Longitudinal flow variability and population characteristics of large-river fishes: Importance of scale in large-river ecology

Many large-river fish populations have experienced dramatic declines as a result of anthropogenic alteration of river systems. The natural flow regime which is often compromised following anthropogenic alteration of river systems. Alteration of the natural flow regime has been linked to changes in many ecological processes including food resource availability and fish growth. Therefore, quantifying the influence of flows on fish populations is a critical piece of information needed for proper conservation and management. Additionally, information regarding fish population structure across river systems is often limited. Conservation and management strategies need information regarding the presence of isolated populations or if populations are maintained through some form of metapopulation connectivity. Insight to both fish response to changing flow patterns and population structure across a riverscape are likely dependent on temporal and spatial scales of observation. In this dissertation, I use hydrological data from in situ gauging stations to describe the spatial and temporal presence of unique flow patterns along the Platte River, NE, USA. I use growth information for channel catfish Ictalurus punctatus to assess changes in growth with respect to the components of the Platte River flow regime. I also assess population structure of channel catfish and shovelnose sturgeon Scaphirhynchus platorynchus across mainstem and tributary environments using a combination of otolith microchemistry and mark-recapture