Geological Survey

Description

One of the goals of the Glen Canyon Dam Adaptive Management Program (GCDAMP) is the conservation of native Colorado River Basin fishes, particularly those protected by the Endangered Species Act of 1973. The federally listed endangered humpback chub is a cyprinid endemic to the Colorado River and is a focal resource of the GCDAMP within Grand Canyon. Recent analysis of the status and trends of this species indicated a decadal decline in abundance likely owing to decreased recruitment. Humpback chub juveniles recruit to the mainstem juvenile population from the Little Colorado River (LCR) as very small juveniles during the spring, and larger juveniles recruit to the mainstem during monsoon-driven flood events in late-summer and fall, or from mainstem spawning events. The quantity and quality of juvenile habitat in the mainstem is driven by variation in flow and temperature regimes and also channel morphology. Habitat characteristics are determined by the monthly average discharge and hourly variation in discharge from Glen Canyon Dam, as well as sediment supply in the mainstem, and the frequency and timing of flows from Glen Canyon Dam designed to create habitat believed to be important for native fish (e.g., backwaters). Survival rates of humpback chub juveniles in the mainstem depend on the quantity and quality of physical habitat, food availability, and the intensity of competition and predation from both native and non-native fishes. Otoliths are often used to estimate fish age and growth rates by enumerating and measuring daily increments in larval and juvenile fish or annual increments in adult fish. Additionally, combining otolith chemistry with age/growth analyses is a powerful tool for retrospectively linking habitat residency with growth.The USGS is offering a funding opportunity to a CESU partner to provide research to complete the following objectives:• Characterize definitively the δ13C and δ18O otolith signatures obtained by resident (larval/early juvenile) Colorado River and LCR fish• Analyze stable isotope otolith chemistry of fish collected throughout the summer and fall of 2010• Expand water chemistry monitoring study to include monthly samples from four locations in the Little Colorado River• Link otolith chemistry to growth rates derived from enumerating and measuring growth increments using light and electron microscopy techniques• Investigate the possibility that scales of these fishes carry the same chemical information and “signatures,” in terms of C and O stable isotopic ratios, as do the otoliths

Who can apply

• Others

Contact

FAITH GRAVES <br/>Contract Specialist <br/>Phone 703-648-7356
fgraves@usgs.gov