Identification key for fishes from coastal streams of the Atlantic forest of southeastern Brazil

In recent decades, current knowledge about fish from Neotropical streams has greatly increased, but is still deficient. Here we present an identification key for fishes from coastal freshwater streams from a large conservation area of Atlantic rainforest of southeastern Brazil, including 39 species. Considering that most of these species (61.2%) are endemic to the coastal streams, this identification key will be useful not only for the species recognition of the sampled area, but also for the surrounding coastal region.


Introduction
The Serra do Mar was formed from an uplift process during the Cretaceous, which originated a sequence of 1,000 km of mountains near the newly formed coast.Its current relief was shaped over millions of years by erosion and tectonic activities and currently covers the states of Rio de Janeiro to Santa Catarina (Oyakawa et al. 2006).The Atlantic forest is a complex biome that covers practically the entire Serra do Mar, and although human occupation has degraded 90% of its area, this biome harbors a significant part of the Brazilian biodiversity (Joly et al. 1999); 40% of the 2,000 vertebrate species are endemic (Oyakawa et al. 2006).
In this region, there are mountain streams with clear and fast waters due to the high slope of the relief, low temperatures and high concentration of dissolved oxygen, and the lowland streams that drains the less steep coastal plain forming meanders with black, slower, turbid and acidic waters with higher temperatures, lower dissolved oxygen concentration and sandy bottom (Por 2004).Due to the altitudinal gradient, coastal streams rise with waters typical of mountain streams that change when they reach the plains and with the proximity of the mouth in the sea (Gonçalves & Braga 2012).
These and other habitat characteristics influence the ichthyofauna of coastal streams (Abilhoa et al. 2011, Barrella et al. 2014, Gonçalves et al. 2015).The conservation of riparian forest is important since deforestation negatively impacts the survival of fish due to silting, increased sunlight incidence and decreased invertebrate fauna, among other impacts (Lorion & Kennedy 2009, Leite et al. 2015).This can lead to drastic consequences such as changes in reproductive and feeding behaviors of many species (Menezes et al. 2007, Ferreira et al. 2012, Lobón-Cerviá et al. 2016).
The Juréia-Itatins Ecological Station is a conservation unit on the south coast of the state of São Paulo with streams that protects several endemic species (and some endangered) of the Atlantic forest (Gonçalves & Braga 2013, Gonçalves et al. 2016, Gonçalves & Pérez-Mayorga 2016).Characiformes and Siluriformes are predominant, but other orders such as Cichliformes and Gobiiformes (sensu Betancur-R et al. 2017), Synbranchiformes, Cyprinodontiformes, and Gymnotiformes are also present (Gonçalves & Pérez-Mayorga 2016), as well as primarily marine families (Sabino & Silva 2004).Fish occupy different stream reaches according to their feeding habits and swimming capacity, varying between rapids, marginal backwaters or position in the water column (Sabino & Silva 2004).In the freshwater streams of of Juréia-Itatins Ecological Station, fish feed primarily on resources provided by riparian forest, such as terrestrial insects and vegetable debris (also consumed by immature forms of aquatic insects that will feed aquatic insectivorous fish), stressing the importance of legally protected areas in Atlantic forest (Gonçalves et al. 2013).The small size of most species of these coastal streams and the scarcity of keys can make it difficult to identify the fish of this region.The objective of this paper is to provide an identification key for fishes from coastal streams of Juréia-Itatins Ecological Station.

Material and Methods
The material used in this study was collected every three months between April 2009 and February 2010, and once in June 2013 (cf.Gonçalves & Braga 2012, 2013, Gonçalves & Pérez-Mayorga 2016) at the Juréia-Itatins reserve, an Atlantic rainforest pristine area with 79.240 ha on the south coast in the State of São Paulo, Brazil (24°18', 24°32' S and 47°00', 47°30' W).Average annual rainfall and temperature are 2,277 mm and 21.4 °C, respectively.A hot and rainy season occurs from October to April, and the less rainy season from May to September (Marques & Duleba 2004).Altitudes vary from sea level at alluvial plains to 1,240 m a.s.l. at steep mountains (Por 1986, Souza & Souza 2004).Due to this, local hydrography is influenced by the different vegetation types of dense ombrophilous forest found at different elevation: black waters (rich in humic substances with pH ca. 4) drains the alluvial dense ombrophilous forest and the lowland dense ombrophilous forest (also known as restinga forest), and clear waters (nutrient poor with pH ca. 6) drains the submontane dense ombrophilous forest and the montane dense ombrophilous forest (Por 1986, Por & Lopes 1994, Por 2004).Fish were sampled at 73 locations, using electrofishing, fishing nets, traps, and sieve (Gonçalves & Pérez-Mayorga 2016).Specimens were anesthetized with benzocaine, fixed in 10% formalin, and then kept in 70% ethanol until the analysis.Counts were taken on the left side of specimens as proposed by Fink & Weitzman (1974).The identification key provided was based on easily recognizable external morphological characters in most cases.The fishes classification followed Betancur-R et al. (2017).Voucher specimens (Table 1) are deposited in the fish collections of Universidade Estadual Paulista "Júlio de Mesquita Filho" (UNESP/DZSJRP), Câmpus São José do Rio Preto, and Museu de Zoologia of Universidade de São Paulo (MZUSP), São Paulo, Brazil.Identification key for fishes from coastal streams of the Atlantic forest of southeastern Brazil.

Results
Seven orders, 17 families, and 39 fish species were identified (Table 1).Siluriformes were the most representative order (five families and 13 species), followed by Characiformes (four families and 12 species), Gobiiformes (two families and five species), and Cyprinodontiformes (two families and four species).Gymnotiformes and Synbranchiformes were represented by one species, each one.Twenty-four species (61.5%) are endemic to the Atlantic forest, and three are endangered (Table 1).An identification key for fishes from coastal streams of Juréia-Itatins Ecological Station is provided.

Discussion
In recent decades, current knowledge about fish from Neotropical streams has increased but is still deficient, even in better-exploited regions as southeastern Brazil.Juréia-Itatins Ecological Station represents an important refuge for the conservation of stream fishes, especially Characidium schubarti, Scleromystax macropterus, and S. prionotos that are threatened with extinction in the state of São Paulo since 2014 (State Decree 60.133), as well as Pseudocorynopoma heterandria, Hoplias lacerdae, and Brachyhypopomus jureiae, sampled during other studies (Sabino & Silva 2004, Oyakawa et al. 2006).The main threat to species found in lowland streams such as S. macropterus is the deforestation of restinga (Gonçalves et al. 2016).Furthermore, the studied area has a great regional diversity of fishes, since the high diversity of aquatic environments (e.g.mountain streams with clear waters, lowland streams with black waters, and estuarine rivers with brackish waters), allows a greater diversity of species (Gonçalves & Braga 2012, Ferreira et al. 2014).
An identification key for Atlantic forest fish was published by Oyakawa et al. (2006), but only mentioned 16 of the 39 species reported by us in Juréia-Itatins Ecological Station streams.The present identification key will be useful for the recognition of species in the studied area, especially if used jointly with the color guide available online for free (Gonçalves 2014), which contains 38 photos of the Juréia-Itatins Ecological Station fish.Considering that most of these species are endemic to the coastal streams, this identification key will be useful not only for the species recognition of the sampled area, but also for the surrounding coastal region.