Full recovery of the endangered humpback chub in Grand Canyon will require ultimately that habitat conditions be improved in the Colorado River. Fluctuating flows from Glen Canyon Dam eliminates much of the designated critical habitat needed to ensure the chub’s survival and recovery. Because water released from the dam is too cold and fluctuations destabilize habitat along the mainstem, other suitable habitat is needed. Tributaries to the Colorado River are the answer, at the least for the near term.
This month hundreds of young humpback chub are being moved to Havasu Creek, a tributary that empties into the Colorado River in Grand Canyon at River Mile 157. It is similar to the Little Colorado River in water chemistry and physical habitat and has few non-native fish predators. This will be the second translocation made in Havasu Creek during the last two years by the National Park Service. The Grand Canyon Trust is supporting this work through its participation in the Glen Canyon Dam Adaptive Management Program.
Translocations in tributaries can benefit the population in two ways: first, they may lead to the establishment of additional spawning populations of humpback chub, increasing the odds for their survival in Grand Canyon. Second, tributaries provide a refuge where young chub can grow to a size large enough to survive the colder temperatures of the Colorado River.
Translocations have also occurred in Shinumo Creek, a small tributary stream that joins the Colorado River at River Mile 109. In 2009, over 300 humpback chub were successfully moved. One of Shinumo Creek’s positive features is the presence of barrier falls just above its confluence. The 15-foot waterfall isolates chub habitat in the creek from non-native predatory fish in the Colorado River.
The humpback chub is an endangered, 4-million-year-old fish found only in the Colorado River basin. It is one of eight species of fish native to the Colorado River basin. Because of changes caused by Glen Canyon Dam and the introduction of non-native fish such as rainbow trout, the humpback chub population has seriously declined. Today the largest remaining population in the world is found in the Little Colorado River and its confluence with the Colorado River in Grand Canyon. Now the chub recovery effort includes moving young fish into additional tributaries.
— Nikolai Lash