Diversity of Shenango River Fish at Sites with Varying Types of Land Use

Abstract

Globally, fishes have the highest rate of discovery of new species and exist in greater numbers than all other vertebrates combined. However, over the course of only a few decades the amount of inland fishes in North America considered imperiled or extinct has increased 20-40%. The main threats contributing to the decline in diversity of North American fresh water fishes include destruction of habitat, water depletion, point and non-point source pollution, erosion and sedimentation, overexploitation, disease and parasitism, introduced species, and climate change (Walsh et al. 2009). A modification of the Index of Biotic Integrity (IBI) was used to evaluate the fish diversity in the modified Shenango River system. An IBI is an index that evaluates and measures the health of a stream ecosystem based on multiple attributes of the resident fish assemblage. Each site was sampled and classified based on its deviation from the reference site and then classified as poor, fair, good or excellent. The IBI data was used to determine biological criteria, select sites for further studies, provide biological impact assessments, and assess status and trends of local freshwater fish assemblages. Species richness, Menhinick's index, species diversity and Shannon's index were determined for every site and sampling. All sites varied in IBI classification during different months. Site classifications were: no fish, poor, fair and good. In addition to the IBI, additive partitioning was used to measure diversity. Additive partitioning is an operational method which allows the analysis of patterns of species diversity across multiple spatial scales and is usually expressed by the number of species or species richness. The total or gamma diversity found in a pooled set of communities sampled from the river at any scale can be partitioned into the average diversity occurring within a sample (alpha diversity) and the average diversity among samples (beta diversity) (Pegg and Taylor, 2007). Alpha diversity was lower than beta diversity fo