Non-native anadromous salmonids in the La Plata Basin: long distance colonization?

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BioInvasions Records (2024) Volume 13, Issue 1: 251–2
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Espínola et al. (2024), BioInvasions Records 13(1): 251–265, https://doi.org/10.3391/bir.2024.13.1.23 251
CORRECTED PROOF
Research Article
Non-native anadromous salmonids in the La Plata Basin:
long distance colonization?
Luis Alberto Espínola1, Claudio Baigún2, Carla Riva-Rossi3, Pamela Quiroga3, Elie Abrial1, Ana Pia Rabuffetti1, Cecilia
Di Prinzio4, Martín Cesar Maria Blettler1 and Luciano Neves dos Santos5,6
1Instituto Nacional de Limnología (CONICET-UNL), Laboratorio de Hidroecología, Ciudad Universitaria “Paraje El Pozo”, Santa Fe, Argentina
2Instituto de Investigación e Ingeniería Ambiental (3iA) Campus Miguelete, 25 de Mayo y Francia (1650) San Martín, Buenos Aires, Argentina.
Laboratorio de Ecología Pesquera Aplicada UNSAM-CONICET, Argentina
3Instituto de Diversidad y Evolución Austral (IDEAus-CONICET), Puerto Madryn, Chubut, Argentina
4Centro de Investigacion Esquel de Montana y Estepa Patagonica (CONICET-FCNyCS - UNPSJB), Roca 780, Esquel, Chubut, Argentina
5Programa de Pos-Graduacao em Biodiversidade Neotropical (PPGBIO), Universidade Federal do Estado do Rio de Janeiro (UNIRIO),
Av. Pasteur, 458 – R509, CEP 22290-240, Rio de Janeiro, RJ, Brazil
6Laboratorio de Ictiologia Teorica e Aplicada (LICTA), Universidade Federal do Estado do Rio de Janeiro (UNIRIO), Av. Pasteur, 458 – R314A,
CEP 22290-240, Rio de Janeiro, RJ, Brazil
Corresponding author: Luciano Neves dos Santos (luciano.santos@unirio.br)
Abstract
The introduction and dispersal of salmonids have been widespread in Patagonian basins,
including anadromous species such as Chinook salmon (Oncorhynchus tshawytscha),
rainbow trout or steelhead (O. mykiss), sea-run brown trout (Salmo trutta), and, to a
lesser extent, coho salmon (Oncorhynchus kisutch). In recent years, Chinook salmon
and steelhead have been reported in the Paraná and Uruguay rivers and in the estuary of
La Plata River. This could be a result of long-distance movements, where stray
individuals travel northward along the cold Malvinas current. They enter these rivers
when it collides with the warm current originating from Brazil. However, this entry
takes place within a specific timeframe when the water temperature remains below
its lethal thermal threshold. Due to this temperature constraint and their reproductive
characteristics, the introduction of salmonids into this basin would not present a risk to
the native species. The projected impact of climate change, which anticipates an
increase in river temperatures and a southward shift of the Brazilian current, would
further support this hypothesis.
Key words: non-indigenous salmonids, Malvinas and Brazil current, Paraná, Uruguay
and La Plata rivers
Introduction
Salmonids are non-native fish species in the southern hemisphere but they
have been continuously introduced into cold temperate regions of South
America, through escapes from fish farms and intentional stockings programs
for sportfishing. The presence of salmonids in Argentina can be traced
back to the first stockings carried out at the beginning of the 20th century
in Patagonia (Baigún and Quiros 1985; Pascual et al. 2002). These programs
resulted in the establishment of freshwater resident stocks comprising
Citation: Espínola LA, Baigún C, Riva-
Rossi
C, Quiroga P, Abrial E,, Rabuffetti
AP
, Prinzio CD; Blettler MCM, dos Santos
LN
(2024) Non-native anadromous
salmonids in the La Plata Basin:
long
distance colonization?
BioInvasions
Records
13(1): 251–265, https://doi.org/10.
3391/bir.2024.13.1.23
Received:
25 February 2023
Accepted:
29 October 2023
Published:
30 November 2023
Handling
editor: Darragh Woodford
Thematic editor:
Kenneth Hayes
Copyright:
© Espínola et al.
This is an open acces s article distributed under terms
of the Cr eative C ommons Attribution Lic ense
(
Attributio n 4.0 Internat ional - CC BY 4.0).
OPEN ACCESS.

Non-native salmonids in the La Plata River basin
Espínola et al. (2024), BioInvasions Records 13(1): 251–265, https://doi.org/10.3391/bir.2024.13.1.23 252
mainly rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta)
and, to a lesser extent, brook trout (Salvelinus fontinalis), but failed to
introduce typically anadromous stocks or species at that time (Baigún and
Quiros 1985). The introduction of salmonids in Patagonia is controversial
because, despite high social and economic value for recreational fishing
(Pascual et al. 2009), several impacts on native fauna have been detected
through direct predation and habitat displacement (Baigún et al. 2022).
Currently, freshwater populations of rainbow, brown trout, and brook trout
have been recorded beyond the Patagonia region, even in areas with
suboptimal environmental conditions (high water temperatures, Carter 2005)
for their establishment (Espínola et al. 2022).
Anadromous salmonids have also been found more recently in Argentina.
In the Santa Cruz River (50º0.7'S; 68º2'W, Santa Cruz Province), Patagonia
ecoregion, rainbow trout was probably introduced from the McCloud River,
USA (Riva Rossi et al. 2004), showing either freshwater resident or anadromous
life histories (Pascual et al. 2001). In addition, sea-run brown trout, derived
from German domestic stocks of mixed origins (Valiente et al. 2007;
Colihueque 2015) is found in the Gallegos ( 51°35'S; 68°59'W, Santa Cruz
Province), the Grande (53°47'S; 67° 4'W), Ewan (54°0.6'S; 67°0.9'W, San
Pablo (54°16'S; 66°44'W) and Irigoyen (54°31'S, 66°17'W) rivers in Tierra
del Fuego Province and more recently in the Santa Cruz River (Santa Cruz
Province) (Casalinuovo et al. 2018; Baigún et al. 2022). The typically
anadromous Chinook salmon is, however, much more widespread across
the Argentinean and Chilean Patagonia (Correa and Gross 2008; Figueroa-
Muñoz, et al. 2023). In the Argentinean Patagonia, this species has invaded
rivers flowing towards the Pacific coast (Di Prinzio and Pascual 2008),
small tributaries of the Santa Cruz basin (Ciancio et al. 2005), and streams
draining the south of Tierra del Fuego Island (Fernandez et al. 2010; Nardi
et al. 2019). The invasion of Chinook salmon in those ecosystems is attributed
to feral populations that have migrated from rivers of south Chile (Riva
Rossi et al. 2012; Ciancio et al. 2015; Di Prinzio et al. 2015).
Recently, a single Chinook salmon was found in the Paraná River Delta,
in the lower La Plata River, on the Atlantic coast of Argentina (Liotta 2019).
In addition, further anecdotal reports of salmonid catches by local recreational
and artisanal fishermen have stressed the potential of anadromous salmonids
to invade the La Plata River. In this context, our study offers an updated
review of the records of captured salmonids in Argentina, specifically outside
the Patagonian ecoregion and particularly within the La Plata River basin.
Our primary focus in this study is to describe novel reports of salmonid
species never previously registered in this basin, which may be indicative of
an ongoing population expansion. We also discuss the potential dispersal
mechanisms and the risks that these species may pose to the native fish
assemblages.

Non-native salmonids in the La Plata River basin
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Materials and methods
The La Plata Basin accounts for 17 % of the surface area of the South American
continent and is the fifth largest river basin in the world, extending over
3,100,000 km2. The average annual temperature varies from 13 °C to over
25 °C from the south to the north, respectively. In the central region, the
annual temperature exhibits a fluctuation of approximately 12 °C. In winter
(June, July, and August), the temperature gradient from north to south
varies between 20 °C and 8 °C respectively. In summer (December, January
and February) the northwest of Argentina exceeds 28 °C, while the coastal
areas of Brazil and Uruguay reach 23 °C. Regarding the transition seasons,
spring (September, October, and November) is warmer than autumn
(March, April and May, Barros et al. 2006). The La Plata Basin covers an
extensive part of central and northern Argentina, southeast Bolivia, almost
all the southern part of Brazil, the whole of Paraguay and a large part of
Uruguay. The basin is formed by the Paraná, Paraguay and Uruguay rivers
systems and the La Plata sub-basin itself, with the Paraná River system
being the most extensive. These rivers make up the ecoregions called the
Lower Paraná and Lower Uruguay (Abell et al. 2008). The lower Paraná
forms a large subtemperate alluvial plain, free of dams, where most
ecological processes are driven by flood (November-March) – drought
(August and October) cycles. This ecoregion is characterized by a great
heterogeneity of habitats and a diverse biota adapted to the great spatio-
temporal heterogeneity. The Paraná River has an average flow of 15,000–
17,000 m3/s. In winter (June, August and July), the average minimum flow
is 13,842 m3/s with an average minimum temperature of 10 °C. The
average maximum flow in summer (December, January and February) is
15,773 m3/s with an average maximum temperature of 32 °C (Giacosa et al.
2020). The Lower Uruguay ecoregion includes the middle and lower Uruguay
River, which with the confluence of the Paraná River forms the estuary of
La Plata River. In turn the Uruguay river presents a flow of 45,00 m3/s.
Average temperature in winter is 16 °C and 25 °C in summer.
Data collection and identification
First, a literature search, using “salmon” and “Argentina” as keywords, was
performed on scientific (Web of Science, Scopus, Google scholar) and non-
scientific (Google, electronic newspapers and fishing magazines) databases
until 31th December 2022. All scientific and non-scientific reports were
checked for the occurrence of salmonids outside the Patagonia region and
reported if they provided reliable evidence of a salmonid record. Artisanal
and recreational fishermen were kindly invited to send pictures of the
salmonid caught, together with data on fish size and weight, fishing gear,
and the location of the capture. All the data sent on salmonids captured
between 2020 and 2021 were initially checked for veracity and accuracy through

Non-native salmonids in the La Plata River basin
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Table 1. Estimated total length, weight and sex data of non-native salmonids captured in the Lower Paraná and Uruguay
ecoregions. BA = Buenos Aires; ER = Entre Ríos; and SF = Santa Fe Tl = total length; F = Female. The first record of each species
is typed in bold.
Code
Date
Localization
River
Latitude - longitude
Species
Tl (cm)
Weight (g)
Sex
1*
24/10/2018
San Pedro, BA
Paraná
−33.083333° ; −33.083333°
O. tshawytscha
72.3
4,500
F
2
26/09/2020
Concepción del Uru guay, ER
Uruguay
−32.466667° ; −58.233333°
O. tshawytscha
70
5,000
?
3
17/10/2020
Concepción del Uru guay, ER
Uruguay
−32.466667° ; −58.233333°
O. tshawytscha
60
4,000
?
4
15/09/2021
Hudson, BA
La Plata
−34.733333° ; −58.133333°
O. mykiss
60
4,700
F
5
04/11/2022
Arroyo Seco, SF
Paraná
−33.150000° ; −60.433333°
O. tshawytscha
65
5,260
F
6
14/11/2022
Arroyo Seco, SF
Paraná
−33.150000° ; −60.433333°
O. tshawytscha
104.3
11,760
F
7
25/09/2023
General Lag os, SF
Paraná
−33.083333° ; −60.533333°
O. tshawytscha
100
11000
?
*See Liotta (2019)
telephone calls or direct contact with the fishermen. Whenever the fish
specimen could not be retrieved (i.e. due to local sales and/or consumption),
high quality photographs and videos sent by the fishermen were used to
identified salmonid species, by comparisons with pictures and descriptions
available in Scott and Grossman (1973). All salmonid specimens recovered
from the fishermen in 2022 (see Table 1), were secured, identified and
subsequently preserved at the Centro Científicos Tecnológicos y Educativo
“Acuario del Río Paraná” located in the city of Rosario, Santa Fe.
The individual identified as steelhead shows a longer, skinnier body
shape than those identified as Chinook salmon, and small numerous spots
aligned in straight lines on both lobes of the caudal fin. The most definitive
characteristic for distinguish from salmon was its pure white mouth.
Results
From 2020 to 2023, seven individuals corresponding to two species of the
genus Oncorhynchus, O. tshawytscha (six specimens) and O. mykiss (one
specimen), were caught outside the Patagonia region, in systems belonging
to the La Plata River basin (Figure 1; Table 1).
In the Paraná River, the first record of Oncorhynchus tshawytscha
occurred in the delta of this river (Lower Paraná ecoregion). It was
captured in Buenos Aires Province, San Pedro, in the Paraná River main
course near the mouth of San Pedro creek, 33°37'S; 059°45'W. The second
and third reports occurred on September 26th and October 17th of 2020,
respectively (Figures 2a and 2b). Both individuals were captured in the
vicinity of the city of Concepción del Uruguay in the Uruguay River
(Lower Uruguay ecoregion). One specimen of Oncorhynchus mykiss was
captured for the first time in September 2020 at the Hudson area, in the de
La Plata River (province of Buenos Aires, Figure 3). Two individuals of
O. tshawytscha (Figure 4) were captured between November 4th (Figure 4a, b).
and 14th of 2022 Figure 4c, b), in the Santa Fe Province. Both records were
in the main course of the Paraná River, near Arroyo Seco, close to Rosario
a city. Finally, an individual of this species was captured in the province of
Santa Fe, on September 25th, 2023. It also occurred on the main channel of

Non-native salmonids in the La Plata River basin
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Figure 1. Distributions of anadromous salmonids Argentina. Orange circles: individual Chinook
records, but not established populations; White/orange circle: individual steelhead records, but
not established populations.
the Paraná River, near to the city General Lagos, located between the cities
of Arroyo Seco and Rosario (Figure 5).
Except for the first and sixth individual shown in Table 1, weight and
size estimates correspond to fishermen’s observations.
Discussion
Initial colonization, local establishment and subsequent spread of a non-
native species into a new area is fundamental for a successful invasion
process. The success of an invasion depends on the biological attributes of
the non-native species as well as the ecological characteristics (biota and
environment) of the invaded environment (Colautti et al. 2006). This process
can be favored by human-mediated repeated introductions (propagule pressure,
Colautti et al. 2006) as it is the case of the aquaculture of non-native fish
(Casal 2006).

Non-native salmonids in the La Plata River basin
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Figure 2. Second and third record of Oncorhynchus tshawytscha. (a) captured in September and (b) October 2020 on the Uruguay
river. The Chinook salmon of 2 a resembles a male showing sexual dimorphic traits associated with the reproductive period, such
as pink coloration on its belly, incipient curvature of jaws and snout, and hump formation. Photographs by Fabio Baena and Pablo Foldesi.
Figure 3. First record of a mature female of rainbow trout Oncorhynchus mykiss captured in September 2021 (a) and (b) in the La
Plata River; (c) Zoom on mature eggs found in one of the ovaries. Photographs by Wilmar Merino.

Non-native salmonids in the La Plata River basin
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Figure 4. Fourth and fifth record of O. tshawytscha in the Paraná River. (a) teeth in the lower
jaw and (b) maturing eggs of Oncorhynchus tshawytscha captured on November 4th of 2022; (c)
and (d) Female of O. tshawytscha captured on November 14th of 2022. Photographs by
https://m.facebook.com/p/Rios-Sanos-100041376166542/

Non-native salmonids in the La Plata River basin
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Figure 5. Sixth record of O. tshawytscha in the Paraná River captured on September 2023.
Photographs by https://www.facebook.com/groups/PecesArgentinos/permalink/6614046305358
494/?app=fbl.
Anadromous salmonids are non-native to Argentina, but they have been
introduced for sport and aquaculture purposes across Patagonia during the
first decades of the 20th century or have naturally propagated from Chile
since the 1980s. Since then, they have rapidly spread and colonized numerous
Atlantic and Pacific basins throughout Patagonia (Di Prinzio and Pascual 2008).
In Patagonia, the steelhead, the anadromous ecotype of the rainbow trout,
has only been reported for the Santa Cruz River, thus suggesting that the
specimen captured in the La Plata River estuary would correspond to a
stray individual from this population, representing the first record of this

Non-native salmonids in the La Plata River basin
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Figure 6. Distributions of anadromous salmonids and their relationship with marine currents. Inside the red square the recent
records are depicted.
species in a basin located at a latitude so far north. Previously, the highest
latitude at which straying steelheads had been found was in the coast of
Negro River province, where an individual from the Santa Cruz River was
caught in the nearby of the Negro River mouth in January 2000 (Pascual et al.
2001). In the case of the Chinook salmon, the increase in its records reflects
the spread of this species across the Patagonian rivers, where adult
specimens of established self-sustaining populations might be colonizing
other rivers and streams (Baigún et al. 2022). Currently, the most conspicuous
Chinook salmon populations are located in the Santa Cruz River basin,
where self-sustaining spring runs of this species have colonized different
tributaries in the upper basin that have favorable conditions for reproduction
(Ciancio et al. 2015).
The presence of anadromous salmonids in the La Plata River, however,
appears to be a typical case of straying, where individuals that have failed
to reach their home, natal streams for breeding, disperse to other streams,
thus expanding their distribution range (Keefer and Caudill 2014). This
phenomenon may be attributed to the long-distance movement of individuals
that travel northward along the marine corridor driven by the Malvinas
current, which transport cold (< 7 °C), low-salinity water northward from
the subpolar South Atlantic into the subtropical South Atlantic (Piola et al.
2000; Figure 6). The Malvinas current collides with the warm-salty (up to

Non-native salmonids in the La Plata River basin
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26 °C) poleward flowing Brazil current at about 38° S, forming the Brazil-
Malvinas Confluence (Combes and Matano 2014). This confluence is
characterized by warm- and cold- meanders, eddies and water fronts (water
temperature can fluctuate from 0 °C to over 25 °C; 14–16 °C during winter
and early spring months, Combes and Matano 201), that induce strong
interactions between the shelf and the deep ocean, generating intense cross-
shelf exchanges, that have important consequences for marine life, as they
provide nutrients to the oligotrophic deep ocean from organisms that live
on the shelf (Manta et al. 2022). A distinct characteristic of this confluence
is the effect of the discharge of the La Plata River estuary, which provides
freshwater, suspended sediment, nutrients, and pollutants to the neighboring
shelf waters (Piola et al. 2000). The waters of the La Plata River plume, of
considerably low salinity, spread northward over the coastal shelf and are
exported to the open ocean (e.g., Guerrero et al. 2014).
This hypothesis is consistent with Ciancio et al. (2010) who suggested that
considering the distribution of sea-surface water temperatures and prey
distributions, the entire Patagonian shelf and up to the slope boundary
constitute potential areas of distribution of Chinook salmon and steelhead.
Both, nearby and long-distance dispersal, resulting from straying appear to
be crucial for the early spread and colonization of non-native Chinook
salmon across several non-native environments (Quinn et al. 2001; Correa
and Gross 2008; Gomez-Uchida et al. 2018). Both homing (the tendency to
return to the natal stream for breeding) and straying rates exhibit substantial
variation among salmon populations (Quinn 1993). Homing rates for
native salmon species can reach up to 99% (Ford et al. 2012). In fact, it has
been documented that introduced, non-native populations tend to stray
more than both native salmon and hatchery stocks reared and released on-
site (Quinn 1993; Jonsson et al. 2003). Of particular interest are non-native
populations originating from introductions, such as in New Zealand,
where straying rates vary between 4 and 20% (Unwin and Quinn 1993).
While most strays occur near natal areas, long-distance straying also occurs,
especially in hatchery populations introduced or transported as juveniles
(Keefer and Caudill 2014). Quinn (1993) suggested that straying may be
more frequent when salmon densities are low, which could be applied to
the Patagonian Chinook populations found only in few small rivers in
Tierra del Fuego and the Santa Cruz River, where spawning take place
exclusively in the upper basin’ small rivers with limited spawning grounds.
However, a smaller fraction of the population strays and breeds in non-
natal areas, enabling them to colonize new basins (Keefer and Caudill 2013).
Therefore, the presence of salmonids in this basin could be attributed to
migrant individuals dispersing in search of prey across the Malvinas current
and the Patagonian shelf. When they encounter the low salinity nutrient-
rich waters of La Plata River plume at the Brazil-Malvinas Confluence
zone, they move towards the continent aiming to enter this basin to reproduce.

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Figure 7. Thermal regime of maximum and minimum water temperature recorded from 2008
to 2019 at Nueva Palmira (see location in Figure 5). Critical threshold values for: 1) Chinook
migration; 2) steelhead migration; 3) Lethal temperature for adults of steelhead; 4) lethal
conditions for eggs and embryos of Chinook; 5) Lethal conditions for eggs and embryos of
steelhead; 6) Lethal temperature to adults of Chinook. The grey rectangle indicates the time
window of entry into the La Plata River of chinook, while the black line indicates the steelhead
record. Data from Carter (2005).
It is interesting to note that the timeframe during which salmonids were
caught into La Plata and Uruguay rivers coincided with the spring season
(Table 1, Figure 7). This entrance corresponds with the time period when
the Chinook salmon spring run initiates their upstream migration from the
ocean and into the Santa Cruz River. The significant influence of large-scale
dominant currents, such as the Malvinas current, also account for the presence
of anadromous salmon along the Brazilian coast. Apart from the coho salmon
(TL:76.1; 2,788 gr and Male), which was detected in 2002 at the Lagoa dos
Patos estuary, this species was also reported in the area of Bombinhas (Santa
Catarina Brazil) 1,100 km north of the confluence of the Malvinas and
Brazil currents (Soto and Rocha 2022).
While the expansion of Chinook salmon in South America appears to be
an ongoing process (Correa and Gross 2008; Gómez-Uchida et al. 2018,
Figueroa-Muñoz et al. 2023), the potential of this species to become invasive
in the La Plata Basin appears to be minimal (Liotta 2019). Adult salmonids
migrating upstream for breeding exhibit specific habitat requirements and
operate during specific time windows to ensure successful reproductive
migration and spawning. For instance, streams that are excessively warm
may impede or pose delays in upstream migration, rendering them unsuitable
for reproduction and egg survival. Thermal conditions of the Paraná and
Uruguay rivers are not suitable for salmonid reproduction. Moreover, the
water temperature of these rivers would not be adequate for the persistence
of salmonids beyond the delta of the Paraná River and in the lower Uruguay

Non-native salmonids in the La Plata River basin
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River, and only during a brief time window, up to October and November,
and as long as the water temperature remains below 25 °C (Figure 7).
Salmonids also require clear and relatively fast- waters with gravel-dominated
substrates to migrate upstream and build nests (Bjornn and Reiser 1991).
However, the water quality, velocity and substrate composition of the Paraná
and Uruguay river basin would not be favorable either, as it they are
characterized by slow, sluggish currents, fine-substrate with elevated
suspended silt and clay (Amsler and Prendes 2000). Furthermore, the potential
impact of these anadromous salmonids on the native fauna appears to be
insignificant.
Given that salmonids are species known for constructing nests, the risk
of competition with native species for spawning habitats remains low,
primarily due to a substantial proportion of fish species in the La Plata
River being free spawners (Agostinho et al. 2004). Furthermore, anadromous
salmonids, regardless of being semelparous or iteroparous, do not feed during
their reproductive migrations, as they have developed an intense trophic phase
in the sea. Consequently, any direct predation impacts on native species
are not anticipated. In the eventuality that these individuals were to reproduce,
their juveniles might indeed exert an ecological impact (competition for
preferred habitat, Vargas et al. 2010), as happens in so many Patagonian rivers.
In fact, the primary impacts of salmonids are usually attributed to their
juvenile stage when they compete with both native and non-native species
for food and habitat (Macchi and Vigliano 2014, Di Prinzio and Arismendi
2018). Moreover, the anticipated climate change within the basin (e.g. Barros
et al. 2005) and the increasing advance of warm waters from the Brazil
current towards the Patagonian shelf in recent years (Chidichimo et al. 2022)
would also serve to curtail the potential invasion of salmonids in the future.
In summary, we conclude that the presence of anadromous salmonids in
the temperate waters of the La Plata River is an occasional phenomenon
that has been previously recorded for other Patagonian anadromous species in
the past, such as the Patagonian lamprey (Geotria macrostoma, Riva Rossi
et al. 2020) and the Patagonian blennie (Eleginops maclovinus, González-
Castro et al. 2013). Given the scale of these movements, it is plausible that
these occurrences involve stray specimens carried by the Malvinas cold
current. However, over the last three decades, there has been a consistent
increase in sea surface temperatures across the Southwestern Atlantic Ocean.
This warming trend is accompanied by a rise in the frequency, duration
and intensity of positive sea surface temperature anomalies (Ortega et al.
2016). Due to the projected temperature elevation in the La Plata basin and
the broader Atlantic Ocean, the risk of dispersal and invasion of
anadromous salmonids from more temperate basins will likely be constrained.
Consequently, concerns about anadromous salmonids posing a serious
threat to native species should be minimized. Nonetheless, conducting
further assessments of new captures and records is imperative to confirm
the migration routes of these species.

Non-native salmonids in the La Plata River basin
Espínola et al. (2024), BioInvasions Records 13(1): 251–265, https://doi.org/10.3391/bir.2024.13.1.23 263
Authors’ contribution
LAE, CB and LNS Conceptualization, Methodology, Writing – Original Draft. CRR, PQ and CDP
Review and Editing and provided specific information on the life strategy of the salmonids. EA,
APR and MCMB, Formal analysis, Review and Editing and provided useful insight into the
structuring of the manuscript. All authors contributed and approved the final version of this letter.
Acknowledgements
The authors would like to thank all the fishermen who provided photographs, biological data
and the donation of salmonids caught. The authors are especially grateful to the Centro
Científico, Tecnológico y Educativo “Acuario del Río Paraná” for sharing the information on
the salmonids examined. The authors would also like to thank the anonymous reviewers whose
suggestions undoubtedly improved the final manuscript.
Funding declaration
This manuscript is a research line supported by Consejo Nacional de Investigaciones Científicas
y técnicas (CONICET). LNS was supported by Conselho Nacional de Desenvolvimento
Científico e Tecnológico (CNPq; research grant ref. 314379/2018-5) and Fundação Carlos Chagas
Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ).
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