Study Uncovers Migration Patterns of Native Fish in the Colorado River
A study conducted by the USGS provides new insights into the migration patterns of three native fish species in the Colorado River: humpback chub, flannelmouth sucker, and bluehead sucker. This research highlights the importance of understanding native fish population dynamics within the Colorado River ecosystem in Grand Canyon, AZ.
This study evaluated the time of year that humpback chub (Gila cypha), flannelmouth sucker (Catostomus latipinnis), and bluehead sucker (Catostomus discobolus) migrate from the Colorado River into the Little Colorado River, a warmwater tributary, and estimated the number of fish involved in these migrations.
The findings reveal crucial patterns that contribute to understanding population dynamics of native fish in the Colorado River ecosystem.
Animal migration is a widespread, complex phenomenon across many different types of animals and environments that often involves trade-offs, such as the potential for increased reproduction or growth, balanced against the inherent risks associated with migrating.
As many migratory species exhibit partial migration, biologists differentiate between "migrants" and "residents" within populations. Often, the decision for an individual fish to migrate or remain resident is made early in life, making switches between these strategies uncommon.
Successful migration relies heavily on habitat connectivity and quality across large areas. Many studies have found that anthropogenic and environmental stressors may put migrants at a disadvantage.
By monitoring the relative abundances of migrants and residents, researchers can identify which groups are experiencing greater stress and develop targeted conservation strategies.
Understanding the timing of migrations can help researchers determine the cues that trigger these movements. For example, mismatched cues between migration and food availability can affect the success of migratory behavior.
The act of migration can present opportunities for detection and improved monitoring, as evidenced by development of new technologies and tagging methods to help track animals migrating over large distances.
One common monitoring design for detecting migratory movements is automated telemetry using detection gates of passive receivers – where devices are placed at fixed locations to detect tagged individuals along their migratory route, sometimes at sites where there is natural constriction to funnel individuals over the detectors (Figure 1, below).
For example, some scientists have built tracking towers along coastlines to detect migrating birds, and others have placed arrays of passive integrated transponder (PIT) antennas in rivers near the outlet of a large lake (e.g., in a river mouth) to detect spawning movements of fishes migrating between rivers and lakes.
Employing state-of-the-art technology, this study utilized automated telemetry with detection antenna “gates” and passive receivers to monitor the directionality and migratory movements of the fish.
USGS implemented a population model that pairs physical captures with detections from a PIT antenna array system to compare migration timing and estimate abundance of migrants and residents of humpback chub, flannelmouth sucker, and bluehead sucker moving between the Little Colorado River and Colorado River.
The detection gate used in this study includes two arrays that span the riverbed and continuously detect PIT tags, which allows researchers to estimate which direction the fish are moving and the probability of detection.
The model effectively tackles several unique challenges in describing this data.
They are: unmarked fish (i.e., without a PIT tag) and residents cannot be detected by the detection gates, and fish have staggered arrival and departure times.
Also, their movement directionality (entering and/or exiting breeding habitat) can be identified if the fish are detected on both arrays, but their directionality is unknown if they are only detected on one array and there is uncertainty as to whether the fish are residents or migrants.
The findings highlighted some differences in migration timing among the three fish species, with flannelmouth suckers migrating earlier, in mid-March, and humpback chub and bluehead suckers which exhibited similar movement patterns, migrating in early- to mid-April.
For all three native fishes, the results indicate that there were many more migrants than residents in the Little Colorado River during the spring, which highlights the importance of tributaries in this river system.
The study also revealed that the life history strategy and arrival timing of humpback chub were influenced by body size—larger individuals were more likely to migrate and arrive earlier than their smaller counterparts.
Importantly, the number of migrants for all three fish species remained consistent across years, with and without winter floods, which demonstrates that floods are not necessary to initiate migration into the Little Colorado River for these species.
With additional data collection in future years, models like these could evaluate environmental factors—such as floods, food availability, and temperature—on the timing of migration and partial migration.
Linking models across years offers deeper insights into breeding and survival probabilities and can better answer questions related to ecological trade-offs associated with migration, which supports more targeted conservation actions specific to life history strategy.
This research provides a modeling framework that may benefit future studies analyzing partial migration and migration phenology (life history events), particularly those utilizing antenna “gate” designs with automated telemetry.
Special thanks to co-authors Michael Pillow and Kirk Young (US Fish and Wildlife Service), David R. Van Haverbeke (US Fish and Wildlife Service, retired), Joseph Thomas (US Geological Survey), and Peter Mackinnon (Biomark Inc., Utah State University).
Additionally, thanks to the U.S. Bureau of Reclamation for helping fund this work, and the Navajo Nation for permission to work on Navajo Land. Lastly, thanks to the numerous volunteers, technicians, and biologists that were part of data collection efforts.
Humpback Chub in the Colorado River, Grand Canyon
Effects of water clarity on humpback chub
A study conducted by the USGS provides new insights into the migration patterns of three native fish species in the Colorado River: humpback chub, flannelmouth sucker, and bluehead sucker. This research highlights the importance of understanding native fish population dynamics within the Colorado River ecosystem in Grand Canyon, AZ.
This study evaluated the time of year that humpback chub (Gila cypha), flannelmouth sucker (Catostomus latipinnis), and bluehead sucker (Catostomus discobolus) migrate from the Colorado River into the Little Colorado River, a warmwater tributary, and estimated the number of fish involved in these migrations.
The findings reveal crucial patterns that contribute to understanding population dynamics of native fish in the Colorado River ecosystem.
Animal migration is a widespread, complex phenomenon across many different types of animals and environments that often involves trade-offs, such as the potential for increased reproduction or growth, balanced against the inherent risks associated with migrating.
As many migratory species exhibit partial migration, biologists differentiate between "migrants" and "residents" within populations. Often, the decision for an individual fish to migrate or remain resident is made early in life, making switches between these strategies uncommon.
Successful migration relies heavily on habitat connectivity and quality across large areas. Many studies have found that anthropogenic and environmental stressors may put migrants at a disadvantage.
By monitoring the relative abundances of migrants and residents, researchers can identify which groups are experiencing greater stress and develop targeted conservation strategies.
Understanding the timing of migrations can help researchers determine the cues that trigger these movements. For example, mismatched cues between migration and food availability can affect the success of migratory behavior.
The act of migration can present opportunities for detection and improved monitoring, as evidenced by development of new technologies and tagging methods to help track animals migrating over large distances.
One common monitoring design for detecting migratory movements is automated telemetry using detection gates of passive receivers – where devices are placed at fixed locations to detect tagged individuals along their migratory route, sometimes at sites where there is natural constriction to funnel individuals over the detectors (Figure 1, below).
For example, some scientists have built tracking towers along coastlines to detect migrating birds, and others have placed arrays of passive integrated transponder (PIT) antennas in rivers near the outlet of a large lake (e.g., in a river mouth) to detect spawning movements of fishes migrating between rivers and lakes.
Employing state-of-the-art technology, this study utilized automated telemetry with detection antenna “gates” and passive receivers to monitor the directionality and migratory movements of the fish.
USGS implemented a population model that pairs physical captures with detections from a PIT antenna array system to compare migration timing and estimate abundance of migrants and residents of humpback chub, flannelmouth sucker, and bluehead sucker moving between the Little Colorado River and Colorado River.
The detection gate used in this study includes two arrays that span the riverbed and continuously detect PIT tags, which allows researchers to estimate which direction the fish are moving and the probability of detection.
The model effectively tackles several unique challenges in describing this data.
They are: unmarked fish (i.e., without a PIT tag) and residents cannot be detected by the detection gates, and fish have staggered arrival and departure times.
Also, their movement directionality (entering and/or exiting breeding habitat) can be identified if the fish are detected on both arrays, but their directionality is unknown if they are only detected on one array and there is uncertainty as to whether the fish are residents or migrants.
The findings highlighted some differences in migration timing among the three fish species, with flannelmouth suckers migrating earlier, in mid-March, and humpback chub and bluehead suckers which exhibited similar movement patterns, migrating in early- to mid-April.
For all three native fishes, the results indicate that there were many more migrants than residents in the Little Colorado River during the spring, which highlights the importance of tributaries in this river system.
The study also revealed that the life history strategy and arrival timing of humpback chub were influenced by body size—larger individuals were more likely to migrate and arrive earlier than their smaller counterparts.
Importantly, the number of migrants for all three fish species remained consistent across years, with and without winter floods, which demonstrates that floods are not necessary to initiate migration into the Little Colorado River for these species.
With additional data collection in future years, models like these could evaluate environmental factors—such as floods, food availability, and temperature—on the timing of migration and partial migration.
Linking models across years offers deeper insights into breeding and survival probabilities and can better answer questions related to ecological trade-offs associated with migration, which supports more targeted conservation actions specific to life history strategy.
This research provides a modeling framework that may benefit future studies analyzing partial migration and migration phenology (life history events), particularly those utilizing antenna “gate” designs with automated telemetry.
Special thanks to co-authors Michael Pillow and Kirk Young (US Fish and Wildlife Service), David R. Van Haverbeke (US Fish and Wildlife Service, retired), Joseph Thomas (US Geological Survey), and Peter Mackinnon (Biomark Inc., Utah State University).
Additionally, thanks to the U.S. Bureau of Reclamation for helping fund this work, and the Navajo Nation for permission to work on Navajo Land. Lastly, thanks to the numerous volunteers, technicians, and biologists that were part of data collection efforts.