Spatial ecology and life-history diversity of Snake River finespotted cutthroat trout Oncorhynchus clarkii behnkei in the upper Snake River, WY

Abstract

Life-history diversity, movement patterns, and habitat associations of cutthroat trout Oncorhynchus clarkii have been widely studied in smaller river systems and are critical components of conservation planning. However, much less is known about how the patterns observed in smaller systems may "scale up" in larger, complex river systems. In my dissertation, I evaluated the life-history variation and spatial ecology of Snake River finespotted cutthroat trout O. c. behnkei in the upper Snake River, WY and collaborated on a statistical method to characterize habitat occupancy from radio-telemetry data. For my first chapter, I identified the life-history diversity and movement patterns of cutthroat trout in a large river network using radio-telemetry. Spawning occurred from May through July throughout the upper Snake River in spring creeks, tributaries, and side channels over a spatial extent > 100 km. Postspawning movement patterns varied among spawning areas and life-history forms. Results indicated that life-history diversity in large river networks is substantially more complex than may be observed in headwater systems, reflecting increased habitat complexity and availability in larger systems. For my second chapter, I collaborated on a method to address three biases in radio-telemetry datasets: (1) data may be collected at sparse, unequal sampling intervals, (2) encountering an individual in a location does not imply occupancy, and (3) all locations between where individuals are encountered are occupied to some extent, despite the lack of observations. The resulting adaptive kernel density interpolation method treated location as a utilization distribution for each tracking interval (e.g., a week) and estimated time spent per location as a function of individual movement speed and time since last relocation. For my third chapter, I evaluated habitat occupancy and movement patterns at multiple spatiotemporal scales. Spatial variation and hierarchical structure in the physical template interacted to produce contextual variation in the availability and function of habitat attributes (e.g., wood functioning as cover or as a velocity break). Collectively, these studies provide a more complete understanding of life-history diversity in a large river network and the way in which variation in the physical template shapes habitat occupancy, and movement patterns.