Little Colorado River (LCR) Projects

Coyote Reach, Little Colorado River. Watercolor by David R. Van Haverbeke

Humpback chub monitoring in the Little Colorado River Since 2000, monitoring using hoop nets has been conducted in the lower 13.57 river kilometers (rkm) of the Little Colorado River (LCR) to estimate abundance and track trends in abundance of the endangered Humpback Chub (Gila cypha), and to monitor other fishes. These monitoring activities occurred during the spring and fall seasons. Native fish species continue to dominate the LCR, comprising 92 percent of fish captures since 2000. We used closed Chapman Petersen mark-recapture methods and catch per unit effort data to estimate either absolute or relative abundances of Humpback Chub of various size classes. Between 2000 and 2006, adult Humpback Chub (≥200 mm) maintained stable but low abundances of <3,000 individuals during the spring and fall seasons. From 2007 to 2014, the spring abundance of adult Humpback Chub significantly increased, and remained at elevated levels (~4,000 to 7,000 individuals). Fall abundances of adult Humpback Chub were also generally elevated during 2007-2014, but to a lesser extent. In 2015 and 2016, both the spring and fall abundances of adult chub in the LCR were depressed compared to the 2007-2014 timeframe. The reason why is uncertain, but it is thought that a large portion of the population remained in the mainstem during those two years. From 2017 to 2019, the spring adult Humpback Chub abundance in the LCR returned to levels equal to or exceeding those during 2007-2014. Spring abundance estimates of sub-adult Humpback Chub (150-199 mm) were more variable than adults, but have also increased since 2006, with annual abundances ≥1,000 fish from 2007-2014, after which they declined to <1,000 fish during 2015-2016. Like adult Humpback Chub, from 2017-2019 sub-adults in the 150-199 mm size class returned to the elevated levels seen during the 2007-2014 period. Smaller size classes of Humpback Chub (<150 mm) displayed significant annual variation in abundance and catch per unit effort, which is thought to be related to the LCR hydrograph. [1]

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Project Descriptions Spring and Fall LCR surveys (4 trips/yr) [1] The LCR is divided into three contiguous reaches (Boulders, Coyote, and Salt) Uses hoopneting in the lower 13.57 river kilometers of the LCR to generate marks and get recaptures Closed Chapman Petersen mark-recapture to estimate absolute abundance of ≥150 mm and ≥200 mm humpback chub (spring and fall) and age-0 humpback chub (40-99 mm) in the fall. Catch per unit effort (CPUE) data = estimate relative abundance The two spring mark-recapture efforts (generally during April and May) are aimed to coincide with the peak of humpback chub spawning in the LCR and provides an annual estimate of the spring spawning abundance. The two fall mark-recapture efforts (generally during September and October) temporally expand marks and recaptures of humpback chub in the LCR, thereby strengthening other open or multistate models. Humpback chub, flannelmouth sucker, and bluehead sucker >150 mm are PIT tagged. From 2010 onward, humpback chub 40-99 mm received a Visible Implant Elastomer (VIE) tag Humpback chub and other fish were visually checked for the presence of the external copepod parasite (Lernaea cyprinacea), but the internal Asian fish tapeworm (Bothriocephalus acheilognathi) is no longer monitored. Juvenile Chub Monitoring (JCM) Near Shore Ecology (NSE) Study of the 2009-2011 fall steady flow test LCR PIT tag array Migration timing [2]

Links and Information The Humpback Chub Page Presentations and Papers 2020 Van Haverbeke et al., 2020. Mark-Recapture and Fish Monitoring Activities in the Little Colorado River in Grand Canyon from 2000 to 2019. Submitted to USGS Grand Canyon Monitoring and Research Center, Flagstaff, Arizona. U.S. Fish and Wildlife Service, Flagstaff, Arizona. 47 pp. 2017 Mark-Recapture and Fish Monitoring Activities in the Little Colorado River in Grand Canyon from 2000 to 2016 Humpback Chub that Spawn in the LCR: Status and Drivers 2016 Spring 2016 Lower LCR humpback chub sampling trip report Mark-Recapture and Fish Monitoring Activities in the Little Colorado River in Grand Canyon Colorado River in Grand Canyon from 2000 to 2015 Humpback chub (Gila cypha) that Spawn in the Little Colorado River: Status and Potential Drivers 2013 Humpback Chub and Non-native Fish Control Update An Overview of Humpback Chub Monitoring in the Little Colorado River Other Stuff Adult chub: >200mm Subadult chub: 150-199mm Juvenile chub: <150mm Catch per unit effort (CPUE): courser measure that can show trends in abundance