del
Recurso Hı´drico y el Ambiente (CIDERA), Facultad de Ciencias Básicas y Tecnologı´as, Universidad del Quindı´o, Armenia,
Colombia, 6 Laboratório de Ecologia Comportamental e Bioacustica, Programa de PósGraduacão em Ecologia, Universidade
Federal de Juiz de Fora, Juiz de Fora, Brazil, 7 Instituto Aqualie, Juiz de Fora, Minas Gerais, Brazil, 8 Grupo de Pesquisa em
Mamı´feros Aquáticos Amazônicos, Instituto de Desenvolvimento Sustentável Mamirauá, Tefé, Brazil, 9 WWF-Colombia, Cali,
Colombia, 10 ProDelphinus, Lima, Peru, 11 School of BioSciences, Penryn, University of Exeter, Exeter, United Kingdom,
12 Carrera de Biologı´a Marina, Universidad Cientı´fica del Sur, Lima, Peru, 13 Museo de Historia Natural “Vera Alleman
Haeghebaert”, Universidad Ricardo Palma, Lima, Peru, 14 Asociación Solinia, Iquitos, Peru, 15 Laboratorio de Biologı´a de
Organismos, Centro de Ecologı´a, Instituto Venezolano de Investigaciones Cientı´ficas, San Antonio de los Altos, Venezuela,
16 Fundación Neotropical Cuencas, Arauca, Colombia, 17 Faunagua, Sacaba, Cochabamba, Bolivia
Unsustainable fisheries practices carried out in large parts of the Amazon, Tocantins, and
Orinoco basins have contributed to the decline in the populations of the Amazon River
dolphins (Inia spp.), considered Endangered by the International Union for Conservation of
Nature (IUCN). Amazon River dolphin byproducts are often obtained through unregulated
fisheries and from stranded and incidentally caught individuals that are traded for the flesh
and blubber used for Calophysus macropterus fisheries, traditional and other medicinal
purposes, and more recently for human consumption. To identify localities of use of
Amazon River dolphins, we conducted a systematic review of the related literature
published since 1980, complemented with structured surveys of researchers that
allowed the identification of 57 localities for uses of Inia (33 in the Amazon, two in the
Tocantins, and 22 in the Orinoco basins), and two more on the Brazilian Atlantic coast,
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Areas of Use of Inia
with recent reports of targeted consumption in the upper Orinoco River. Subsequently,
the localities of use or bushmeat markets where Amazon River dolphin byproducts are
trafficked were identified. This information was integrated with a kernel density analysis of
the distribution of the Inia spp. populations establishing core areas. Our spatial analysis
indicated that the use of Inia spp. is geographically widespread in the evaluated basins. It
is urgent that decision-makers direct policies towards mitigating the socioeconomic and
cultural circumstances associated with illegal practices affecting Amazon River dolphin
populations in South America.
Keywords: amazon basin, Inia spp, artisanal fisheries, conservation, fishery-dolphin interactions, intentional
catches, orinoco basin, tocantins basin
individuals in the last three decades due to conflicts with
fishermen in a significant portion of its distribution (da Silva
V. et al., 2018) and in smaller proportion as traditional uses or
consumption (da Silva V.M.F. et al., 2018; Trujillo et al., 2020). In
addition, the populations of this top predator of aquatic food
webs (Gó mez-Salazar et al., 2011) and regulator of the structure
and composition of fish populations (da Silva, 1983; Best and da
Silva, 1989) are being threatened by the degradation of their
habitats by tensors like the following: (1) construction and
operation of 307 dams in the Amazon basin, 10 in Tocantins
basin, and four in the Orinoco basin, (2) mining, (3) high rates of
deforestation and fire in flood plains, and (4) the negative effects
of climate change on the flood pulse (Mosquera-Guerra et al.,
2018; Anderson et al., 2019; Mosquera-Guerra et al., 2019a;
Mosquera-Guerra et al., 2019b; Campbell et al., 2020;
Armenteras et al., 2021; Barbosa et al., 2021; Brum et al., 2021;
Fearnside et al., 2021; Pivari et al., 2021). In this context, Amazon
River dolphins are considered among the most threatened
aquatic mammals globally (Reeves et al., 2003; Trujillo
et al., 2010).
In this paper, we identify the geographic distribution of illegal
practices using Amazon River dolphins across their area of
occurrence. Additionally, we implemented spatial analyses to
determine areas of risk for the Inia spp. populations. Specifically,
our objectives were the following: (1) to identify the localities
where these types of practices have been reported, and (2) to
establish the core areas for Amazon River dolphin populations.
INTRODUCTION
The use of aquatic mammals for bait in fisheries for traditional
and medicinal purposes or as human consumption is
geographically widespread and affects at least 42 species
(Mintzer et al., 2018). The incidental capture of whales,
dolphins, manatees, and pinnipeds with fishing gear, as well as
targeted harvesting, is recognized as a major threat for these
aquatic mammals and represents a significant cause of mortality
that remains poorly quantified (Crespo and Hall, 2002; Heppell
et al., 2005; Clapham and Van Waerebeek, 2007; Costello and
Baker, 2011; Diniz, 2011; Lewison and Moore, 2012; Iriarte and
Marmontel, 2013a; Mintzer et al., 2013). Products from wild
aquatic megafauna are obtained through illegal or unregulated
hunting, as well as from stranded (dead or alive) and/or
incidentally caught animals and are defined with the term
“aquatic bushmeat” (CMS, 2016).
The use of body parts of Amazon River dolphins has been
reported for traditional and medicinal purposes and as bait in the
Amazon, Tocantins, and Orinoco basins (Best and da Silva, 1993;
Cravalho, 1999; Aliaga Rossel, 2003; Alves and Rosa, 2008;
Gravena et al., 2008; da Silva et al., 2017; da Silva V.M.F. et al.,
2018; Siciliano et al., 2018). Individuals are often obtained as
products from fishing activities (e.g., such as operational and
ecological interactions) or targeted captures (Mintzer et al., 2013;
Mintzer et al., 2018). Since the beginning of the 2000s, Inia spp.
have been hunted illegally for their meat to use as bait for fishing
the scavenger catfish Calophysus macropterus (known as
blanquillo in Bolivia, piracatinga or douradinha in Brazil, mota
or zamurito in Colombia and Ecuador, simi or mota punteada in
Peru, and mapurite in Venezuela; Flores et al., 2008; Trujillo
et al., 2010; Alves et al., 2012; Cosentino and Fisher, 2016;
Trujillo et al., 2020). This catfish largely replaces either
explicitly or implicitly the overfished Pimelodus grosskopfii, or
capaz distributed in the Magdalena-Cauca basin in Colombia
(Gó mez et al., 2008; Salinas et al., 2014; Mosquera-Guerra et al.,
2015); and its trading has spread to domestic markets in Brazil
(Cunha et al., 2015), and Venezuela (Diniz, 2011).
One of the main reasons for the current re-categorization
of I. geoffrensis from Data Deficient to Endangered by the
International Union for Conservation of Nature (IUCN) Red
List of Threatened Species is the increase in mortality of
Frontiers in Marine Science | www.frontiersin.org
METHODS
Systematic Review of Literature
and Surveys
We accessed 57 literature references (dated between 1980 and
2021) to obtain information on the use of Amazon River
dolphins as bushmeat, medicinal and traditional purposes, and
human consumption. The search and selection of publications
followed the PRISMA methodological approach (Moher et al.,
2009; Nakagawa et al., 2017). A search for information was
conducted in the following databases: (1) Scopus, (2) Science
Direct, (3) Springer Link, and (4) Google Scholar. Different
search terms were used: (1) Amazon River dolphin (TI) AND
2
April 2022 | Volume 9 | Article 838988
Mosquera-Guerra et al.
Areas of Use of Inia
locations) in Amazon (n = 20 individuals) and Orinoco basins
(n = 13 individuals; Figure 1) were integrated into a kernel
density (KD) estimation analysis on percentage volume contours
from (K10) 10% to (K90) 90% at 10% intervals (Oshima et al.,
2010; Sveegaard et al., 2011; Wells et al., 2017; Mosquera-Guerra
et al., 2021). This means that the area within the (K10) 10%
contour represented the areas with the highest density or core
area and the (K90) 90% contour represented almost the entire
range of Amazon River dolphins (Sveegaard et al., 2011). Kernel
density analyses allowed us to spatially locate the Inia spp.
populations at greater risk from use by calculating the
following spatial metrics: (1) number of the core areas (K50),
(2) distance from the nearest the Amazon River dolphin core
area to a locality use, and (3) distance from the nearest core area
to a protected area for the assessed basin (Protected Planet
Report, 2020). Mapping was performed using the geostatistical
analyst and spatial analyst extensions in ESRI ArcGIS version
10.8.1 (ESRI Environmental Systems Research Institute,
2021; Table 1).
targeted captures AND bushmeat AND piracathinga fishery*, (2)
Amazon River dolphin (TI) AND flesh and blubber OR
bushmeat (TI) AND piracathinga fishery*, (3) [TITLE-ABS
KEY (Amazon River dolphin * AND piracathinga fishery) *
AND (flesh * OR blubber * OR bushmeat * OR traditional
medicine * AND piracathinga fishery *) AND TITLE (Amazon
River dolphin *)]. In addition, 14 structured surveys were carried
out with researchers of Bolivia, Brazil, Colombia, Perú , and
Venezuela to identify areas where Amazon River dolphin are
captured and opportunistic uses are reported. Subsequently, the
information was classified in a database considering the
following criteria: (1) country, (2) locality, (3) river, (4) basin,
(5) subspecies, (6) category of use: traditional/medicinal
purposes, bycatch/bushmeat, and consumption, (7) period(s)
of recorded bushmeat use (1980-2000/2001-2021), and
(8) references.
Spatial Analysis
Spatial analyses included the mapped localities of use of Inia spp.
in the assessed basins, derived from the literatura review.
Additionally, 39,135 georeferenced locations from 23 boatsurveys (n = 11,519 locations) conducted in the Amazon (n =
16), Tocantins (n = 1) and the Orinoco basins (n = 6), and 33
tagged individuals from satellite monitoring (n = 27,616
Statistical Analysis
Shapiro-Wilk normality test was performed to the variables:
(1) Inia spp. population size, (2) Inia spp. population density,
(3) Number of the Amazon River dolphin use localities,
A
B
C
FIGURE 1 | Locations of Amazon River dolphins obtained through boat surveys and satellite monitoring that were used in the spatial analyses. (A) Amazon basin,
(B) Tocantins basin, and (C) Orinoco basin.
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Areas of Use of Inia
TABLE 1 | Locations of Inia spp. used in the spatial analyses in South America.
Basin
Upper
Amazon
Rivers
Number of records
obtained in boatsurveys
Number of records
obtained from satellite
monitoring
3,602
9,190
Trujillo-Gonzá lez et al., 2019; Paschoalini et al.,
2021
2,892
2,640
137
2,865
Trujillo-Gonzá lez et al., 2019; Paschoalini et al.,
2021
Pavanato et al., 2016; Trujillo-Gonzá lez et al., 2019
979
–
1,946
12,921
Orinoco
Colombia,
and
Venezuela.
Venezuela
83
–
Orinoco
Venezuela
1,880
–
Napo, Amazonas, Loretoyacú ,
Pú rus, Samiria, Marañon, and
Caquetá /Japurá .
Amazonas, Ité nez, Mamoré , and
Grande.
Tapajos
Middle
Amazon
Lower
Amazon
Lower
Tocantins
Tocantins
Upper
Guayabero, Guaviare, Inıŕ ida,
Orinoco
Orinoco, Bita, Meta, and Arauca.
Middle
Orinoco
Lower
Orinoco
Countries
Peru,
Colombia,
and Brazil.
Bolivia and
Brazil.
Brazil
Brazil
(4) Number of core areas (K50) in the assessed river basin
sections, (5) Distance of core area (K50) to the nearest locality
of use, and (6) Distance of core area (K50) to the nearest
protected areas. These tests were developed using the opensource software R.4.0.3 (R Core Team, 2020). In all cases, a value
of p < 0.05 was considered statistically significant.
Trujillo-Gonzá lez et al., 2019; Paschoalini et al.,
2020
Trujillo-Gonzá lez et al., 2019; Mosquera-Guerra
et al., 2019b; Mosquera-Guerra et al., 2019c;
Paschoalini et al., 2021
Trujillo-Gonzá lez et al., 2019; Mosquera-Guerra
et al., 2019b; Paschoalini et al., 2021
Trujillo-Gonzá lez et al., 2019
Tocantins Basin
The Tocantins basin is currently isolated from the Amazon River
basin. This condition makes it a biogeographic area of interest for
genetic and ecological studies of Inia spp.; recently populations
of this basin were proposed as a new species I. araguaiaensis
(Hrbek et al., 2014). Since the 2000s, the use of the Amazon River
dolphin individuals in the Mocajuba in the Tocantins River and
Ouré m in the Guamá River have been documented. In addition,
the following are reported Bragança and Tracuateua localities in
the Caeté River in the Brazilian Atlantic Coast (see Figure 2 and
Supplementary Table 1).
RESULTS
Localities that Reported the Use of
Amazon River Dolphins
Orinoco Basin
We identified 57 localities where Inia spp. individuals were used
under the evaluated categories in the study areas, and reported
two more on the Brazilian Atlantic coast. The localities were
distributed in the basins as follow: Amazon (n = 33, 58%),
Tocantins (n = 2, 3%), and Orinoco basins (n = 22, 39%).
Based on the number of records, the country with the highest
number of localities is Brazil (n = 20, 34%), followed by Venezuela
(n = 17, 29%), Peru (n = 13, 22%), Colombia (n = 7, 12%), and
Bolivia (n = 2, 3%; see Figure 2 and Supplementary Table 1).
In the Upper Orinoco the Amazon River dolphin use is
documented from the San Miguel River to the confluence of
the Meta-Orinoco rivers in 12 localities located at the border
between Colombia and Venezuela. In this section of the basin,
consumption of individuals of I. g. geoffrensis is reported for the
locality of Puerto Ayacucho (Venezuela). Smoked meat of the
Amazon River dolphin is marketed as the meat of lowland tapir
(Tapir terrestris) traditionally consumed by local communities.
Furthermore, Inia geoffrensis oil is marketed from the city of
Puerto Ayacucho to other localities such as Casuarito, Puerto
Carreño and Inı́r ida in Colombia to treat symptoms of
respiratory ailments. In the middle basin, the use of Amazon
River dolphins has been evidenced in the Camaguá n, Caicara del
Orinoco, San Fernando de Apure, and Puruey localities. In these,
the use of Inia’s oil for the treatment of SARS-CoV-2 derived
respiratory symptoms by indigenous communities who live in
these localities has been documented. Finally, in the lower basin
this use has been reported in the Ciudad Bolivar, Uverito, Puerto
Barranca, San Felix, Tucupita, and Curipao localities (see
Figure 2 and Supplementary Table 1).
The most represented use category for Amazon River dolphins
in the basins was bushmeat (n = 55, 64%), followed by traditional/
medical purposes (n = 30, 35%), and finally consumption (n = 1,
1%). The taxa of the genus Inia that report the highest number of
Amazon Basin
The use of I. g. geoffrensis in the upper Amazon basin has been
reported in 20 localities. The highest number of these is situated
on the Amazon River from the Napo River to the tripartite
border of Peru, Colombia, and Brazil. In the middle basin,
six localities of use have been identified from the confluence
of the Putumayo/Iç á and Caquetá /Japurá rivers with the
Amazon River to the Negro River in Brazil and in the
Tijamuchi and Mamoré rivers in Bolivia in these last two
rivers, where use is made of I. g. boliviensis individuals. Finally,
in the lower basin, seven localities from the confluence of the
Tapajos and Amazon rivers to the island of Marajó in the vicinity
of the Belé m city and the mouth of the Amazon River at the
Atlantic Ocean in Brazil were identified (see Figure 2 and
Supplementary Table 1).
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References
4
April 2022 | Volume 9 | Article 838988
Mosquera-Guerra et al.
Areas of Use of Inia
A
B
C
FIGURE 2 | Locations where use categories assessed for Amazon River dolphins are reported. (A) Amazon basin, (B) Tocantins basin, and (C) Orinoco basin.
C. macropterus fisheries. This practice is an unsustainable
practice that is widespread in the Amazonian countries of
Bolivia, Brazil, Colombia, and Peru, along the lower Tocantins
River in Brazil, and along the Orinoco basin shared between
Colombia and Venezuela. It is considered a significant threat to
the populations of these species (Brum, 2011; Iriarte and
Marmontel, 2013a; Iriarte and Marmontel, 2013b; Mintzer
et al., 2013; Botero-Arias et al., 2014; Brum et al., 2015; da
Silva V.M.F. et al., 2018; Mintzer et al., 2018; Trujillo et al., 2020).
In the last thirty years, the increase of the human population
in the hydrographic areas assessed, as well as the internal and
external demand for the fishery resources in these countries, have
led to overexploitation and the rapid decline of stocks of fishes of
commercial interest to fisheries (e.g., large catfish
Brachyplatystoma spp.), and has resulted in a shift of target
species of fisheries from increasingly scarce large fish to smaller
species (e.g., small catfishes with C. macropterus; Gó mez et al.,
2008; Barthem, 2013; Barthem et al., 2017). Change in the
fisheries in the Amazon, Tocantins and Orinoco basins has
involved the use of unsustainable practices (e.g., monofilament
nets, trammel nets, and even the use of endangered species such
as bait) thus increasing the biological and operational
interactions with aquatic vertebrates (e.g., Amazon River
dolphins). These events generally result in the incidental
capture and retaliatory killing of individuals that in some cases
are traded in the bushmeat markets for bait or traditional
use localities in the basin evaluated is I. g. geoffrensis (n = 53, 90%),
subsequently of I. araguaiaensis (n = 4, 7%), and finally I. g.
boliviensis (n = 2, 3%; see Figure 2 and Supplementary Table 1).
Spatial Analysis
Kernel density analyses show that most of the core areas (K50) of
Inia spp. are in heterogeneous habitat types as follow: (1) main
rivers, (2) confluences, (4) lagoons, and (5) channels of the river
basins. In the Amazon basin there are four core areas: (1) NapoAmazonas rivers confluence, (2) Loretayacu-Amazonas rivers
confluence, including the wetland complex of Tarapoto, (3)
Iténez River, and (4) Tapajó s River. The Orinoco basin has three
core areas: (1) Guayabero River, (2) Guaviare-Inı́rida rivers
confluence, and (3) Meta-Bita-Orinoco rivers confluence, and in
the Tocantins basin, the core area was in the lower basin (Figure 3).
The values of the Shapiro-Wilk normality test concluded that
the data for all variables do not come from a normal
distribution (Table 2).
DISCUSSION
Geographic Distribution of the Illegal Uses
of Amazon River Dolphin
Our results are in line with previous reports on the widespread
use of Amazon River dolphin (Inia spp.), such as bait in the
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Areas of Use of Inia
A
B
C
FIGURE 3 | Kernel density (KD) estimation analysis for the Inia spp. in the basins with percentage volume contours from (K10) 10% to (K90) 90% at 10% intervals.
The black line indicates high-density areas for the Amazon River dolphins defined as the 50% kernel contour or core areas. (A) Amazon basin, (B) Tocantins basin,
and (C) Orinoco basin.
management of the fishery resource (e.g., moratoriums and ban
unified between neighboring countries), (2) reduced institutional
capacity to control extensive areas in transboundary zones, and
(3) high levels of economic vulnerability and low levels of
education of the local communities that facilitate their
insertion into extractive models (e.g., illegal trade of wild
species), and the use of species of fauna (e.g., river dolphins)
for the treatment of diseases without scientific evidence.
purposes and in lower proportions for consumption (Herná ndez
and Gonzalves, 2009; Diniz, 2011; da Silva et al., 2011; da Silva
V.M.F. et al., 2018; Escobar-WW et al., 2020; Trujillo et al., 2020;
Brum et al., 2021).
Governments of Brazil and Colombia have generated
instruments such as moratoriums to regulate or prohibit the
commercialization of C. macropterus (da Silva V.M.F. et al., 2018;
Trujillo et al., 2020). This interaction is considered a serious
threat for Inia spp. populations in management plans formulated
in Brazil, Bolivia, Colombia, Peru, and Venezuela. However, the
implementation of actions proposed in these strategies for the
mitigation of this threat has not been effective due to factors such
as a: (1) lack of transboundary regulatory instruments for the
Spatial Ecology of Amazon River Dolphins
Our kernel density results (K 10 – K 95 ) coincide with
those reported by Mosquera-Guerra et al. (2021) on the
heterogenous distribution of the core areas in the different
TABLE 2 | Summary of the significance values of the Shapiro-Wilk test for the variables.
Category
Ecological
Ecological
Ecological
Environmental
Spatial metric
Spatial metric
Variables
Type
p value
Inia spp. population size
Inia spp. population density
Number of the Amazon River dolphin use localities
Number of core areas (K50) in the assessed river basin sections
Distance of core area (K50) to the nearest locality of use
Distance of core area (K50) to the nearest protected areas
Continuous
Continuous
Continuous
Continuous
Continuous
Continuous
4,2 x 10-5*
0,02*
0,03*
4,1 x 10-6*
0,02*
0,0002*
Those significant for the explanatory predictors are marked with an asterisk (*).
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(Williams et al., 2016; Martin and da Silva, 2021), possibly due to
the special reproductive conditions of Inia spp. including (1)
extended periods to reach sexual maturity of individuals that on
average is considered to be 9.7 years, (2) extensive gestation
periods (12.3–13 months), (3) prolonged parental care of calves
(1.5–5.8 years), and (4) average intervals between births of 4.6
years (Martin and da Silva, 2018).
habitat types used by Amazon River dolphins (e.g., confluences,
channels, tributaries and lagoons) that are influenced by the
ecology of the species and environmental aspects of the basin,
such as: (1) wide variations in the home range sizes (K95 = 6.2 –
234 km², mean = 59 ± 13.5 km²), and core area sizes (K50 = 0.6 –
54.9 km², mean = 9 ± 2.6 km ²), (2) broad and specific habitat
uses, (3) movements influenced by the lateral and longitudinal
migration of fish, (4) sexual segregation of Inia individuals, and
(5) ecological characteristics of the aquatic systems where they
occur (productivity levels; Mosquera-Guerra et al., 2021).
Although Inia spp. is distributed over >1,000,000 km2 of the
Amazon, Orinoco, and Tocantins basins, its occurrence is
represented by only 15% of their distribution inside protected
areas (Mosquera-Guerra et al., 2018). This is evidence that Inia
spp. populations throughout much of their range are exposed to
different types of human-induced threats such as bycatch
(Herná ndez and Gonzalves, 2009; da Silva et al., 2011; Diniz,
2011; da Silva V.M.F. et al., 2018; Escobar-WW et al., 2020;
Trujillo et al., 2020; Brum et al., 2021).
The results obtained through our statistical analysis show that
the variables do not come from a normal distribution. This
condition may be due to the widespread occurrence of this
practice on the Inia spp. and the reduced management and
control of the protected areas in the basins evaluated (da Silva
V.M.F. et al., 2018; Trujillo et al., 2020). The population aspects
considered in our analyses-such as population size of Amazon
river dolphins- are influenced by: (1) the abundance and
availability of fish prey, (2) the accessibility to foraging
locations, determined mainly by the flooding pulse and river
geomorphology, and (3) group sizes (Martin and da Silva, 1998;
McGuire and Winemiller, 1998; Trujillo, 2000; Martin and da
Silva, 2004; McGuire and Henningsen, 2007; Yamamoto et al.,
2015; Mintzer et al., 2016; Mosquera-Guerra et al., 2021). Amazon
River dolphins make up one of the smallest group sizes among
odontocetes as a strategy to increase individual fitness and reduce
competition for prey during declines in fish abundance during the
high-water period (Gó mez-Salazar et al., 2011).
Additionally, the spatial ecology of Amazon River dolphins is
influenced by strong sexual segregation of individuals. The
documented differential behaviors in the intensity of habitat
use between males and females is reported by Trujillo (2000)
for the lakes of Tarapoto and the Colombian Amazonas, Martin
and da Silva (1998) and Martin and da Silva (2004) using data
from 24 individuals monitored with radio telemetry in the
Mamirauá Sustainable Development Reserve, and MosqueraGuerra et al. (2021) from 24 individuals monitored by satellite
in Bolivia, Brazil, Colombia, and Peru. This sexual segregation of
Inia spp. differentially exposes males and females to targeted or
incidental captures as well as other types of threats (Mintzer
et al., 2016). The interactions between Amanimals with 20
individuals killed for use as bait inazon River dolphins and
fisheries generally occur in highly productive habitats, such as:
(1) confluences, (2) channels, and (3) lagoons, where capturing
mostly sexually mature individuals and possibly larger numbers
of females that have minor movements and are restricted to
specific habitats where they care for their calfs. This could
explain the rapid population decline in their area of occurrence
Frontiers in Marine Science | www.frontiersin.org
Knowledge Gaps
Our study highlights the need to continue with Inia population
trend studies in order to monitor in a standardised way the fast
population decline of Amazon River dolphins reported in the last
three decades in the study areas (Williams et al., 2016; Martin and
da Silva, 2021). This information is essential to complement spatial
analyses and to focus conservation efforts in priority areas.
Population studies conducted in the upper and middle Amazon
and Orinoco rivers highlight the negative impact of bycatch on I. g.
geoffrensis populations. For example, Williams et al. (2016) assess
Amazon River dolphin abundance estimates made in the
Colombian Amazon trapezoid in 1993, 2002 and 2007, and
report an annual decline probability for I. geoffrensis of > 0.75.
Herná ndez and Gonzalves (2009) report that the population of I.
geoffrensis in the Javari River, a tributary of the Amazon River, is
250 animals with 20 individuals killed for use as bait in C.
macropterus fisheries annually (8%). da Silva et al. (2011), and
Martin and da Silva (2021) report between the 5.5–10% annual
decline of populations of I. g. geoffrensis in the Central Amazon in
the vicinity of the Mamiruá Reserve and document that 1650
Amazon River dolphins are captured annually near the Brazilian
Amazonian city of Tefé. Finally, in the Venezuelan Orinoco basin,
Diniz (2011) estimates that 840 individuals are killed for
piracatinga fisheries (da Silva V.M.F. et al., 2018). In this
context, it is a priority to continue with this type of population
dynamic studies and thus contribute to an understanding of the
effect of this threat on the health of Inia populations.
In this context, it is necessary to clarify the taxonomy of the
genus Inia using integrative taxonomy studies since currently
only two subspecies are recognized (Committee on Taxonomy,
2021); I. g. geoffrensis distributed across the Amazon, and
Orinoco basins and I. g. boliviensis, found along the Mamoré ,
Ité nez, and Madeira rivers (Aliaga-Rossel, 2002; Aliaga-Rossel
et al., 2006; Gravena et al., 2014; da Silva and Martin, 2014; da
Silva V. et al., 2018; Aliaga-Rossel and Guizada-Durá n, 2020;
Pivari et al., 2021). This condition does not allow for evidence of
possible effects on the loss of genetic diversity for the genus
caused by the reduction of populations. This is the case of the
Inia spp. that are pressured by targeted and incidental catches in
the middle Amazon (Bolivia and Brazil), and Tocantins Basins
(Brazil). It has been proposed that I. boliviensis corresponds to a
valid species (Banguera-Hinestroza et al., 2002; Ruı́z-Garcı́a,
2010, and Gravena et al., 2014); in the same way, Hrbek et al.
(2014) have suggested I. araguaiaensis (Tocantins basin) as a
new species in the genus, with a population size >3,000
individuals, seriously threatened by infrastructure projects
like dams (Hrbek et al., 2014; Paschoalini et al., 2020; Brum
et al., 2021). Although these taxa have not yet been recognized
as valid species by a section of the scientific community
7
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Areas of Use of Inia
strategies for the conservation of Amazon River dolphin
populations. However, despite the efforts made by civil society
and governments, the implementation of these actions lacks
effectiveness due to aspects such as the absence of transnational
instruments to sustainably manage the habitats and the
conservation of healthy populations of this endangered cetacean
on a basin scale. The current state of decline Inia spp. populations
mainly are caused by of the directed and incidental catch as well as
the ecosystemic degradation of the natural environments suitable
for Amazon River dolphins. One of the identified problems
compromising the effectiveness of management is the reduced
management capacity at the transnational level. Finally, in the
context of the global health crisis caused by SARS-CoV-2, it is
urgent to prevent future pandemics through public health
surveillance strategies and the social management of the
bushmeat markets, while considering the cultural and economic
needs of local populations of these basins.
(Committee on Taxonomy, 2021), a precautionary principle
should be considered and efforts should be made to preserve
the taxonomic diversity of the genus Inia (Trujillo et al., 2010; da
Silva V.M.F. et al., 2018).
Additionally, it is a priority to promote the implementation of
public health programs in the countries of the region that
monitor concentrations of heavy metals in aquatic ecosystems
as well as the zoonotic risks generated by the illegal bushmeat
market. The best biological models for evidence of mercury
concentrations in aquatic food webs are top predators (e.g.,
Amazon River dolphins; Mosquera-Guerra et al., 2019a;
Barbosa et al., 2021), and benthic fish with omnivorous habits
(C. macropterus; Mosquera-Guerra et al., 2015). These aquatic
vertebrates are extensively used in the region, and this situation
could become a public health problem for local communities and
external consumers who make multiple uses of these species.
Finally, the bushmeat markets are widely distributed in the
Neotropical region, illegally trading massive numbers of wildlife
rodents, primates, xenarthrans, and ungulates (Olival et al.,
2017), with a significant increment in the trading of Inia since
the 2000s for bait for C. macropterus fisheries, and more recently
for human consumption. The use of other products of Inia such
as oil, eyes, and genitals organs for traditional purposes and nonevaluated treatments of respiratory ailments since the 1980s
(Cravalho, 1999; Gravena et al., 2008; Loch et al., 2009; Trujillo
et al., 2010; Martins, 2015; Cosentino and Fisher, 2016; Santos,
2017; da Silva V.M.F. et al., 2018; Mintzer et al., 2018; Siciliano
et al., 2018), constitutes a risk for the emergence and transmition
of zoonotic diseases and future pandemics. Bushmeat markets
are centers for the interaction of viral loads of various vertebrate
species (Olival et al., 2017), that could, at any time, cause a
zoonotic jump in densely populated places with the Amazon
basin where recent censuses have reported more than 40
million inhabitants.
DATA AVAILABILITY STATEMENT
The raw data supporting the conclusions of this article will be
made available by the authors, without undue reservation.
ETHICS STATEMENT
The animal study was reviewed and approved by Pontificia
Universidad Javeriana.
AUTHOR CONTRIBUTIONS
FM-G led and executed the systematic review and spatial
analyses, synthesis, and preparation of the first draft. FT, JP-T,
HM-M, NF-L, MP, MV, JU, EC, JA-S, JLM, JCM, CG, MZ, YB,
KV, PT-F, LS, AF, SB, PD, and DA-P contributed the initial idea
and from the first draft on, edited and organized the
development of the manuscript. All authors contributed to the
article and approved the submitted version.
CONCLUSION
Spatial analyses are powerful tools that at different scales
contribute to an understanding of the distribution of areas of
the ecological importance of the species with wide ranges of
occurrence such as Inia spp.; as well they contribute to the
identification of their threats, and focus conservation efforts.
Species such as the Amazon River dolphin erroneously have been
considered relatively safe from human-induced threats due to its
wide area of distribution. However, this consideration ignores
the broad and specific ecological requirements of river dolphins,
as well as the cumulative effect of the multiple threats facing their
populations and habitats throughout their range. An example of
this condition was the recent ecological extinction in 2006 of the
baiji (Lipotes vexillifer) that was widely distributed along 1,700
km in the middle of the Yangtzé River in China.
Over the last three decades in South America, researchers have
endeavored to identify threats to the conservation of taxa of the
genus Inia, including quantifying the number of individuals that
have been captured and killed for illegal use. This scientific
knowledge has been essential in the construction of different
Frontiers in Marine Science | www.frontiersin.org
FUNDING
This work was supported by the Whitley Fund For Nature
(WFN), World Wildlife Fund (WWF), CORMACARENA,
CORPORINOQUIA, CORPOAMAZONIA, Projects Design
and Development (PDD), and Pontificia Universidad Javeriana
(PUJ). The views expressed are those of the authors and do not
necessarily reflect the views of these organizations.
ACKNOWLEDGMENTS
This program is part of the strategic plan of the South American River
Dolphin Initiative (SARDI) supported by WWF in Brazil, Colombia,
8
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Mosquera-Guerra et al.
Areas of Use of Inia
Peru, Ecuador, and Bolivia. Partial support for two tag transmitters
installed in individuals from Peru was obtained from the Rufford
Foundation through RSG. Special gratitude goes to M. Oliveira da
Costa, D. Willems, K. Berg, L. Sainz, J. Rivas, J. Surkin, R. Maldonado,
D. Embert, V. Tellez, F. La Rosa, and M. Wulms from WWF. FMG
received a Postdoctoral Fellowship from PUJ (ID project: 20389 to
2021). EC received a doctoral scholarship from WWF-EFN. A.
Echeverrı́a, L. Cordova, and A. Salinas are acknowledged for their
support during tagging campaigns in Bolivia and M. Marmontel in
Brazil. We acknowledge the WFN, CORMACARENA,
CORPORINOQUIA, CORPOAMAZONIA, PDD, the fishing
communities, and the local and national authorities for
participating in the Amazon River dolphin capture process.
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Conflict of Interest: The authors declare that the research was conducted in the
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