Ecological Risk Assessment

Ecological risk assessment is defined herein as a process that evaluates the likelihood that adverse ecological effects may either occur or are occurring to indigenous as a result of exposure to selected invasive species. The assessment will be divided into four principal components according to Landis (2004) and Schleier et al. (2008). The assessment determined both the risk of of the stated invasive species establishment and spread, and the potential detrimental effects it may have on indigenous species and other species of concern. The first component described the organism of interest, or stressor, as invasive species and outlined its kenned or potential adverse ecological impacts on receiving environments.

The second component identified

The highest risk scenarios are liable to unfold when there is both a high probability of the establishment of invasive species in recipient river systems and associated adverse ecological impacts. In most tropical rivers the genuine impact of introduced species is arduous to ascertain because data on the community structure and functioning afore the preludes are often unavailable. Despite this, the well-documented prosperity of invasive species in invading novel tropical river systems global and associated deleterious effects, provide vigorous circumstantial evidence to fortify the hypothesis of incremented extinction rates and hybridisation risk to indigenous species in recipient river systems as a result of invasive species incursions. The mechanism of potential adverse ecological impact of invasive species include competition for victuals and the space obligatory for spawning. In areas where it has become established, invasive species have been shown to rapidly displace indigenous species through competitive omission, to the extent that some populations have become locally extinct. Few studies have assessed the potential of invasive species to transmit diseases into novel aquatic

A fish survey will be additionally conducted within the study period and its associated tributaries to ascertain the extent of the current distribution of invasive species within the province from aforetime kenned prelude sites. The presence or absence of invasive species within a given river segment will be attested through genetic and morphological identification of sampled populations in a parallel perpetual study.

Characterization of risk

Invasion vulnerability

The incursion susceptibility score (IVS) will be derived as the sum of all physical variables (minimum temperature), dam score and river flow (either perennial or episodic/ephemeral) for each given river section. The minimum possible IVS will be 3 and the maximum possible will be 7. The IVS values will be then divided into three risk categories utilizing the natural break (Jenks), in Arc-Map® 9.3 where rivers with river segments with IVS values < 4 will be characterized as of low risk, 4 - 5 as of medium peril, and 6 - 7 as of high