Widespread colonisation of Tanzanian catchments by introduced Oreochromis tilapia fishes: the legacy from decades of deliberate introduction

From the 1950s onwards, programmes to promote aquaculture and improve capture fisheries in East Africa have relied heavily on the promise held by introduced species. In Tanzania these introductions have been poorly documented. Here we report the findings of surveys of inland water bodies across Tanzania between 2011 and 2017 that clarify distributions of tilapiine cichlids of the genus Oreochromis. We identified Oreochromis from 123 sampling locations, including 14 taxa restricted to their native range and three species that have established populations beyond their native range. Of these three species, the only exotic species found was blue-spotted tilapia (Oreochromis leucostictus), while Nile tilapia (Oreochromis niloticus) and Singida tilapia (Oreochromis esculentus), which are both naturally found within the country of Tanzania, have been translocated beyond their native range. Using our records, we developed models of suitable habitat for the introduced species based on recent (1960–1990) and projected (2050, 2070) East African climate. These models indicated that presence of suitable habitat for these introduced species will persist and potentially expand across the region. The clarification of distributions provided here can help inform the monitoring and management of biodiversity, and inform policy related to the future role of introduced species in fisheries and aquaculture

Monitoring the impacts of feral Horses on vegetation condition using remotely sensed fPAR: a case study in Australia's alpine parks

Throughout the world, feral horses (Equus caballus) are causing environmental degradation and a decline in ecological integrity. Evidence from scientific monitoring is needed to inform the public debate and help land managers make informed decisions. We used field observations of vegetation condition at a network of sites in the Australian Alps where horses were present or absent. The data were combined with the remotely -sensed fraction of photosynthetic active radiation (fPAR) and topographic condition. Vegetation condition was assessed in the field by rangers using a modified version of the Landscape Function Analysis (LFA) index. We found significant differences in the LFA index between sites where horses were present or absent. Sites with presence of horses have 10 per cent lower fPAR than sites with absence of horses. The results also indicated a significant correlation between LFA and fPAR. Our analysis supports the hypothesis that feral horses have a negative impact on the condition of Australian alpine vegetation. This study provides a useful and relatively cost-effective method for monitoring the impact of feral horses on native vegetation, and can be used to support decision making and management interventions