Population dynamics of Melanorivulus rossoi, a restricted geographic distribution killifish species

Abstract

Species of Melanorivulus present behaviour and physiological traits that allow them to live in marginal aquatic habitats. In particular, Melanorivulus rossoi is a small nonannual fish only known from its type locality in the Brazilian Cerrado. In this study, we aimed to characterize the distribution and temporal variation in body size, sex ratio, density, length-weight relationship (LWR) and condition factor (CF) of M. rossoi in its natural habitat. To accomplish this, fish samples were taken monthly for a year using sieve nets every 30 min. Body size of males and females increased throughout the year until early summer. LWR was significant, and general coefficient of determination (r 2) was 92%. Juveniles showed negative allometric growth, but adults showed positive allometric growth. Both sexes presented the same tendency of temporal variation in CF, with lower values in October and January and peaks in September and February. Fire occurred in June, but no difference in population parameters was observed after this event. A decrease in the abundance of Melanorivulus was related with an increase in the abundance of Erythrinidae juveniles. This might be explained by an increased predation of this species over the M. rossoi individuals, when the population was reduced to about 30% of that in the previous months. We report four new locations where this species was recorded; thus, similar to most Rivulidae members, M. rossoi has a restricted distribution area and is threatened with extinction. Therefore, our results may be useful in developing management strategies aimed at conservation of this species and its habitat in Brazil.

Annual and non‐annual fish assemblages respond differently to environmental and spatiotemporal variations of temporary wetlands from southern Brazil

“…This situation is probably one of the reasons behind the low density and reduced time of permanence of the A. ephemerus in the wetlands of the Brazilian Chaco. After flooding events, which resulted in the connection of the wetlands, A. ephemerus was not recorded in the pools, having been replaced by non‐annual species with assemblages of up to 15 species in a single wetland, including piscivorous fishes, known as rivulid predators (Severo‐Neto & Volcan, 2018). In the present study, there was also a change in fish composition and abundance after the increase of the level of the permanent water body as well as the annual fish population reduction.…”

“…Baber, Childers, Babbitt, & Anderson, 2002;Pazin et al, 2006). This factor, in turn, is directly related to the flooding stage of the adjacent permanent water body (Drago, 1989) and precipitation (Sanderson, Eyre, & Rushton, 2005).…”

Conservation status of Astyanax biotae (Characiformes: Characidae) in Mato Grosso do Sul, upper Paraná River basin, Brazil

“…These environments are similar to the type locality, Água Mole Stream, which is also located in an area of agricultural activity with a corresponding loss of native forest. These types of habitats are quite common in the landscape of Mato Grosso do Sul, especially from the central to the southern part of the state, but remain neglected in terms of ichthyofaunal surveys, although important information about the biology of species with restricted ranges can be obtained from them (e.g., SEVERO-NETO;VOLCAN, 2018).…”

Ficha de Melanorivulus rossoi

“…Endêmica do Brasil: Sim Melanorivulus rossoi é endêmica do Brasil e conhecida de banhados na margem direita do rio Anhanduí, bacia do rio Paraná, municípios de Campo Grande e Sidrolândia, estado do Mato Grosso do Sul (Costa, 2005;Severo-Neto & Volcan, 2018).…”