Snake River fall Chinook salmon were listed as “threatened” under the ESA in 1992. My entire career has focused conducting applied research to provide information that would increase our understanding of this unique stock and facilitate recovery efforts. The work of myself and colleagues from other agencies have produced most of the contemporary information on Snake River fall Chinook salmon.
M.S. 1992. Fishery Biology, Colorado State University, Fort Collins, CO
B.S. 1987. Fishery Biology, Colorado State University, Fort Collins, CO
The main focus of my work is understanding Snake River fall Chinook salmon life history and ecology to support recovery of this listed stock. Over the years research topics have included migratory behavior, habitat use and quantification, physiology, and feeding ecology of juvenile fish in the Snake and Columbia rivers. Other research areas have included understanding the effects of elevated flows on chum salmon spawning behavior, and investigating recent food web changes to lower Snake River reservoirs.
1992 to Present – Research Fish Biologist, U.S. Geological Survey, Western Fisheries Research Center, Columbia River Research Laboratory, Cook, WA
Science and Products
Snake River fall Chinook salmon were listed as “threatened” under the Endangered Species Act in 1992. At that time, little was known about the spawning, rearing, migration, and life history of this species. This long-term research and monitoring project has produced much of the contemporary knowledge on fall Chinook salmon that has been used by fish managers to implement recovery measures. The...
Fall Chinook salmon (Oncorhynchus tshawytscha), sand roller (Percopsis transmontana), and smallmouth bass (Micropterus dolomieu) interactions in a Snake River reservoir: A tale of three species
We studied some of the relationships between federally listed fall Chinook Salmon, Oncorhynchus tshawytscha, endemic Sand Roller, Percopsis transmontana, and non-native Smallmouth Bass, Micropterus dolomieu, in Lower Granite Reservoir on the Snake River. Because of its recent reappearance and population increase, the Sand Rollers...Hemingway, Rulon J.; Tiffan, Kenneth F.; Erhardt, John M.; Rhodes, Tobyn N.; Bickford, Brad K.
Post‐release predation mortality of age‐0 hatchery‐reared Chinook salmon from non‐native smallmouth bass in the Snake River
Release of age‐0 hatchery‐reared fall Chinook salmon, Oncorhynchus tshawytscha(Walbaum), in the Snake River resulted in up to 30‐fold increases in salmon consumption by non‐native smallmouth bass, Micropterus dolomieu Lacepѐde. In an upper river reach, smallmouth bass fed intensively during a release in May, but Chinook salmon...Erhardt, John M.; Tiffan, Kenneth F.
Upstream migration and spawning success of Chinook salmon in a highly developed, seasonally warm river system
This review summarizes what is known about the influence of water temperature and velocity on the migration and spawning success of an inland population of Chinook salmon Oncorhynchus tshawytscha. Models are then developed and used to illustrate how migration and spawning success might change if temperatures and velocities increase under a...Connor, William P.; Tiffan, Kenneth F.; Chandler, James A.; Rondorf, Dennis W.; Arnsberg, Billy D.; Anderson, Kelvin C.
Juvenile Chinook Salmon mortality in a Snake River Reservoir: Smallmouth Bass predation revisited
Predation by nonnative fishes has been identified as a contributing factor in the decline of juvenile salmonids in the Columbia River basin. We examined the diet composition of Smallmouth Bass Micropterus dolomieu and estimated the consumption and predation loss of juvenile Chinook Salmon Oncorhynchus tshawytscha in Lower...Erhardt, John M.; Tiffan, Kenneth F.; Connor, William P.
Migratory behavior and physiological development as potential determinants of life history diversity in fall Chinook Salmon in the Clearwater River
We studied the influence of behavior, water velocity, and physiological development on the downstream movement of subyearling fall‐run Chinook Salmon Oncorhynchus tshawytscha in both free‐flowing and impounded reaches of the Clearwater and Snake rivers as potential mechanisms that might explain life history diversity in this stock....Tiffan, Kenneth F.; Kock, Tobias J.; Connor, William P.; Richmond, Marshall C.; Perkins, William A.
Smallmouth bass predation on subyearling fall Chinook salmon in Lower Granite Reservoir, 2016–2017
Predation by nonnative fishes is one factor that has been implicated in the decline of juvenile salmonids in the Pacific Northwest. Impoundment of much of the Snake and Columbia Rivers has altered food webs and created habitat favorable for species such as smallmouth bass Micropterus dolomieu. Smallmouth bass are common throughout the Columbia...Erhardt, John M.; Tiffan, Kenneth F.; Hemingway, Rulon J.; Bickford, Brad K.; Rhodes, Tobyn N.
Research, monitoring, and evaluation of emerging issues and measures to recover the Snake River Fall Chinook Salmon ESU, 1/1/2016 - 12/31/2016
The portion of the Snake River fall Chinook Salmon Oncorhynchus tshawytscha ESU that spawns upstream of Lower Granite Dam transitioned from low to high abundance during 1992–2016 in association with U.S. Endangered Species Act recovery efforts and other federally mandated actions. This annual report focuses on (1) numeric and habitat use responses...Connor, William P.; Mullins, Frank L.; Tiffan, Kenneth F.; Plumb, John M.; Perry, Russell W.; Erhardt, John M.; Hemingway, Rulon J.; Bickford, Brad K.; Rhodes, Tobyn N.
Snake River Fall Chinook Salmon life history investigations
Predation by nonnative fishes is one factor that has been implicated in the decline of juvenile salmonids in the Pacific Northwest. Impoundment of much of the Snake and Columbia rivers has altered food webs and created habitat favorable for species such as Smallmouth Bass Micropterus dolomieu. Smallmouth Bass are common throughout the Columbia...Erhardt, John M.; Bickford, Brad K.; Hemingway, Rulon J.; Rhodes, Tobyn N.; Tiffan, Kenneth F.
Ecology of the Opossum Shrimp (Neomysis mercedis) in a Lower Snake River Reservoir, Washington
The opossum shrimp Neomysis mercedis has expanded its range from the lower Columbia River upstream 695 kilometers into Lower Granite Reservoir where it is now very abundant. We studied Neomysis ecology in the reservoir during 2011–2015 to better understand the physical and biological factors that shape their distribution as...Tiffan, Kenneth F.; Erhardt, John M.; Bickford, Brad K.
Ecology of nonnative Siberian prawn (Palaemon modestus) in the lower Snake River, Washington, USA
We assessed the abundance, distribution, and ecology of the nonnative Siberian prawn Palaemon modestus in the lower Snake River, Washington, USA. Analysis of prawn passage abundance at three Snake River dams showed that populations are growing at exponential rates, especially at Little Goose Dam where over 464,000 prawns were collected...Erhardt, John M.; Tiffan, Kenneth F.
Feeding ecology of non-native Siberian prawns, Palaemon modestus (Heller, 1862) (Decapoda, Palaemonidae), in the lower Snake River, Washington, U.S.A.
We used both stomach content and stable isotope analyses to describe the feeding ecology of Siberian prawns Palaemon modestus (Heller, 1862), a non-native caridean shrimp that is a relatively recent invader of the lower Snake River. Based on identifiable prey in stomachs, the opossum shrimp Neomysis mercedis Holmes, 1896 comprised up to 34-55% (by...Tiffan, Kenneth F.; Hurst, William
Survival, growth, and tag retention in age-0 Chinook Salmon implanted with 8-, 9-, and 12-mm PIT tags
The ability to represent a population of migratory juvenile fish with PIT tags becomes difficult when the minimum tagging size is larger than the average size at which fish begin to move downstream. Tags that are smaller (e.g., 8 and 9 mm) than the commonly used 12-mm PIT tags are currently available, but their effects on survival, growth, and tag...Tiffan, Kenneth F.; Perry, Russell W.; Connor, William P.; Mullins, Frank L.; Rabe, Craig; Nelson, Doug D
Partnership Paves the Way for Understanding Biology of Threatened Snake River Basin Fall Chinook