Ichthyological research in the Sorocaba River basin, State of Sao Paulo, southeastern Brazil: trajectory of knowledge, advances, and future directionsAbstract
Ichthyological knowledge of the Sorocaba River basin dates to the 19th century, with initial surveys by Johann Natterer. These were followed by expeditions at the turn of the 20th century by researchers from the University of São Paulo’s (USP) Zoology Museum, which resulted in the description of five new species. After a hiatus of nearly a century, research resumed in 1992. Here, we present a comprehensive review of 64 publications to assess the current state of knowledge on the basin’s ichthyofauna. The most frequently studied topics were community ecology (34.4%), followed by species inventory (14%), population ecology (12.5%), and feeding ecology (7.8%). The reviewed articles documented 109 fish species, with the majority belonging to the order Characiformes and the family Aces-trorhamphidae. This total comprises 93 native and 16 non-native species. Despite a recent increase in publications, we identify critical knowledge gaps. We conclude that the basin has a well-known ichthyofauna, meaning that future efforts should prioritize research on diet, reproduction, and invasive species, while also incorporating emerging topics such as microplastic pollution and modern techniques, such as stable isotope analysis, to effectively guide conservation and management.
Key words
fish; freshwater ecosystems; impact; upper rio Paraná basin; neotropical region
INTRODUCTION
The Neotropical region is home to a rich ichthyofauna, with records of 4,225 fish species (Tonella et al. 2023). Within this region, the Upper Paraná River basin records 341 species (Dagosta et al. 2024). This study updates the previous species inventory for the Sorocaba River basin, compiled by Smith et al. (2007), which documented 71 species. We expect this number to have increased due to recent research compiled in this work. While early inventories were conducted by naturalists in the 18th and 19th centuries (Vanzolini 1996, Dagosta et al. 2024), ichthyological research in Brazil was significantly consolidated throughout the 20th century, with advances in various subdisciplines of biology and ecology across nearly all river basins.
The post-war economic expansion during the second half of the twentieth century led to mounting pressures and impacts on Brazilian drainage basins (Araújo et al. 2009). The proliferation of human activities, particularly agriculture, dam construction, aquaculture, ur-banization, mining, fishing, and the introduction of non-native species has profoundly trans-formed the structure, dynamics, and function of inland aquatic ecosystems (Pelicice et al. 2021). By systematizing historical data and identifying knowledge gaps, the present study provides a crucial baseline for understanding these long-term changes and guiding future research.
Brazilian freshwater ecosystems have undergone profound alterations due to pollution, eutrophication, habitat destruction, dam construction, fishing, and the introduction of non-native species (Agostinho et al. 2005). These widespread impacts have significantly changed native fish communities, making historical data essential for understanding baseline conditions prior to severe degradation. However, comprehensive historical inventories and analyses of long-term change remain uncommon for many Brazilian river systems.
This study focuses on the Sorocaba River basin, part of the Water Resources Mana-gement Unit 10 in the Middle Tietê River region (CBH-SMT 2013). This river system drains 18 municipalities and is located in southeastern Brazil, near the São Paulo metropolitan region. This area is the most urbanized in the country, accounting for over 40% of the Brazilian population, and is subject to intense agricultural and livestock farming pressures common to the Upper Paraná River basin (Pelicice et al. 2021, IBGE 2023). Economically developed regions such as this are often where biodiversity is most gravely threatened, as conservation efforts frequently lag behind the pace of development. This con-text underscores the critical relevance of historical data systematization for this basin.
The Sorocaba River basin lies in a transition zone between the Atlantic Forest and Cerrado biomes and is situated within a highly urbanized region. Consequently, its rivers and streams are critically threatened by real estate speculation and agriculture, placing its ichthyofauna under severe pressure. Despite these threats, considerable research has been conducted since 1993, significantly advancing our understanding of the local fish communities. Conservation efforts are partially supported by a network of federal, state, and municipal protected areas, such as the Corredores da Biodiversidade Municipal Park, the Itupa-raranga Environmental Protection Area (APA), and the Ipanema National Forest. For instance, the Ipanema National Forest alone harbors 89 fish species, representing a significant proportion of the basin’s total diversity (Smith et al. 2021). Notably, despite intense urbani-zation, streams within the basin’s municipalities continue to support a significant ichthyofauna. The municipality of Sorocaba, for example, recorded 63 fish species in its most recent inventory (Smith et al. 2020). This persistence highlights the resilience of the local fauna and underscores the critical need for continued research and targeted protection efforts, even in highly modified landscapes.
We developed a comprehensive reference database of fish species recorded in the Sorocaba River basin, compiling information on their occurrence, sub-basin distribution, habitat use, and the sampling methodologies employed in previous studies. By synthesizing this dataset, we address the following key questions: 1) What are the historical trends and primary research themes in ichthyological studies within the basin, and what are the main knowledge gaps for future research? 2) What is the current taxonomic and ecological com-position of the basin’s ichthyofauna, including the prevalence of native versus non-native species? 3) How are fish species distributed across the basin’s primary habitats, such as the main river channel, tributaries, and floodplain lakes?
MATERIALS AND METHODS
The Sorocaba River basin is located in the state of São Paulo, Southeastern Brazil, covering an area of 5,269 km² across 18 municipalities (Figure 1). The river system consists of the main Sorocaba River, its headwaters (the Sorocamirim, Sorocabuçu, and Una rivers), and other major tributaries, including the Pirapora, Tatuí, Sarapuí, Pirajibu, and Ipanema rivers. Originating in the Serra de São Francisco, the Sorocaba River flows through the municipality of Votorantim before reaching the city of Sorocaba. In its middle reach, the river is characterized by extensive wetlands and several floodplain lakes, which are primarily marginal (Smith & Barrella 2000, Silva et al. 2020). These landscape features extend down-stream through the municipalities of Iperó, Tatuí, Boituva, Cerquilho, and Laranjal Paulista.
The main rivers of this system are the Sorocaba, Sarapuí, and Ipanema (Atlas Socio-Ambiental 2009). Located in the Upper Sorocaba sub-basin, the Itupararanga Reservoir serves multiple purposes. It supplies water to the urban region of Sorocaba - the municipality with the highest population density in UGRHI-10 (>1,337 inhabitants/km2) - as well as to other municipalities bordering the reservoir (CBH-SMT 2013). The most prevalent eco-nomic activities are extractive, metallurgical, and food industries, while sugarcane, corn, and vegetables dominate agriculture (CETESB 2023). The climate varies across the basin, with classifications ranging from hot and humid with a dry winter to hot and humid without a dry season and temperate and humid without a dry season. Only 13.6% of the original vegetation cover remains, consisting primarily of Dense Ombrophylous Forest and Semideciduous Sea-sonal Forest. The remaining Cerrado biome is fragmented and under significant pressure from urbanization and real estate development (Atlas Socioambiental 2009).
The reviewed literature provided the basis for dividing this study into five chronolo-gical periods. These periods were defined as follows: 1) the 19th century; 2) 1900 - 1992, the period prior to the establishment of Biological Sciences programs in the basin region; 3) 1993 - 2003, following the creation of these programs and the beginning of formal ichthyo-logical research; 4) 2004 - 2013, corresponding to the first major species inventory; and 5) 2014 - 2025, characterized by the expansion of studies and the publication of an updated spe-cies list. A scientific literature search was conducted from November 2023 to January 2025, targeting publications released between 1990 and 2025. Using the HistCite software (Garfield 2009), the retrieved articles were classified by author, journal, institution, year, and country. Articles published before this main search period were also considered for historical context and comparison.
The information presented in this study was gathered through a systematic review. Articles were selected based on the following inclusion criteria: i) addressing the subject of ichthyology; ii) being conducted in the Sorocaba River basin (including the main river or its tributaries); and iii) having the full text accessible. Publications from 1990 to 2025 were identified using the Scopus, Web of Science, and Google Scholar electronic databases. We conducted distinct searches for ichthyological studies focusing on each of the basin’s major rivers.
The process of reading, organizing, selecting, and excluding articles was managed using the Start 3.0.3 software (State of the Art through Systematic Review). This program, developed by the Software Engineering and Research Laboratory at the Federal University of São Carlos (UFSCar), facilitates the organization of publications according to a pre-defi-ned review protocol. Full-text articles were accessed through the CAPES Journals Portal via an institutional subscription of the Universidade Paulista (UNIP). Finally, the following data were extracted from each selected article: a) year of publication; b) species reported; c) river; d) specific location; and e) study category (Table I).
Data extracted from the articles, description of the classification and application for each theme analyzed.
Furthermore, historical data on the basin’s ichthyofauna were obtained by consulting the collections of the Zoology Museum of the University of São Paulo (MZUSP) and the Sorocaba Historical Museum. From each publication or report, we extracted information on the investigation type, sampling methods, species list, abundance (where available), and spa-tial distribution. Species were then classified according to their origin: Autochthonous - species native to the Sorocaba River basin; Allochthonous - species native to other Brazilian basins and introduced to the Sorocaba basin; Invasive - species originating from other con-tinents that have established populations in the basin.
Species that could not be identified to the species level, as well as those lacking con-firmed occurrence records or even species introduced but not established in the basin, were excluded from the analysis. The vouchers presented in this manuscript were obtained from the collections (SpeciesLink) and published articles. In cases where the nomenclature was outdated, it was corrected. Taxonomic classification and nomenclature follow Fricke et al. (2025). The conservation status of each species was assessed according to the official list for the State of São Paulo (State Decree 63.853/2018) and the Brazilian National List of Endangered Species (MMA Ordinance Nº 148, 7 June 2022; ICMBio, 2023). For datasets where abundance data were available, we calculated species richness, the Shannon-Wiener diver-sity index, and Pielou’s evenness using PAST software (v. 4.06; Hammer 2021).
RESULTS
Ichthyological studies in the Sorocaba River basin prior to 1992
Many naturalists visited the Sorocaba River basin. Among them, the Austrian Johann Natterer stands out, having collected specimens in Brazil for 18 years (1818-1836). Accord-ing to Straube (2000), Natterer “headed south, traveling along the Fluminense coast, passing through the Paraíba River valley to the Iron Plant at ‘Ypanema’, near Sorocaba.” This loca-tion, situated on a tributary of the Sorocaba River, is now the Ipanema National Forest (Vanzolini 1993). Natterer’s work contributed significantly to the understanding of the ichthyofauna of the Upper Paraná River basin (Dagosta et al. 2024). As documented by Heckel (1840), his notes included the collection date, sex, and provenance of the collected fish spec-imens.
Scholars such as Friedrich Siebenrock, Rudolf Kner, Johann Jacob Heckel, and Le-opold Fitzinger later studied the fish collected by Natterer (Heckel, 1840). Notably, species Natterer collected from the Ipanema River, a tributary of the Sorocaba, were formally described by Rudolf Kner, Franz Steindachner, and Jacob Heckel. For its time, Natterer’s work constituted one of the most significant ichthyological collections from Brazil. The specimens from the Sorocaba region, particularly the Ipanema River, were deposited in the Natural History Museum of Vienna. According to Heckel (1840), Natterer’s journal, which contained information on other potential discoveries, was unfortunately lost in a shipwreck.
Several species were formally described based on specimens collected in the Sorocaba River basin during this period. These include:
-
Prochilodus vimboides Kner 1859 (Prochilodontidae): Described by Rudolf Kner from specimens that Johann Natterer collected in the Ipanema River.
-
Hisonotus depressicauda (Miranda Ribeiro 1918) (Loricariidae): A small catfish collected in the Sorocaba River by E. Von Zeidler and described by Miranda-Ribeiro.
-
Hypostomus ancistroides (Ihering 1911) (Loricariidae): An armoured catfish collec-ted in the Tatuí River and described by R. von Ihering.
While studying the collections of the Paulista Museum (now the MZUSP), Miranda-Ribeiro (1918) also described other notable species. From the Tatuí River, he described Curimatus insculptus Fernández-Yépez (1948) (Curimatidae), which was later reassigned to the genus Steindachnerina Fowler, 1906 by Fernández-Yépez (1948). From the Sorocaba River, he described Pimelodella rudolphi Miranda Ribeiro 1918 (Heptapteridae), a species now considered a junior synonym of Pimelodella meeki Eigenmann 1910. The type specimens for these species described by Miranda-Ribeiro and Ihering are deposited at the Museu de Zoologia da Universidade de São Paulo (MZUSP). A total of eighteen fish species were recognized (Table II) considering collections from the 19th and 20th centuries (up to 1992). Prochilodus vimboides is not included in this table because the specimens are deposited outside of Brazil, and only specimens deposited in collections in the country are considered here.
Species collected in the 19th century and between 1900 and 1992. 1) species deposited at MZUSP; 2) species deposited at ZUEC; 3) species deposited at LIRP. *Itupararanga Reservoir.
Studies carried out since 1993
Ichthyological research in the basin resumed in 1992 with the creation of the Biolo-gical Sciences program at the Pontifical Catholic University (PUC-SP). Research efforts ex-panded further with the establishment of similar programs at the Paulista University (UNIP Sorocaba) in 2005 and the Federal University of São Carlos (UFSCar) in 2008. The evolution of this research, illustrated in Figure 2, shows a sharp increase in scientific output starting around 1993, with productivity sustained over the following decades. Consequently, the number of inventoried species in the basin has steadily increased over the last 30 years. Figure 3 presents all the locations sampled to date, revealing the most sampled regions and gaps where future sampling could be targeted. The surveys conducted have concentrated their sampling along the main channel of the Sorocaba River, its main tributaries, and the Itupararanga Reservoir, areas often corresponding to higher order and more urbanized rea-ches. In contrast, many areas remain unsampled or undersampled, particularly streams loca-ted in rural and less urbanized areas of the basin.
The geographic location of the main ichthyological studies carried out in the Sorocaba River basin.
The primary research themes were community ecology (34.4%), followed by species inventory (14%), population ecology (12.5%), and feeding ecology (7.8%). The other the-mes together account for 31.3%, including biotic integrity, environmental impacts, invasive species, reproduction, and more current topics such as microplastics, extreme events, and biomarkers. While the main collection methods have been gillnets and sieves, the use of electrofishing has increased. The most investigated habitats were rivers, reservoirs, and flo-odplain lakes. In recent years, the number of studies focusing on streams has grown, as these environments are important for documenting new species occurrences and applying novel methods in trophic and functional ecology.
Taxonomic Characterization of the Ichthyofauna of the Sorocaba River Basin
Our literature review identified a total of seven orders, 30 families, and 109 species cited for the basin, of which 93 are native and 16 are non-native (Table III). In total, 69.7% (76) of the species have specimens deposited in five different institutional collections. The orders Characiformes (51 species) and Siluriformes (37 species) were the most speciose, along with the families Acestrorhamphidae (14 species) and Loricariidae (12 species). Most species were categorized as Least Concern (LC). However, several are listed under a threat category at either the national (Brazil) or state (São Paulo) level. Characidium oiticicai Travassos 1967 (Crenuchidae) as vulnerable for Brazil, Prochilodus vimboides Kner 1859 (Prochilodontidade) as vulnerable for Brazil and São Paulo. According to Dagosta et al. (2024) Prochilodus vimboides is a very rare species in the upper Paraná river basin. Furthermore, Bunocephalus larai Ihering 1930 (Aspredinidae), Piaractus mesopotamicus (Holmberg 1887) (Serrasalmidae), Pseudopimelodus mangurus (Valenciennes 1835) (Pseudopimelodidae) and Pimelodella meeki Eigenmann 1910 (Heptapteridae), respectively as Vulnerable, Endangered, Insufficient Data and Insufficient Data (Table III).
Inventory of fish species in the Sorocaba River basin, according to published studies. † non-natives species.
Finally, Table IV highlights the temporal increase in inventoried species. It shows that the highest abundance, richness, and diversity were recorded between 2004 and 2013, whereas ecological dominance was highest in the subsequent period (2014-2025). The most abundant species were Poecilia reticulata Peters 1859 (Poeciliidae) (n = 1911), Psalidodon fasciatus (Cuvier 1819) (Characidae) (n = 1826), Geophagus iporangensis Haseman 1911 (Cichlidae) (n = 1565), and Phalloceros circummontanus Souto-Santos, Mejia, Arcila & Buckup 2025 (Poeciliidae) (n = 1114). The highest species richness was found in the upper Sorocaba and Ipanema rivers, likely because these are the most intensively sampled sites. In terms of total abundance, the upper Sorocaba ranked highest, followed by the associated floodplains and floodplain lakes, the main Sorocaba River channel, and the Ipanema River. The greatest diversity occurred in the Ipanema, upper Sorocaba, and Sarapuí rivers, while dominance was highest in the Pirapora River and the Itupararanga Reservoir (Table V).
Occurrence and abundance of fish species in the Sorocaba River, main tributaries, marginal lagoons and Itupararanga reservoir. *Species documented but number of individuals captured not available. **Species richness considering the species without the number of individuals captured.
Occurrence and/or abundance of fish species in the Sorocaba River basin according to chronological period, species status (N - native or NN - Non-Native species) and threat status according to MMA Ordinance No. 148, of June 7, 2022 (Brazil) and Decree 63.853/2018 of the State of São Paulo (SP). Threat status: Endangered (EN), Vulnerable (VU), Least Concern (LC), Data Deficient (DD) and Near Threat-ened (NT). *species documented, but number of individuals captured not available; **species collected by ongoing research; ***species richness considering the species, without the number of individuals captured.
DISCUSSION
Academic institutions have played a pivotal role in advancing the understanding of the ichthyofauna of the Sorocaba River basin. Since 1993, numerous studies have provided crucial data on species composition, their biological and ecological characteristics, and species-habitat relationships within critical environments such as floodplain lakes, streams, rivers, and reser-voirs. The growth in the species inventory over this period is also noteworthy, jumping from 65 species recorded in 2003 to 71 in 2007, and culminating in the 109 species documented in the present study. The basin’s ichthyofauna represents 27.7% of the 393 species recorded for the state of São Paulo (Oyakawa & Menezes 2011) and 31.9% of the 341 species inventoried for the entire upper Paraná River basin (Dagosta et al. 2024). This species richness is substan-tial for a hydrographic basin of this size (5,269 km²).
Between 1993 and 2009, research in the basin primarily focused on ecology, with an emphasis on fish assemblage composition and structure (Smith 2003). A key study on biotic integrity was also conducted during this period (Marciano et al. 2004). Despite the predominance of these community evel studies, research into species-specific biology began to emerge (Takahashi 2006, Villares et al. 2008). In the subsequent period, while studies on fish assemblages continued (e.g., Stefani & Smith 2014, Nascimento & Smith 2016, Smith et al. 2021), there was a marked increase in research focused on the biology of individual species (e.g., Ribeiro et al. 2014, Villares Junior et al. 2015, Costa & Smith,2019, Lima & Smith 2024, Santos et al. 2024, Miranda et al. 2024, Lima et al. 2025). More recently, research has expanded into new areas, including a focus on stream ecology (e.g., Vaz et al. 2017, Cetra et al. 2017), emerging threats like microplastic pollution (Oliveira et al. 2020, De Paiva et al. 2024), biomarkers (Ludgero et al. 2025), extreme events (Rodrigues et al. 2024, Smith et al. 2024), assessment of the effects of land use and cover and dam failure in a stream on the fish community of a neotropical stream (Nicomedes et al. 2025), and continued assessments of biotic integrity (Viana & Cetra 2018, Silva & Cetra 2021).
Our results show a high concentration of research on fish communities, with a primary focus on the main channel of the Sorocaba River and its tributaries. Studies on community structure are typically common in regional ichthyology, as they are comprehensive and provide a foundational understanding of the local fish fauna and its organization. Fish assemblages in river systems reflect the prevailing biotic and abiotic conditions, including the availability of food resources, shelter, and breeding sites (Bennemann et al. 2000). Therefore, the study of community structure can offer valuable insights into the overall health of an ecosystem. Con-sequently, fish are widely used as bioindicators of environmental quality and serve as crucial tools for ecosystem assessment (Karr 1981, Araújo 1998, Viana & Cetra 2018).
Given this extensive body of work, the Sorocaba River basin is now one of the most well studied in the state of São Paulo. The knowledge generated, which confirms that the basin supports a rich ichthyofauna (e.g., Rodrigues et al. 2008), provides a solid foundation to sup-port future conservation policies and management initiatives. Following community-level in-ventories, research typically progresses to studies on population dynamics and trophic ecology, which address the functional components of the ecosystem. Our literature review reveals that these functional research areas, along with others, remain underexplored in the Sorocaba River basin and represent important knowledge gaps. Despite the extensive research in the main river channels, many smaller sub-basins and headwater streams remain largely unknown. New sur-veys in these areas are needed, integrating taxonomic inventories with ecological and biological investigations. Understanding the trophic structure and functional traits of the ichthyofauna is crucial for comprehending how the aquatic ecosystem functions as a whole.
For instance, studies on invasive species are particularly important, as they offer critical insights into ecosystem integrity by examining the competitive interactions for food and habitat between non-native and native species (Agostinho et al. 2006). Similarly, studies on reproductive biology are essential, as they provide crucial data on species recruitment and identify critical habitat requirements for spawning and larval development (Nascimento & Nakatani 2006). Given these gaps, we recommend that future research in the basin prioritize these underexplored functional topics and geographic areas.
The 16 non-native species identified in this study reveal a complex scenario, with many species yet to be inventoried. This could significantly increase the total number of species that have spread throughout the basin. This issue is complex, especially when it comes to species whose evidence of introduction is controversial or incipient. Furthermore, attention should be given to the species Cyphocharax gillii (Eigenmann & Kennedy 1903), not considered non-native in the inventoried articles for the Sorocaba River basin, but reported by Langeani et al. (2007) as non-native to the Upper Paraná basin and maintained by Dagosta et al. (2024), and Lepthoplosternum pectorale (Boulenger 1895), considered autochthonous by Langeani et al. (2007) for the Upper Paraná but considered non-native by Otta et al. (2018), these being likely to be considered non-native species for the Sorocaba River basin. Future studies are needed to expand knowledge about these species.
It’s crucial to distinguish between introduced species with established populations and those that originate from occasional escapes from fish farms or deliberate releases that fail to establish breeding populations. Records of certain non-native species cited in the literature, such as Colossoma macropomum (Cuvier 1816) (Serrasalmidae), Megaleporinus macrocephalus (Garavello & Britski 1988) (Anostomidae), and Brycon amazonicus (Agassiz 1829) (Bryconidae), likely fall into this latter category and were not included in the inventory for this article. It should be noted that the species Piaractus mesopotamicus (Holmberg 1887), although native to the Upper Paraná and recorded for the basin, has no collections attributed to experimental collections over the years. This may be associated with fish stocking or escapes, a fact that could also be attributed to other native species of the Upper Paraná that are not recorded in the studies carried out, but are reported by fishermen. Species cited in the literature but without proven establishment, like Triportheus signatus (Garman 1890) (Triportheidae), Metynnis lippincottianus (Cope 1870) Serrasalmidae, Clarias gariepinus (Burchell 1822) (Clariidae), and Satanoperca setepele Ota, Deprá, Kullander, da Graça & Pavanelli 2022 (Cichlidae) should be treated with caution. These specimens have not been deposited in collections, and their captures are likely occasio-nal, indicating they may not be established.
Other species, such as tilapia (Coptodon rendalli and Oreochromis niloticus), the com-mon guppy (Poecilia reticulata and Poecilia vivipara), the common armored catfish (Pterygo-plichthys ambrosettii), and carp (Cyprinus carpio and Ctenopharyngodon idella), are all esta-blished in the basin. The species Xiphophorus maculatus (Günther 1866) (Poeciliidae) has been documented in the Sorocaba River (Stefani et al. 2023) and more recently in urban streams within the municipality of Sorocaba. The observation of individuals at different life stages, including fry, suggests this species is in the process of becoming established (unpublished data). The species Heterotilapia buettikoferi (Hubrecht 1881) (Cichlidae) was recently captured in the Ipanema River basin (unpublished data), though information about its origin is limited. Furthermore, we report the presence of Hyphessobrycon flammeus Myers, 1924 (Acestrorham-phidae), an introduced species in the upper Paraná River basin (Dagosta et al. 2024), likely through the aquarium trade. We also report Megalamphodus eques (Steindachner 1882) (Aces-trorhamphidae), which, according to Ota et al. (2015), should be provisionally considered in-vasive, pending further studies to clarify its status.
Another factor affecting the accuracy of literature based species lists is the presence of unresolved taxonomic issues. The lack of modern taxonomic reviews for certain groups may lead to an underestimation of true species richness by masking cryptic diversity. For example, the genus Pimelodella (Heptapteridae) is known to require a comprehensive taxonomic revi-sion, making species-level identification challenging (F.C.T. Lima, pers. comm. 2023). Some species of tetras (Acestrorhamphidae) from the upper Paraná River basin, especially smaller ones with a color pattern of few spots/markings, are difficult to identify specifically due to their subtle diagnostic characteristics. Hemigrammus marginatus Ellis 1911 (Acestrorhamphidae) is an example. The species was described for the São Francisco River basin but was also identified throughout the entire upper Paraná River basin. However, recent studies (e.g., Ota et al. 2015 and Dagosta et al. 2024) have shown that some morphotypes similar to Hemigrammus margi-natus, e.g., Moenkhausia cf. gracilima Eigenmann 1908 (Acestrorhamphidae) and M. bonita Benine, Castro & Sabino 2004 (Acestrorhamphidae) - two non-native species, were being mis-takenly identified as Hemigrammus marginatus, especially in areas close to the Paraná River channel. In fact, Mota et al. (2018) recognized Hemigrammus marginatus lineages only for the São Francisco River basin; the similar morphotype in the upper Paraná River basin is a probable new species. Therefore, the more appropriate identification for this native species in the upper Paraná River basin is Hemigrammus aff. marginatus Ellis 1911 (Acestrorhamphidae).
Synthesizing decades of research data, as done in this study, is crucial for revealing knowledge gaps. Therefore, the present work contributes significantly to the understanding of the ichthyofauna of the Sorocaba River basin an important tributary of the Tietê and upper Paraná systems by identifying under-researched themes to guide future scientific efforts. Nota-bly, official biodiversity maps for São Paulo do not classify the Sorocaba River basin as a high priority for conservation and restoration initiatives (Rodrigues et al. 2008). This low-priority designation is questionable, given that the basin is densely populated and its aquatic habitats are significantly degraded. Furthermore, the basin contains numerous under-explored habitats, such as floodplains and headwater streams, which likely harbor undocumented biodiversity.
The aquatic ecosystems of the Sorocaba River basin including its rivers, floodplains, and streams, are environmentally fragile due to intense urbanization and real estate speculation. Consequently, current land use patterns pose a significant threat to the conservation of these environments. This fragility is exacerbated by the weakening of regulations requiring the main-tenance of native riparian buffers around water bodies, as well as by the increasing anthropiza-tion of formerly protected areas (Silva et al. 2020, 2021). Specifically, recent chan-ges in environmental legislation have made wetlands smaller than one hectare particularly vul-nerable by removing the legal obligation to preserve surrounding native vegetation (Grasel et al. 2018).
Furthermore, recent federal legislation governing Permanent Preservation Areas (APPs) along urban watercourses is a critical factor. This law allows municipalities to establish diffe-rent regulations for riparian zones than those mandated by the national Forest Code. This can seriously threaten fish conservation in urban streams, as commercial and real estate interests may take precedence over the ecological function of APPs (Silva et al. 2020). This contributes to what Pelicice et al. (2021) describe as a pessimistic scenario, characterized by unsustainable policies and pressure for short-term development based on high-impact activities.
Potential solutions include establishing protected “free-flowing” rivers (Azevedo-Santos et al. 2019) and strictly preserving remaining riparian habitats (Dala-Corte et al. 2020). However, implementing such measures is often incompatible with current development models. The lack of effective conservation policies exacerbates the regional biodiversity crisis and jeo-pardizes essential ecological services that support human well being (Pelicice et al. 2021). The challenges facing the Sorocaba River basin exemplify this conflict. Concerted action is urgently needed, bringing together the basin committee, municipal environmental councils, government agencies, and other sectors of society to address the severe degradation and mitigate the extin-ction risk facing several fish species. Ultimately, balancing economic development with envi-ronmental conservation remains a significant and ongoing challenge.
CONCLUSIONS
The Sorocaba River basin comprises a rich ichthyofauna that is widely distributed in sev-eral environments and, according to the numerous published works, is also recognized. Re-search is still required, particularly in delicate yet significant ecosystems like floodplains and streams. This work serves as a crucial guide for the ongoing research because of the information presented. While there may still be species that the scientific community is unaware of, it is hoped that new studies will be proposed with themes and in locations that have not been inves-tigated extensively or at all. At the same time, systematic research will be developed.
The Sorocaba River basin supports a rich and widely distributed ichthyofauna, a fact now well-established by numerous scientific publications. However, further research is still needed, particularly in sensitive yet ecologically significant habitats such as floodplains and headwater streams. By synthesizing the available knowledge and identifying these key research gaps, the present study serves as a crucial guide for future investigations.
Acknowledgements
The authors expresstheir gratitude to the Vice-Rectory of Postgraduate Studies and Research for granting a research scholarship, and to the Laboratory of Structural and Functional Ecology of Ecosystems at UNIP’s Sorocaba campus for providing logistical support. We would also like to thank Luis Gustavo Nogueira Carvalho for preparing the maps and Natália Silva Alves for her assistance in formatting and compiling data from scientific collections. We are also grateful to professors Mauricio Cetra, Francisco Langeani Neto, Flávio C. T. Lima, and Fernando Carvalho, as well as the anonymous reviewers, for their careful rea-ding of the manuscript and insightful suggestions. Finally, we dedicate this manuscript to the memory of Prof. Dr. Walter Barrella (in memoriam). He not only inspired me to become an ichthyologist but also pioneered ichthyological studies in the Sorocaba River basin. The authors declare that they have no conflict of interest related to the publication of this manuscript.
References
- AGOSTINHO AA, PELICICE FM & JÚLIO JR HF. 2006. Biodiversidade e introdução de espécies de peixes: unidades de conservação. Unidades de Conservação: ações para valorização da biodiversidade. In: Campos JB, Tossulino MGP & Muller CRC (Eds), Instituto Ambiental da Paraná, Curitiba, p. 95-117.
- AGOSTINHO AA, THOMAZ SM & GOMES LC. 2005. Conservação da biodiversidade em águas continentais do Brasil. Megadiversidade 1(1): 70-78.
- ARAÚJO FG. 1998. Adaptação do índice de integridade biótica usando a comunidade de peixes para o rio Paraíba do Sul. Rev Bras Biol 58(4): 547-558.
-
ARAÚJO L, SOUSA F, MORAES NETO J, SOUTO J & REINALDO L. 2009. Bacias hidrográficas e impactos ambientais. Qualitas Revista Eletrônica 8(1): http://dx.doi.org/10.18391/qualitas.v8i1.399.
» https://doi.org/10.18391/qualitas.v8i1.399 - ATLAS SOCIO AMBIENTAL. 2009. Um retrato da bacia hidrográfica dos Rio Sorocaba e Médio Tietê. Instituto de Educação e Pesquisa Ambiental, 40 p.
-
AZEVEDO-SANTOS VM ET AL. 2019. Protected areas: A focus on Brazilian freshwater biodiversity. Divers Distrib 25(3): 442-448. https://doi.org/10.1111/ddi.12871.
» https://doi.org/10.1111/ddi.12871 - BENNEMANN ST, SHIBATTA OA & GARAVELLO JC. 2000. Peixes da bacia do rio Tibagi: uma abordagem ecológica. Londrina: EDUEL.
- CBH-SMT. 2013. Relatório de Situação do CBH-SMT, ano base 2012. Sorocaba, SP, 36 p.
-
CETESB. 2023. Relatório de qualidade ambiental do Estado de São Paulo 2022. Disponível em: https://cetesb.sp.gov.br/aguas-interiores/wp-content/uploads/sites/12/2023/09/Relatorio-de-Qualidade-das-Aguas-Interiores-no-Estado-de-Sao-Paulo-2022.pdf
» https://cetesb.sp.gov.br/aguas-interiores/wp-content/uploads/sites/12/2023/09/Relatorio-de-Qualidade-das-Aguas-Interiores-no-Estado-de-Sao-Paulo-2022.pdf -
CETRA M, PETRERE JR M & BARRELLA W. 2017. Relative influences of environmental and spatial factors on stream fish assemblages in Brazilian Atlantic rainforest. Fish Manag Ecol 24: 139-145. http://dx.doi.org/10.1111/fme.12207
» http://dx.doi.org/10.1111/fme.12207 -
COSTA MS & SMITH WS 2019. Population structure and natural diet of Astyanax cf. paranae Eigenmann 1914 a typical species of neotropical headwaters streams. Acta Scientiar Biol Sci 41: e45400. http://dx.doi.org/10.4025/actascibiolsci.v41i1.45400.
» https://doi.org/10.4025/actascibiolsci.v41i1.45400 -
DAGOSTA FCP ET AL. 2024. Fishes of the upper Paraná river basin: diversity, biogeography and conservation. Neotrop Ichthyol 22(1): e230066. https://doi.org/10.1590/1982-0224-2023-0066.
» https://doi.org/10.1590/1982-0224-2023-0066 -
DALA-CORTE RB ET AL. 2020. Thresholds of freshwater biodiversity in response to riparian vegetation loss in the Neotropical region. J Appl Ecol 57: 1391-1402. https://doi.org/10.1111/1365-2664.13657.
» https://doi.org/10.1111/1365-2664.13657 -
DE PAIVA FC ET AL. 2024. Evaluation of microplastic pollution in gills of freshwater fish in a neotropical hydrographic basin, Brazil. WaterAir Soil Pollut 35: 677. https://doi.org/ 10.1007/s11270-024-07492-9.
» https://doi.org/10.1007/s11270-024-07492-9 -
FRICKE R, ESCHMEYER WN & FONG JD. 2023. Eschmeyer’s catalog of fishes: genera/ species by family/subfamily [Internet]. San Francisco: California Academy of Science; 2023. Available at: https://researcharchive.calacademy.org/research/ichthyology/catalog/SpeciesByFamily.asp
» https://researcharchive.calacademy.org/research/ichthyology/catalog/SpeciesByFamily.asp -
GARFIELD E. 2009. From the Science of Science to Scientometrics Visualizing the History of Science with HistCite Software. J Informetr. 3: 173-179. http://dx.doi.org/10.1016/j.joi.2009.03.009.
» https://doi.org/10.1016/j.joi.2009.03.009 -
GRASEL D, MORMUL RP, BOZELLI RL, THOMAZ SM & JARENKOW JA. 2018. Brazil’s native vegetation protection law threatens to collapse pond functions. Perspect Ecol Conserv 16(4): 234-237. https://doi.org/10.1016/j.pecon.2018.08.003.
» https://doi.org/10.1016/j.pecon.2018.08.003 -
HAMMER Ø. 2021. PAST – PAleontological STatistics, Version 4.06. Natural History Museum, University of Oslo. Disponível em: https://www.nhm.uio.no/english/research/resources/past/
» https://www.nhm.uio.no/english/research/resources/past/ - HECKEL J. 1840. Johann Natterer’s neue Flussfische brasilien’s. Annalen des Wiener Museums der Naturgeschichte 2: 327-479.
-
IBGE. 2023. Censo Demográfico 2022: População e domicílios. Rio de Janeiro. Disponível em: https://www.ibge.gov.br/cidades-e-estados/rj/rio-de-janeiro.html Acesso em: 31 jul. 2026.
» https://www.ibge.gov.br/cidades-e-estados/rj/rio-de-janeiro.html -
ICMBIO. 2023. Sistema de Avaliação do Risco de Extinção da Biodiversidade – SALVE. Disponível em: https://salve.icmbio.gov.br/ Acesso em: 08 de março de 2024.
» https://salve.icmbio.gov.br/ - KARR JR. 1981. Assessment of biotic integrity using fish communities. Fisheries 6: 21-27.
-
LANGEANI F, CASTRO RMC E, OYAKAWA OT, SHIBATTA OA, PAVANELLI CS & CASATTI L. 2007. Diversidade da ictiofauna do Alto Rio Paraná: composição atual e perspectivas futuras. Biota Neotrop 7(3): 181-197. https://doi.org/10.1590/S1676-06032007000300020.
» https://doi.org/10.1590/S1676-06032007000300020 -
LIMA TRF, DOS SANTOS TMR & SMITH WS. 2025. Dieta, relação peso-comprimento e uso de habitat de Piabina argentea Reinhardt 1867 em um rio neotropical. Oecologia Australis 29(2): 158-166. http://doi.org/10.4257/oeco.2025.2902.05.
» https://doi.org/10.4257/oeco.2025.2902.05 -
LIMA TRF & SMITH WS. 2024. Aspects of the ecology of Leporinus striatus Kner 1858 as a support for its conservation in a Federal Conservation Unit. Acta Scientiar Biol Sci 46(1): e69943. https://doi.org/10.4025/actascibiolsci.v46i1.69946.
» https://doi.org/10.4025/actascibiolsci.v46i1.69946 -
LUDGERO M, XAVIER JG, DOS SANTOS TMR, CARVALHO LGN, SILVA LLM & SMITH WS. 2025. Melanomacrophage Centers as a Histological Indicator of the Influence of Land Use on the Health of Prochilodus lineatus (Vallenciennes, 1837): Comparison between Two Neotropical Rivers. Ecotoxicol Environ Contam 20(1): 35–44. https://doi.org/10.5132/eec.2025.01.04.
» https://doi.org/10.5132/eec.2025.01.04 -
MIRANDA JFCT, LIMA TRF, SANTOS TMR, ALVES, NS, CONCEIÇÃO DE PAIVA F, ALVES NS & SMITH WS. 2024. Population structure and weight-length relations-hip of Hyphessobrycon bifasciatus Ellis 1911 in a dammed stream. Acta Scientiar Biol Sci 46(1): e71181. https://doi.org/10.4025/actascibiolsci.v46i1.71181.
» https://doi.org/10.4025/actascibiolsci.v46i1.71181 - MOTA TF ET AL. 2018. Molecular characterization of Moenkhausia (Pisces: Characiformes) populations with different lateral line developmental levels. An Acad Bras Cienc 90(3): 2815-2825.
- NASCIMENTO FL & NAKATANI K. 2006. Relações entre fatores ambientais e a distribuição de ovos e larvas de peixes na sub-bacia do rio Ivinhema, Estado de Mato Grosso do Sul, Brasil. Acta Scientiar Biol Sci 28(2): 117-122.
- NASCIMENTO MB & SMITH WS. 2016. A ictiofauna da bacia do rio Sarapuí, SP, Brasil: estrutura das assembleias e a influência de diferentes variáveis ambientais. Rev Braz J Aquat Sci Technol 20(1): 29-42.
-
NICOMEDES NP, SANTOS TMR, CARVALHO LGN DE, PRIETO BCG, BENTO CS, SILVA LLM, PAIVA FC DE, ALVES NS & SMITH WS. 2025. Long-Term Effects of Land Use and Cover Change and Dam Rupture on Ichthyofauna in a Neotropical Stream International. Rev Hydrobiol: e70006. https://doi.org/10.1002/iroh.70006
» https://doi.org/10.1002/iroh.70006 -
OLIVEIRA CWS, CORRÊA CS & SMITH WS. 2020. Food ecology and presence of microplastic in the stomach content of neotropical fish in an urban river of the upper Paraná River Basin. Rev. Ambient. Água 15(4): e2551. doi:10.4136/1980-993X.
» https://doi.org/10.4136/1980-993X -
OTA RP, LIMA FCT & PAVANELLI CS. 2015. A new species of Hemigrammus Gill, 1858 (Characiformes: Characidae) from the central and western Amazon and rio Paraná-Paraguai basins. Zootaxa 3948(2): 218-232. doi.org/10.11646/zootaxa.3948.2.4.
» https://doi.org/10.11646/zootaxa.3948.2.4 - OYAKAWA OT & MENEZES NA. 2011. Checklist of fresh water fishes from São Paulo State, Brazil. Biota Neotrop 11(1a): http://www.biotaneotropica.org.br/v11n1a/en/abstract?inventory+bn0021101a2011.
-
PELICICE FM, BIALETZKI A, CAMELIER P, CARVALHO FR, GARCÍA-BERTHOU E, POMPEU PS, MELLO FT & PAVANELLI CS. 2021. Human impacts and the loss of Neotropical freshwater fish diversity. Neotrop Ichthyol 19(3): e210134. https://doi.org/10.1590/1982-0224-2021-0134.
» https://doi.org/10.1590/1982-0224-2021-0134 - RIBEIRO AR, BIAGIONI RC & SMITHWS. 2014. Estudo da dieta natural da ictiofauna de um reservatório centenário, São Paulo, Brasil. Rev Iheringia Sér Zool 104(4): 404-412.
- RODRIGUES KFS, FERRARI F, PRIETO BCG, MIRANDA JFCT, SILVA LLM & SMITH WS. 2024. A seca de 2019: operações de resgate e realocação de peixes conduzidas na Floresta Nacional de Ipanema, Iperó, São Paulo, Brasil. Biodivers Bras 14(4): 29-42. https://doi.org/10.37002/ biodiversidadebrasileira.v14i4.2508.
- RODRIGUES RR ET AL. 2008. Diretrizes para conservação e restauração da biodiversidade no Estado de São Paulo. Governo do Estado de São Paulo, São Paulo.
- SANTOS TMR, MIRANDA JFCT, LIMA TRF, PAIVA FC, ALVES NS & SMITH WS. 2024. Population structure and weight-length relationship of Hyphessobrycon bifasciatus Ellis 1911 in a dammed stream. Acta Scientiar Biol Sci 46: e71181.
-
SILVA FL, STEFANI MS, SMITH WS, CUNHA-SANTINO MB & BIANCHINI JÚNIOR I. 2021. Áreas úmidas brasileiras: bases para o gerenciamento, serviços ecossistêmicos e estratégias de manejo. Revista Caminhos de Geografia 22(79): 97-111. http://doi.org/10.14393/RCG227953473.
» https://doi.org/10.14393/RCG227953473 -
SILVA FL, STEFANI MS, SMITH WS, SCHIAVONE DC, CUNHA-SANTINO MB & BIANCHINI JÚNIOR I. 2020. An applied approach for the assessment of anthropogenic disturbances in urban wetlands and the contributor river. Ecol Complex 43: 1-12. https://doi.org/10.1016/j.ecocom.2020.100852.
» https://doi.org/10.1016/j.ecocom.2020.100852 - SILVA GRCA & CETRA M A. 2021. Stream multimetric fish index in a large-sized city in southeastern Brazil. Acta Limnologica Brasiliensia 33: e14.
- SMITH WS. 2003. Os peixes do rio Sorocaba: a história de uma bacia hidrográfica. TCM.
- SMITH WS & BARRELLA W. 2000. The ichthyofauna of the marginal lagoons of the Sorocaba river, SP, Brazil: Composition, abundance and effect of the anthropogenic actions. Rev Bras Biol 60: 627-632.
- SMITH WS, HALCSIK L, BIAGIONI RC, PINHEIRO LAS & STEFANI MS. 2021. An updated list of the ichthyofauna of Ipanema National Forest, São Paulo, Brazil. Check List 17(3): 827-840.
-
SMITH WS ET AL. 2024. Extreme events and ichthyofauna: case report of a neotropical river. Rev Ambient Água, 19:e3011. https://doi.org/10.4136/ambi-agua.3011.
» https://doi.org/10.4136/ambi-agua.3011 - SMITH WS, PETRERE M & BARRELLA W. 2007. Lists of species. Fish, Sorocaba river sub-basin, state of São Paulo, Brazil. Check List 3(3): 282-286.
- SMITH WS, STEFANI MS, SOINSKI TA, CETRA M, SILVA GRCA, BERNARDO RH & PINHEIRO LAS. 2020. Ictiofauna do Município de Sorocaba, SP, Brasil. In: Smith WS (Ed), Biodiversidade do Município de Sorocaba: Atualização e subsídios para a sua conservação, p. 200–214.
- STEFANI MS & SMITH WS. 2014. A ictiofauna do rio Tatuí, SP, Brasil sob influência de impactos ambientais. Rev Braz J Aquat Sci Technol 18(2): 43-52.
-
STEFANI MS, SILVA FL & SMITH WS. 2023. First record of the exotic species platyfish Xiphophorus maculatus (Günther, 1866) in an urban floodplain of a Brazilian neotropical river. Acta Limnol Brasiliensia 35: e7. https://doi.org/10.1590/S2179-975X3622 ISSN 2179-975X.
» https://doi.org/10.1590/S2179-975X3622 - STRAUBE FC. 2000. Johann Natterer (1787 – 1843) Naturalista-Maior do Brasil. Nattereria 1: 1-13.
- TAKAHASHI ELH. 2026. Ciclo reprodutivo da tabarana, Salminus hilarii (Valenciennes, 1849) (Characidae, Salmininae) na região do Baixo rio Sorocaba, SP. Jaboticabal, 202 p. Dissertação de Mestrado, Universidade Estadual Paulista. Disponível em: http://www.caunesp.unesp.br/publicacoes/dissertacoes_teses/dissertacoes/Dissertacao%20Erico%20Luis%20Hoshiba%20Takahashi.pdf. (Unpublished).
-
TONELLA LH ET AL. 2023. NEOTROPICAL FRESHWATER FISHES: A dataset of occurrence and abundance of freshwater fishes in the Neotropics. Ecology 104(4): e3713. doi: 10.1002/ecy.3713.
» https://doi.org/10.1002/ecy.3713 - VANZOLINI PE. 1993. As viagens de Johann Natterer no Brasil, 1817–1835. Pap Avulsos Zool 38(3): 17-60.
-
VANZOLINI PE. 1996. A contribuição Zoológica dos primeiros naturalistas viajantes no Brasil. Revista USP 30: 190-238. https://doi.org/10.11606/issn.2316-9036.v0i30p190-238.
» https://doi.org/10.11606/issn.2316-9036.v0i30p190-238 -
VIANA MA & CETRA M. 2018. Adaptação de um índice de integridade biótica (IIB) com Peixes de riachos do alto rio sorocaba (SP). REGA 15: e14. doi: 10.21168/rega.v15e15.
» https://doi.org/10.21168/rega.v15e15 - VILLARES GA, GOMIERO LM & GOITEIN R. 2008. Alimentação de Serrasalmus maculatus (Kner, 1858) (Characiformes; Serrasalmidae) no trecho inferior bacia do rio Sorocaba, São Paulo, Brasil. Acta Sci Biol Sci 30(3): 267-273.
- VILLARES JR GA, GOMIERO LM & GOITEIN R. 2015. Variations of Salminus hilarii diet (Ostariophysi, Characidae): seasonal and ontogenetic effects. Braz J Biol 75(3): 574-580.
Edited by
-
Handling editor
Alexander Kellner
Supporting data are available at https://data.scielo.org/dataset.xhtml?persistentId=doi:10.48331/scielodata.WYEM79.
