Discovery of endangered annual killifish Austrolebias cheradophilus (Aplocheiloidei: Rivulidae) in Brazil, with comments on habitat, population structure and conservation status

Abstract

Austrolebias genus comprises about 40 small annual killifishes endemic to South America and their highest diversity occurs in southern Brazil and Uruguay, especially in drainages of Patos-Mirim system. Austrolebias species are severely threatened with extinction because their life cycle and restricted ranges. Low dispersal ability and the extensive loss and fragmentation of freshwater wetlands contribute to this threat. Accurate information on the geographic distribution and ecology of the species, vital to plan conservation and management strategies, are scarce. In order to provide basic knowledge for annual fish conservation this paper reports the presence of Austrolebias cheradophilus and present data about its population structure (CPUA, size, sex ratio, length-weight relationships and condition factor) and conservation status in southern Brazil. The estimated CPUA of populations was 0.86 fish/m 2 . Standard length (SL) of males ranged between 32.14 and 49.17 mm and for females between 25.11 and 41.6 mm. There were no differences in SL between the sexes (t-test = -1.678; P = 0.105), and Chi-squared test demonstrated marginal differences in proportions of sexes (2.25:1; χ2 = 3.846; P = 0.07). Allometric coefficient of the LWR was slightly hyperallometric (b = 3.08) and K of the specimens ranged from 1.84 to 2.42 (mean ± S.E. = 2.12 ± 0.04). Populations have low density and their biotopes are under critical threat, mainly due to suppression by agriculture, pastures for livestock and increase housing. The species is considered "Critically Endangered" in Brazil, furthermore is strongly recommended its inclusion on lists of endangered fauna and ensures the protection of their remaining habitats.O gênero Austrolebias compreende cerca de 40 espécies de peixes anuais endêmicos da América do Sul, cuja maior diversidade está concentrada no sul do Brasil e Uruguai, especialmente nas drenagens do sistema hidrográfico Patos-Mirim. A combinação de seu ciclo de vida peculiar com suas restritas distribuições, baixa capacidade de dispersão e ampla fragmentação das áreas úmidas fazem com que suas espécies sejam consideradas ameaçadas de extinção. Entretanto, informações sobre sua distribuição e ecologia são escassas. Visando fornecer informações básicas para a conservação, este estudo registra a presença de Austrolebias cheradophilus no sul do Brasil e apresenta dados sobre sua estrutura populacional (CPUA, tamanho, razão sexual, relação peso-comprimento e fator de condição) e estado de conservação. O CPUA total das populações foi de 0,86 peixe/m 2 . Não foram encontradas diferenças no tamanho padrão entre os sexos (t-test = -1,678; P = 0,105) e o teste do Qui-quadrado apresentou um valor marginalmente significativo para a proporção dos sexos (2,25:1; χ2 = 3.846; P = 0.07). O coeficiente de "b" calculado com base na relação peso-comprimento indica um padrão de crescimento levemente alométrico positivo (b = 3,08). O fator de condição dos indivíduos variou entre 1,84 e 2,42 (média ± S.E. = 2,12 ± 0,04). As populações identifica...

Trait evolution and historical biogeography shape assemblages of annual killifish

“…Leitão et al (2016) showed, using fish, trees and birds, how rare species had a disproportionate role in the functional structure of assemblages. This may also be the case in Austrolebias, where large species are typically rarer than smaller species (Lanés, Gonçalves, & Volcan, 2014) and occupy different functional niches, therefore widening the functional richness of assemblages. Analyses of the co-occurrence of related species of hummingbirds highlighted the importance of multiple mechanisms including competition, dispersal and the environment, in shaping assemblages (Weinstein, Graham, & Parra, 2017).…”

Ontogenetic variations and feeding habits of a Neotropical annual fish from southern Brazil

“…Despite the large diversity of the Cynolebiidae family (Costa, 2008) and the vulnerability of some species Rosa & Lima, 2008), ecological characteristics such as feeding, reproduction, behavior patterns, growth, species richness and abundance of annual fishes in temporary environments are poorly known (Arenzon et al, 1999(Arenzon et al, , 2001(Arenzon et al, , 2002Errea & Danulat, 2001;Shibatta & Rocha, 2001;Shibatta, 2005Shibatta, , 2006García et al, 2008;Laufer et al, 2009;Arim et al, 2010;Gonçalves et al, 2011;Canavero et al, 2013;Lanés et al, 2013Lanés et al, , 2014aLanés et al, , b, 2016Keppeler et al, 2013Keppeler et al, , 2015Ortiz & Arim, 2016).…”

Seasonal dynamics in community structure, abundance, body size and sex ratio in two species of Neotropical annual fishes

“…The diet of sympatric annual fishes is often similar (Arim et al , ; Polačik & Reichard, ; Polačik et al , ) and opportunistic feeding was suggested as an important adaptation to ephemeral habitats (Polačik & Reichard, ; Gonçalves et al , ), despite distinctive diet preferences when food availability permits (Nico & Thomerson, ; Laufer et al , ; Polačik & Reichard, ). Given that the natural habitat of annual fishes is under increasing pressure from agriculture, urbanization and forestry development, annual killifish populations face high levels of habitat degradation (Volcan et al , ) and have been proposed as flagship species for small wetland conservation (Lanés et al ., 2014 a , b ), a move already implemented in Brazil (ICMBio, ).…”