Endangered Humpback chub translocations to Colorado River tributaries in Grand Canyon National Park

Authors: Emily Omana Smith, Brian D. Healy, Clay Nelson, Melissa Trammell

Year: 2013 (xlv)

Abstract

Historic fish communities in Grand Canyon National Park (GCNP) consisted of eight species, six of which are endemic to the Colorado River Basin. Today, reproducing populations of only four native species occur in GCNP, including humpback chub, Gila cypha, which is listed under the Endangered Species Act. The Colorado River in Grand Canyon contains the largest remaining population of humpback chub. Nevertheless, significant threats remain to this population and to other remaining native species, including the presence of non-native fish and parasites, and altered temperature and flow regimes. In addition, the Grand Canyon population spawns in one location, the Little Colorado River, which is threatened by watershed-wide impacts. In accordance with National Park Service native species management policies and mandates (e.g., Organic Act of 1916), GCNP, with the assistance of the Bureau of Reclamation and others, initiated a series of humpback chub translocations in Havasu and Shinumo creeks, both tributaries of the Colorado River, to contribute towards the long-term goals of establishing additional spawning aggregations and/or increasing mainstem aggregations of the humpback chub within the park. After five years of humpback chub translocations, juvenile survival and growth rates are higher or comparable to those rates found for humpback chub inhabiting the Colorado River and Little Colorado River. Emigration remains a concern for long-term success of the projects; however, initial results of an alternative release technique experiment have resulted in reduced emigration immediately following translocation in Shinumo Creek. In Havasu Creek, the presence of individuals in spawning condition and of untagged juvenile humpback chub suggests that reproduction is occurring. Monitoring programs associated with translocations, along with research that examines relationships between native and non-native fish in Bright Angel and Shinumo creeks and fish population modeling will assist managers in planning and adapting fish restoration actions to meet NPS goals.