The recapture of Leptopanchax opalescens (Aplocheiloidei: Rivulidae), a critically endangered seasonal killifish: habitat and aspects of population structure

Abstract

Leptopanchax opalescens (Myers, 1942) is a small seasonal killifish endemic to coastal drainages in the state of Rio de Janeiro, Brazil. Leptopanchax opalescens was recaptured in temporary open vegetation pools (22°42.35’S, 43°41.59’W) in the hydrographic basin of the Guandu River, state of Rio de Janeiro, Brazil, after eight years without records. Information on habitat and population parameters (Capture per unit area (CPUA), size, sex ratio and length-weight relationship (LWR)) are given to provide subsidies for the conservation of this species. Specimens were captured during the rainy season (January-April 2020) in shallow pools (mean depth = 21 ± 12 s.d. cm), with relatively acidic pH (5.2 ± 0.8) and low concentrations of dissolved oxygen (3.5 ± 1 mg/L). The estimated CPUA of the population was 0.89 fish/m2. The total length (TL) of males ranged from 21.1 to 28.8 cm, and females ranged from 17.0 to 31.2 mm. Males were significantly larger (t-test = 2.04, p < 0.05) than females, which were in greater proportion (2.83Female: 1Male, p < 0.001). A positive allometric coefficient (b = 3.19) was found through length-weight relationship curve, indicating that individuals of the species gain proportionally more increment in weight than in length. Leptopanchax opalescens is a critically endangered species, and the results of this study contribute to the knowledge of the distribution, population structure and conservation of the species and its natural habitats.

Reproductive Strategy of the Annual Fish Leptopanchax Opalescens (Rivulidae) and Trade-Off Between Egg Size and Maximum Body Length in Temporary Wetlands

“…Four out of the six species are listed as Critically Endangered (CR) in the Red Book of Brazil's Endangered Fauna (ICMBio 2018), including one possibly extinct species (Costa 2019). Information on reproductive traits of Leptopanchax species is minimal and diffuse (e.g., Costa and Leal 2009;Guedes et al 2020). The scarcity of reproductive information of Leptopanchax species and other annual rivulids is a bottleneck that makes it di cult conservation strategies of species in imminent threat of extinction.…”

“…Guedes et al 2020), but the populations show small color variations di cult to analyze by photographs taken with different parameters(Costa 2019;Souto-Santos et al 2021). Therefore, it is desirable that specimens from the type locality of L. opalescens (or at least from some locality associated with Guanabara Bay) be sequenced and compared with the Sepetiba sequences made available here.Spawn type and phases of maturationThe reproductive cycle in females of L. opalescens is discontinuous and spawning in batches, indicated by the presence of oocytes at different stages of development and post-ovulatory follicles in specimes capable of spawning.…”

Reproductive strategy of the annual fish Leptopanchax opalescens (Rivulidae) and trade-off between egg size and maximum body length in temporary wetlands

“…Four out of the six species are listed as Critically Endangered (CR) in the Red Book of Brazil's Endangered Fauna (ICMBio 2018), including one possibly extinct species (Costa 2019). Information on reproductive traits of Leptopanchax species is minimal and diffuse (e.g., Costa and Leal 2009;Guedes et al 2020). The scarcity of reproductive information of Leptopanchax species and other annual rivulids is a bottleneck that makes it di cult conservation strategies of species in imminent threat of extinction.…”