Evaluating the Movement Patterns of Snake River Finespotted Cutthroat Trout in the Snake River Below Jackson Lake Dam, Grand Teton National Park

Abstract

The Snake River finespotted cutthroat trout Oncorhynchus clarkii behnkei has been formally recognized as a subspecies of cutthroat trout Oncorhynchus clarkii, but it is more generally perceived as a morphologically divergent ecotype of the more broadly distributed Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri. This large-river cutthroat trout has persisted in the Snake River downstream of Jackson Lake Dam through a century of flow regulation. Although there is a popular sport fishery focused on this native trout, spawning and distribution patterns throughout its range are poorly understood. Consequently, it is difficult to predict how future disturbances (e.g., climate change or an increase in the prevalence of nonnative species) may affect behavior or persistence. In 2008, radio telemetry techniques were used to identify spawning patterns of cutthroat trout. From August-October, 2007, 49 radio telemetry tags were implanted into cutthroat trout in the Snake River, Grand Teton National Park and fish movements were tracked during the spawning season. Significant temporal and spatial variability in spawning behavior was observed (n = 22 fish with distinct spawning migrations). The earliest spawning migration began at the end of April, and the last spawning migration was initiated in mid-July. Spawning was observed in the mainstem and side channels of the Snake River, several tributaries, and three major spring creek complexes. Although the majority of this spawning activity occurred within 40 km of the respective original tagging location, three fish migrated to spawning areas 75-100 river kilometers away. Ultimately, developing a comprehensive understanding of the behavioral variability of Snake River finespotted cutthroat trout and the habitat connectivity required to complete the life cycle will provide new insights into the management of this portion of the Snake River.