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

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°42.35S, 43°41.59W) 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.

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

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°42.35S, 43°41.59W) 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.(AU)

Taxonomic and functional distinctness of the fish assemblages in three coastal environments (bays, coastal lagoons and oceanic beaches) in Southeastern Brazil.

Several species of marine fish use different coastal systems especially during their early development. However, these habitats are jeopardized by anthropogenic influences threatening the success of fish populations, and urgent measures are needed to priorize areas to protect their sustainability. We applied taxonomic (Δ+) and functional (X+) distinctiveness indices that represent taxonomic composition and functional roles to assess biodiversity of three different costal systems: bays, coastal lagoons and oceanic beaches. We hypothesized that difference in habitat characteristics, especially in the more dynamism and habitat homogeneity of oceanic beaches compared with more habitat diversity and sheltered conditions of bays and coastal lagoons results in differences in fish richness and taxonomic and functional diversity. The main premise is that communities phylogenetically and functionally more distinct have more interest in conservation policies. Significant differences (P < 0.004) were found in the species richness, Δ+ and X+ among the three systems according to PERMANOVA. Fish richness was higher in bays compared with the coastal lagoons and oceanic beaches. Higher Δ+ was found for the coastal lagoons compared with the bays and oceanic beaches, with the bays having some values below the confidence limit. Similar patterns were found for X+, although all values were within the confidence limits for the bays, suggesting that the absence of some taxa does not interfere in functional diversity. The hypothesis that taxonomic and functional structure of fish assemblages differ among the three systems was accepted and we suggest that coastal lagoons should be priorized in conservation programs because they support more taxonomic and functional distinctiveness.