Oscar Fraas

Four anguillid eel species occur in the western Indian Ocean rivers of Africa: Anguilla bengalensis, Anguilla bicolor, Anguilla marmorata and Anguilla mossambica. These catadromous fishes face multiple stressors, including habitat alteration and deterioration, barriers to migration, pollution and the adverse impacts of alien species, but knowledge of eel species occurrence, abundance and ecology in Africa remains poor.This study investigated the present and historical distribution of anguillid eels and the potential associated drivers of declines at the southern extremities of their ranges in South Africa. Data analysed included sampling conducted in KwaZulu–Natal and Eastern Cape between 2015 and 2020, and secondary data extracted from databases, museums and local management agencies.The median extent of inland penetration increased as follows: 22 km for A. bicolor, 29 km for A. marmorata, 94 km for A. bengalensis and 293 km for A. mossambica. The median altitude followed a similar pattern.Extent of occurrence analyses were carried out at the regional level in KwaZulu–Natal. The sampling data on present distribution (2015–2020), compared with historical data, suggests declines in the extents of occurrence of the four eel species in KwaZulu–Natal, ranging between 31 and 48% in the last 30 years and between 35 and 82% since the 1950s.With increasing human threats in the region, especially from watercourse modification and water abstraction, further declines for these species are expected. Conservation measures recommended include the maintenance or restoration of the ecological connectivity of important rivers and the implementation of freshwater protected areas. Although eels are at present not widely exploited in South Africa, there is a need for fisheries regulations to manage sustainable commercial exploitation.

Cities have been shown to be biodiverse, but it is unclear what fraction of a regional species pool can live within city borders and how this differs between taxa. Among animals, most research has focused on a few well-studied taxa, such as birds or butterflies. For other species, progress is limite…

The ongoing contemporary biodiversity crisis may result in much of ocean’s biodiversity to be lost or deeply modified without even being known. As the climate and anthropogenic-related impacts on marine systems accelerate, biodiversity knowledge integration is urgently required to evaluate and monit…

The present study aims to use systematic conservation planning to analyse and review the national protected areas (PAs) network in Jordan. The analysis included the application of three modules: the environmental risk surface (ERS), the relative biodiversity index (RBI), and the application of Marxa…

The study of the distribution of protected animal species in Europe is especially relevant in a changing climate. Therefore, in this work, we tried to solve the problem of the possibility of habitation of tortoises Testudo graeca Linnaeus, 1758 and Testudo hermanni Gmelin, 1789 in Eastern Europe by …

Invasive herpetofauna are a significant threat to native wildlife and when colonizing higher latitudes, they must cope with greater seasonality that likely exposes them to temperatures below their preferred temperature range and reduced physiological performance. Therefore, it is important to unders…

Species distribution data are fundamental to the understanding of biodiversity patterns and processes. Yet, such data are strongly affected by sampling biases, mostly related to site accessibility. The understanding of these biases is therefore crucial in systematics, biogeography and conservation. …

In multiple regression Y ~ β0 + β1X1 + β2X2 + β3X1 X2 + ɛ., the interaction term is quantified as the product of X1 and X2. We developed fractional-power interaction regression (FPIR), using βX1M X2N as the interaction term. The rationale of FPIR is that the slopes of Y-X1 regression along the X2 gr…