Final Finding of No Significant Impact: Tilapia Removal Program on the Virgin River, Clark County, Nevada and Mohave County, Arizona

摘要

This project is part of a program developed by the Lower Virgin River Recovery Implementation Team (RIT), whose goal is to recover endangered fishes within the Virgin River in Arizona and Nevada. The purpose of the project is to prevent the spread of tilapia from the Bunkerville irrigation diversion to the Littlefield Springs area near Littlefield, Arizona and further upstream. It is imperative that tilapia are prevented from becoming established in the lower Virgin River in order to keep them from invading and threatening native fish populations in the upper Virgin River watershed, as well. The need for the proposed project arises from the probability of severe impacts to native fishes due to the introduction of a new non-native competitive and predatory fish. If tilapia reach and inhabit the Littlefield Springs reach of the Virgin River, then eradication within the springs would be extremely difficult due to the continuous outflow of spring water, as well as the existence of a large localized population of native fish. In addition, there are no fish barriers between Littlefield Springs and the Virgin River Gorge, Arizona, thereby complicating fish removal projects in this river reach. Therefore, implementation of the proposed project would prevent tilapia from becoming established within the lower Virgin River above the Bunkerville irrigation diversion and moving upstream to further impact populations of native fish.