Intra-reach Headwater Fish Assemblage Structure

INTRODUCTION The global connectedness of ecological systems and ecological problems is becoming ever more apparent, as are the associated complexities. As a result, effective large-scale conservation is relying more on regional modeling and assessment. These regional approaches allow for evaluation of resource conditions over large areas and often have multiscale capabilities allowing examination of conditions at finer scales, within limits (Prior-Magee et al. 2007, National Fish Habitat Board, 2010, McKenna and Johnson 2011, McKenna et al. 2015). Data management and analysis limitations, as well as the scale of the problems to be addressed, require these broad-scale efforts to assume uniform average habitat conditions and/or species assemblages or populations within stream reaches (McKenna et al. 2006, Sowa et al. 2007, Kanno et al. 2014). Stream reaches (in the Great Lakes Region) are typically small (< 3 km) rarely exceeding 10 km. They may be clearly defined on a map by upstream and downstream confluences and are often the minimum reporting units for broad scale analyses. The National Hydrography Database (NHD) is widely used as a geographic foundation of these analyses and is an effective information management and analysis tool, allowing for association of local and broad-scale habitat and biological information with each stream reach within a region or the entire nation (Huang and Frimpong 2016). The NHD stream network consists of confluence-to-confluence stream reaches that range widely in length and vary with spatial resolution (e.g., 1: 100,000 or 1: 24, 000).