The federally-listed threatened humpback chub is a native fish of the Colorado River. Despite the environmental changes to the river following the construction of Glen Canyon Dam, humpback chub persists alongside nonnative species, including rainbow trout. The pre-dam Colorado River experienced seasonal variation in temperature and discharge. Seasonal flooding resulted in sediments carried downstream causing turbid conditions. These are the conditions under which humpback chub evolved. The post-dam Colorado River is less variable in terms of water temperature and discharge and is generally not turbid. Some of these nonnative fish species introduced to the Colorado River or its tributaries thrive in the altered environment. Some eat juvenile humpback chub and compete with all life stages of the native fish. The goal of this project is to monitor all life stages of humpback chub (juvenile, subadult, and adult), estimate survival, growth, movement and abundances for various life stages and develop population models to predict responses to potential management strategies focused on either controlling nonnative species or restoring aspects of the physical environment.
Background & Importance
Prior to introduction of nonnative fishes and completion of many dams, humpback chub (Gila cypha) were widely distributed throughout the Colorado River. Humpback chub abundance has since declined throughout their range and the species is restricted to five recognized populations. One of the largest of these, and the focus of our research, lives in Grand Canyon near the confluence between the Little Colorado and Colorado Rivers. This portion of the Colorado River is regulated and highly altered in terms of temperature, turbidity, and flow. Additionally, this river reach contains multiple nonnative fish species, which are numerically dominated by rainbow trout (Oncorhynchus mykiss). Humpback chub population decline observed in the late 1990s and early 2000s coincided with cooler water temperatures and higher salmonid, abundances. Humpback chub abundance in Grand Canyon increased during the latter part of 2000s, when water temperatures were warmer and salmonid abundances were lower. Recently, this population has been relatively stable. An inability to determine the relative importance of different potential drivers (i.e., environmental conditions versus nonnative fish densities) has often been cited as hampering management decisions.
Understanding the relative importance of different factors (e.g., nonnative fish, temperature, turbidity) was difficult until recently. Sampling and modeling were focused on adult humpback chub mostly in the Little Colorado River, where most humpback chub spawning occurs. As a result, researchers were forced to infer early-life history from recruitment to adults. This inference is difficult for such a long-lived species, which is now known to have a complicated life history. Recently, it has been shown that humpback chub are double partial migrants. Some individuals reside only in the Little Colorado River for many years in a row, while others reside primarily in the Colorado River and only enter the Little Colorado River to spawn every few years. Furthermore, there is considerable variation in the life history of juveniles depending on whether they rear in the Little Colorado River or Colorado River. In recent years, direct studies of juvenile humpback chub early life history in these two systems using mark-recapture methods has led to a much improved understanding of the relative importance of different factors (e.g., environmental conditions, nonnative fish densities) in determining humpback chub population dynamics. These insights have been used to develop predictive simulation models, which in turn are being used to predict outcomes of management alternatives and inform decisions.
General Methods
Mark-recapture studies are ongoing both in the Little Colorado River and a reference site in the Colorado River. We individually mark adult and subadult humpback chub with passive integrated transponder (PIT) tags, and we give size- and trip-specific visual implant elastomer marks to juvenile humpback chub. We use mark-recapture models to estimate parameters of interest, including survival rates, movement rates, growth rates, and abundances. These data inform ecological and economic modeling specific to the question of interest. For more details about field methods, mark-recapture models, and statistical analyses, please refer to the listed publications.
Important Results
A subset of humpback chub reside in the Little Colorado River year round (i.e., residents), whereas other adults move between the Little Colorado and Colorado Rivers to spawn (i.e., migrants). Growth of all size classes is much faster in the Little Colorado River; however, in some years, annual survival in the Colorado River is much higher, suggesting a potential tradeoff between growth and survival. Rainbow trout abundance is negatively related to juvenile chub survival in the mainstem Colorado River, whereas temperature is positively related to growth rates in both the Colorado and Little Colorado Rivers. Food availability and turbidity are also positively related to growth in the Little Colorado and Colorado Rivers respectively. The seasonal timing of growth also differs between the two systems. In the Little Colorado River, maximum growth occurs from April to June; whereas in the Colorado River, maximum growth occurs from July to September. We have developed simulation model using mark-recapture data to support the Long-Term Experimental and Management Plan (LTEMP) Environmental Impact Statement and the expanded nonnative environmental assessment.
Future Directions
We are continuing to evaluate juvenile humpback chub population dynamics in both the Little Colorado River and Colorado River to refine our understanding and improve our predictive models. Key sources of uncertainty are the drivers of and variation in both juvenile recruitment and juvenile outmigration from the LCR. In addition, we are working to incorporate detections from autonomous PIT-tag antennas into sampling efforts, as these technologies will allow us to evaluate behavior and size effects on capture probability and minimize biases in our current study design. Recent work has also focused on quantifying the impacts of ongoing translocations within the Little Colorado River. In recent years, we have begun applying the same approach in the western Grand Canyon where humpback chub abundances are increasing.
Below are publications associated with this topic.
Vital rates of a burgeoning population of Humpback Chub in western Grand Canyon
Water storage decisions and consumptive use may constrain ecosystem management under severe sustained drought
Incorporating antenna detections into abundance estimates of fish
Assessing the population impacts and cost‐effectiveness of a conservation translocation
Partial migration and spawning movements of humpback chub in the Little Colorado River are better understood using data from autonomous PIT tag antennas
Water storage decisions will determine the distribution and persistence of imperiled river fishes
Remarkable response of native fishes to invasive trout suppression varies with trout density, temperature, and annual hydrology
A primer of fishery studies in Grand Canyon: The nonnative fish removal story
What's in the hump of the humpback chub?
Effects of water temperature, turbidity, and rainbow trout on humpback chub population dynamics
Safety in numbers: Cost-effective endangered species management for viable populations
Effects of high flow experiments on warm-water native and nonnative fishes
What environmental conditions reduce predation vulnerability for juvenile Colorado River native fishes?
Below are partners associated with this project.
- Overview
The federally-listed threatened humpback chub is a native fish of the Colorado River. Despite the environmental changes to the river following the construction of Glen Canyon Dam, humpback chub persists alongside nonnative species, including rainbow trout. The pre-dam Colorado River experienced seasonal variation in temperature and discharge. Seasonal flooding resulted in sediments carried downstream causing turbid conditions. These are the conditions under which humpback chub evolved. The post-dam Colorado River is less variable in terms of water temperature and discharge and is generally not turbid. Some of these nonnative fish species introduced to the Colorado River or its tributaries thrive in the altered environment. Some eat juvenile humpback chub and compete with all life stages of the native fish. The goal of this project is to monitor all life stages of humpback chub (juvenile, subadult, and adult), estimate survival, growth, movement and abundances for various life stages and develop population models to predict responses to potential management strategies focused on either controlling nonnative species or restoring aspects of the physical environment.
Background & Importance
Prior to introduction of nonnative fishes and completion of many dams, humpback chub (Gila cypha) were widely distributed throughout the Colorado River. Humpback chub abundance has since declined throughout their range and the species is restricted to five recognized populations. One of the largest of these, and the focus of our research, lives in Grand Canyon near the confluence between the Little Colorado and Colorado Rivers. This portion of the Colorado River is regulated and highly altered in terms of temperature, turbidity, and flow. Additionally, this river reach contains multiple nonnative fish species, which are numerically dominated by rainbow trout (Oncorhynchus mykiss). Humpback chub population decline observed in the late 1990s and early 2000s coincided with cooler water temperatures and higher salmonid, abundances. Humpback chub abundance in Grand Canyon increased during the latter part of 2000s, when water temperatures were warmer and salmonid abundances were lower. Recently, this population has been relatively stable. An inability to determine the relative importance of different potential drivers (i.e., environmental conditions versus nonnative fish densities) has often been cited as hampering management decisions.
A view of the lower Little Colorado River (July 2013) a spawning site of humpback chub. Understanding the relative importance of different factors (e.g., nonnative fish, temperature, turbidity) was difficult until recently. Sampling and modeling were focused on adult humpback chub mostly in the Little Colorado River, where most humpback chub spawning occurs. As a result, researchers were forced to infer early-life history from recruitment to adults. This inference is difficult for such a long-lived species, which is now known to have a complicated life history. Recently, it has been shown that humpback chub are double partial migrants. Some individuals reside only in the Little Colorado River for many years in a row, while others reside primarily in the Colorado River and only enter the Little Colorado River to spawn every few years. Furthermore, there is considerable variation in the life history of juveniles depending on whether they rear in the Little Colorado River or Colorado River. In recent years, direct studies of juvenile humpback chub early life history in these two systems using mark-recapture methods has led to a much improved understanding of the relative importance of different factors (e.g., environmental conditions, nonnative fish densities) in determining humpback chub population dynamics. These insights have been used to develop predictive simulation models, which in turn are being used to predict outcomes of management alternatives and inform decisions.
General Methods
Mark-recapture studies are ongoing both in the Little Colorado River and a reference site in the Colorado River. We individually mark adult and subadult humpback chub with passive integrated transponder (PIT) tags, and we give size- and trip-specific visual implant elastomer marks to juvenile humpback chub. We use mark-recapture models to estimate parameters of interest, including survival rates, movement rates, growth rates, and abundances. These data inform ecological and economic modeling specific to the question of interest. For more details about field methods, mark-recapture models, and statistical analyses, please refer to the listed publications.
Understanding the population dynamics humpback chub is imporant when making management decisions. (Public domain.) Important Results
A subset of humpback chub reside in the Little Colorado River year round (i.e., residents), whereas other adults move between the Little Colorado and Colorado Rivers to spawn (i.e., migrants). Growth of all size classes is much faster in the Little Colorado River; however, in some years, annual survival in the Colorado River is much higher, suggesting a potential tradeoff between growth and survival. Rainbow trout abundance is negatively related to juvenile chub survival in the mainstem Colorado River, whereas temperature is positively related to growth rates in both the Colorado and Little Colorado Rivers. Food availability and turbidity are also positively related to growth in the Little Colorado and Colorado Rivers respectively. The seasonal timing of growth also differs between the two systems. In the Little Colorado River, maximum growth occurs from April to June; whereas in the Colorado River, maximum growth occurs from July to September. We have developed simulation model using mark-recapture data to support the Long-Term Experimental and Management Plan (LTEMP) Environmental Impact Statement and the expanded nonnative environmental assessment.
Future Directions
We are continuing to evaluate juvenile humpback chub population dynamics in both the Little Colorado River and Colorado River to refine our understanding and improve our predictive models. Key sources of uncertainty are the drivers of and variation in both juvenile recruitment and juvenile outmigration from the LCR. In addition, we are working to incorporate detections from autonomous PIT-tag antennas into sampling efforts, as these technologies will allow us to evaluate behavior and size effects on capture probability and minimize biases in our current study design. Recent work has also focused on quantifying the impacts of ongoing translocations within the Little Colorado River. In recent years, we have begun applying the same approach in the western Grand Canyon where humpback chub abundances are increasing.
- Publications
Below are publications associated with this topic.
Vital rates of a burgeoning population of Humpback Chub in western Grand Canyon
The Colorado River ecosystem has experienced habitat alterations and non-native species invasions, and as a result, many of its native species have experienced extirpations, abundance declines, and range constrictions. Despite these pitfalls, Humpback Chub, Gila cypha, have persisted and, in the last 10-15 years, expanded their range to become abundant in western Grand Canyon, a river segment in wAuthorsMaria C. Dzul, Charles Yackulic, Mariah Aurelia Giardina, David R. Van Haverbeke, Michael D. YardFilter Total Items: 49Water storage decisions and consumptive use may constrain ecosystem management under severe sustained drought
Drought has impacted the Colorado River basin for the past 20 years and is predicted to continue. In response, decisions about how much water should be stored in large reservoirs and how much water can be consumptively used will be necessary. These decisions have the potential to limit riverine ecosystem management options through the effect water-supply decisions have on reservoir elevations. WeAuthorsLindsey Ann Bruckerhoff, Kevin Wheeler, Kimberly L. Dibble, B.A. Mihalevich, B.T. Nielson, J. Wang, Charles Yackulic, J.C. SchmidtIncorporating antenna detections into abundance estimates of fish
Autonomous passive integrated transponder (PIT) tag antennas are commonly used to detect fish marked with PIT tags but cannot detect unmarked fish, creating challenges for abundance estimation. Here we describe an approach to estimate abundance from paired physical capture and antenna detection data in closed and open mark-recapture models. Additionally, for open models, we develop an approach thaAuthorsMaria C. Dzul, Charles Yackulic, William L. Kendall, Dana L. Winkelman, Mary M Conner, Mike YardAssessing the population impacts and cost‐effectiveness of a conservation translocation
Managers often move, or translocate, organisms into habitats that are assumed to be suitable, however the consequences of these translocations are usually not rigorously assessed. Robust assessment of these management experiments should consider impacts to both donor and recipient populations and compare the cost‐effectiveness of translocations to other actions.Here we evaluate translocations of aAuthorsCharles B. Yackulic, David R. Van Haverbeke, Maria C. Dzul, Lucas S. Bair, Kirk L. YoungPartial migration and spawning movements of humpback chub in the Little Colorado River are better understood using data from autonomous PIT tag antennas
Choosing whether or not to migrate is an important life history decision for many fishes. Here we combine data from physical captures and detections on autonomous passive integrated transponder (PIT) tag antennas to study migration in an endangered fish, the humpback chub (Gila cypha). We develop hidden Markov mark-recapture models with and without antenna detections and find that the model fit wiAuthorsMaria C. Dzul, William Louis Kendall, Charles Yackulic, Dana L. Winkelman, David Randall Van Haverbeke, Mike YardWater storage decisions will determine the distribution and persistence of imperiled river fishes
Managing the world’s freshwater supply to meet societal and environmental needs in a changing climate is one of the biggest challenges for the 21st century. Dams provide water security, however, the allocation of dwindling water supply among reservoirs could exacerbate or ameliorate the effects of climate change on aquatic communities. Here, we show that the relative sensitivity of river thermal rAuthorsKimberly L. Dibble, Charles Yackulic, Theodore Kennedy, Kevin R. Bestgen, John C. SchmidtRemarkable response of native fishes to invasive trout suppression varies with trout density, temperature, and annual hydrology
Recovery of imperiled fishes can be achieved through suppression of invasives, but outcomes may vary with environmental conditions. We studied the response of imperiled desert fishes to an invasive brown (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) suppression program in a Colorado River tributary, with natural flow and longitudinal variation in thermal characteristics. We investigated tAuthorsBrian D Healy, Robert Schelly, Charles Yackulic, Emily Omana Smith, Phaedra E. BudyA primer of fishery studies in Grand Canyon: The nonnative fish removal story
Globally, rivers have become the most altered of ecosystems, chiefly due to pollution, water withdrawals, and dams that have modified their former function, and led to large and unforeseen impacts, particularly for fish populations. Extensive research is directed at studying impacts of dams because they sever migration routes and change the physical template (flow, temperature, and sediment and orAuthorsMike YardWhat's in the hump of the humpback chub?
The function of the nuchal hump on adult humpback chub (Gila cypha) has been the subject of longtime conjecture. Hypotheses about the purpose of the hump range from it being a feature that confers hydrodynamic advantages in swift water to speculation about how the hump may have reduced predation vulnerability to Colorado pikeminnows (Ptychocheilus lucius). We used comparative histology of the headAuthorsDavid Ward, Michael B. WardEffects of water temperature, turbidity, and rainbow trout on humpback chub population dynamics
Humpback chub (Gila cypha Miller 1946), found only in the Colorado River Basin, was one of the first species to be given full protection under the Endangered Species Act of 1973. Habitat alterations, such as changes in flow and water temperature caused by dams, and the introduction of nonnative fish have contributed to population declines in humpback chub and other native fish. These habitat alterAuthorsCharles Yackulic, Julia B. HullSafety in numbers: Cost-effective endangered species management for viable populations
We develop a bioeconomic model to identify the cost-effective control of an invasive species (rain-bow trout) to achieve a population viability goal for an endangered species (humpback chub) in the Grand Canyon of the U.S. southwest. The population viability optimization problem is no-toriously difficult to solve due to a probabilistic restriction on joint outcomes (survival) over many periods. WeAuthorsPierce Donovan, Lucas S. Bair, Charles B. Yackulic, Michael R. SpringbornEffects of high flow experiments on warm-water native and nonnative fishes
The harsh environmental conditions and extreme flooding that created Grand Canyon also shaped the unique native fish that evolved in the Colorado River. Native fish have evolved their physiology, morphology and behavior to withstand high flood events. Flooding has been shown to benefit spawning, survival and recruitment of juvenile native fishes in many southwestern rivers. Annual pre-dam floodingAuthorsDavid WardWhat environmental conditions reduce predation vulnerability for juvenile Colorado River native fishes?
The incompatibility of native Colorado River fishes and nonnative warm-water sport fishes is well documented with predation by nonnative species causing rapid declines and even extirpation of native species in most locations. In a few rare instances native fishes are able to survive and recruit despite the presence of nonnative warm water predators, indicating that specific environmental conditionAuthorsDavid L. Ward, Benjamin Vaage - Partners
Below are partners associated with this project.