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Photo by Unknown Photographer
Photo Courtesy of Utah Division of Wildlife Resources; Utah Division of Wildlife Resources
Humpback Chub
Gila cypha
NatureServe conservation status
Global (G-rank): G1
State (S-rank): S2
External links
Species range
Populations occur in the Colorado River in Westwater Canyon and Cataract Canyon and in the Green River in Desolation and Gray canyons (USFWS 2002). Historically the occupied range was larger; records suggest that much, if not all, of the Green River and perhaps some of the major tributaries (e.g., the White River) supported populations.
Habitat
This species occurs in large rivers, primarily in canyon-bound reaches. Spawning habitat is deep, swift water over clean gravel or cobbles. Adults are often found in deep, recirculating eddies, although other deep water habitats are used. Sub-adults occupy rather shallow water with slow currents. (see Berg 1983, USFWS 2002).
Food habits
The Humpback Chub is an omnivorous fish with a variable diet that includes aquatic invertebrates like insects, crustaceans, and diatoms, as well as algae, terrestrial vegetation, seeds, and occasionally other fish and fish eggs. Its feeding strategy varies by age and habitat, with younger chubs consuming more zooplankton in shallow areas and adults feeding on more benthic invertebrates and terrestrial matter in faster currents
Reproductive characteristics
Humpback chub spawn from April to July, when snowmelt increases river flows and water temperatures are between 15-21°C (59-70°F). They deposit their eggs over cobble and gravel in slower-moving backwaters or sheltered areas. Young fish stay in shallow sheltered areas before dispersing 1-3 months after emergence
Threats or limiting factors
The numerous threats to this species are derived primarily from the fundamental ecological changes that have followed the damming of major rivers and tributaries in the Colorado River drainage. Changes in sediment deposition patterns, flow, and temperature caused by dams have resulted in loss and alteration of aquatic habitats and have favored non-native competitors and predators. Increased hybridization among native Gila species may be symptom of changes in habitat and movement patterns, and genetic introgression is now an important threat. Small population sizes resulting from population decline and fragmentation may have implications for the long-term genetic diversity of populations.
