Where have all the catfish gone?

Authors: David Rogowski, Dale Fonken

Year: 2024

Abstract

Channel Catfish are an invasive species in the Colorado River Basin. At one point they were one of the most common species within the Colorado River, Grand Canyon. Over time the relative abundance of Channel Catfish has declined to a point where it is unusual to catch a Channel Catfish within our study area (Glen Canyon Dam to Pearce Ferry Rapid (480 km). There are a couple of hypotheses that might account for the decline in Channel Catfish. When Lake Mead was near full pool, numerous side canyons were inundated that provided habitat and appropriate temperatures for spawning and growth of Channel Catfish. As Channel Catfish increased in size they were able to move upstream into the Grand Canyon. As the water level of Lake Mead has declined over the past ~15 years lentic habitat has reverted to lotic habitat as the reservoir receded. Almost 80 km of riverine habitat has re-emerged from the former Lake Mead reservoir. In addition, a new rapid has formed, Pearce Ferry Rapid which is a partial barrier to upstream fish movement. In recent years as a result of climate change and an ongoing drought, water releases from Glen Canyon Dam have been increasing in temperature over time. Despite the “warmer” water, we have not seen an increase in Channel Catfish in our study area. However Channel Catfish remain relatively abundant below Pearce Ferry Rapid and are still a popular fish for anglers in Lake Mead.