00:00:00 Introductions. Q: What positions have you held in GCDAMP (Glen Canyon Adaptive
Management Program) during the years you participated? A: In 1989, Valdez worked under
contract with USBR (U.S. Bureau of Reclamation), studying humpback chub in Grand Canyon
for GCES (Glen Canyon Environmental Studies). The study surveyed fish populations along 280
miles of river.
00:01:00 In 1999 Valdez convened a scientific panel on strategies to increase humpback chub
populations, and in 2000 he participated in the LSSF (Low Steady Summer Flow) experiment. In
2003 he worked on a team assessing the need for a TCD (Temperature Control Device) for Glen
Canyon Dam.
00:02:00 In 2004 Valdez worked with Steve Carothers on a fisheries survey of the Colorado
River and its tributaries in Grand Canyon. He worked in 2010 on a razorback sucker
reintroduction team. The Colorado River Basin states asked Valdez to convene a panel in 2012 to
evaluate alternatives for the 2016 LTEMP (Long-Term Experimental and Management Plan) EIS
(Environmental Impact Statement).
00:03:00 Valdez recently joined the brown trout management team with Mike Runge and
Charles Yackulic. Q: How much of your work was contract research work with SWCA [SWCA
Environmental Consultants] versus work directly as a participant with AMWG (Adaptive
Management Work Group) or TWG (Technical Work Group)?
00:04:00 A: It was mostly contract work through BIO-WEST or SWCA. Valdez attended
numerous AMWG and TWG meetings while working with those companies. Q: Let’s drill down
on the role of humpback chub in GCDAMP. You’re probably going to be the most
knowledgeable expert we interview on life history and recovery efforts for humpback chub. How
did that get started and develop over time?
00:05:00 A: The humpback chub is probably the keystone species in GCDAMP. He has served
as recovery team leader since 2015. Valdez is very familiar with humpback chub populations in
Grand Canyon. He started studying fish populations in the Upper Colorado River Basin in 1968.
00:06:00 Before the Endangered Species Act (ESA) was passed in 1973, humpback chub were
included in the Endangered Species Preservation Act (1966) and the Endangered Species
Conservation Act (1969). The ESA mandated better protections, but nobody knew exactly how
to protect endangered fish in Grand Canyon.
00:07:00 Valdez was involved in early Environmental Assessment (EA) and EIS processes
concerning endangered native fish, especially in the Upper Colorado River Basin. He started

with U.S. Fish and Wildlife Service (USFWS) in 1979 to evaluate native fish populations above
Lake Powell, which were declared to be in jeopardy on passage of the ESA.
00:08:00 Amendments to the ESA in 1980 introduced the concept of reasonable and prudent
alternatives, “which really opened the door and allowed agencies, now, to start doing good things
for the species to offset or mitigate those potential bad things.” The alternatives developed for
native fish affected by Glen Canyon Dam operations became the heart of the 1995 EIS.
00:09:00 In 2008, USFWS changed to a non-jeopardy determination for humpback chub. New
conservation measures were finalized in 2010. Now USBR and NPS are working “not just to
mitigate the potential jeopardy effects, but also to benefit the species.” Because Grand Canyon
has the largest population of humpback chub in the Basin, it was the stage for determining how
the ESA would apply to the species.
00:10:00 The humpback chub was the main driver of management actions in the area. Q: In
terms of modifying dam operations, improving habitat, or reducing predation? A: All of those
things. Glen Canyon Dam put about 200 miles of what used to be native fish habitat under a lake.
Razorback suckers can survive in a reservoir, but pikeminnow and humpback chub do not. The
dam also changed downstream habitat by releasing cold water drawn from the depths of the
reservoir.
00:11:00 Because native fish in Grand Canyon are adapted to warm water, biologists speculated
that cold-water releases through the turbine penstocks may need to be offset with a Temperature
Control Device (TCD). Proposed around 2002, the controversial TCD would have modified the
dam to mix warmer surface water with the deeper cold water going into the penstocks.
00:12:00 In retrospect, biologists may not have adequately understood the situation. Cold-water
releases may benefit native species by inhibiting the incursion of non-native warm-water fish
into the system. Humpback chub still have access to the Little Colorado River (LCR), where the
seasonally warm water is good for spawning.
00:13:00 Managers could target a water temperature using a selective withdrawal TCD, which
would employ elevators to withdraw water from any level of the reservoir and release it through
the penstocks.
00:14:00 The cost to install a selective withdrawal TCD would have been about $100 million.
While making careful evaluations in the face of concerns about the cost, scientists were
reminded that despite our efforts at control, nature usually drives the system.

00:15:00 Elevations in Lake Powell and Lake Mead were dropping due to long-term drought
since 2000. Water releases from Glen Canyon Dam that had been 8-10 degrees centigrade
increased to up to 16 degrees centigrade. The warmest water came through in the fall due to
“reservoir overturn.”
00:16:00 The warmer water in the fall was of little benefit to humpback chub, which are spring
spawners. Ironically, it could now be argued that a TCD may be needed cool the releases. Q:
Have humpback chub always spawned in the LCR, or did that develop after the dam was built?
00:17:00 A: It has always occurred, at least in recent history. The Kolb brothers [historic Grand
Canyon photographers] observed numerous fish in the LCR at spawning time early in the 20th
century, and 1970s studies documented spawning in the system. Scientists suspect humpback
chub also spawned in the mainstem before the closure of Glen Canyon Dam.
00:18:00 Post-dam spawning in just the LCR provides enough young to sustain the population.
The other surprise from nature was the lowering elevation of Lake Mead, similar to that
occurring at Lake Powell. This increased the length of the Colorado River into the Lake Mead
basin.
00:19:00 The area that was once underwater in the upper reaches of Lake Mead has a layer of
thick accumulated sediment brought down by the Colorado River that is now exposed. The river
is re-carving out its original channel through those sediment layers and riparian habitat is
regenerating. Humpback chub in that area have become the most productive of the monitored
populations.
00:20:00 Native fish are thriving in the area between Diamond Creek and Pearce Ferry.
Sometimes nature provides a twist that defies plans and expectations. Q: Science is a practice of
developing a hypothesis, doing research, and developing a limited knowledge base of
understanding. In adaptive management, we do a management action, try to monitor the effects,
and find out if the response is what we expected. So it’s constant learning.
00:21:00 A: Adaptive management also provides an opportunity to assess past hypotheses,
analyses, and management actions from the vantage of many years later, “to see how right or
wrong we were.”
00:22:00 Carl Walters emphasized that adaptive management is a learning process. “If one were
to believe that you could structure something in a way that’s definitive, with predictable results
and responses, that of course is not true at all. You learn as you do. You learn as you go.” Nature
always throws in unanticipated variables.

00:23:00 The benefit of being involved with GCDAMP over a long time period is realizing how
much its participants have learned, whether or not they got things right. Q: Some of our other
interviewees talked about how early hypotheses about predation evolved over time as we learned
more. Can you talk a little bit about that?
00:24:00 A: The Colorado River has been isolated from nearby river basins for at least 3 to 4
million years. The river in the Upper Basin has not changed much through that time. In Grand
Canyon, the river captured streams as the plateau rose.
00:25:00 Fish diversity is low in the river due to its historical isolation. Not counting marine fish
in the estuary, only about 14 species are native to the entire Colorado River Basin, compared to
other rivers with hundreds of species. The Colorado River has historically supported a “unique
evolutionary scheme.” Native species evolved with limited native predators and have few
adaptive traits to cope with predators introduced into the system.
00:26:00 Valdez says of native species in the Colorado River, “all you have to do is look at them
and you can tell, these are special. Very, very special fish. They’re very uniquely adapted.” The
humpback chub’s torpedo-shaped body and large falcate fins help it “soar,” rather than swim, in
high-velocity currents. A poor swimmer in laboratory experiments, it knows how to find eddies
or pockets of low water velocity.
00:27:00 Valdez has worked with humpback chub throughout the Colorado River Basin. He
enjoys watching the fish maneuver in the clear water of Grand Canyon. He equates them with
raptors that ride thermals, making minor adjustments to maintain position with little energy
expenditure. “Well, humpback chub do the same thing, except that they’re in a water
environment.” The river delivers food to them as they stay in one place.
00:28:00 They have deeply embedded scales and thick skins to withstand the scouring of
sand-laden water. The top of the humpback chub’s head is flattened to allow water to pass by,
and it has its namesake hump. Q: What is the purpose of that hump? A: Robert Rush Miller, who
provided the fish’s first taxonomic description in 1946, thought the fleshy structure of the hump
was a hydrodynamic feature.
00:29:00 The razorback sucker also has a hump, formed around a bony structure, along with
thick skin and large fins. It and the humpback chub are highly adapted to the Colorado River
environment.
00:30:00 Starting in the 1930s with Lake Mead, the Colorado River Basin states looked at dams
and reservoirs as opportunities to develop recreational fisheries. Up to now, more than 35

non-native fish have been introduced to the system. Humpback chub are ill-adapted to cope with
alien species who prey on or compete with them.
00:31:00 Non-native fish are vectors for diseases and parasites. Now scientists understand that
cold-water releases from the dam may be discouraging movement of warm-water adapted
predatory fish into Grand Canyon. The fish currently preying on humpback chub in Grand
Canyon are cold-water brown and rainbow trout.
00:32:00 Q: And they were introduced for fisheries recreation, right? A: Yes. NPS introduced
them in the 1920s, starting in Bright Angel Creek. Grand Canyon National Park had just been
established, and while the muddy, turbid Colorado River mainstem was not appealing for sport
fishing, the side streams were.
00:33:00 Trout did well, and a hatchery was set up on Bright Angel Creek. Q: We have native
trout in Arizona, like the Apache trout. Were there any native trout in the side streams, or were
they all imported? A: The Apache and Gila trout are more closely related to salmon species than
to mountain cutthroat trout.
00:34:00 They are native to Gila River tributaries, upstream of where it meets the Colorado
River. Arizona native trout do not occur in waterways that flow into Grand Canyon.
00:35:00 The introduced rainbow trout came from California hatcheries, and the brown trout, a
European species, from hatcheries in Michigan. Q: You were talking about their role in predation
on the humpback chub. Where does that come in? A: Rainbow trout are concentrated between
Glen Canyon Dam and Lees Ferry, forming a blue-ribbon sport fishery.
00:36:00 That area is usually too cold for brown trout, which were concentrated in the area of
Bright Angel Creek and sometimes in the mainstem near the LCR. Warmer releases from Glen
Canyon Dam seem to have enabled brown trout to spend more time in the mainstem.
00:37:00 Now, a sizeable number of brown trout are found at Lees Ferry, where it is feared they
will compete with rainbow trout. In 2017, GCDAMP formed a science panel to explore
alternatives for managing brown trout impacts on rainbow trout and humpback chub.
00:38:00 Q: A previous interviewee mentioned that early on, the thinking was that both species
of trout were probably eating humpback chub and depressing the population. After further
research, it was determined that the rainbow weren’t, and the brown trout were. Is that correct in
your mind? A: Yes.

00:39:00 Mike Yard found that both trout species prey on humpback chub, but brown trout eat 3
to 4 times the number of fish that rainbow trout eat. The smallmouth bass, which can tolerate
cool water, is another potential predator.
00:40:00 Smallmouth bass have recently migrated into Grand Canyon, but there is no evidence
that they have reproduced there. Q: And you expect them to be predators on humpback chub? A:
They are intensive predators. The Upper Colorado River Endangered Fish Recovery Program
spends about 40% of its budget removing smallmouth bass and northern pike. Q: There are
northern pike in the Colorado River? A: Yes. The state of Colorado introduced them into
Elkhead Reservoir some years back, and they escaped, along with smallmouth bass.
00:41:00 There are guided fishing tours in the Yampa River for northern pike, which prefer cold
water and seldom leave the area. Smallmouth bass can tolerate a range of temperatures and may
prove problematic in Grand Canyon. “It fills that intermediate niche between the cold-water
species and the warm-water species, and could probably do quite well.” Q: Where are we at
today with the recovery of the humpback chub? I heard recently that there was talk about
downlisting it from “endangered” to “threatened.” What’s the status now and where do you think
we’re going in the near future?
00:42:00 A: The humpback chub is currently listed as endangered. It was included in the original
list of endangered species in 1966 and grandfathered into the Endangered Species Act in 1973.
Today, the species is doing well in all parts of Grand Canyon.
00:43:00 There are six or seven aggregations, or small groups of humpback chub populations,
outside the LCR area in warm-water areas. Humpback chub readily interact with boaters and are
one of the fish most commonly sighted on river trips.
00:44:00 Humpback chub are very social and travel in groups. There are five populations outside
Grand Canyon, in the Upper Colorado River Basin. A population in Yampa Canyon was recently
declared functionally extirpated. The humpback chub recovery team is exploring the prospect of
translocating humpback chub back into the Yampa River.
00:45:00 The Upper Basin populations are not doing quite as well as those in Grand Canyon, but
they are currently self-sustaining. USFWS initiated a downlist proposal in February 2020.
00:46:00 If the proposal is deemed appropriate, it could be implemented within the next year.
Valdez thinks it will be, as the Grand Canyon populations are doing well and the Upper Basin
groups are mostly stable.

00:47:00 The endangered Colorado pikeminnow is being evaluated for reintroduction into Grand
Canyon. It had been extirpated there since 1975. Q: As a result of the changes in the river due to
the construction of Glen Canyon Dam, or something else? A: Probably several factors.
00:48:00 The Colorado pikeminnow is highly migratory within a given river system. In the
pre-dam Colorado River it probably migrated from as far as Yuma, perhaps even feeding in the
estuary. Evidence shows this fish could reach 6 feet long and 100 pounds. Now restricted to the
Upper Basin by Glen Canyon Dam, Colorado pikeminnow weigh no more than 30 pounds.
00:49:00 Some Colorado pikeminnow were introduced into the Salt and Verde rivers but are not
part of a recovery program. USFWS, NPS and Arizona Game and Fish Department (AZGFD)
are looking at reintroducing the species in Grand Canyon. Such a population would likely not be
self-sustaining.
00:50:00 The life history requirements for Colorado pikeminnow are not present in Grand
Canyon due to the current state of the dammed river.
00:51:00 A downlisting for humpback chub would not significantly change Glen Canyon Dam
operations. The difference between an endangered species and a threatened species is small
relative to Section 7 of the ESA. The states would have a more active part in conservation
measures, providing some flexibility in management.
00:52:00 Q: To what extent is the improved health of the humpback chub population in Grand
Canyon traceable to GCDAMP and changes in dam operations? How much of it is just
serendipity, and how much of it is the results of our efforts to recover the species? A: It is a
“scientist’s nightmare” to look back on the management decisions made in a program and realize
that many of them did not make much of a difference.
00:53:00 The humpback chub’s recovery is partly attributable to GCDAMP management
decisions, but part of it is serendipitous, stemming from the results of lowering elevations in
Lake Powell and Lake Mead [due to the long-term drought].
00:54:00 One helpful management action, implemented in 1995, was reducing the large flow
fluctuations created when maximizing hydropower generation. The daily 20-foot river elevation
increase at the foot of Glen Canyon Dam generated a wave “that was almost a daily flushing of
the Grand Canyon.”
00:55:00 The daily fluctuations not only disrupted boat trips, they were detrimental to young
humpback chub that used the shoreline for nursery areas.

00:56:00 The fluctuating flows displaced young fish from protected areas and exposed them to
predation. The Modified Low Fluctuating Flow (MLFF) alternative resulted from studies
conducted prior to 1995. Valdez argued at the time that flows needed to be even more stable,
since the historic river was low and fluctuated very little in the summer.
00:57:00 The Low Steady Summer Flow (LSSF) concept was implemented in 2000 to test the
low flow hypothesis. Scientists discovered that humpback chub adapt to modified fluctuating
flows quite well by staying near talus slopes.
00:58:00 While high flow fluctuations were not good for humpback chub, moderate fluctuations
may actually benefit them. Another highly beneficial management tactic was mechanical
removal of trout, carp and channel catfish.
00:59:00 Q: Are catfish also predators on humpback chub? A: Absolutely. Q: But not carp? A:
Carp are voracious predators of fish eggs. Valdez remembers watching red shiners spawn in
Spencer Creek, and a few minutes later an “entire herd” of carp “vacuumed” the area of eggs.
The effect of predation on native fish eggs and larvae may not get the attention it deserves.
01:00:00 High Flow Experiments (HFEs) also benefit native fish.
01:01:00 HFEs build beaches and deposit sediment into large recirculating eddy complexes,
creating backwater habitat for fish. Native flannelmouth and bluehead suckers and speckled dace
use the backwaters more than humpback chub do.
01:02:00 Q: How has the science of HFEs and our understanding of their impacts evolved over
time? A: The first HFE was in 1996. “We called it the controlled flood through Grand Canyon.”
01:03:00 Valdez and others edited a book on the flood, archiving many of the studies done on the
first HFE. [Webb, Robert H., John C. Schmidt, G. Richard Marzolf, and Richard A. Valdez, eds.
The Controlled Flood in Grand Canyon. Vol. 110, Geophysical Monograph Series. Washington,
DC: American Geophysical Union, January 1, 1999.
https://agupubs.onlinelibrary.wiley.com/doi/book/10.1029/GM110.] HFEs were formerly called
Beach Habitat Building Flows (BHBFs). Dave Wegner asked the National Academy of Sciences
to do a review of GCES in the mid-1980s, soon after the emergency dam releases during the
flood years of 1983-1984.
01:04:00 The National Academy of Sciences concluded high flows were bad for the river
ecosystem through Grand Canyon because they transport large amounts of sediment out of the
system.

01:05:00 A subsequent review a few years later was more nuanced, proposing high flows could
be used to build beaches by suspending sediment and entraining it in recirculating eddies.
01:06:00 The Secretary of the Interior approved the first HFE. It was notable because the 30,000
cfs (cubic feet per second) release involved the bypass tubes, which did not generate electricity.
The 1996 HFE lasted for almost 2 weeks.
01:07:00 Most of the sediment influenced by the HFE moved in the first 2 or 3 days, so 48-96
hours is enough time to get the desired effect. Managers later developed a protocol for doing
HFEs when sediment was available in spring or fall. Because sediment from the Upper Basin is
trapped in Lake Powell, the LCR and the Paria River provide most of the sediment downstream
of the dam.
01:08:00 The Paria contributes sediment in late summer, and the LCR contributes in spring.
HFEs were initially done in spring because that better simulated the natural hydrograph.
01:09:00 Because the Paria contributes the majority of sediment and is closer to the dam, and
many of the large recirculating complexes are upstream of the LCR, the HFE protocol changed
to fall releases.
01:10:00 A recent decline in production of insects and algae–the Grand Canyon food base–may
be tied to fall HFEs. Production is inhibited by the scouring effect of 40,000 cfs releases in the
Lees Ferry reach and a low sun angle in fall that limits photosynthesis, followed by winter
weather that does not allow for recovery.
01:11:00 Fall HFEs may be a net negative for the system. Q: We’ve been hearing about low Bug
Flows lately. Can you explain that? A: Releases from Glen Canyon Dam are a uniform
temperature rather than fluctuating with the seasons, and although recent releases are warmer, the
river still does not reach pre-dam temperatures.
01:12:00 Cold and unvarying water temperatures, along with fluctuating flows, have a negative
effect on certain invertebrate species that fish rely on as food. Species that require both a warm
and a cold period to complete their life cycles cannot currently exist in Grand Canyon.
01:13:00 Ted Kennedy of Grand Canyon Monitoring and Research Center (GCMRC) proposed
the Bug Flow concept. Bugs crawl onto rocks to lay their eggs, and a steady release can keep the
rocks wet long enough for the eggs to hatch before drying out. Q: Is that working? A: It appears
to be, in that certain insects that fish feed on are doing better. The scouring effects of HFEs are
still an issue under consideration.

01:14:00 Q: As I understand it, they won’t even do an HFE if they haven’t determined that a
certain amount of sediment has come down one of those two tributaries and is available to push
down the Colorado. A: Yes. Two factors determine if an HFE will take place: availability of a
volume of water aside from that needed for normal dam operations, and availability of sediment.
01:15:00 There are years when an HFE is not authorized. Q: How about if we take a short break
now, and then come back in about five minutes? (Recording paused.) Q: One of the topics we
touched on earlier was mechanical removal of predatory fish that impact the chub population.
What role has mechanical removal of brown and rainbow trout played in fish management, and
what happened when it was adopted for GCDAMP?
01:16:00 A: Predation on humpback chub, especially the young, was a concern across the
Colorado River Basin. The most direct management solution was mechanical removal of as
many non-native predatory fish as possible.
01:17:00 Going back to the 1996 Record of Decision (ROD), predation was identified as a major
threat to native fish in Grand Canyon.
01:18:00 Although brown trout had been identified as the biggest threat to humpback chub, they
were outnumbered by rainbow trout.
01:19:00 Water in the Colorado River mainstem was too cold for rainbow trout to self-sustain, so
AZGFD introduced them annually to sustain the fishery. They were able to reproduce after
implementation of the MLLF alternative. Younger trout began to move downstream, closer to
prime humpback chub territory near the LCR.
01:20:00 Managers proposed intensive removal between Lees Ferry and Badger Creek at key
times of the year, when they suspected rainbow trout would be moving downstream. They did
removal experiments and coordinated an Environmental Assessment.
01:21:00 Q: Was the research on that before the 1995 EIS, or at the time it was being developed?
A: Immediately after. In the early 2000s, the idea of removing trout when they got to the LCR
area, rather than trying to intercept them on their way, was proposed. The multi-year experiment
involved several removal trips.
01:22:00 Mass trout removal led to some complicating issues. The first was what to do with the
dead fish. NPS would not allow them to be ground up and returned to the water or buried
alongside the river. Instead, the ground fish remains were put in barrels and used as fertilizer.

01:23:00 The second issue was that Native American tribes had concerns about the taking of life
in Grand Canyon. Removal was effective in reducing trout numbers as long as it was ongoing.
01:24:00 It only took a year or two for rainbow trout to repopulate a designated area, leading to
doubts about mechanical removal as a sustainable management action. Managers considered how
many adult humpback chub there needed to be for a population to sustain a certain amount of
predation by rainbow trout, and developed triggers for mechanical removal based on numbers of
both species.
01:25:00 The research was incorporated into the 2016 LTEMP EIS. Predation by brown trout,
which primarily spawn in Bright Angel Creek, continued to be a problem.
01:26:00 In about 2012, NPS put a fish weir at the mouth of Bright Angel Creek to remove
brown and rainbow trout.
01:27:00 Q: So rainbow trout were spawning also in Bright Angel Creek. A: Yes. In the last 5
years, NPS has removed trout directly from Bright Angel Creek. Valdez cites a paper reporting a
decline in these non-native trout of 75%-80% following removal actions. [Healy, Brian D.,
Robert C. Schelly, Charles B. Yackulic, Emily C. Omana Smith, and Phaedra Budy. “Remarkable
Response of Native Fishes to Invasive Trout Suppression Varies with Trout Density,
Temperature, and Annual Hydrology.” Canadian Journal of Fisheries and Aquatic Sciences.
Ottawa: NRC Research Press e-First Article, June 3, 2020.
https://www.nrcresearchpress.com/doi/10.1139/cjfas-2020-0028#.Xz8YHDV7mUn.] Q: Let’s
pause. (Recording paused.)
01:28:00 The NPS interception of large, spawning adult trout was also controversial. People
made annual hikes down Bright Angel trail to catch the big fish in the fall.
01:29:00 The paper reporting the sharp decline in trout after removal efforts in Bright Angel
Creek (see Minute 87) also cited a 400% increase in that area of native flannelmouth and
bluehead suckers.
01:30:00 The costs of maintaining management actions for as long as needed has to be
considered at the outset. Another option is to do them periodically.
01:31:00 GCMRC and AZGFD monitor the river through Grand Canyon, so any sudden increase
of a given species should be detectable before it becomes a big problem. Smallmouth bass may
be the next problematic species. Q: So as far as you know, there isn’t an active mechanical
removal program today, but it’s still a possibility and may become necessary in the future?

01:32:00 A: The mechanical removal program in Bright Angel Creek is ongoing. There is also
some removal in Havasu Creek. Humpback chub were translocated there, as well as to Shinumo
Creek. In light of Native American concerns, the approach is to improve humpback chub
population so that it can sustain a certain level of predation.
01:33:00 The brown trout management team has developed an incentivized removal program at
Lees Ferry that pays “bounties” on brown trout brought in by anglers.
01:34:00 The incentivized removal program has the potential to be cheaper overall than
mechanical removal.
01:35:00 Q: Are you aware of any objections by the Havasupai Tribe of mechanical removal of
trout in Havasu Creek? A: Valdez is aware of concerns, but has no recent involvement in the
issue. Q: Who do you think have been the most important researchers and participants in
GCDAMP over time? A: Valdez says he knows more scientists than administrators or managers.
01:36:00 Dave Wegner was instrumental in bringing together scientists under GCES. The
GCMRC facilitated Carl Walters’ participation in GCDAMP. Walters “shook up the scientific
community in Grand Canyon. Because we thought we were pretty darn good at what we were
doing. Carl made us realize that we could do more, much more.”
01:37:00 Walters urged GCDAMP participants to understand how adaptive management really
works, and to be alert to “natural experiments that were taking place right in front of our eyes.”
01:38:00 Scientists and managers must remember that conditions in Grand Canyon varied from
year to year. “It was basically conducting a huge outdoor experiment over which you have little
control over environmental variables.” Condition dependency allowed for conducting
experiments only in years when the conditions were suitable.
01:39:00 Bill Pine initiated the Near Shore Ecology Studies that broadened understanding of
young humpback chub survival.
01:40:00 Pine also introduced the use of laser ablation sampling of fish inner ear bones, which
can reveal in detail the life events of individual fish.
01:41:00 Lew Coggins also introduced new analytical techniques. Coggins earned his PhD under
Pine and Walters, who both have strong marine fish backgrounds.
01:42:00 The study of marine fisheries involves large scales and much uncertainty, so its
analytical techniques are more advanced than those used in freshwater fisheries. Coggins

developed a mark-recapture model to better estimate the numbers of humpback chub in Grand
Canyon
01:43:00 Josh Korman applied his research experience with trout in Canada and Alaska to better
determine how brown and rainbow trout behave in Grand Canyon.
01:44:00 Korman and Mike Yard found out that rainbow trout in Grand Canyon are late winter
spawners. After hatching in spring, the fry stay in shallow, sheltered areas around Lees Ferry. A
fluctuating flow dam operations scenario strands the young because they are in shallow water.
01:45:00 Young trout seek out rocky, steeper shorelines as they get older. This knowledge
inspired the concept of trout management flows for regulating their population.
01:46:00 Intentionally stranding fry before they have a chance to grow and migrate downstream
is an alternative to mechanical removal. Q: Has anyone tried that option yet? 01:00:00 A:
Experimental trout management flows have worked to a certain degree.
01:47:00 Part of the trout population in the Lees Ferry reach was spawning not in shallow areas,
but more toward the middle of the channel. Warmer releases from the dam expanded the
spawning window, so there are young of different ages in the area over a longer time.
01:48:00 There may be competition for spawning areas between rainbow and brown trout.
Browns spawn from October into January, and rainbows from late December to February. “I
think the important message here is that, if you understand the life history of the species, it may
not be a direct sledgehammer that’s the solution.”
01:49:00 That understanding illustrates the value of Walters’ and Pine’s influence. Jack Schmidt
pioneered understanding of sediment distribution and the HFE concept. Schmidt has mentored
many graduate students in studying Grand Canyon, including Paul Grams of GCMRC.
01:50:00 Most recently, Charles Yackulic joined GCMRC around 2010. He has an extensive
ecosystem modeling background.
01:51:00 Yackulic has especially advanced understanding of the relationship between the
Colorado River mainstem and the LCR for humpback chub. He coordinated work across the
different Grand Canyon science disciplines for evaluating the 2016 EIS alternatives. Larry
Stevens is knowledgeable in almost every aspect of Grand Canyon science.
01:52:00 Stevens has an “almost insurmountable” understanding of Grand Canyon. Steve
Carothers conducted one of the first fish surveys through Grand Canyon.

01:53:00 Carothers started environmental consulting company SWCA in the 1970s. Valdez
joined SWCA in the late 1980s, when Carothers got tired of competing against him for research
contracts. Q: What key reports or studies would you highlight as particularly important, that have
retained their value over time?
01:54:00 A: The 1996 EIS is pivotal. Glen Canyon Dam was built before NEPA (National
Environmental Policy Act) compliance was a factor. The 2016 LTEMP EIS is a good archival
document for GCDAMP research and management. The four reviews from the National
Academy of Sciences show “evolution of thinking by scientists in the Grand Canyon.”
01:55:00 The first review was done right after the natural high flows of 1983-1984. Flows
through Grand Canyon peaked at almost 90,000 cfs. The National Academy of Sciences
cautioned that an HFE would flush all the sediment into Lake Mead, a contention subsequent
NAS reviews revised.
01:56:00 Jack Schmidt was a proponent of common-sense management policy. There are many
reports and manuscripts detailing Grand Canyon Science. In his own work, Valdez is most proud
of an article he co-authored in BioScience. [Schmidt, John C., Robert H. Webb, Richard A.
Valdez, G. Richard Marzolf, and Lawrence E. Stevens. “Science and Values in River Restoration
in the Grand Canyon: There is No Restoration or Rehabilitation Strategy That Will Improve the
Status of Every Riverine Resource.” BioScience 48, no. 9 (1998): 735–747.
https://doi.org/10.2307/1313336.]
01:57:00 In a “wonderful conversation” that happened before the time of GCDAMP, Schmidt
encouraged Valdez and his other co-authors to document what they had learned in studying
Grand Canyon.
01:58:00 The paper introduced the “intractable dilemma” concept, the recognition that no single
management action in Grand Canyon could simultaneously benefit all resources.
01:59:00 The idea that different conditions are available at different times of the year and
management should be conducted accordingly “opened the door, beautifully, for adaptive
management.” Experiments are designed and continuously evaluated and adjusted over time.
02:00:00 Yackulic and others recently published a paper that nicely visualizes how humpback
chub spend their lives in the Grand Canyon system. [Yackulic, Charles B., Michael D. Yard, Josh
Korman, and David R. Haverbeke. “A Quantitative Life History of Endangered Humpback Chub
That Spawn in the Little Colorado River: Variation in Movement, Growth, and Survival.”
Ecology and Evolution 4, no. 7 (2014): 1006-1018. doi:10.1002/ece3.990.]

02:01:00 Q: What do you think is the value of adaptive management in trying to manage
complex resources in a environment that we can’t predict or control? A: That is the most
pressing question for many systems.
02:02:00 The system in Grand Canyon is similar to others in the western U.S. in that dams and
diversions have fundamentally altered the ecosystem. The Colorado River ecosystem, while
dynamic, had persisted over 3 to 4 million years. Evidence shows lava flows dammed the river in
parts of Grand Canyon before slowly eroding.
02:03:00 It was a dynamic system long before it was subject to large-scale human influences.
02:04:00 It is unlikely that the system could be restored to its pre-human state. The components
of the historical river cannot be replicated, and managers have to work with the system in its
current form.
02:05:00 Ideas about how the current components might work can be expressed as hypotheses,
making the system a good setting for adaptive management.
02:06:00 Surprises from nature and condition-dependent frameworks complicate experiments.
“You’re basically doing experimentation in a large open laboratory, with no control whatsoever,
except for perhaps a large spigot called Glen Canyon Dam.”
02:07:00 Now that Valdez is not as involved in GCDAMP, he finds value in the ability to look at
it objectively. Mechanical removal of non-native fish was more complicated than first
hypothesized. HFEs had unanticipated effects that had to be incorporated into subsequent
experiments.
02:08:00 Carl Walters cautioned that experiments need to be conducted and evaluated before
policy is implemented. Many GCDAMP participants have trouble understanding how long that
experimentation and evaluation actually takes.
02:09:00 There are few definite answers for managers, even after over 30 years of
experimentation. Ongoing involvement, and ongoing understanding of the system’s dynamics,
are critical.
02:10:00 Q: Will there be some point in the future when we’ve learned enough that we don’t
really need GCDAMP anymore? Or is the constant evolution and accretion of knowledge so
valuable that it should be continued, at least for the foreseeable future?

02:11:00 A: Yes, it should be continued, but not simply for the sake of science. Society has
decided that Grand Canyon is one of North America’s most valuable resources. “It’s important to
maintain the Grand Canyon as well as we can, and maintain all the resources within the Grand
Canyon. When it is a societal decision, and it is a societal value, I think it does rise to the level of
justifying an ongoing funding of the program.”
02:12:00 AMWG is a federal advisory committee under the authority of the Secretary of the
Interior. This reduces complexity, especially in funding. Only the program managers can decide
if paring down the budget is necessary.
02:13:00 The role of scientists in Grand Canyon is to gather information objectively, and the role
of GCDAMP administrators is to facilitate science-based decision-making. Those roles are
necessary to protect resources in Grand Canyon and downstream.
02:14:00 If GCDAMP were to go away, the situation might be similar to the “water wars” that
happened before the Upper Colorado River Endangered Fish Recovery Program was
implemented.
02:15:00 Q: What advice would you have for people coming newly into GCDAMP about how to
be successful in advancing the program?
02:16:00 A: Patience and humility. New members have to realize that many people before them
have been working toward the best balance of water management and protection of resources.
Understanding of roles. Scientists, especially, need to understand their function in GCDAMP.
02:17:00 Humility is essential. No one person is going to be able to solve every problem.
02:18:00 Have patience with fellow stakeholders. Understand that the intent of adaptive
management is to figure out how to do things better.
02:19:00 GCDAMP does well at coordinating the science. Having GCMRC under USGS means
reports are easily accessible and kept current, which is not the case with all river basin programs.