GRAND CANYON, Ariz. - For the first time, National Park Service (NPS) biologists found evidence of humpback chub reproduction in Havasu Creek.
The biologists found spawning relocated humpback chub in the creek during a recent fisheries monitoring trip between May 6 and May 15. The discovery marks an important milestone in the long-term effort to improve the species' odds of survival through the establishment of a second spawning population outside of the Little Colorado River within Grand Canyon.
The humpback chub is an endangered fish species found only in the Colorado River basin. The fish once flourished in the natural conditions of the Colorado River in its warm cloudy waters and seasonally fluctuating flows. However, the humpback chub now faces serious declines associated with changes in habitat, like the construction and operation of dams and the introduction of non-native fish species.
Since 2009 the Park Service, along with the U. S. Bureau of Reclamation, U.S. Fish and Wildlife Service, the Arizona Game and Fish Department, and U.S. Geological Survey, has been relocating juvenile humpback chub from the Little Colorado River, which supports the largest remaining population, to other tributaries to the Colorado River within Grand Canyon National Park.
Prior to the most recent monitoring trip, biologists released 543 juvenile humpback chub in Havasu Creek between 2011 and 2012. In the six days before the May 14, 2013 relocation of 300 humpback chub to Havasu Creek, NPS and U.S. Geological Survey - Grand Canyon Monitoring and Research Center staff monitored the growth, survival, abundance and spawning condition of previously relocated humpback chub.
Biologists captured a large number of humpback chub during monitoring efforts, including several males and at least two female humpback chub in spawning condition. Ultrasound images of the body cavity of several females appeared to show fully developed eggs, suggesting the fish were almost ready to spawn. Although biologists need further testing, these results are promising and show the potential usefulness of ultrasonic imaging as a non-invasive method of evaluating the species' spawning condition.
Biologists also captured two juvenile humpback chub without identification tags, indicating they were not relocated previously. The small size of these two un-tagged fish suggests they hatched in Havasu Creek during the spring of 2012.
Finally, biologists captured a newly hatched fish that they provisionally identified as a humpback chub. Biologists are waiting for confirmation of this species identification in a laboratory setting.
Together, these findings suggest that Havasu Creek humpback chub relocations have, at least to some extent, resulted in a spawning population of humpback chub. However, future monitoring is needed to figure out whether spawning leads to the survival of juveniles to maturity.
Fisheries biologists will continue to monitor the growth, survival and reproduction of relocated humpback chub in Havasu Creek twice a year.
"We are all really encouraged by these results, although based on the high growth rates and retention of translocated fish we've seen during past monitoring trips, the detection of spawning fish this year wasn't totally unexpected," Grand Canyon National Park Fisheries Program Manager Brian Healy said. "It will be really interesting to see whether spawning by these adult fish continues, and whether it leads to a larger number of juveniles and their survival to maturity."
There are no closures at Havasu Creek related to relocation activities. Anglers should be familiar with the identifying characteristics of humpback chub to avoid any accidental capture of these endangered fish. Young humpback chub are silver, have small eyes and large fins, but have not yet developed the pronounced hump behind their head. If any humpback chub are incidentally caught, they must be immediately released unharmed.
More information is available from Healy at (928) 638-7453 or Maureen Oltrogge, public affairs officer, at (928) 638-7779. Additional information on humpback chub relocations and Grand Canyon National Park's fisheries program is available online at www.nps.gov/grca/naturescience/fish.htm.