About
62
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Introduction
Research fish biologist at USGS-Grand Canyon Monitoring and Research Center. Former post doc, Eastern Ecological Science Center, and fisheries biologist and program manager of the Grand Canyon National Park Native Fish Ecology and Conservation Program. My research involves the study of the effectiveness of conservation actions for imperiled native fish communities, understanding drivers of demographic rates in fish populations, invasion biology, and decision analysis.
Additional affiliations
Education
June 2018 - May 2022
January 1999 - August 2002
September 1993 - May 1998
Publications
Publications (62)
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 varia...
Understanding the relative strengths of intrinsic and extrinsic factors regulating populations is a long‐standing focus of ecology and critical to advancing conservation programs for imperiled species. Conservation could benefit from an increased understanding of factors influencing vital rates (somatic growth, recruitment, survival) in small, tran...
Invasive species can dramatically alter ecosystems, but eradication is difficult, and suppression is expensive once they are established. Uncertainties in the potential for expansion and impacts by an invader can lead to delayed and inadequate suppression, allowing for establishment. Metapopulation viability models can aid in planning strategies to...
Rehabilitation of large Anthropocene rivers requires engagement of diverse stakeholders across a broad range of sociopolitical boundaries. Competing objectives often constrain options for ecological restoration of large rivers whereas fewer competing objectives may exist in a subset of tributaries. Further, tributaries contribute toward building a...
Tradeoffs among objectives in natural resource management can be exacerbated in altered ecosystems and when there is uncertainty in predicted management outcomes. Multicriteria decision analysis (MCDA) and value of information (VOI) are underutilized decision tools that can assist fisheries managers in handling tradeoffs and evaluating the importan...
Fragmentation isolates individuals and restricts access to valuable habitat with severe consequences for populations, such as reduced gene flow, disruption of recolonization dynamics, reduced resiliency to disturbance, and changes in aquatic community structure. Translocations to mitigate the effects of fragmentation and habitat loss are common, bu...
Objective
Tributaries may play a vital role in maintaining populations of large river fishes, although the specific contributions of tributaries toward recruitment of river‐wide populations are not often understood. Tributaries may experience fewer cumulative anthropogenic impacts relative to main‐stem rivers and may offer more natural conditions s...
Spawning phenology and associated migrations of fishes are often regulated by factors such as temperature and stream discharge, but flow regulation of mainstem rivers coupled with climate change might disrupt these cues and affect fitness. Flannelmouth sucker (Catostomus latipinnis) persisting in heavily modified river networks are known to spawn i...
KEY FINDINGS
• Five monitoring trips were conducted in FY 2022: two to the Colorado River inflow areas around Bright Angel, Shinumo, and Havasu creeks, two to Havasu Creek, and one to Bright Angel Creek.
• There were 382 Humpback Chub (Gila cypha) captures during monitoring or trout suppression trips in FY 2022 including 272 in Havasu Creek, 21 in...
KEY FINDINGS
• Annual Bright Angel Creek-wide backpack electrofishing was conducted from October 21, 2021 – January 22, 2022. The weir was in place and operational from September 30 – October 5, 2021.
• The Bright Angel Creek fish weir and the PIT-tag antenna array were destroyed in high-magnitude monsoon flooding on October 5 and August 17, 2021,...
River ecosystems have been altered by flow regulation and species introductions. Regulated flow regimes often include releases designed to benefit certain species or restore ecosystem processes, and invasive species suppression programs may include efforts to restrict access to spawning habitat. The impacts of these management interventions are oft...
Invasive species can dramatically alter ecosystems, and once established, eradication is difficult and suppression is expensive. Uncertainties in potential expansion and impacts by invaders can lead to delayed and inadequate suppression, allowing for establishment. Metapopulation viability models can aid in planning suppression actions to lessen in...
Approved National Park Service research proposal outlining the implementation plan for a pilot-level razorback sucker augmentation study in Grand Canyon National Park, Arizona, USA.
Magazine article published by the Grand Canyon Conservancy (Canyon Views) describing the threat of climate-driven aridification and low Colorado River reservoir levels, and invasive warmwater fishes to the Grand Canyon's native fishes.
River regulation, human water use, and the introduction of invasive predators are primary factors leading to the imperilment of many fishes. In the Grand Canyon, Arizona, native fish conservation actions are in progress, including invasive fish suppression and translocations of the endangered humpback chub (Gila cypha) to habitats with natural flow...
Systematic larval fish surveys increase the probability of detecting rare species and provide ecological insights for more common species that can be difficult to infer from surveys of older life-stages. To characterize the reproductive success of the extant fish assemblage in the western Grand Canyon portion of the Colorado River, we conducted sys...
Understanding fish population status and trends are fundamental to effective research and management. Challenges in understanding population status include recognizing and accounting for sources of variation in capture probability (p ̂) that can obscure patterns in count data and bias inferences about the population. In systems where management act...
This report describes results of invasive trout suppression and native fish monitoring results for Bright Angel Creek, Grand Canyon National Park, for the 2020-2021 fall-winter season.
This report details results of demographic monitoring (2009-2021) for humpback chub translocated to Colorado River tributaries in Grand Canyon National Park, Arizona.
Widespread introductions of invasive fishes have led to continental-scale homogenization of fish assemblages and biodiversity loss. Once established in new habitats, invasive fishes are costly and difficult to remove. Salmonids are damaging introduced predators that can exert top-down controls on ecosystem function by altering food web dynamics and...
The presentation included an annual update of 2020 activities related to translocations of endangered humpback chub (Gila cypha) in tributaries of the Colorado River in Grand Canyon National Park. A summary of preliminary analyses of hypothesized drivers of demographic rates (e.g., survival, recruitment) and somatic growth rates of translocated hum...
KEY FINDINGS
1. During federal fiscal year (FY) 2020 (October 1, 2019 – September 30, 2020), the Grand Canyon National Park (GCNP) Native Fish Ecology and Conservation Program (NFEC) conducted 2 monitoring events on the Colorado River in the Shinumo Inflow reach, in Bright Angel Creek (1 translocation trip), and Havasu Creek (1 trip) to complete hu...
This annual report describes results of ongoing suppression of invasive brown trout and rainbow trout and monitoring of native fishes in Bright Angel Creek, Grand Canyon, Arizona. Trout suppression and fish monitoring is conducted through watershed-wide three-pass electrofishing. Additionally, a weir is installed near the mouth of Bright Angel Cree...
The Colorado River in Grand Canyon is highly regulated, with hypolimnetic releases that are generally unfavorable for endemic native fishes. However, both long-term drought and changes in dam operations have led to changes in river conditions, including the addition of approximately 125 km of riverine environment due to the contraction of Lake Mead...
This 2019 annual report describes humpback chub translocations and associated activities implemented by the Native Fish Ecology and Conservation Program, Grand Canyon National Park, and funded by the U. S. Bureau of Reclamation. The activities described herein contribute toward the implementation of conservation measures included in the U. S. Fish...
The Colorado River that runs through Grand Canyon National Park is home to many endemic species of fishes. Yet, extensive water withdrawals and hydroelectric dam development have drastically altered riverine conditions of the Colorado River, including the populations of its unique fish species. Further, introduced fish such as trout are well-adapte...
A summary of a knowledge assessment of the status and trends of native fish (razorback sucker, flannelmouth sucker, bluehead sucker, speckled dace) in the Colorado River and its major tributaries within Grand Canyon, Arizona.
Translocations, defined herein as the human-assisted movement of individuals from a source population to other waters within their historical range, are prevalent in recovery plans for endangered fishes. Many translocations fail to establish new populations, however, and outcomes are often poorly documented. Endangered Humpback Chub Gila cypha pers...
Predation and competition by invasive species are among the most pervasive threats to aquatic biodiversity, particularly in arid-land rivers where human water demand is intense. Once established, invasive fishes are difficult and costly to remove, and environmental variation can confound attempts to quantify population-level responses of native fis...
Like many imperiled riverine ecosystems, the Colorado River was subjected to extensive damming and water withdrawals, which homogenized flow, fragmented habitats, and facilitated establishment of numerous invasive fishes, including salmonids in dam tailwaters. Native large river fishes have since declined, and several were listed under the Endanger...
Annual report summarizing 2018-2019 invasive trout suppression activities, with a data summmary.
Water infrastructure updates at Grand Canyon National Park (GRCA) provide an opportunity to restore natural flow to Bright Angel Creek, adding an additional ~20% to baseflow. This creek provides habitat for endangered humpback chub (Gila cypha) and invasive brown trout (Salmo trutta). We assess how increased flow may alter habitat and how that chan...
Predation and competition by invasive species are among the most pervasive threats to aquatic biodiversity. Native river fishes of arid regions are particularly vulnerable to the impacts of invasive species and habitat alteration, as many evolved specialized life history strategies for highly dynamic ecosystems subject to extreme variation in tempe...
Endangered Humpback Chub Gila cypha persist as a self-sustaining population in Grand Canyon, Arizona, despite habitat alterations following the construction of Glen Canyon Dam. This warmwater species has been sustained primarily through reproduction in a single spawning aggregation centered on the Little Colorado River and its inflow reach of the C...
Habitat loss as a result of water storage and diversion projects, and basin-wide introductions of nonnative species have led to the decline and listing of several endemic Colorado River fishes under the Endangered Species Act (ESA). Grand Canyon National Park (GCNP) provides some protection from anthropogenic impacts to aquatic habitats in tributar...
Nonnative species introductions and habitat modifications due to the construction of Glen Canyon Dam upstream have caused the decline of native fishes in Grand Canyon National Park. Nonnative salmonids that prey on or compete with native fish, including the Brown Trout (Salmo trutta) and Rainbow Trout (Oncorhynchus mykiss), are particularly threate...
Endangered Humpback Chub (Gila cypha) persist as a self-sustaining population in Grand Canyon, Arizona, despite habitat alterations following the construction of Glen Canyon Dam, and the introduction of nonnative competitors and predators. The species has been sustained primarily through reproduction in a single spawning aggregation centered on the...
Multiple stressors, including construction and operation of Glen Canyon Dam, nonnative predators and competitors, and fire and flooding, impact the aquatic invertebrate and fish communities both
directly and indirectly. These stressors also interact to impact the fish community at multiple scales, potentially reducing the overall system’s resistanc...
During the last century, populations of the endangered Razorback Sucker (Xyrauchen texanus) have declined in the Colorado River Basin. Dramatic changes in habitat resulting from altered flow regimes and the presence of nonnative fishes were likely major factors contributing to this decline. Since 1996, studies in Lake Mead have resulted in the disc...
Invited presentation of preliminary results of brown trout suppression operations in Bright Angel Creek, Grand Canyon, during the Glen Canyon Dam Adaptive Management Program, Brown Trout workshop.
From 1944 to 1990, only 10 razorback suckers (Xyrauchen texanus) were captured in the Colorado River within the Grand Canyon, Arizona. Except for a single larval razorback sucker captured in 1998 near Havasu Creek, the species was not found during fish surveys conducted between 1990 and 2011. Biologists confirmed the presence and spawning of razorb...
The Humpback Chub Gila cypha, a large-bodied, endangered cyprinid endemic to the Colorado River basin, is in decline throughout most of its range due largely to anthropogenic factors. Translocation of Humpback Chub into tributaries of the Colorado River is one conservation activity that may contribute to the expansion of the species’ current range...
Nonnative fishes have been linked to the decline of native fishes and may affect aquatic food webs through direct and indirect pathways. These concerns have led to efforts to remove nonnative Brown and Rainbow Trout, which are abundant in tributaries of the Colorado River, to enhance native fish communities. We sampled fish, benthic, and drifting m...
Diet interactions between native and non-native fishes may influence the establishment of native species within their historical range (i.e., reintroduction). Therefore, we illustrated the food web structure of and followed the transition of the federally endangered humpback chub Gila cypha into a novel food web following translocation and determin...
We developed an individual‐based population viability analysis model (females only) for evaluating risk to populations from catastrophic events or conservation and research actions. This model tracks attributes (size, weight, viability, etc.) for individual fish through time and then compiles this information to assess the extinction risk of the po...
Humpback chub is an endangered species endemic to the Colorado River. Translocation of humpback chub into Grand Canyon tributaries has been identified as a tool for mitigating impacts of dam operations and providing population redundancy in the lower Colorado River basin. Havasu Creek is one of the larger tributaries to the Colorado River in Grand...
Non-native trout removal is being conducted by the National Park Service and other stakeholders to restore and enhance native fish communities in Bright Angel Creek (BAC), Grand Canyon. To assess resource availability and evaluate the effects non-native brown (BNT) and rainbow (RBT) trout have on the food web in BAC, we sampled fish, benthic invert...
Efforts to restore native fish communities may depend on translocation into suitable habitats. However, success of translocations has been mixed. The federally endangered humpback chub Gila cypha (HBC) is endemic to the Colorado River Basin and populations continue to decline, so conservation of HBC may depend on translocation. However, incomplete...
In October, 2010, Grand Canyon National Park reinitiated the Bright Angel Creek Trout Reduction project to enhance native fish populations and contribute towards the fulfillment of humpback chub conservation measures (USFWS 2008) by reducing the population of non-native brown (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) (NPS 2006). This p...
The humpback chub (Gila cypha), found only in the Colorado River Basin, is a long lived fish that has adapted to historically turbulent waters of the Colorado River. Today, only six populations of humpback chub are known to exist, the largest of which resides in the Grand Canyon. Alteration of habitat and introduction of nonnative fish species have...
Nonnative rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) are often implicated in the reduction of native fishes through resource competition and predation. However, relatively little is known concerning food web dynamics between native and nonnative species, particularly in systems with relatively undisturbed natural flow regime...
The U.S. Geological Survey (USGS), in cooperation with the Colorado River Water Conservation District, Eagle County, Eagle River Water and Sanitation District, Upper Eagle Regional Water Authority, Colorado Department of Transportation, City of Aurora, Town of Eagle, Town of Gypsum, Town of Minturn, Town of Vail, Vail Resorts, Colorado Springs Util...
The San Jacinto River system lies just east of Houston, Texas in the Coastal Plains. The watershed is bounded on the north primarily by rural and agricultural land, on the east by the Sam Houston National Forest (SHNF), and on the west by the city of Houston. The SHNF is made up of fragmented forest imbedded in a matrix of rural farm land and oil a...
Relationships between environmental variability and natural communities have been extensively studied. However the relative strengths of abiotic and biotic factors in structuring stream communities continues to be debated. Although North American crayfish are taxonomically diverse, occur across a variety of habitats, and are important components of...
Greater redhorse Moxostoma valenciennesi is designated as a Regional Forester Sensitive Species on the Chippewa, Chequamegon-Nicolet, and Huron-Manistee National Forests in the Eastern Region of the Forest Service. The species is documented but not
designated as sensitive on the Hiawatha National. The purpose of this document is to
provide the back...
The aquatic habitats of the Keechi Creek Wildlife Management Area in central east Texas were surveyed in May, June and August of 1999. A total of 34 species from 12 families were documented. These records serve to establish the initial database for fishes in this management area as a part of the conservation program of the Texas Parks and Wildlife...
The aquatic habitats of the Richland Creek Wildlife Management Area in central east Texas were surveyed in April, May, June and August of 1998 and 1999. A total of 49 species from 15 families was documented, including a juvenile grass carp (Ctenopharyngodon idella). These records serve to establish the initial database for fishes in this management...
Little is known about the behavior of coho salmon Oncorhynchus kisutch established in the Lake Superior drainage in the late 1960s. Unlike in their native range of the Pacific coast, Lake Superior coho salmon juveniles inhabit streams characterized by low winter flows and highly variable summer flows. Because high stream flows can profoundly affect...
Questions
Question (1)
Hello,
I'm wondering if any other researchers have modeled relationships between Bluehead Sucker capture probabilities, size, and environmental variables (or any other factors).
I've analyzed our Bright Angel Creek Bluehead Sucker 3-pass depletion data using Program MARK (Closed Capture - Huggins models with covariates), and found an unexpected relationship between fish length and capture probability that I'm struggling to interpret. P-caps are higher for smaller fish. This pattern is opposite of those we have seen in 6 years of sampling. Differences over time include: a) the fish and possibly the invertebrate community has changed significantly since we have reduced nonnative trout by approx. 90%; b) it could be that lower flows due to lack of snowmelt, temperature changes, or other factors could have made small fish more vulnerable to electrofishing?
Any thoughts or ideas would be appreciated.
Thank you