Biodiversity Data Journal 11: e98632 OO) doi: 10.3897/BDJ.11.e98632 open access Taxonomy & Inventories Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern Brazil Lucas O. Vieira#$, Diego S. CamposS!, Rafael F. Oliveira$-l, Josie South*, Marcony S.P. Coelho§, Mauricio J.S. Paiva$, Pedro H.N. Braganca™", Erick C. Guimaraes“: , Axel M. Katz , Pamella S. Brito”: , Jadson P. Santos , Felipe P. Ottonit$- + Universidade Federal do Maranhao, Centro de Ciéncias de Chapadinha, Campus de Chapadinha, Programa de Pos- Gradua¢ao em Ciéncias Ambientais, BR-222, KM 04, Boa Vista, CEP: 65500-000, Chapadinha, Brazil § Universidade Federal do Maranhao, Centro de Ciéncias de Chapadinha, Campus de Chapadinha, Laboratorio de Sistematica e Ecologia de Organismos Aquaticos, BR-222, KM 04, S/N, Boa Vista, CEP: 65500-000, Chapadinha, Brazil | Universidade Federal do Maranhao, Programa de Pés-Graduagao em Biodiversidade e Biotecnologia da Amazénia Legal, Av. dos Portugueses, 1966, Cidade Universitaria Dom Delgado, 65080-805, Sao Luis, Brazil 4 Universidade Federal do Maranhdo, Programa de Pés-Graduagao em Biodiversidade e Conservacao, Av. dos Portugueses, 1966, CEP: 65085-580, Sao Luis, Brazil # School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom = South African Institute for Aquatic Biodiversity, Grahamstown, South Africa « Universidade Federal do Oeste do Para, Instituto de Ciéncias da Educagao, Programa de Pds-graduacao Sociedade Natureza e Desenvolvimento, Av. Marechal Rondon s/n, CEP: 68040-070, Santarém, PA, Brasil, Belém, Brazil » Universidade Federal do Maranhado, Departamento de Biologia, Laboratério de Genética e Biologia Molecular, Av. dos Portugueses 1966, Cidade Universitaria do Bacanga, CEP: 65080-805, Sao Luis, Brazil “ Universidade Estadual do Maranhao, Laboratorio de Ictiofauna e Piscicultura Integrada, Centro de Ciéncias Agrarias, Campus Paulo VI, avenida Lourengo Vieira da Silva, n. 1000, bairro Jardim Sao Crist6vao, CEP: 65.055-310, Sao Luis, Brazil ” Universidade Federal do Rio de Janeiro, Laboratorio de Sistematica e Evolucdo de Peixes Teledsteos, Programa de Pés- Graduagao em Biodiversidade e Biologia Evolutiva, Instituto de Biologia, CEP: 21.941-902, Rio de Janeiro, Brazil Corresponding author: Felipe P. Ottoni (fpottoni@gmail.com) Academic editor: Rupert Collins Received: 09 Dec 2022 | Accepted: 03 Feb 2023 | Published: 10 Feb 2023 Citation: Vieira LO, Campos DS, Oliveira RF, South J, Coelho MS.P, Paiva MJ.S, Bragancga PH.N, Guimaraes EC, Katz AM, Brito PS, Santos JP, Ottoni FP (2023) Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern Brazil. Biodiversity Data Journal 11: e€98632. https://doi.org/10.3897/BDJ.11.e98632 Abstract Background The Maranhao State harbours great fish diversity, but some areas are still undersampled or little known, such as the Munim River Basin in the northeast of the State. This lack of © Vieira L et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 2 Vieira L et al knowledge is critical when considering anthropogenic impacts on riverine systems especially in the face of major habitat destruction. These pressing threats mean that a comprehensive understanding of diversity is critical and fish checklists extremely relevant. Therefore, the present study provides a checklist of the fish species found in the Munim River Basin, Maranhao State, north-eastern Brazil, based on collected specimens. New information A total of 123 species were recorded for the Munim River Basin, with only two non-native species, Oreochromis niloticus and Colossoma macropomum, showing that the fish assemblage has relatively high ecological integrity. In addition, 29 species could not be identified at the species level, indicating the presence of species that are probably new to science in the Basin. A predominance of species belonging to the fish orders Characiformes and Siluriformes, with Characidae being recovered as the most species-rich family (21 species) agrees with the general pattern for river basins in the Neotropical Region. The total fish diversity was estimated by extensive fieldwork, including several sampling gears, carried out in different seasons (dry and rainy) and exploring different environments with both daily and nocturnal sampling, from the Basin's source to its mouth. A total of 84 sites were sampled between 2010 and 2022, resulting in 12 years of fieldwork. Fish assemblages were distinct in the Estuary and Upper river basin sections and more similar in the Lower and Middle sections indicating environmental filtering processes. Species were weakly nested across basin sections, but unique species were found in each section (per Simpsons Index). High variability of species richness in the Middle river basin section is likely due to microhabitat heterogeneity supporting specialist fish communities. Keywords biodiversity, endemism, freshwater, migratory species, taxonomy. Introduction The Neotropical Region comprises the most biodiverse freshwater ichthyofauna on the planet, with more than 6000 described species (Reis et al. 2016, Albert et al. 2020). Within the Neotropics, South America harbours the world's greatest diversity of freshwater fishes, including about 5160 described species, which represents about one-third of all known freshwater species (Reis et al. 2016, Pelicice et al. 2017, Castro and Polaz 2020). Studies on diversity of the region have produced estimates which are much higher, predictions being between 8000 to 9000 described and undescribed freshwater fish species (Reis et al. 2016, Birindelli and Sidlauskas 2018, Castro and Polaz 2020, Albert et al. 2020, Koerber et al. 2022). This high diversity is mainly comprised of medium- to small-sized species (species that do not surpass 15 cm standard length), corresponding to 70% of the species (Reis et al. 2003, Castro and Polaz 2020). Small and medium-sized species are broadly distributed throughout all aquatic habitats, which is most likely due to niche Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... 3 partitioning, life history traits adapted to stochastic environments and high trophic plasticity (Vazzoler 1996, Castro 1999, Lowe-Mcconnell 1999, Abelha et al. 2001, Guimaraes et al. 2020, Castro and Polaz 2020, Corréa and Castro 2021). Despite the description of small- and medium-sized fish diversity in scientific journals, they remain largely unnoticed by the general public and neglected by conservation agencies and policies (Castro 1999, Castro et al. 2005, Abell et al. 2011, Albert et al. 2011, Castro and Polaz 2020). Brazil possesses the highest number of freshwater fish species in South America (Buckup et al. 2007, Castro and Polaz 2020), with about 100 new species being described every year over the last decade (Nelson et al. 2016, Reis et al. 2016, Fricke et al. 2022). However, several of these species represent endemics, with narrow distributions and some are highly threatened due to increased anthropogenic pressure on their natural habitats (Reis et al. 2003, Nogueira et al. 2010, Darwall et al. 2018, Reid et al. 2019). Brazilian freshwaters are subject to multitude anthropogenic threats, such as: deforestation resulting in suppression or reduction of the original vegetation cover, due to logging and expansion of agricultural and urban areas; release of domestic and industrial effluents and chemical products from agricultural activities in aquatic environments, resulting in pollution; irregular water abstraction for different urban, industrial and agricultural uses; soil erosion and silting of the environments; river damming and construction of hydroelectric power plants, disrupting fish migration routes and destroying the natural habitats of fish species; extraction of sand from the riverbeds; mining, resulting in modification of habitats and water pollution and contamination; modification and diversion of the river channels; introduction of non-native species; overharvesting for the aquarium trade; ghost fishing; and overfishing of food fishes (Dudgeon et al. 2006, Pereira et al. 2016, Pelicice et al. 2017, Reid et al. 2019, Zarfl et al. 2019, Zeni et al. 2019, Bergmann et al. 2020, Castro and Polaz 2020, Ottoni et al. 2021, Azevedo-Santos et al. 2021, Doria et al. 2021, Vitorino et al. 2022, Rocha et al. 2023). Despite the high freshwater native fish diversity, non-native fish species have proliferated in Brazil and in Brazilian hydrographic systems where they do not occur naturally due to several human activities, such as: aquaculture, intentional introductions and release, aquarium trade, mosquito larvae biological control interventions, transposition of water between isolated river basins, sport fishing, amongst other activities (Figueredo and Giani 2005, Azevedo-Santos et al. 2011, Vitule et al. 2015, Latini et al. 2016, Padial et al. 2017, Braganga et al. 2020, Doria et al. 2021, Ottoni et al. 2021, Franco et al. 2022, Rocha et al. 2023). Non-native species have caused changes in the local assemblage composition and in the abundance of native species populations, causing major environmental impacts (Giacomini et al. 2011, Latini et al. 2016, Padial et al. 2017, Doria et al. 2021, Ottoni et al. 2021, Rocha et al. 2023). Maranhao is the westernmost state in north-eastern Brazil, bordered by the Piaui State in the east, from whom it is separated by the Parnaiba River; by Tocantins State in the south and southeast, from which it is separated by the Tocantins River; and by Para State in the west, from which it is separated by the Gurupi River (Rebélo et al. 2003). Maranhao total area is about 330000 km?, corresponding to 3.9% of Brazil's territory (Rebélo et al. 2003, Rios 2005, Batistella et al. 2014, Spinelli-Araujo et al. 2016). Maranhao is an extremely important State in terms of biodiversity, housing three of the main Brazilian biomes, as well 4 Vieira L et al as transition areas between them. The Cerrado biome is present in the central, eastern and southern portion of the State; the Amazon biome is present in the western and central portion; and the Caatinga biome is found in the easternmost portion of the State (Rebélo et al. 2003, Rios 2005, Batistella et al. 2014, Spinelli-Araujo et al. 2016). Thus, Maranhao includes a phytogeographic mosaic due to the presence and overlap of floral elements typical of these three distinct biomes, besides the presence of complex transition areas, making the State extremely biodiverse, ecologically relevant and a key area for conservation (Rebélo et al. 2003, Rios 2005, Batistella et al. 2014, Spinelli-Araujo et al. 2016). In the past two decades, several fish surveys were carried out in Maranhao, in both freshwater and estuarine environments, increasing the knowledge of the State's fish fauna (Castro 2001, Castro et al. 2002, Piorski et al. 2003, Pinheiro-Junior et al. 2005, Soares 2005, Piorski et al. 2007, Castro et al. 2010, Barros et al. 2011, Sousa et al. 2011, Fraga et al. 2012, Almeida et al. 2013, Ribeiro et al. 2014, Ramos et al. 2014, Lima et al. 2015, Matavelli et al. 2015, Melo et al. 2016, Nascimento et al. 2016, Piorski et al. 2017, Brito et al. 2019, Lima et al. 2019, Teixeira et al. 2019, Nunes et al. 2019, Guimaraes et al. 2020, Brito et al. 2020, Oliveira et al. 2020, Guimaraes et al. 2021c, Guimaraes et al. 2021a, Guimaraes et al. 2021b). Information about the ichthyofauna of the coastal Munim River Basin, however, is scarce. At the same time, this river basin is under severe anthropogenic pressure from deforestation of marginal vegetation, pollution, contamination of the water, erosion, siltation and even the loss of water bodies (Ribeiro et al. 2006, Ribeiro and Nunes 2017). The Munim River Basin has only five published studies documenting its fish diversity (Ribeiro et al. 2014, Matavelli et al. 2015, Nunes et al. 2019, Oliveira et al. 2020, Guimaraes et al. 2021c). These, however, focused on specific localities and environments and, in many cases, surveying only similar and neighbouring sites within this river basin. As a consequence, the fish fauna of the Munim River Basin still awaits a more comprehensive checklist. The main goal of the present study is to present a detailed inventory of the fish diversity in the Munim River Basin, through the analysis and study of data sampled over 12 years of fieldwork, providing species-level identifications when possible. The study covered the entire river basin and includes relevant information about the importance of checklists in contributing to the knowledge of the river basin, species conservation and distribution. In addition, we provide here ecological and biogeographical comments. Materials and methods Study area Sampling was carried out in rivers, streams, lagoons, swamps, marshes, lakes and the estuary of the Munim River Basin, northeast of the Maranhao State, north-eastern Brazil. The Munim River Basin source is at the Caxias Municipality, in the Cerrado Biome and its mouth is at baia of Sao José in a region known as "Golfao Maranhense" between the Axixa and Icatu municipalities, within the Cerrado and Amazon biomes (Fig. 1). The Munim River Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... 5 Basin has an area of about 15918.04 km2, with 331.74 km from its source to its mouth (Nugeo 2016, Rios 2005). ~~ 0 7.3) @u75 xy Ks L70 3°0'0.00°S 3°18'0.00"S ae Ce _ Boundaries ..[" States ‘Sampling sites @ Collections a () Capital River basin sections 7) . S S o $? ” 4°12'0.00"S 3°54'0.00"S 4°30'0.00°S 44°6'0.00°W 43°48'0.00°W 43°30'0.00"W 43°12'0.00"W 42°54'0.00"W 42°36'0.00"W Figure 1. EES] Map with sampling sites along the Munim River Basin. Sample sites are listed in Table 1 and illustrated on the map as L1-L84. MA = State of Maranhao and PI = State of Piaui. In the highlighted squares are the geographically close sample sites, for better visualisation. River basin sections: Estuary section (green), Lower section (orange), Middle section (lilac) and Upper section (pink). Sampling sites Sampling was carried out in 84 collecting sites, covering four different sections of the Munim River Basin, in both rainy (January to May) and dry (June to December) seasons according to Passos et al. (2016). The sampling was done between 2010 and 2022 (about 65% of the surveys were carried out between 2019 and 2022), including sites close to its source and to its mouth (Fig. 1). The sampled environments included rivers, streams, Vieira L et al lagoons, swamps, marshes, lakes and the estuary (Table 1, Fig. 2, Suppl. material 1). Table 1. Sampling sites at the Munim River Basin, Maranhao, Brazil. *Localities with the presence of non- native species. Locality number (L) 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 Locality Stream in the balneario at the entrance of Anapurus *Stream at balneario Sao Loureng¢o Stream at balneario Recanto do Buriti Riacho crossing the road at Pocgos community Stream at Caraibas community Riacho Xoror6 at Aparecida neighbourhood Stream at Aldeia neighbourhood Stream at Aldeia neighbourhood Stream at Terra Duras neighbourhood Riacho Feio, Boa Vista community *Riacho Feio, Boa Vista community Riacho Feio, Sao José community *Riacho Feio, Sao José community Riachinho, Cumbre community Riachinho, Agua Branca community Municipality Anapurus - MA Anapurus - MA Anapurus - MA Anapurus - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Coordinates 03°40'15.28"S 043°07'9.7"W 03°39'16.30"S 043°6'50.2"W 03°40'53.04"S 043°7'23.0"W 03°33'44.61"S 043°3'52.4"W 03°56'7.71"S 043°26'14.8"W 03°44'2.23"S 043°22'1.21"W 03°45'7.75"S 043°21'32.7"W 03°44'53.1"S 043°21'32.6"W 03°45'6.42"S 043°22'24.7"W 03°50'51.8"S 043°18'50.5"W 03°50'46.8"S 043°18'48.9"W 03°51'6.30"S 043°17'53.0"W 03°51'18.7"S 043°17'14.4"W 03°51'46.8"S 043°17'10.2"W 03°53'13.5"S 043°16'37.1"W Altitude River basin section 81m Middle 75m Middle 76m Middle 71m Middle 51m Middle 81m Middle 74m Middle 80m Middle 65m Middle 44m Middle 40m Middle 45m Middle 47m Middle 52m Middle 59m Middle Locality number (L) 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Locality Riacho Feio, Riacho Feio community Rio Iguara, Malhadinha community Rio Iguara, Malhadinha community Rio Iguara, Pogo Cumprido community Stream at Itamacaoca forest Stream at balneario Repouso do Guerreiro Stream at Itamacaoca forest Itamacaoca dam Stream just after Itamacaoca dam Jabuti community, Tinguis road Rio Preto at Bom Sucesso community Swampy areas at Brejo do Meio community Stream behind the Mix Atacarejo Mateus store Rio Munim, Carnauba Amarela community Rio Munim, Porgées bridge *Rio Munim, Cedro community Rio Munim, Riacho Fundo community Rio Munim, bridge at Mangabeira community Stream at Pai Gongalo community Stream at Mucambo community Riacho da Raiz Municipality Chapadinha - MA Vargem Grande - MA Vargem Grande - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Mata Roma - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Chapadinha - MA Sao Benedito do Rio Preto - MA Chapadinha - MA Coordinates 03°51'42.84"S 043°16'1.7"W 03°54'27.8"S 043°44'55.8"W 03°54'3.25"S 043°44'55.8"W 04°2'54.24"S 043°34'58.4"W 03°44'45.2"S 043°19'15.0"W 03°44'57.4"S 043°20'24.0"W 03°44'27.2"S 043°19'36.5"W 03°44'56.5"S 043°19'55.8"W 03°45'7.42"S 043°20'4.05"W 03°46'11.9"S 043°20'25.2"W 03°34'0.40"S 043°19'0.40"W 03°55'38.7"S 043°30'13.1"W 03°45'6.00"S 043°20'23.0"W 03°51'51.3"S 043°19'36.8"W 03°50'50.0"S 043°19'19.4"W 03°50'15.5"S 043°19'41.1"W 03°42'22.7"S 043°31'47.1"W 03°48'34.1"S 043°24'33.2"W 04°2'38.12"S 043°28'40.7"W 03°29'1.01"S 043°33'39.5"W 03°53'45.1"S 043°29'21.3"W Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... Altitude River 52m 30m 32m 41m 90m 66m 85m 74m 68m 50m 45m 53m 59m 39m 41m 41m 25m 33m 82m 92m 45m basin section Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Middle Locality number (L) 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 Locality Riacho Sao Joao, Sao Joao dos Pilao Riacho Pau Preto, Pau Preto community Riacho da Cruz, close to Palestina Rio Preto, Agua Rica community Corrego Agua Rica Riacho do Muquém Stream, Laranjeira community Rio Munim, Capoeira Grande community Rio Sao Gongalo Stream crossing the road Stream crossing the road Riacho barrigudinho Riacho do boi Stream crossing the road Riacho do boi *Rio Bandeira, Belagua Riacho Agua Fria on the road MA-110 Rio Bandeira Rio Mocambo Stream on the road MA-224 Rio Preto, Sao Benedito do Rio Preto Vieira L et al Municipality Brejo - MA Brejo - MA Brejo - MA Brejo - MA Anapurus - MA Mata Roma - MA Buriti - MA Afonso Cunha - MA Afonso Cunha - MA Afonso Cunha - MA Afonso Cunha - MA Afonso Cunha - MA Afonso Cunha - MA Aldeias Altas - MA Aldeias Altas - MA Belagua - MA Belagua - MA Urbano Santos - MA Urbano Santos - MA Sao Benedito do Rio Preto - MA Sao Benedito do Rio Preto - MA Coordinates 03°41'2.64"S 042°56'31.9"W 03°39'54.9"S 042°56'35.5"W 03°41'18.0"S 042°58'39.8"W 03°41'34.92"S 043°0'56.1"W 03°41'41.24"S 043°1'44.8"W 03°42'21.2"S 043°13'57.1"W 03°52'31.09"S 043°3'0.60"W 04°10'2.79"S 043°13'28.0"W 04°7'58.77"S 043°19'16.1"W 04°10'53.63"S 043°14'1.5"W 04°12'23.9"S 043°14'46.8"W 04°18'46.1"S 043°13'39.1"W 04°19'12.38"S 043°13'9.8"W 04°22'14.3"S 043°12'17.6"W 04°26'4.96"S 043°11'46.9"W 03° 9'22.7"S 043°30'35.4"W 03°10'9.49"S 043°28'45.3"W 03°11'49.0"S 043°24'29.3"W 03°12'34.6"S 043°24'23.8"W 03°18'46.2"S 043°30'25.1"W 03°19'59.0"S 043°31'34.8"W Altitude River basin section 89m Middle 84m Middle 88m Middle 78m Middle 86 m Middle 68m Middle 96 m Middle 54m Upper 64m Upper 58m Upper 68m Upper 67m Upper 67m Upper 69m Upper 82m Upper 65m Middle 68m Middle 41m Middle 38m Middle 40m Middle 29m Middle Locality number (L) 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 Locality Stream on the road MA-224 Rio Munim, on the road MA-224 Rio Munim, at the quilombola community Eviena Riacho Paulica on the road MA-020 Rio Munim at Nina Rodrigues City Riacho Paulica on the road BR-222 Rio Iguara on the road BR-222 Rio Munim mouth at Icatu Rio Una, between the municipalities of Morro and Icatu Rio das Cobra, Santa Helena community Riacho at the entrance to Icatu Rio Munim, Cachoeira Grande Stream crossing the road MA-020 Stream next to the road MA-402 Rio Munim between the municipalities of Axixa and Presidente Juscelino Stream between the municipalities of Axixa and Presidente Juscelino Rio Munim, Presidente Juscelino Rio Una, Cachoeira do Arruda Riacho das Pacas Stream next to the road MA-402 Municipality Sao Benedito do Rio Preto - MA Nina Rodrigues - MA Presidente Vargas -MA Presidente Vargas -MA Nina Rodrigues - MA Vargem Grande - MA Vargem Grande - MA Icatu - MA Morros - MA Morros - MA Icatu - MA Cachoeira Grande -MA Cachoeira Grande -MA Axixa - MA Axixa - MA Axixa - MA Presidente Juscelino - MA Morros - MA Morros - MA Morros - MA Coordinates 03°29'29.0"S 043°35'25.9"W 03°35'14.1"S 043°39'50.4"W 03°22'31.0"S 043°58'18.5"W 03°25'54.98"S 043°58'1.0"W 03°27'36.1"S 043°54'15.1"W 03°31'11.5"S 043°58'30.7"W 03°33'9.64"S 043°52'23.0"W 02°46'33.86"S 044° 4'1.3"W 02°50'3.06"S 044°2'24.82"W 02°49'22.1"S 044° 2'34.8"W 02°46'58.50"S 044°2'48.2"W 02°55'36.25"S 044°3'39.2"W 02°55'14.62"S 044°2'31.5"W 02°51'37.1"S 044° 3'14.5"W 02°52'35.63"S 044°3'41.8"W 02°53'50.06"S 044°4'15.9"W 02°55'39.38"S 044°3'50.5"W 02°53'31.5"S 043°58'13.8"W 02°51'4.94"S 043°57'52.1"W 02°51'19.5"S 044°01'03.0"W Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... Altitude River basin section 50m Middle 21m Middle 14m Middle 16m Middle 14m Middle 23m Middle 22m Middle im Estuary 8m Lower 9m Lower 19m Lower 4m Lower 34m Lower 4m Lower 15m Lower 4m Lower 6m Lower 28m Lower 28m Lower 19m Lower 10 Vieira L et al Locality Locality Municipality Coordinates Altitude River number (L) basin section 78 Rio Munim, Axixa Axixa - MA 02°50'14.60"S 1m Lower 044°3'3.81"W 79 Rio Munim, Balceiro community Chapadinha-MA 03°46'44.9"S 33m Middle 043°26'42.7"W 80 Stream at the Paiol community Chapadinha-MA 04°1'13.56"S 74m Middle 043°29'27.6"W 81 Stream at SA€o Pedro community Chapadinha-MA 03°54'4.66"S 73m Middle 043°35'12.3"W 82 Stream crossing a road in the Chapadinha-MA = _03°56'10.0"S 61m Middle Resex 043°30'29.5"W 83 Riacho Xoror6 at Aparecida Chapadinha-MA = 03°44'7.77"S 69m Middle neighbourhood 043°22'8.94"W 84 Riachinho, Agua Branca Chapadinha-MA = _03°52'37.67"S 60m Middle community 043°16'59.37"W Sampling and specimens identification All (about 160) sampling events were carried under the permits issued by Instituto Chico Mendes de Conservagao da Biodiversidade (ICMBIO; License n° 54949, 57258, 57787, 64415, 73267). In addition, material already housed at the Colegao Ictiologica do Centro de Ciéncias Agrarias e Ambientais (CICCAA) of the Universidade Federal do Maranhao, was also used in this study. The specimens were sampled by using different sampling gear, such as fishing line, hand net, seine net, cast net, gill nets and crayfish-type traps (Souza and Auricchio 2002). All the sampling activities and procedures followed the best practices and standards for animal welfare as presented in Leary et al. (2020). Specimens were euthanised by immersion in a 250 mg/l Tricaine methane sulphonate (MS-222) solution until the cessation of opercular movements. Following the euthanasia, the specimens for morphological studies were preserved in formalin (10%) and moved to a 70% ethanol solution after 10-15 days. Specimens selected for future molecular studies were preserved in 99% ethanol. The processing and identification of specimens were made at the Laboratorio de Sistematica e Ecologia de Organismos Aquaticos (LASEOA), at the Universidade Federal do Maranhao, by the use of specialised bibliography for each taxonomic group and by consulting specialists. The specimens were identified to the lowest taxonomic rank possible. All biological material is catalogued and housed at the Colecao Ictioldgica do Centro de Ciéncias Agrarias e Ambientais (CICCAA) of the Universidade Federal do Maranhao (UFMA) (Suppl. materials 1, 2). The taxonomic classifications, species names, authorship and year, original descriptions, habitat of occurrence and geographic distributions were verified and presented according to Fricke et al. (2022a), Fricke et al. (2022b) and Froese and Pauly (2022). Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... 11 Figure 2. EE Samples sites: L1, L18, L19, L30, L31, L36, L38, L43, L49, L53, L54, L55, L62, L65, L66, L69, L75, L77, L78 and L84 according to Table 1. Photographed by Lucas Vieira and Rafael Oliveira, edited by Axel Katz. Map and Munin River Basin sections distinction The geographic coordinates of each collection site along the Munim River Basin were registered from a GPS device and then converted to the shapefile format, with place names and respective codes in the attribute table. Additional data on boundaries from river basins and political division of territory were acquired from the official data service IBGE (Brazilian Institute for Geography and Statistics). The map was composed in QGIS 3.22.12 (Qgis development team 2022). Due to scale, each point on the map may correspond to one or more collection sites, depending on the geographic proximity. The Munim River Basin was divided into four sections: Estuary section with an area of 78.89 km*, comprising one collecting site; Lower river basin section with an area of 2891.89 km*, comprising 13 collecting sites; Middle river basin section with an area of 10722.29 km, comprising 62 collecting sites; and Upper river basin section with an area of 12 Vieira L et al 2224.90 km?, comprising eight collecting sites (Fig. 1, Table 1, Suppl. material 2). The criterion for the sectorisation of the basin was based on the average slope calculated from the elevation values (meters above sea level) of the digital elevation model SRTM/USGS, available at the TOPODATA/INPE project (http://www.dsr.inpe.br/topodata/). Based on the analysed area, this river basin varies from 0 to 162 meters above the sea level. The parameters considered for the sectorisation were: Estuary section - average slope of 1.09 (standard deviation 1.59); Lower river basin section - average slope of 1.41 (standard deviation 1.33); Middle river basin section - average slope of 2.63 (standard deviation: 2.43); and Upper river basin section - average slope of 3.11 (standard deviation 2.61) (Fig. 1, Table 1, Suppl. material 2). Figure 3. EES Selected fish species collected in the Munim River Basin of the Order Characiformes: A Acestrorhynchus falcatus (CICCAA 06398, 112.60 mm SL), B Aphyocharax sp. (CICCAA 06636, 32.91 mm SL), C Charax awa (CICCAA 06430, 80.22 mm SL), D Gasteropelecus sternicla (CICCAA 06366, 39.50 mm SL), E Hemiodus parnaguae (CICCAA 06238, 94.99 mm SL), F Leporinus aff. friderici (CICCAA 02755, 102.31 mm SL), G Metynnis lippincottianus (CICCAA 06383, 64.06 mm SL), H Moenkhausia cf. intermedia (CICCAA 06634, 50.38 mm SL), | Moenkhausia sp. (CICCAA 06635, 35.10 mm SL), J Poptella compressa (CICCAA 06429, 42.46 mm SL), K Prochilodus lacustris (CICCAA 06340, 84.94 mm SL), L Psectrogaster rhomboides (CICCAA 06270, 121.08 mm SL), M Pygocentrus _nattereri (CICCAA 06271, 138.08 mm SL), N Schizodon dissimilis (CICCAA 06344, 99.03 mm SL), O Serrasalmus rhombeus (CICCAA 06269, 70.99 mm SL), P Triportheus signatus (CICCAA 06339, 86.62 mm SL). Photographed by Lucas Vieira and Rafael Oliveira, edited by Axel Katz. Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... 13 Species photographs Specimens of some species were photographed in the laboratory to illustrate the diversity of species that occur in the Munim River Basin (Fig. 3, Fig. 4 and Fig. 5). Additional photographs of Munim River fish species can be seen in Guimaraes et al. (2018b): figs. 1, 2, Oliveira et al. (2020): fig. 3, Guimaraes et al. (2021c) and Aguiar et al. (2022): fig.2b. Figure 4. EES Selected fish species collected in the Munim River Basin of the Order Siluriformes: A Ancistrus sp. (CICCAA 06652, 76.85 mm SL), B Auchenipterus menezesi (CICCAA 06534, 98.38 mm SL), C Batrochoglanis sp. (CICCAA 06654, 64.16 mm SL), D - Callichthys callichthys (CICCAA 03927, 102.12 mm SL), E Corydoras julii (CICCAA 06378, 34.33 mm SL), F Corydoras vittatus (CICCAA 06418, 34.19 mm SL), G Hassar affinis (CICCAA 06263, 109.79 mm SL), H Hoplosternum littorale (CICCAA 06657, 81.91 mm SL), I Hypoptopoma incognitum (CICCAA 06315, 70.81 mm SL), J /tuglanis cf. amazonicus (CICCAA 06643, 30.53 mm SL), K Loricaria cf. cataphracta (CICCAA 06628, 105.80 mm SL), L Loricariichthys sp. (CICCAA 06328, 160.18 mm SL), M Pimelodella sp.1 (CICCAA 06629, 83.02 mm SL), N Platydoras brachylecis (CICCAA 04608, 58.36 mm SL), O Pseudoplatystoma fasciatum (CICCAA 04549, 208.39 mm SL), P Sorubim lima (CICCAA 06272, 204.01 mm SL), Q Tatia intermedia (CICCAA 02736, 46.17 mm SL), R Trachelyopterus galeatus (CICCAA 06243, 122.56 mm SL). Photographed by Lucas Vieira and Rafael Oliveira, edited by Axel Katz. Migratory species Species were classified as migratory based on Carolsfeld et al. (2003). When any species was not listed in Carolsfeld et al. (2003), we considered the genus to indicate if it is a migratory species. 14 Vieira L et al Figure 5. EES Selected fish species collected in the Munim River Basin of the Orders Cichliformes and Gymnotiformes: A Geophagus parnaibae (CICCAA 06229, 98.62 mm SL), B Satanoperca jurupari (CICCAA 06377, 105.36 mm SL), C Apteronotus albifrons (CICCAA 06266, 168.59 mm TL), D Eigenmannia robsoni (CICCAA 06631, 180.36 mm TL), E Sternopygus macrurus (CICCAA 06261, 183.50 mm TL). Photographed by Lucas Vieira and Rafael Oliveira, edited by Axel Katz. General species accumulation curve A matrix of occurrence and abundance data over the sampling period, for this study, was used to plot the general species accumulation curve with Primer-e statistical software (Clarke and Gorley 2006), based on a spreadsheet containing relevant data for this analysis (Suppl. material 2). Given that the order of samples in the analysis affects the shape of the curve produced, due to heterogeneity amongst the species in the samples (Ugland et al. 2003), 1000 permutations were calculated to overcome this effect. Species Richness and Fish assemblage composition The statistical and ecological analyses were based on a spreadsheet containing relevant data for these analyses (Suppl. material 2). Species Richness Species richness (Sprich) (i.e. number of species in each river basin section) was compared using Kruskal-Wallis tests, on account of non-normal distribution (per Shapiro- Wilk test) and Dunn post-hocs with Holm adjusted p-values to account for multiple comparisons were used to determine section level differences. Visualisation was completed through the R package “ggstatsplot” (Patil 2021). Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... 15 Fish assemblage composition Fish assemblage composition was compared between basin sections, at the basin section level, using presence-absence data due to surveys not being standardised for sampling methods. Only native species were included in the analysis. First, nestedness was assessed using the NODF method (Almeida-Neto et al. 2008), which is bound between 0 and 100 where 100 is perfect nestedness, via vegan::nestednodf, then S@rensen dissimilarity and Simpsons Index were calculated using vegan::nestedbetasor. S@rensen dissimilarity closer to 0 indicates more shared species. Simpsons Index is not affected by species richness and represents true turnover, i.e. the the replacement of some species by other species from section to section, independent of potential differences in species richness between the sections. Areas with Simpsons Index values over 66% are considered to have similar faunal composition (Sanchez and Lopez 1988). Jaccard Index was calculated using vegan::nestedbetajac where values closer to one indicate higher similarity. A cluster analysis and dendrogram was completed on the section Jaccard coefficients using the Ward.D2 method. All statistical analyses were performed within the R software environment version 4.0.2 and the package “vegan” (Oksanen et al. 2019, R Core Team 2020). Checklist of the fish fauna of the Munim River Basin Class Actinopteri Notes: The checklist is presented in Table 2. Table 2. List of fish species recorded for the Munim River Basin in the present study. “endemic species to the hydrological units Maranhao and Parnaiba sensu Hubert and Renno (2006). CLASS/ ORDER/ FAMILY/ SPECIES New Migratory Non-native Habitat of Common name records species species occurrence (Portuguese) CLASS ACTINOPTERI ACANTHURIFORMES Ephippidae Chaetodipterus faber (Broussonet, 1782) x Marine, Peixe enxada Estuary and Freshwater Gerreidae Eugerres plumieri (Cuvier, 1830) x Marine, Mojarra Estuary and Freshwater Haemulidae Conodon nobilis (Linnaeus, 1758) x Marine, Estuary and Freshwater 16 CLASS/ ORDER/ FAMILY/ SPECIES Genyatremus luteus (Bloch, 1790) Lutjanidae Lutjanus jocu (Bloch & Schneider, 1801) Sciaenidae Cynoscion steindachneri (Jordan, 1889) Macrodon ancylodon (Bloch & Schneider, 1801) Menticirrhus americanus (Linnaeus, 1758) Micropogonias furnieri (Desmarest, 1823) Plagioscion squamosissimus (Heckel, 1840) Stellifer naso (Jordan, 1889) BATRACHOIDIFORMES Batrachoididae Batrachoides surinamensis (Bloch & Schneider, 1801) BELONIFORMES Hemiramphidae Hyporhamphus roberti (Valenciennes, 1847) CARANGIFORMES Achiridae Achirus achirus (Linnaeus, 1758) Carangidae Chloroscombrus chrysurus (Linnaeus, 1766) Oligoplites palometa (Cuvier, 1832) Centropomidae Centropomus parallelus Poey, 1860 CHARACIFORMES Acestrorhynchidae Vieira L et al New Migratory records species species X Non-native Habitat of occurrence Marine and Estuary Marine, Estuary and Freshwater Marine, Estuary and Freshwater Marine and Estuary Marine and Estuary Marine, Estuary and Freshwater Freshwater Estuary and Freshwater Marine and Estuary Marine and Estuary Marine, Estuary and Freshwater Marine and Estuary Marine, Estuary and Freshwater Marine, Estuary and Freshwater Common name (Portuguese) Curvina Curvina Pacamao Agulha Linguado Palombeta Tibiro Robalo Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... 17 CLASS/ ORDER/ FAMILY/ SPECIES Acestrorhynchus falcatus (Bloch 1794) Anostomidae Leporinus aff. friderici Schizodon dissimilis (Garman 1890) Characidae Aphyocharax sp. Astyanax cf. bimaculatus Brachychalcinus parnaibae Reis 1989 Charax awa Guimaraes, Brito, Ferreira & Ottoni, 2018* Ctenobrycon cf. spilurus Hemigrammus sp. 1 sensu Oliveira et al. (2020) Hemigrammus sp.2 sensu Oliveira et al. (2020) Hemigrammus cf. rodwayi Hyphessobrycon piorskii Guimaraes, Brito, Feitosa, Carvalho-Costa & Ottoni, 2018* Knodus guajajara Aguiar, Brito, Ottoni & Guimaraes, 2022* Microschemobrycon sp. Moenkhausia sp. Moenkhausia cf. intermedia Moenkhausia oligolepis (Giinther, 1864) Phenacogaster cf. pectinata Poptella compressa (Gunther, 1864) Psellogrammus kennedyi(Eigenmann, 1903) Roeboides margareteae Lucena, 2003* Roeboides sazimai Lucena, 2007* Serrapinnus sp. Tetragonopterus argenteus Cuvier 1816 Crenuchidae Characidium sp. Curimatidae Curimatopsis aff. cryptica Psectrogaster rhomboides Eigenmann & Eigenmann 1889 Steindachnerina notonota (Miranda Ribeiro, 1937) Cynodontidae New records Migratory species Non-native Habitat of species occurrence Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Common name (Portuguese) Lubarana Piau de coco Piau de vara Enfermerinha Piaba rabo de fogo Piaba chatinha Cacunda Piaba Piaba Piaba Piaba Tetra Piaba Piaba Piaba Piaba Piaba rabo preto Lambarizinho Piaba chatinha Cacunda Cacunda Piabinha Piaba Canivete, mocinha Branquinha Joao duro 18 Vieira L et al CLASS/ ORDER/ FAMILY/ SPECIES Non-native species New records Migratory species Cynodon gibbus (Agassiz, 1829) Erythrinidae Hoplias malabaricus (Bloch, 1794) Hoplerythrinus unitaeniatus (Spix & Agassiz, 1829) Gasteropelecidae Gasteropelecus sternicla (Linnaeus, 1758) Hemiodontidae Hemiodus parnaguae Eigenmann & Henn, 1916* Iguanodectidae Bryconops aff. affinis Lebiasinidae Copella arnoldi (Regan, 1912) Nannostomus beckfordi Gunther, 1872 Triportheidae Triportheus signatus (Garman, 1890) Xx Prochilodontidae Prochilodus lacustris Steindachner, 1907* xX Serrasalmidae Colossoma macropomum (Cuvier, 1816) x x x Metynnis lippincottianus (Cope, 1870) Myloplus rubripinnis (Miller & Troschel, x 1844) Serrasalmus rhombeus (Linnaeus, 1766) Xx X Pygocentrus nattereri Kner, 1858 x CICHLIFORMES Cichlidae Aequidens tetramerus (Heckel, 1840) Apistogramma piauiensis Kullander, 1980* Cichlasoma zarskei Ottoni, 2011* Crenicichla brasiliensis (Bloch, 1792) Geophagus parnaibae Staeck & Schindler, 2006* Oreochromis niloticus (Linnaeus, 1758) X X Satanoperca jurupari (Heckel, 1840) CLUPEIFORMES Habitat of occurrence Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Estuary and Freshwater Freshwater Common name (Portuguese) Gata Traira lu Borboleta Flecheiro Dorico Peixe lapis Sardinha de agua doce Curimata Tambaqui Pacu Pacu folha Pirambeba Piranha vermelha Cara, Acara Carazinho Cara preto, Acara, Cara Lope, Joana, Sabao Cara Tilapia do nilo Cara bicudo Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... 19 CLASS/ ORDER/ FAMILY/ SPECIES Engraulidae Anchovia surinamensis (Bleeker, 1865) Anchoviella guianensis (Eigenmann, 1912) Anchoviella lepidentostole (Fowler, 1911) Clupeidae Opisthonema oglinum (Lesueur, 1818) Rhinosardinia amazonica (Steindachner, 1879) CYPRINODONTIFORMES Anablepidae Anableps anableps (Linnaeus, 1758) Poeciliidae Poecilia sarrafae Bragancga & Costa, 2011 Rivulidae Anablepsoides vieirai Nelson, 2016* GYMNOTIFORMES Apteronotidae Apteronotus albifrons (Linnaeus, 1766) Gymnotidae Gymnotus carapo Linnaeus, 1758 Hypopomidae Brachyhypopomus sp. Sternopygidae Eigenmannia robsoni Dutra, Ramos & Menezes 2022* Sternopygus macrurus (Bloch & Schneider, 1801) Rhamphichthyidae Rhamphichthys atlanticus Triques, 1999* MUGILIFORMES Mugilidae Mugil curema Valenciennes, 1836 SILURIFORMES Ariidae Non-native Habitat of occurrence Estuary and Freshwater Estuary and Freshwater Marine, Estuary and Freshwater Marine and Estuary Estuary and Freshwater Estuary and Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Marine, Estuary and Freshwater Common name (Portuguese) Manjuba Manjuba Manjuba Sardinha Sardinha Tralhoto Barrigudinho Peixe de pocga Sarapo, Catana Sarapo, Catana Sarapo, Catana Sarapo, Catana Sarapo, Catana Tubiba, Sarapé Sardinha 20 CLASS/ ORDER/ FAMILY/ SPECIES Amphiarius rugispinis (Valenciennes, 1840) Aspistor quadriscutis (Valenciennes, 1840) Bagre bagre (Linnaeus, 1766) Cathorops spixii (Agassiz, 1829) Aspredinidae Aspredo aspredo (Linnaeus, 1758) Pseudobunocephalus timbira Leao, Carvalho, Reis & Wosiacki, 2019 Auchenipteridae Auchenipterus menezesi Ferraris & Vari, 1999* Tatia intermedia (Steindachner, 1877) Trachelyopterus galeatus (Linnaeus, 1766) Callichthyidae Aspidoras cf. raimundi Callichthys callichthys (Linnaeus, 1758) Corydoras julii Steindachner, 1906 Corydoras vittatus Nijssen, 1971* Hoplosternum littorale (Hancock, 1828) Megalechis thoracata (Valenciennes, 1840) Doradidae Hassar affinis (Steindachner, 1881)* Platydoras brachylecis Piorski, Garavello, Arce H. & Sabaj Pérez, 2008 Loricariidae Ancistrus cf. damasceni Ancistrus sp. Hemiodontichthys acipenserinus (Kner, 1853) Hypostomus cf. krikati Hypostomus sp. Hypoptopoma incognitum Aquino & Schaefer, 2010 Vieira L et al New Migratory records species X Non-native Habitat of occurrence Marine and Estuary Marine, Estuary and Freshwater Marine and Estuary Marine, Estuary and Freshwater Marine, Estuary and Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Freshwater Common name (Portuguese) Bagre Bagre Bagre Bagre Banjo catfish Bagre Bagrinho Cangati, Bagrinho Cari Cascudo Cari Cari Cascudo Cascudo Cabega de cavalo Guirri Mao na cara, Cascudo, Bodo Mao na cara, Cascudo, Bodo Cachimbo Boi de carro, Cascudo, Bodo Boi de carro, Cascudo, Bodo Cascudo Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... 21 CLASS/ ORDER/ FAMILY/ SPECIES New Migratory Non-native Habitat of Common name records species species occurrence (Portuguese) Loricaria cf. cataphracta Estuary and Cachimbo, Freshwater Cascudo Loricariichthys derbyi Fowler, 1915 Freshwater Cachimbo, Cascudo Rineloricaria sp. Freshwater Cachimbo, Cascudo Heptapteridae Imparfinis sp. Freshwater Mandi Pimelodella parnahybae Fowler, 1941* Freshwater Mandi Pimelodella sp1. Freshwater Mandi Pimelodella sp2. Freshwater Mandi Rhamdia quelen (Quoy & Gaimard, 1824) Freshwater Jundia Pimelodidae Hemisorubim platyrhynchos (Valenciennes, Freshwater Mandi trés pinta 1840) Pimelodus blochii Valenciennes, 1840 Estuary and Mandi Freshwater Pimelodus ornatus Kner, 1858 Freshwater Mandi dourado Pseudoplatystoma fasciatum Freshwater Surubim (Linnaeus, 1766) Sorubim lima (Bloch & Schneider, 1801) Freshwater Bico de pato Pseudopimelodidae Batrochoglanis sp. Freshwater Trichomycteridae Ituglanis cf. amazonicus Freshwater SCOMBRIFORMES Stromateidae Peprilus paru (Linnaeus, 1758) Marine and Estuary SYNBRANCHIFORMES Synbranchidae Synbranchus marmoratus Bloch 1795 Freshwater Mucgum and Estuary TETRAODONTIFORMES Tetraodontidae Lagocephalus cf. lagocephalus Marine and Baiacu arara Estuary Analysis The present study recorded about 32500 specimens belonging to 123 fish species (94 identified at the species level) for the Munim River Basin, divided into 49 families and 14 22 Vieira L et al orders (Table 2, Suppl. materials 1, 2). The most diverse orders are the Characiformes, with 43 species (35%); Siluriformes, with 38 species (30.9%); Acanthuriformes, with 11 (8.9%); Cichliformes, with seven species (5.7%) and Gymnotiformes, with six species (4.9%), representing 85.4% of all species known from the river basin. The remaining orders (Clupeiformes, Carangiformes, Cyprinodontiformes, Batrachoidiformes, Beloniformes, Mugiliformes, Scombriformes, Synbranchiformes and_ Tetraodontiformes) together represent only 14.6% of the Munim River Basin species. The most diverse family was the Characidae, with 21 species (17.1%), followed by the Loricariidae, with nine (7.3%) and the Cichlidae, with seven (5.7%). Further, from all 123 recorded species, only two, Oreochromis niloticus and Colossoma macropomum are non- native species for the studied region and 13 are migratory species (see Table 2). Amongst the species identified at the species level, 16 are endemic to the hydrographic regions of Maranhao and Parnaiba sensu Hubert and Renno (2006) (Mrn and Prn, respectively). According to the General plotted curves (General species accumulation curve), the sampling effort can be considered sufficient (Fig. 6), given that the observed values of Sops (125 +14) are aligned with those calculated in the estimator Chao1 (136.25) and the asymptote estimates of the Michaelis-Menten equation (113), as well as the Bootstrap (140.8) and Jackknife1 (162.85) variation indicators (Fig. 6). 200 4 Sobs ¢@ Chaol Jackknife1 ¢ Bootstrap =a MM Species Count 3 Oo Samples Figure 6. EESI General species accumulation curve over the sampling period for this study. Species Richness There were significant differences in species richness between sections (X7= 16.207, df = 3, p < 0.001) where the Lower and Upper river basin sections had significantly more species than the Middle river basin section (p < 0.05, p < 0.01 respectively; Fig. 7). Fish assemblage composition There was weak nestedness across the four basin sections (NODF = 37.67) and indices of species composition similarity and dissimilarity were moderate. Where S@rensen dissimilarity was 0.70 and Simpsons Index (i.e. true turnover) was 56%, suggesting that Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... 23 fish assemblage is distinct between basin sections but only moderately. Jaccard similarity was 83% indicating many shared species compared to unique species across river basin sections. Cluster analysis showed that the Estuary and Upper river sections were more distinct from the Lower and Middle river sections, which formed their own cluster (Fig. 8). Discussion This long-term icthyological survey, covering 12 years, conducted between 2010 and 2022 (65% of the surveys were carried out between 2019 and 2022), applied different sampling gears over different water bodies and environments along the Munim River Basin and recorded a predominance of fishes belonging to the Characiformes and Siluriformes, agreeing with a pattern expected for the Neotropics (Lowe-Mcconnell 1999, Pelicice et al. 2005, Langeani et al. 2007, Polaz et al. 2014, Reis et al. 2016, Brito et al. 2019, Dagosta and de Pinna 2019, Guimaraes et al. 2020, Castro and Polaz 2020). The study also recorded the predominance of small-sized characid fishes, which have a great diversity in the Neotropical Region, due to several traits, such as their high trophic plasticity (Abelha et al. 2001, Van Der Sleen and Albert 2018, Dagosta and de Pinna 2019, Castro and Polaz 2020, Guimaraes et al. 2020, Corréa and Castro 2021). Xkruskal-watis(3) = 16.18 p — 1.04e-03 2 4...) 0.06 Close, [0.03 1.00] nop, = 285 40 - Pioim_adj = 0-01 Proim_ad), = 0.05 30- : fa . 4s ala Lower Estuary queoyjuBys :umoys sueg UUNg :1s9} esiNUIeg Upper Section Figure 7. EESl Species richness values for all sample sites across river basin sections. A total of 123 species were recorded, with only two of them representing introduced species to the studied river basin (Table 2 and Suppl. materials 1, 2). Colossoma macropomum (tambaqui) occurs naturally in the Amazon and Orinoco River Basins, thus being native to Brazil, but not the Munim River Basin (Latini et al. 2016, Fricke et al. 2022b); and Oreochromis niloticus (tilapia) which is native to northern and eastern Africa (Figueredo and Giani 2005, Latini et al. 2016, Fricke et al. 2022b). All the other 121 species are native to the studied area. Therefore, the fish assemblage composition of the Munim River Basin is currently little affected by the presence of alien fish species. However, the policy regarding non-native species and push for economic 24 Vieira L et al development indicates this may soon change (Azevedo-Santos et al. 2011, Doria et al. 2021, Faria et al. 2022). % Jaccard Similarity Figure 8. EESl Hierachial cluster diagram of fish assemblage based on Jaccard Index per basin section using species presence-absence data. The occurrence of non-native fish species usually comes from fish farming and, in some cases, from intentional release and aquarium trade (Latini et al. 2016, Rocha et al. 2023). Oreochromis nilotus is an omnivorous fish which has broad abiotic tolerances, rapid growth and high survival in environments with high population density, traits which facilitate invasiveness and are favoured in aquaculture species (Figueredo and Giani 2005, Latini et al. 2016). In Brazil, the cultivation of this species is increasing, frequently without any control (Figueredo and Giani 2005, Latini et al. 2016). The species C. macropomum was recorded at only one collection site (a single specimen) (see Suppl. materials 1, 2). This makes us believe that the specimen had probably accidentally escaped from local or home fish-farming. On the other hand, O. niloticus was recorded in four locations (some of these locations far from each other), on different dates (i.e. several specimens). These data suggest establishment in the river basin and, thus, should be considered an established species in the Munim River Basin. Aquaculture initiatives with poor biosecurity are the probable pathway of invasion and rapid expansion facilitated by favourable climatic conditions should be expected and monitored in the Munim River Basin (Charvet et al. 2021, Wilgen et al. 2022). There is likelihood of negative ecological impacts as a result of this burgeoning invasion, in particular O. niloticus is a highly efficient filter feeder and may disrupt the food-web (Vasconcelos et al. 2018, Charvet et al. 2021). Biological invasions are a direct cause of biodiversity decline globally and are an increasing threat, especially in aquatic systems with high endemicity (Havel et al. 2015, Gallardo et al. 2016). This study reported 13 migratory fish species occurring in the Munim River Basin. Therefore, the eventual construction of dams and hydroelectric plants will undoubtedly negatively impact these species as migration routes will be interrupted. Locally, Oliveira et al. (2020) have already reported this situation occurring in the Mata de Itamacaoca, Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... 25 Chapadinha Municipality, State of Maranhao. They verified that the reservoir dam constructed in the Mata de Itamacaoca inhibits the dispersion of fish occurring below the dam, which possesses higher species diversity. In addition, migratory species were also not found by Oliveira et al. (2020) above the dam, in the reservoir, which would be a suitable habitat for these species. This may illustrate the effects of increased dam construction along the Munim River Basin. When comparing the present checklist with previous ones listing the fish species found in the hydrographic regions of Maranhao and Parnaiba sensu Hubert and Renno (2006) (Mrn and Prn, respectively) (e.g. Soares (2005), Barros et al. (2011), Nascimento et al. (2016), Piorski et al. (2017), Brito et al. (2019), Brito et al. (2020), Guimaraes et al. (2020)), it is evident that the fish diversity from the Munim River Basin has been underestimated. In fact, the present study showed a surprisingly high fish species diversity occurring in the Munim River Basin, when compared to the species richness found in other larger drainage systems and river basins from Maranhao. For example, Munim River Basin outnumbered the Itapecuru River Basin, a larger river basin, with 29 more species being recorded, where 94 fish species are known to occur (e.g. Barros et al. (2011), Nascimento et al. (2016), Koerber et al. (2022)). In addition, we recorded 67 more species than in the Preguigas and Peria River Basin, where 56 fish species are known to occur (e.g. Piorski et al. (2017), Brito et al. (2019), Brito et al. (2020), Koerber et al. (2022)); 22 more fish species than Guimaraes et al. (2020) recorded for the Pindaré River drainage (101 fish species); and more than twice the number of fish species for the coastal river basins of Gurupi, Maracagume, and Turiagu, where less than 50 species are known for each of these river basins (Koerber et al. 2022). There are only three studies surveying Maranhao coastal drainage systems, which presented a higher number of species than this study. Ramos et al. (2014), who recorded 146 species for the Parnaiba River Basin and, later, Silva et al. (2015) provided an updated list with six additional species (152). Koerber et al. (2022) published a checklist of the freshwater species in Maranhao (CLOFFBR-MA), listing 136 species for the Mearim River Basin. The Munim River Basin had 13 fewer species than those recorded in the Mearim River Basin, one of the largest river basins in Maranhao and 29 fewer species than the Parnaiba River Basin, which is the largest hydrographic basin in north-eastern Brazil (Ramos et al. 2014, Silva et al. 2015, Koerber et al. 2022). When analysing the present results in light of the previous surveys in the Munim River Basin, it is clear that all previous studies were geographically restricted to specific localities, extremely close to each other, thus were not able to depict and represent the wider basin diversity. Ribeiro et al. (2014) recorded only 20 fish species (103 less than the present study), using a traditional fishing technique called "moita" commonly used by local traditional communities in the Chapadinha Municipality. However, this method is biased toward the capture of medium to large-sized fishes and is generally applied by subsistence fisheries. Matavelli et al. (2015) surveyed the tadpoles occurring in lentic and lotic environments in Cerrado and Restinga vegetation types, sampling in localities in the Munim and Parnaiba river basins. Fish species were also sampled and a total of 13 species were recorded from the Munim River Basin (110 less than the present study). Nunes et al. (2019) carried out a weight-length ratio study of the fish community in one 26 Vieira L et al locality in Munim River Basin, recording 15 fish species (108 less than the present study). More recently, Oliveira et al. (2020) published a freshwater fish species list of a conservation unit in the Chapadinha Municipality after a long monitoring period, with 23 species (100 less than the present study). However, the survey was focused on small streams and consequently recorded mainly small-size species. Guimaraes et al. (2021b) published a book from the same area studied by Oliveira et al. (2020), directed at the general public, which focused on species with an estimated high ornamental value. Finally, in the CLOFFBR-MA, which relied upon literature information, 59 species were identified in the Munim River Basin (64 less than the present study) (Koerber et al. 2022). None of these previous studies had the main goal of identifying the entire species diversity of the Munim River Basin. Within the 121 native species listed in the present study, 29 were not able to be identified to the species level. Guimaraes et al. (2018a) and Guimaraes et al. (2020), hypothesised that probably this is a result of the lack of taxonomic knowledge and information about these species and groups occurring in Maranhao. The taxa which could not be identified to the species level, likely belong to species complexes or represent taxonomically challenging and poorly defined groups and may represent new species to science (see Table 2). Median species richness in the Middle river basin section was lower than in the Upper and Lower river basin sections; however, the Middle section had both more sampling sites and much higher range of species richness. Environmental filtering across river gradients has a strong influence on species richness and diversity (LOpez-Delgado et al. 2019, Walsh et al. 2022). By grouping by section, we are missing local habitat-specific variables which are likely to be driving differences in fish assemblages across a highly heterogenous river network. Investigating habitat specific associations and drivers of beta diversity will vastly improve our understanding of drivers of fish assemblages in the Munim River Basin. Moderate nestedness and similarity/dissimilarity trends, combined with the lack of clear clustering between sites within river basin sections, indicate that fish assemblage structuring in the Munim River Basin is probably driven by both the river continuum concept as well as environmental filtering (Vannote et al. 1980, Heino et al. 2015). However, unobstructed flows facilitating dispersal likely drive high similarity throughout each basin section (Leitao et al. 2018). The Munim River Basin is not high altitude and has neither large rapids nor large waterfalls; therefore, the flow conditions through the sections are also relatively similar, with the lower river section differing through estuarine influence. Further research is needed to understand the specific microhabitats and fish associations throughout the river basin as this is undoubtedly a driving factor of diversity. For example, river slope and flow conditions exert strong environmental filters on fish community and traits in Neotropical and Afrotropical freshwaters and dispersal between heterogenous habitats may be limited by side channels and swamp habitats (Caetano et al. 2021, Walsh et al. 2022). A higher concentration of specialist species is expected to be found in the Upper section as there is more competition for niches (Sternberg and Kennard 2013). The cluster analysis indicated that the Upper section sites were on distinct branches from the other sites, but a standardised sampling methodology combined with implementation of Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern ... a7 functional trait-based approaches will facilitate our understanding of finer scale processes of environmental filtering in each section (Bower and Winemiller 2019a, Bower and Winemiller 2019b). Considering all 92 native species which were identified to the species level, 30 of them (Achirus achirus, Amphiarius rugispinis, Anableps anableps, Anchovia_ surinamensis, Anchoviella guianensis, Anchoviella lepidentostole, Aspistor quadriscutis, Aspredo aspredo, Bagre bagre, Batrachoides surinamensis, Cathorops spixii, Centropomus parallelus, Chaetodipterus faber, Chloroscombrus chrysurus, Conodon nobilis, Cynoscion steindachneri, Eugerres plumieri, Genyatremus luteus, Hyporhamphus roberti, Lutjanus Jocu, Macrodon ancylodon, Menticirrhus americanus, Micropogonias furnieri, Mugil curema, Oligoplites palometa, Opisthonema oglinum, Peprilus paru, Plagioscion Squamosissimus, Rhinosardinia amazonica and Stellifer naso) are commonly found in brackish water or estuaries. Due to this, no biogeographical considerations will be made about them. From the remaining 62 species identified to the species level, 16 are only known from river drainage systems and basins of the Maranhao State and the Parnaiba River Basin (Anablepsoides vieirai, Apistogramma piauiensis, Auchenipterus menezesi, Charax awa, Cichlasoma zarskei, Corydoras vittatus, Eigenmannia robsoni, Geophagus parnaibae, Hassar affinis, Hemiodus parnaguae, Hyphessobrycon piorskii, Pimelodella parnahybae, Prochilodus lacustris, Rhamphichthys atlanticus, Roeboides margareteae and Roeboides sazimai). Three other species (Platydoras brachylecis, Poecilia sarrafae and Schizodon dissimilis) are also known from other drainages in the northeast of Brazil (Teixeira et al. 2017, Silva et al. 2020, Fricke et al. 2022b). The remaining 43 species are also known from different Amazonian drainage systems (Fricke et al. 2022b), a pattern clearly showing the influence and presence of Amazonian fauna in the Munim River Basin. In addition, when comparing the species listed for the Munim River Basin to the list of species in the Parnaiba River (Ramos et al. 2014, Silva et al. 2015), there are 53 native species co-occurring in both drainage systems, showing a high influence of the larger Parnaiba River Basin over smaller coastal drainage systems. Finally, there are a total of 64 new records of fish species for the Munim River Basin and 48 new records considering only the number of taxa identified at the species level (Table 2), showing that, until the present study, the drainage's diversity was underestimated. The Munim River Basin, previously a neglected river system, similar to many other coastal systems in Maranhao, is now one of the better known river basins relative to its fish diversity. A detailed taxonomic investigation of specimens sampled over a 12 year period revealed a much diverse fish fauna. The present study is the most comprehensive carried out in the Munim River Basin so far, adding 64 species (including species identified at the species level and species not identified at species level), which were previously considered not to occur in the drainage, resulting in a total of 123 species. Within this species richness, there was a large number of taxa, which could not be identified at the species level, indicating the urgent need for dedicated taxonomic research in the region. This study puts emphasis on the importance of compiling ichthyofaunal lists for poorly-studied or subsampled areas. This achievement represents a first step in understanding the diversity in the Munim River Basin, with the information presented herein allowing the development 28 Vieira L et al of future ecology, biogeography and conservation studies. Thus, this is an essential contribution to the effort to better understand the fish diversity of Maranhao in the face of rapid global change and habitat alteration. Despite the high number of species found for the Munim River Basin, more collection efforts are recommended, especially in the Lower and Estuary sections. New collection expeditions may find species that may not have been recorded by this work. Acknowledgements We thank Ananda Saraiva for helping to identify some specimens of Loricariinae; Elioenai Oliveira, Antonio Bezerra and Brenda Lima for laboratory assistance; four anonymous reviewers for their important contributions to the manuscript; Coordenagao de Aperfeigoamento de Pessoal de Nivel Superior (CAPES - Finance Code 001), Fundagao de Amparo a Pesquisa e ao Desenvolvimento Cientifico e Tecnologico do Maranhao (FAPEMA), Conselho Nacional de Desenvolvimento (CNPQ), Fundagao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ) and Fundacgao Amazonia de Amparo a Estudos e Pesquisas (FAPESPA) for providing the scholarship under the process (CNPq-FAPEMA, grant PDCTR-08797/22 to PSB), (FAPESPA; grant 028/2021 to ECG), (CNPq; grant 307974/2021-9 to FPO), (CNPq-IC; grant 134775/2020-1 to RFO), (FAPEMA; grant BM-00809/22 to LOV), (FAPEMA-IC; grants BIC-01958/20 and BIC-04123/21 to MSPC), (FAPERJ; grant E-26/202.005/2020 to AMK) and (CAPES; grant 88887 .674455/2022-00 to DSC). This study was supported by the projects “PROCESSO UNIVERSAL-00724/17” and “Processo UNIVERSAL-00437/19”, from FAPEMA. Author contributions Conceptualisation: Felipe Ottoni, Erick Guimaraes, Lucas Vieira. Data collecting, organising and curation: Lucas Vieira, Rafael Oliveira, Diego Campos, Marcony Coelho, Mauricio Paiva, Erick Guimaraes, Pamella Brito, Felipe Ottoni. Specimens identification: Lucas Vieira, Rafael Oliveira, Diego Campos, Marcony Coelho, Mauricio Paiva, Erick Guimaraes, Pamella Brito, Axel Katz, Felipe Ottoni. Supplementary material: Lucas Vieira. Ecological and statistics analyses: Josie South, Diego Campos. Manuscript writing: Lucas Vieira, Felipe Ottoni, Josie South, Pedro Braganga, Diego Campos, Marcony Coelho, Mauricio Paiva, Rafael Oliveira, Erick Guimaraes, Pamella Brito, Jadson Santos, Axel Katz. Map and river basin sectorisation: Diego Campos. Photographs: Lucas Vieira and Rafael Oliveira. Photographs editing: Axel Katz. 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Download file (817.72 kb) Suppl. material 2: Checklist of the fish fauna of the Munim River Basin, Maranhao, north-eastern Brazil EI Authors: Lucas Vieira Data type: Excel csv spreadsheet Brief description: Spreadsheet used in ecological and statistics analyses. Download file (11.23 MB)