Andrew J. Paul, Ph.D., Adjunct Professor, Department of Biological Services – University of Calgary, Canada
Dr. Andrew Paul has been working as an aquatic ecologist in western Canada for 35 years. His work has encompassed the fields of conservation biology, community restoration, non-native species invasions, population ecology and river ecology. Andrew uses quantitative methods to aid in understanding ecological patterns or processes and has worked with the Theoretical Population Dynamics Group (University of Amsterdam) and the Fisheries Centre (University of British Columbia). Andrew spent 15 years with Alberta Fish and Wildlife studying environmental flows and now works with Alberta’s Chief Scientist to support scientific excellence in government. Andrew is an adjunct professor at the University of Calgary (Dept. of Biological Sciences).
2024 Science Symposium Presentation
Day one of the Trinity River Restoration Program Science Symposium covered Fish Populations. Listen in as Andrew J. Paul, Ph.D., Adjunct Professor, Department of Biological Services – University of Calgary, Canada presents, “Importance of experimental design to understanding aquatic ecosystems: how good intentions and experience can be the enemy of knowledge.”
Kurt Fausch, Ph.D. Professor Emeritus, Department of Fish, Wildlife, and Conservation Biology, Colorado State University
Kurt Fausch is Professor Emeritus in the Department of Fish, Wildlife, and Conservation Biology at Colorado State University, where he taught for 35 years. His research collaborations in stream fish ecology and conservation have taken him throughout Colorado and the West, and worldwide, including to Hokkaido in northern Japan. His experiences were chronicled in the PBS documentary RiverWebs, and the 2015 book For the Love of Rivers: A Scientist’s Journey which won the Sigurd F. Olson Nature Writing Award. He has received lifetime achievement awards from the American Fisheries Society and the World Council of Fisheries Societies, and the Leopold Conservation Award from Fly Fishers International.
2024 Science Symposium Presentation
Day one of the Trinity River Restoration Program Science Symposium covered Fish Populations. Listen in as Kurt Fausch, Ph.D., Professor Emeritus, Department of Fish, Wildlife, and Conservation Biology, Colorado State University presents “What is essential about rivers for fish and humans? Lessons on connectivity and connections from four decades.”
The final day of the symposium focused on the physical environment that underpins the complex riparian and aquatic river ecosystem. We learned that while the Trinity River is actually used as an example for successful implementation of a functional flows approach to streamflow management, we are still missing some key components of a functional flow hydrograph that are essential to optimizing the physical and ecological processes of the river.
Day 3 – Physical Channel Form presenters and organizers. From the left; Conor Shea, Dave Gaeuman, John Buffington, Scott McBain, Kiana Abel, Todd Buxton, Sarah Yarnell, Daniele Tonina and Mike Dixon.
Contrary to the prevailing folk wisdom in salmonid streams that all fine sediment in salmonid streams is bad, it was revealed that having too little fine sediment can impede the movement of larger gravels, and that having river flows match tributary flows is important to moving fine sediment in a way that is healthy for the river, rather than harmful. There were insights about what we know about how gravel routes through the upper river and what that means for our approach to sediment augmentation. A uniquely interdisciplinary presentation focused on how flow management influences where riparian plants grow, spurring conversation about how varying base flows could promote willow growth across different active channel widths, which could provide roughness and improve sediment sorting and storage. The takeaways really came down to this; we can’t have healthy fish and other wildlife populations without process, and we have learned a lot about how to improve those processes.
Dr. Tonina holds the mic during the panel discussion on day three of the 2024 Science Symposium.
The panel discussion at the day’s conclusion was moderated by SAB member John Buffington, Ph.D.. The questions from the audience were stimulating and the panelists conversation informative. The discussion can be viewed in its entirety by clicking the YouTube link below.
Day 2 presenters for Habitat, Flow and Temperature. From the left, Kyle De Juilio, Derek Rupert, Eli Asarian, Seth Naman, Don Ashton, Todd Buxton and John Hayes.
Day two of the 2024 Trinity River Restoration Program Science Symposium was intended to explore the function of the Trinity River and other lotic (rapidly moving fresh water) systems. With an emphasis on creating a common understanding that can be applied to management in the future. Much has been learned in the relatively young field of river restoration over the last few decades, and leveraging that learning is critical to successful restoration in our watershed and others.
The day started with new TRRP Science Advisory Board member and world renowned researcher, John Hayes, Ph.D.. Dr. Hayes presented on his work with salmonids in New Zealand to describe their flow requirements through numerical modeling of drifting macroinvertebrates and drift foraging behavior. These innovations have changed the way managers think about the effects of flow management on salmonid populations.
Dr. John Hayes talks about attending the Trinity River Restoration Program 2024 Science Symposium. Dr. Hayes is a new member of the Program’s Science Advisory Board and he opened Day 2 presentations with a talk titled, “How flow affects aquatic invertebrate habitat and drift, and salmonid net energy intake and instantaneous carrying capacity.
We had additional talks on temperature and thermal diversity from Eli Asarian (Riverbend Sciences) Klamath Basin water temperature expert along with Todd Buxton, Ph.D. (TRRP) a physical scientist and an accomplished fisheries researcher. We heard from regional reptile and amphibian expert, Don Ashton (McBain and associates) about the decades of research on the Trinity River and the impacts that flow management have had on these important indicator species of ecosystem health.
Don Ashton (McBain and associates) during his presentation about the decades of research on the Trinity River and the impacts that flow management have had on reptiles and amphibians.
Finally, we heard from Seth Naman, currently with NOAA Fisheries and long time Klamath Basin Fisheries researcher, and Derek Rupert, currently with Reclamation and former USFWS Fisheries Biologist on the Trinity River, about 2 proposed methods to manage flow releases year-round on the Trinity River and Clear Creek respectively. These proposed methods rely on seasonal and annual patterns of run-off to restore the functionality of the river to that which the species evolved with to ensure reproductive success and productivity.
Together this suite of talks described our current understanding of how cold-blooded species feed and behaviorally regulate their body temperature in regulated and unregulated rivers. As well as the known and suspected impacts of flow and temperature management and proposed methods to reduce impacts and improved function of the environments we seek to restore.
The panel discussion at the day’s conclusion was moderated by SAB member and Fisheries Researcher from Canada, Andy Paul, Ph.D.. The conversation was stimulating and informative and can be viewed in its entirety by clicking the YouTube link below. The direct communication between SAB members, scientists within the Program, managers, and the public is critical to moving management forward together to benefit the resource for all.
Day 2 Panel Discussion on Habitat, Flow and Temperature.
The first day of presenters and organizers pose for the 2024 Trinity River Science Symposium. Left to Right: Ken Lindke, Chad Martel, Kurt Fausch, Bill Pinnix, Kiana Abel, Andrew Paul and Nicholas Som.
The first day of the 2024 Trinity River Restoration Program Science Symposium was a great start to the week. Science Advisory Board members Kurt Fausch, Ph.D. and Andrew Paul, Ph.D. (link to bios) started the day by sharing their sage wisdom from decades of scientific practice and learning.
Dr. Fausch took us across the Pacific Ocean to share his experiences with early groundbreaking work on the interconnectedness of streams and riparian ecosystems with colleagues in Hokkaido Japan, reminding us that the human connection to rivers and fish is, perhaps, more important than any scientific finding we can achieve.
Next, Dr. Paul rounded out the morning with a lesson on study design and a cautionary tale on how good intentions can sometimes lead us astray, while sound, well formulated sampling designs can buffer against unintended missteps.
Dr. Andrew Paul speaks to the audience Tuesday morning.
After lunch we welcomed Bill Pinnix from US Fish and Wildlife Service. Pinnix brought the audience back to the Trinity River by showing one of the notable successes of the Restoration Program, a significant increase in juvenile Chinook Salmon production since implementation of the Record of Decision in 2000. Pinnix noted that, in spite of successes with juvenile outmigrants, results for adult Chinook Salmon returns have been mixed.
The rest of the afternoon was dedicated to a short list of the challenges that juvenile salmonids face in their journey to the ocean and back. Chad Martel of the Hoopa Valley Tribal Fisheries Program described a multiagency, multiyear study of juvenile outmigration survival from Lewiston Dam to the Klamath River Estuary, where survival has so far shown to be higher than most area biologists expected.
Chad Martel points at one of his slides during his presentation on Tuesday, April 30.
Dr. Nicholas Som from US Geological Survey and Cal-Poly Humboldt taught us about the fish parasite Ceratanova shasta, the history of learning in the Klamath basin, and successes in translating scientific discovery into water management implementation.
Finally, renowned ocean fish ecologist Nate Mantua, Ph.D. from the National Oceanic and Atmospheric Administration provided a glimpse of insight into the complex world of Pacific Ocean circulation patterns, tropical teleconnections, coastal upwelling, food web dynamics and the perils and opportunities that face young salmon as they survive, die, grow and mature to return to the Klamath river and complete their lifecycle.
Dr. Nate Mantua discussed the climate and changing ocean conditions on Tuesday, April 30.
The evening was rounded out with a panel discussion held at the Lewiston Hotel, Restaurant and Dance Hall which was moderated by Science Advisory Board member John Hayes from the Cawthron Institute in New Zealand. The 90-minute discussion provided insightful questions and educational dialogue between attendees and panelists and we thank everyone who was able to participate.
Panelists get ready for the discussion at the Lewiston Hotel on Tuesday evening.
Many Trinity County residents are attuned to the annual water year forecasting prepared by the California Department of Water Resources, also known as the Bulletin 120 or B-120. Every year, the department gathers real time water accumulation information, snowpack data and uses modeling to forecast what to expect for the major snow bearing watersheds in California. The water bean counting starts October 1 (the nominal beginning of California’s wet season) with a final determination April 10 each year. The forecasts are broken up into several regions throughout California with the Trinity River at Lewiston Lake forecast filed under the North Coast Hydrologic Region. The ultimate goal of the B-120 is to value expected amounts of water inflow to storage locations around the state. These data makes it possible for water managers to make local informed decisions about potential floods, the amount of water that can be released from reservoir systems, as well as what type of dry season residents and fire agencies could expect within their regions.
Each year, the Watershed Research and Training Center along with the U.S. Forest Service – Shasta-Trinity National Forest conduct monthly snow surveys at specific locations in the Trinity Alps which are a part of the statewide California Cooperative Snow Survey program. Together these local organizations help the California Department of Water Resources forecast the quantity of water available for our watershed each water year. Listen into Josh Smith, Watershed Stewardship Program Director for The Watershed Center talk about their efforts in collecting this important yearly data.
For the Trinity River Restoration Program, the April B-120 forecast determines the water year allocation for our yearly restoration flow releases, which were outlined in the 1999 Flow Study Evaluation and adopted in the 2000 Department of Interior – Record of Decision. These five water year types that determine the amount of water released to the river from year to year are categorized as Critically Dry, Dry, Normal, Wet and Extremely Wet. You can see the relative allocation for restoration purposes in the table below.
It is interesting to note that the State’s April B-120 has only overpredicted the water year type once, in 2008. Currently the allocation for river restoration is the only conditioned amount of water released from Trinity & Lewiston Reservoir; where the Restoration Program’s yearly allocation is limited by water year type, the Central Valley Project can divert any amount in any water year type, usually diverting less in wetter years and more in drier years. Safety of dams releases and water releases to the Trinity River for ceremonial purposes or for Klamath River mitigation purposes are not part of the restoration release volume.
Josh Smith and Michael Novak in Bear Basin during the annual snow survey in 2020. Photo by Dillon Sheedy.
As mentioned above the State’s forecast uses a few different methods to determine how much water to expect as inflow into Trinity & Lewiston Reservoir. The most story-worthy data collection type are the on-the-ground, snow surveys which are conducted during a short window every February, March, April and May. The Trinity Alps snow surveys are led by two agencies: The U.S. Forest Service who motor in via snow Cat to several locations in the Trinity Alps Wilderness, and an expert group of backcountry cross country skiers led by The Watershed Research and Training Center. There are nearly a dozen survey courses established throughout the Trinity River watershed and these sites have been measured in exactly the same locations since the 1940s.
A long metal tube is pushed down through the snow to the ground, capturing the depth of the snow in the core of the tube. This photo was taken of Ben Letton by Josh Smith during the March 2021.
Each year The Watershed Center sends out a small team of between two and four backcountry skiers to travel through the Alps Wilderness and measure snowpack at three survey courses: Shimmy Lake, Red Rock Mountain, and Bear Basin. Once the team reaches a survey location, they drive a specialized aluminum tube tool called the Mt. Rose Sampler, into the snowpack until they hit ground. “It takes a few times to get used to doing it,” says Josh Smith who has been conducting surveys in the Alps since 2011, with the first full recorded season in 2012. The surveyors use the tool to measure the height of the snow, then carefully extract the tube from the snowpack and weigh the snow-filled tube using a handheld scale. These measurements allow the surveyors to calculate the Snow Water Equivalent in designated transects within the three courses for which their team is responsible for. The State uses the hand measurements from the snow survey teams to bolster additional data taken from unmanned sensors located across and just outside of the watershed. These data sources together feed into a model that predicts the volume of water that will flow into Trinity Reservoir that year.
The Mt. Rose Sampler tube is being weighed on a specialized handheld scale. Using the height and weight of the snow, surveyors are able to calculate the Snow Water Equivalent (SWE).
A great deal of preparation and expertise goes into the Trinity Alps Snow Survey and participation is not for the faint of heart. When asked if the survey team has had any injuries Smith explained, “mostly broken will, oh, and lots and lots of blisters.” The crews aim for good weather days but do encounter a variety of winter weather patterns that exemplify California’s highly variable winter weather conditions, including blizzard conditions, wet and heavy snowpack, avalanche conditions, and melting snow that leads to flooding creeks.
“These are not groomed trails, and the crews switch off being the lead – when the snow is deep or heavy it’s not easy breaking trail, so we try and spread out that responsibility, especially when trying to conserve energy throughout the multi-day survey,” explained Smith.
That said, the Watershed Center is looking for local Trinity County residents who believe they have a sufficient mental and physical stamina to participate in this long-standing Trinity County tradition. “We get a lot of calls from people who think this is right for them,” Josh continues, “most people only come out once, and then they are done. It’s a real suffer-fest.”
Nick Goulette and Michael Novak during a blizzard in 2019. Photo by Josh Smith, provided by The Watershed Center.
If you’d like to learn more, please reach out to Josh Smith at the Watershed Training and Research Center by calling (530) 628-4206.
While it has not been a focus of the TRRP for many years, infrastructure improvement was one of the foundational tasks that was laid out in the 2000 Trinity River Mainstem Fishery Restoration Record of Decision. Years of low, predictable flows had led riparian property owners to develop very close to the river’s edge. In order to implement restoration releases, the TRRP has worked with willing property owners to upgrade or remove infrastructure that could be damaged by restoration flow releases as guided by the “maximum fisheries flow” boundary.
A photo of the cleared River Acres parcel, post demolition, April 2024.
The maximum fisheries flow is an 11,000 cubic feet per second release from Lewiston Dam (the highest the program can target for restoration objectives) that coincides with a major spring storm event. In the program’s first decade, there was a big push to address permitted infrastructure to clear the floodplain for fisheries releases; we moved roads, replaced several bridges, upgraded dozens of septic and water intake systems, and relocated a house in Douglas City. Another house (391 River Acres Rd in Junction City) was identified as being inside of the maximum fisheries flow boundary, but the owners were not interested in improving or selling their home at that time.
The River Acres House prior to removal, winter 2024.
The circumstances changed in the late 2010’s when the house sold to a new owner who used it as a fishing cabin and was very interested in finding a mutual solution that would benefit Trinity River fisheries. Together with engineers and architects the landowner and TRRP explored moving the house, building a levee, and elevating the living area with a flow-through bottom story. In the end, none of those solutions proved feasible due to flood concerns with adjoining properties and other constraints. The situation led the homeowner to decide to sell the house to the Bureau of Reclamation, who acquired the property in 2023.
In March of 2024, Cal Inc., a certified small business located in Vacaville, California was awarded the contract to demolish the 391 River Acres structures. Cal, Inc., specializes in general construction, abatement and remediation services, and environmental and safety training, and it took their professional staff only a few weeks to gather intel, test for lead and asbestos, and mobilize machinery, crew and subcontractors to begin the demolition.
Over the course of the week of April 8 the domestic water well and septic system was decommissioned, the structures and concrete pads were reduced to splinters and rubble, and an entire fence line of firewood was donated to a local charity.
The first crunch of an excavator bucket flattening an outbuilding occurred Monday morning and by Friday a final few sweeps of a hard-tine rack flattening the vehicle tracks left from construction. The materials left were loaded into what amounted to 12 dumpsters and was hauled-off for proper disposal.
Over the course of the week many of the neighbors wandered over and reminisced about those who had called the River Acres house home (or home away from home) over the years. They were understandably sad about losing a piece of River Acres history but were excited about the open space for their dogs and grandchildren to run and play in. We appreciate their tolerance of the noise, construction and extra visits these past few months. The project will be considered complete once the bare areas have been mulched and seeded, likely to be fully complete by the first of May.
Amaze your river friends by introducing them to the hyporheic zone, an important area where shallow groundwater and surface water mix to support a rich biological habitat of microvegetation that in-turn supports a diverse assemblage of benthic macroinvertebrates, the primary food source for juvenile and adult salmon.
Not only is the hyporheic zone an area that supports great biodiversity, in a 2005 study this zone was also coined the “river’s liver” from findings that carbon and nitrogen cycling in the river was “controlled by the live sediments of the central river channel, which thus represent a “liver function” in the river’s metabolism.”[1] So, the hyporheic zone acts as a filtering mechanism for the river, and an area of rich biodiversity. But that’s not all!
The hyporheic zone provides a multitude of functions and it is critically important to the health of our waterways. Because the hyporheic zone acts as a filtration system through its porous sediments, it also promotes higher levels of dissolved oxygen through photosynthesis. Dissolved oxygen in waterways support anadromous fish species like chinook, steelhead and coho salmon by helping them to maintain a healthy respiratory function.
When Trinity River salmon return to spawn, they dig redds (or nests) to lay their eggs in. The female fish flaps her tail sideways into the river bed, digging down around 12″ to 14″ into the hyporheic zone. After the eggs are laid and fertilized, she covers them with rocks. These rocks protect the eggs and newly hatched alevin from predators. The eggs location in the hyporheic zone provides water flow that flushes metabolic wastes during egg development and provide dissolved oxygen for her embryos to breathe.
The presence of dissolved oxygen, protection from predators, and microvegetation for food makes the hyporheic zone a biologic hotspot for macroinvertebrates. While the insects nestle down in between rocks they feed on leaves, algae, and twigs. In a healthy hyporheic zone where flow and sediments are correctly combined the area supports an abundance of food for the macroinvertebrates which in turn supports an abundance of food for juvenile and adult salmon. And that’s not all! Due to the interaction with upwelling cooler ground water, hyporheic zones help to moderate stream temperatures during the lower flow summer and fall months.
The Significance of the Hyporheic in the Trinity River
The hyporheic zone covers the entire streambed and bank areas of a river bottom and the ability to perform its natural functions are influenced by many things. Some influences include whether the stream is straight or meanders, if there are any obstacles in the channel, such as log, boulder, or even the pier support for a bridge. Factors also include whether the stream has a single channel or multiple channels, and also how porous the streambed sediments are. For example, near Lewiston Dam where there are very few fine sediments, large amounts of the river’s flow go subsurface because they are conveyed in the hyporheic zone. This is an unnatural situation because the river requires all sized sediments, from sand and silt up to cobbles and boulders. So while semi-open pore spaces in the bed are desirable, if the pore spaces are fully open do to the lack of fines in the bed, salmon eggs will jiggle around in redds and die from abrasion as well as the speed of flow between rocks in the hyporheic zone will be too fast for microvegetation to grow and macroinvertebrates to live.
It might be easy to surmise that due to the two dams on the Trinity River, that the hyporheic zone (within the 40-mile restoration reach) lacks diversity. Of course, dams block sediments, nutrients, logs and water from a river’s lower reaches. In a healthy river system, these elements work together to form a river’s structure. It is interesting to note that from 1964-1994 the Trinity River received a year-round baseflow of 200 cubic feet per second. The effect of static water releases was detrimental to the form and function of the river – greatly impacting the hyporheic zone. With the blockage of water, sediments, and logs the river began to stagnate – check out this article from November 3, 1980, “The Wild and the Dammed” where author P. McHugh documents his kayak adventure down the Trinity River in Lewiston.
Thus, to combat a static river system, since 2000, the Trinity River Restoration Program has focused efforts around replenishing the critical building blocks of a river. This is achieved by gravel additions in the upper river, large wood placements along river banks and a yearly spring snowmelt hydrograph that is released from Lewiston Dam. Also, since the Trinity was heavily impacted by hydraulic and dredge mining the program allocates funds for watershed restoration and gives great attention to the diversification of channels and floodplains with mechanical rehabilitation.
These things combined help the dammed Trinity in healing itself, however, many gains are yet to be made with restoration and management. For example, Todd Buxton, PhD, is starting a three year study of the hyporheic zone in the Trinity River. The study will construct a mathematical model to simulate the flow rates and directions, temperatures, and dissolved oxygen in the hyporheic zone. At the same time, macroinvertebrates in the hyporheic zone will be measured where the study is being conducted at sites within the 40-mile restoration reach. This information will be used to develop a statistical model for predicting the density and species composition of macroinvertebrates based on the above characteristics in the hyporheic zone, since these aspects have a strong role in determining how many and what species of macroinvertebrates may be present. Application of the paired models will then enable scientists to better understand how surface flows and temperatures in the river can be better managed to promote macroinvertebrate populations and increase the availability of food for salmon.
Additionally, the program has made significant gains with increases in outmigrating salmon smolts since 2000, but these fish are not returning home at the rates that were observed before this year. Scientist have identified that the Program’s current management of flow timing could be a critical limiting factor for the fish of the Trinity River. If juvenile fish had more food available to them when they are emerging from their nests they may enter the ocean more robust. If elevated flows from the dam are timed with winter storms, then the Trinity River could add to the power of the tributary flows to increase mainstem water levels to prevent delta creation while simultaneously preventing sediments from smothering redds and other important living organisms within the hyporheic zone.
Understanding this unique area has been a challenge for river scientists because the hyporheic function is expansive. It is also unique to each river system and crosses over many scientific disciplines. The zone not only intrigues those interested in studying the microbiome of a river system, but also includes; ecologists, geomorphologists, hydrologists and environmental engineers, just to name a few. With each discipline and study within, scientists learn more and more about the fascinating world that exists beneath and alongside a river’s bed and how river restorationists can better understand to allow it to flourish.
[1] Fischer, H.; Kloep, F.; Wilzcek, S.; Pusch, M.T. A river’s liver–microbial processes within the hyporheic zone of a large lowland river. Biogeochemistry2005, 76, 349–371. [Google Scholar] [CrossRef]
Freshwater mussels are considered to be one of the most sensitive and threatened aquatic species within Northwestern watersheds. In North America, there are 297 known freshwater mussel species. Nearly three-quarters of these are considered imperiled, and more than 35 species have gone extinct in the last century. Eight species are known to exist west of the Continental Divide. Mussels have a fascinating life history strategy, which involves parasitizing on fish during their larval stage, and can live to be over 100 years old. They are considered an indicator species, like the good ole canary in a coal mine, as they require pristine water quality to thrive.
Photo Credit: Western pearlshell Mussel photo by Roger Tabor USFWS
Life History, Strategy and Anatomy
To the unknowing eye, freshwater mussels look very similar to saltwater mussels as they are both bivalves, meaning they have 2 shells connected with a hinge. They are also both filter feeders and both belong to the class Bivalvia in the phylum Mollusca. Despite being named and shaped similarly, saltwater mussels, are however more closely related to oysters and scallops than they are to freshwater mussels, and thus have developed different evolutionary strategies. Saltwater mussels use a byssus thread to attach themselves to underwater structures, while freshwater mussels use a foot to move short distances and bury themselves. There are also differences in their sexual reproduction strategies. Saltwater mussels reproduce by ejecting the sperm and the eggs into the water column, where they fertilize and develop. With freshwater mussels, on the other hand, the sperm is ejected into the water column and inhaled by a female mussel downstream. The egg is then fertilized within a special part of the female mussel’s gills, and she exhales the baby mussels (called glochidia) after they are developed.
All freshwater mussels have:
a hinge, which connects the two shells
a raised, rounded area along the dorsal edge called, a beak
a foot used for motion and feeding
a thin sheet of tissue that envelopes the body within the shell, called a mantle
and inhalant/exhalant features along said mantle
Some mussels have pseudocardinal teeth, which are short, stout structures below the beak. There are many more features with very technical names, but these are the most useful anatomical structures for identification in our region.
Western pearlshell mussel (Margaritifera falcata)
In the Trinity River, there is one confirmed species of freshwater mussel – the Western pearlshell mussel (Margaritifera falcata), which have very prominent pseudocardinal teeth. The Klamath River has also documented populations of the Western ridged mussel (Gonidia angulata), which have an obvious ridge on the outside of the shell, and floaters (Anodonta spp.) which are small and have neither teeth nor ridges.
Check out this article from the Mid-Klamath Watershed Council to learn more about Klamath’s freshwater mussels.
Photo Credit: Klamath River mussel bed above Rock Creek on 7-5-18. Mid-Klamath Watershed Council.
Western pearlshell mussels are known as being the longest-lived and slowest-growing mussel species in North America. In fact, they are the oldest freshwater invertebrates in the world. Their age can be estimated by counting the growth rings on their shells, similar to the growth rings on trees. The black, concentric rings are thought to represent winter rest periods. Some Western pearlshells have been documented to live over 100 years, meaning that some of these mollusks may have been in our river since it was buzzing with dredgers and mining activity in the early 1900s.
Western pearlshell mussels. Akimi King/USFWS
The foot on freshwater mussels aids in movement, but mussels are still very limited in their ability to transport throughout a stream. In order to colonize different parts of a river system, particularly upstream, after being released by the female as described below, the larvae (called glochidia) attach to fish passing by becoming parasitic. In the case of the Western pearlshell, the glochidia are released into the water where they clamp onto the gills of salmonids (particularly chinook salmon and steelhead) to hitch a ride upstream. After a short period (typically between a week and a month), the glochidia drop off into existing mussel beds (see the diagram borrowed from the Mid-Klamath Watershed Council).
Similar to salmonid migration, in which the salmon return to their natal stream, mussels can identify ideal locations to drop from their host and landing in existing beds of freshwater mussels. This life stage is one of the most fascinating aspects of this species. Originally the larval stage mussels were thought to be an entirely different parasitic invertebrate species yet scientists recently realized they are actually freshwater mussels in an immature life phase. Other species of mussels may parasitize different parts of their host fish, with some sending worm-like tendrils into the fish’s gills to sap vital resources. However, it is not thought that the mussels have a significant impact on the health of their host fish.
Pearlshell species can release their glochidia in aggregates, called conglutinates, which are bound by mucus. They seem to reproduce in spring and summer, though few studies have been conducted on the life cycle of our Western pearlshells. Though there is no scientifically defined relationship between water temperature and spawning (due to a lack of study), it has been observed in a study conducted in the state of Washington that mussels in warmer waters spawn earlier than those in cooler waters.
Freshwater mussels have many benefits to stream ecology and have a major influence on the aquatic food web. They are filter feeders and they have separate orifices for inhaling and exhaling, which is how they derive nutrients. They filter tiny, suspended particles, including sediment, algae, bacteria and zooplankton out of the water column. Some of these particles are bound to larger particles within the mussels and expelled, where they sink to the bottom and feed benthic macroinvertebrates. Individuals in some species of freshwater mussels can filter up to 15 gallons of water per day, reducing turbidity and improving water quality. This cycling of nutrients also supports the growth of emergent plants, fostering a riparian habitat that benefits salmonids, which mussels are dependent upon. To be cliché, it’s all connected.
An example of a high-density freshwater mussel bed in the Trinity River near Junction City.
Freshwater mussels also help increase the exchange of nutrients, including oxygen, between sediments and the water column, in a similar mechanism to earthworms in the soil. They increase sediment porosity and allow the sediment to retain more organic matter. This ultimately improves the quality of aquatic habitat, allowing for a higher diversity of benthic macroinvertebrates.
Though not known for being a delicious treat to humans, mussels are an important food source for otters, raccoons and skunks. Healthy mussel populations are unaffected by natural predation, but low populations may be at risk of extirpation, and overly high populations may encourage excessive predator populations.
Trinity River Mussel Surveys and Conservation
In 2020, the Bureau of Land Management conducted a qualitative study of freshwater mussels on the Trinity River. A crew surveyed the upper 40 miles below Lewiston Dam and identified mussel beds as high, medium, and low density, and marked their locations on a map. This effort helps inform necessary conservation actions on project sites. If a mussel bed is known to be directly or indirectly affected from restoration activities, the Best Management Practice is to relocate a percentage of the population to an existing mussel bed upstream of their current location.
Mussels were relocated from a TRRP project in 2017 to an existing mussel bed. The green tags are for monitoring relocation success.
Relocation of freshwater mussels can be a tricky business. The species are incredibly sensitive to temperature and water quality conditions, so efforts must be conducted with efficiency and special care. It’s important to avoid moving mussels during certain times of the year when they are the most sensitive, which is when they are in their reproductive stages between December and July.
Mussels being tagged as part of a relocation effort on a TRRP construction site in 2017
The long lived and sensitive nature of freshwater mussels is one reason it’s important to manage the Trinity River for long term impacts. Since mussels cannot move quickly to escape suboptimal conditions, their population fluctuations can reflect cumulative effects of environmental conditions, so studying and understanding freshwater mussels can be indicative of some aspects of riverine health. Despite being rather uncharismatic and tremendously understudied, the role that freshwater mussels play within aquatic ecosystems is invaluable.
When you go down to the river, it’s hard to ignore the assortment of sediment on the bed and banks – from sand and silt, to gravel, to larger cobbles, to the largest of boulders. Seeing rocks that contrast so strongly with the rough, jagged ones in the surrounding hills might beg the question – how did these get here, where did they come from, and how long ago did they arrive?
Photo: Riparian area along the Trinity River above Trinity Reservoir showing an assortment of sediment, vegetation and large wood. [TRRP]
If a rock is rounded, more likely than not [1] it was transported by the river in a series of floods, originated from higher up in the watershed. Depending on the size these rocks may have arrived recently – perhaps as recently as the last flood. Large, rounded boulders that appear to be too large to have been rolled down the river on their own may have been in place since the last natural 100-year or 500-year flood and may remain there forever, or at least as long as Trinity and Lewiston dams are in place.
[1]Gold miners washed much sediment into Trinity River valleys from ancient riverbeds created from tectonic lifting that are presently high up on mountain slopes.
A river’s function
Besides the ecological benefits that rivers provide us, they have two pivotal functions in nature – to move water and to move sediment from the mountains to the ocean (the process is illustrated below). As both water and sediment flow downstream, they interact with each other to create a mosaic of pools, riffles, runs, islands, meanders, bars, and all of the other physical features that draw people, plants, and animals to a river.
“Conveyor Belt” conceptual model of sediment transport. Rivers move water and sediment from the mountains to the sea.
The Trinity Watershed is situated in a relatively young, steep, and highly erodible mountain range, and is therefore blessed with a plentiful supply of sediment. A healthy sediment supply is beneficial to fish, invertebrates, and floodplain vegetation. However, due to the placement of two dams in the Trinity River’s upper watershed an important element of restoration is giving gravel to the system below a dam since the river’s natural sediment supply is blocked. We know rivers below dams need a replenished sediment supply, however, a key question that geomorphologists continue to study is how much sediment, and what size distribution of sediment should be added? These factors are difficult to determine and are constantly being re-evaluated as part of our adaptive management program.
How we calculate amounts for placement
Gravel augmentations to the river are first determined using a defined sediment budget specific to the Trinity. Also, at some point below most dams, a river’s tributaries provide a sufficient supply of sediment to support the physical processes and biologic populations in the river. On the Trinity, that point is considered to be just below the junction of Indian Creek. In years past, during floods, the amount of sediment moving along the bottom of the river (called ‘bedload’) was directly measured with large strainers placed on the riverbed. Data obtained from the strainer monitoring station have indicated that minor floods may move 2,000-3,000 tons of bedload (the monitoring station that is nearest to Indian Creek is located just upstream of Douglas City campground). At this same location, larger floods may move 15,000-30,000 tons of bedload past the monitoring station. The Trinity Record of decision provided the program with a framework of how much sediment should be applied to the river below the dam with the expectation that geomorphologists study current conditions through time and then adapt management based on results found.
After many years of physically sampling bedloads, program scientists switched to a more efficient and safer technique called acoustical monitoring. This method uses underwater microphones to quantify the amount of sediment during floods by measuring the amount of noise generated by rocks rolling on the bed. The physical data collected from the past is then compared to the measured volume of noise and produces a calculated volume of sediment rolling past. Scientists then scale annual sediment augmentation projects to these measured amounts. Additionally, the riverbed is periodically surveyed below sediment augmentation sites to determine whether the effects of placements are positive or negative. If too much sediment is noted, this information is used to scale back future sediment augmentation plans. If you were to compare the original amounts of sediment proposed in the Trinity Record of Decision to what we add today, ROD volumes were 2-3 times higher!
Above Photo: a 2023 gravel augmentation site pictured prior to high flow. Right Photo: the same site pictured after the gravel was dispersed by high flow.
Size matters
As for size, the high end of the size distribution of sediments is the grain diameter that salmon can move to construct redds, or nests in which they place their eggs for incubation. Salmon can spawn in gravels with a median diameter up to about 10% of their body length. This leads to gravel being placed in the river that was filtered through a 4-inch screen. The lower end of the size distribution of sediment for redd building is considered to be in the size range of small gravel, and so the sediment mixtures for placement in the river are also screened to remove sand and silt. If the sediment is too small, it just flushes all the way down the river during floods and doesn’t remain to provide any benefits. If the sediment is too large, it stays close to the augmentation site and causes the riverbed to become coarser there. The need for small to large gravels for placement makes considering the size distribution between these end points important. Too many small gravels make the riverbed overly mobile and easy to scour, which endangers salmon eggs incubating in the bed. However, a grain-size distribution that is skewed towards larger particles makes the riverbed too stable, so that salmon are unable to move the sediment when attempting to construct a redd. These considerations make the size class of sediment another subject of adaptive management, and over time TRRP has reduced the size of sediment that is added to the river. Studies have also pointed toward ways that coarse sediments (gravel and cobble) interact with fine sediment (sand and silt), and restoring a natural balance of these grain sizes is an objective of the sediment augmentation program at the TRRP. In the future you may hear of sediment with a more natural size distribution (e.g., “bank run material”) being used in sediment augmentation projects.
Salmon spawning in gravel in the Trinity River.
Filling deep pools
When you observe a river during typical baseflows, pools are calm while riffles are noisy, turbulent and swift. From an above water view, its natural to think that sediments would settle from these active riffles to its calmer neighboring pools. During low flow, if you look underwater, the river only has the power to move finer sediments, like sand and silt. Conversely, coarse sediment, such as gravel and cobble move only when the hydrology of the river is powerful with high flow or flooding.
When rivers flood, we see something that river scientists call a “flow reversal”. Flow reversal is when deep pools transition into a high-energy environment where flow velocity is more vigorous than on riffles. In this instance water meets the pool (and its surrounding environment, like bedrock) with force and activates sediments of different sizes within the pool. These sediments are “scoured” from the pool and placed on the riffle below it typically expanding a pool’s depth and also building the riffle below. Next time during a high flow, check out the way a pool churns and take note to notice the way water interacts with the riffle that lye underneath. During high discharges, flows on riffles are comparatively slow because the surface is not as deep. This interaction causes the water to “feel” the bed and slow due to its rough texture. These interactions cause sediment to deposit on riffles and scour from pools during high flows. The size of sediments that move are directly correlated to the amount of water flowing down the river and these events are the force behind building the riffles and pools of the Trinity River.
Dave Gaeuman, Senior Geomorphologist for the Yurok Tribe talks about the importance of variable flows and and how sediment transports from riffles to pools
TRRP sediment augmentation projects have sometimes been thought to contribute to the filling of deep pools in the river and there have been cases where pool depths have decreased in areas that the TRRP has worked to restore the river. However, TRRP studies have shown that this tends to occur where stream power decreases in the channel from lowering the elevation of adjacent floodplains and vegetation, which causes the flow to spread out instead of concentrate in the channel. In many areas of the Trinity River, lowering floodplains is necessary to reconnect them with the river during floods for the benefit of the fish, wildlife and plants that live there. This conundrum is another subject of adaptive management, and TRRP often avoids actions that would have a strong likelihood of affecting pool depths so that holding habitat for over-summering fish such as spring-run Chinook salmon remains available.
The next time you visit the Trinity River, take a close look at the sediments that you see. Depending on the time of year, you may see salmon redds constructed of gravels. You will also most likely find aquatic invertebrates and biofilm living on the gravel and cobbles surfaces. Dig into a sand and silt deposit along the channel margins and you might find juvenile lamprey wriggling around in these materials. You will certainly see how sediment forms the shape of the river. And hopefully you’ll come away with a greater appreciation of sediments that are the building blocks of the Trinity River!
