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About Us

Keeping the rivers running and the native fish swimming!

Our Story

Marsh & Associates, LLC (M&A) is a private company dedicated to efforts that promote conservation, recovery, and public education on behalf of the community of imperiled native fishes of the desert southwest.  This legacy of conservation was pioneered at Arizona State University beginning in the 1960s by the late W. L. Minckley, the preeminent authority on this diverse group of indigenous fishes. 
 
A long-time colleague of Professor Minckley, Dr. Paul C. Marsh, continued these efforts in collaboration with Dr. Thomas E. Dowling (Wayne State University), Dr. Thomas Turner (University of New Mexico), and other professional biologists and conservationists at universities, state and federal resource agencies, non-governmental organizations, and the private sector.

Dr. Paul Marsh retired in 2024, but the legacy of Marsh & Associates lives on under the leadership of Brian Kesner, M.Sc. Brian, a longtime collaborator of Dr. Marsh at Arizona State University, has played an integral role in M&A since its founding in 2008. Now serving as owner and principal investigator, he brings deep expertise and unwavering dedication to the conservation of native fishes in the desert Southwest. Under his guidance, M&A continues to uphold its tradition of scientific excellence and innovation.

 
Marsh & Associates, LLC
1024 East Vista del Cerro Drive
Tempe, Arizona 85281

Desert Landscape at Sunrise

Meet the Marshians

Brian Kesner

M.S. 2004, James Cook University, Queensland, Australia

Owner and PI

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Brian has nearly three decades of experience focusing on native fish communities of the Colorado River basin. Beginning his career with Dr. Paul Marsh at ASU in 1998, he became a key contributor to the Native Fish Lab of Dr. Marsh at ASU, and moved with the lab to the private sector in 2008. He specializes in the quantitative assessment of native fish populations. His work blends standard statistical methods with innovative, custom-designed approaches tailored to the unique challenges of sparse, noisy, and often incomplete data. His research has been instrumental in shaping monitoring and management strategies for species such as the razorback sucker and bonytail. 

Beyond his analytical expertise, Brian is an active field biologist who regularly participates in monitoring programs across Arizona and lower Colorado River basin states. 

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Carol Pacey

M.S. 1996, Texas A&M University

Business Manager

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Carol developed and presented statewide the successful “Sharing Tails” educational program that teaches kindergarten and early elementary school children about native Arizona fishes. She also is responsible for primary maintenance of the lower Colorado River native fishes PIT tag mark and recapture database and analyzes and interprets field data for reports and publications. When not too busy with other duties she assists with field and laboratory work, makes presentations to professional groups, attends meetings, and interacts with M&As myriad cooperators. She has been apart of the team since 1997.

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Alex Marini

B.S. 2021 Environmental Science, Virginia Commonwealth University

Fisheries Scientist III

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Alex started at the Native Fish Lab in February 2022  At M&A, she is leading the Gila River project, focusing on the presence and distributional extent of focal fish species in over 100 tributaries of the basin. She also works on building/maintaining PIT antennas used in the monitoring of native fishes in the Colorado River. When not in the field Alex assists in data entry and analysis, maintaining field equipment, and writing technical reports. She also enjoys hiking, camping, swimming, and bird watching.

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Cora McClelland

B.S. 2020 Wildlife, Fish, and Conservation Biology

Fisheries Scientist II

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Cora started working at Marsh and Associates in September 2023. She has worked with both California and Arizona state agencies (CDFW, AZGFD) studying various species including rainbow trout, steelhead, olive ridley sea turtles, and bald eagles, before joining our team. Currently, at M&A she leads the non-native fish removal project based out of Aravaipa Creek wilderness and runs the native fish lab website. When Cora isn't in the field, she writes trip summaries, annual reports, and builds M&A PIT Tag submersible scanners. She enjoys going to music festivals, hiking, swimming, and traveling to new places.

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Allison Downey

B.S. 2021 Biology, Northern Arizona University

Fisheries Scientist II

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Allison started working at the Native Fish lab in August 2023. At M&A, she leads a project monitoring the population of razorback sucker in Lake Mohave using PIT scanning antennas. When not in the field, she assists with data entry and analysis, maintaining field equipment, and writing technical reports. Allison enjoys traveling, kayaking, and enjoying nature with her friends and family. 

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Mattie Diedrick

B.S. 2024 Biology, Northern Arizona University

Fisheries Scientist I

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Mattie started working at the Native Fish Lab in January 2026. She has worked with desert fish species in Arizona and New Mexico. At M&A, she assists with projects in the Gila River Basin, Lake Mohave, and Aravaipa. She also helps build/maintain PIT Tag submersible scanners for the endangered Razorback Sucker in the Colorado River. When not in the field, Mattie enjoys hiking, hunting, and spending time with friends and family.  

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