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Whirling Disease (Myxobolus cerebralis) and Idaho Fisheries Keith Johnson Retd Supervisor, IDFG Fish Health Program Eagle Fish Health Laboratory Eagle, Idaho

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Myxobolus cerebralis Life Cycle: salmonid tubifex triactinomyxon myxospores

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DOCUMENTED INTRODUCTIONS OF M. cerebralis-POSITIVE TROUT INTO IDAHO WATERS. 1985-87. Lost River Trout Farm. Rainbow trout from California. 1993 & 2004: Canyon Spring Trout Farm. Rainbow trout from Utah. * *Have apparently not lead to established infection. 1966-75. Nevada Div. Wildlife. Rainbow trout from Truckee National Hatchery stocked into streams that cross the state border. 1986. Palouse area farm pond. Rainbow trout from northeast Oregon.*

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Susceptibility of Salmonid Species To M. cerebralis

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Dynamic Relationship of Host/Parasite/Environment HOST ENVIRONMENTPARASITE HOST PARASITE ENVIRONMENT HOST PARASITE Presence, No Disease: M. cerebralis spores rare, no disease signs, host population resilient Ex: S.F. Snake R, S.F. Boise R, M.F. Salmon R Disease, No Impact: Prevalence and intensity of infection high, disease signs occasional, host population resilient Ex: Big Wood R, upper Salmon R, Lemhi R Negative Population Impact: Spores and pathology abundant, disease signs common, host population is parasite limited Ex: Big Lost R, Little Lost R, Pahsimeroi R

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Idaho Department of Fish and Game Hatcheries Sawtooth Pahsimeroi

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Figure 1. Prevalence and intensity of M. cerebralis infection of sentinel rainbow trout exposed for ten days to the Salmon River water supply of Sawtooth Hatchery, Feb, 2000-Jan, 2001. Prevalence (%)0 0209588 80 95855519135 Degrees C2.6 3.66.17.211.214.113.011.47.13.32.93.2 Hydrograph (CFS)110 11025015702190470341304258180123118 7 5 22 53 88 5 22 23 54 109 50 139 5 7 144 24 15 4 44 6 2. 10

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Figure 2. Prevalence and intensity of M. cerebralis infection of sentinel rainbow trout exposed for ten days to the river water supply of Pahsimeroi Hatchery, Feb, 2000- Jan, 2001. Prevalence (%) 6785 100 10090 100 100 80 100869180 Degrees C 5.0 6.4 9.2 10.3 12.0 13.1 13.5 11.9 9.35.83.23.4 Hydrograph 329 327 300 135 133 109 175 175 284300311321 56 26 102 4 7 68 46 25 6 7 21 143 52 127 8 17 266 194 25 3 58 19 4 15 1 139 53 28 3 2 23 43 4 15 52 140 5 18

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Effect of delaying exposure of Chinook juveniles to river water at Sawtooth and Pahsimeroi hatcheries on detection of M. cerebralis at pre-release sampling the following spring. E xposure Date

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Detection of M. cerebralis from Chinook and steelhead adults at Upper Salmon River trap locations. Return years 1987-2006. Return Years

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UPPER SALMON R

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Distribution of Myxobolus cerebralis within the Salmon River during the migration period of 2001 for juvenile anadromous salmonids Wade Cavender JAAH 2003

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Snake River 1 2 NF Salmon River 3 4 5 6 7 8 9 10 EF Salmon Lemhi R. Pahsimeroi R.

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April EF Salmon Pahsimeroi R. Snake River NF Salmon River STFH PFH OFH Lemhi R. 60% 0% 100% 15% 100%

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May EF Salmon Pahsimeroi R. Snake River NF Salmon River STFH PFH OFH Lemhi R. 100% 90% 100% 20% 15% 100%

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Myxobolus cerebralis Observations in Natural Steelhead and Chinook for the Period 1987 2006 Organized by IDFG Regions REGION STEELHEAD CHINOOK Clearwater 0/301 0/428 Southwest 0/57 0/493 Salmon 22/192 (11.5%) 262/2066 (12.7%)

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Implications of Tributary Reconnection to Establishing Myxobolus cerebralis in the Lemhi River Drainage, Idaho Keith Johnson and Tom Curet Eagle Fish Health Laboratory and Salmon Region Idaho Department of Fish and Game

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Lemhi Exposure I June 03 Positive Negative

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100% Hayden Cr Lemhi Exposure II Oct03 Positive Negative

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Reconnection of Lemhi River Tributaries: Would not expand the existing range of the parasite since it is already present, regardless of tributary connection status Basin Creek may be the origin of infectivity in the Hayden Creek drainage but ponds a source also

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Does M. cerebralis limit natural Trout production in the Teton River ? Martin Koenig Utah State University Application of the UofI epidemiological model of Anlauf, Colvin, & Moffitt

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Fox Creek Trail Creek Teton Creek Teton River Teton R. Flow Teton I exposure (Aug,03) prevalence and intensity (x000) of M. cerebralis infection

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Anemic challenges in the first Teton River exposure indicate a low probability that M. cerebralis infections could limit natural production of salmonids.

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Fox Creek Trail Creek Teton Creek Teton River Teton R. Flow Teton II exposure (July,04) prevalence and intensity (x000) of M. cerebralis infection 100 (40) (69) (16) 50 (2) (23) (39) (18) (41) Unnamed Creek

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Implications from Teton River Trials Exposures made in 2004 resulted in higher prevalence and intensity of M. cerebralis infection than in 2003, annual variation in exposure must be considered Habitat differences throughout study area varied only slightly Population declines were apparent in Yellowstone cutthroat, not rainbow trout even though both species are highly susceptible Tubifex habitat characteristics and susceptibility lineages are needed Unnamed Creek may provide fry a refuge from intense challenge

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Application of Risk Assessment to Whirling Disease in Idaho Introduction Isolation of new waters, prevent movement Establishment & Amplification Need an understanding of what environmental mechanisms operate to limit parasite numbers Persistence Need to demonstrate the probability that M. cerebralis will not persist and in what time period, the incentive for painful change

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Persistence of M. cerebralis: Will the infection fade into the sunset? Modin (1998) reported infections decreased to below detectable limits when positive rearing facilities in California were closed in 3 of 22 waters over a 32-year period Cache de Poudre River (Colorado Division of Wildlife) infections were no longer detectable two years after an earthen rearing pond ceased rearing trout (Nehring, 2003) Hayspur Hatchery (IDFG) switched to well water in 1993 and we can no longer detect the parasite These examples show the parasite may not persist in certain waters and support enforcement of IDFGs role in private pond management

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PROBABLE INFLUENCE OF IRRIGATION WATER DIVERSION ON Myxobolus cerebralis-INFECTIVITY AT HAYSPUR HATCHERY AND IN LOVING CREEK, A TRIBUTARY TO SILVER CREEK IN SOUTH CENTRAL IDAHO

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Gannett Bellevue Loving Creek Stalker Creek Hayspur Hatchery Silver Creek 5 km Big Wood River N S WE

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HISTORY OF HAYSPUR HATCHERY Built 1906. Peak annual production of 1 million rainbow trout fingerling and 350,000 rainbow catchables. Myxobolus spores first detected from adult fish in the brood pond in 1988; confirmed M. cerebralis in 1989. Reconstruction began in 1989. All use of surface water for production ceased in 1995.

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SENTINEL EXPOSURE DATES 4/036/039/033/045/046/0410/04 HATCHERY INTAKE XXXX BROOD POND XXXX GAVER LAGOON XXXX RAILROAD TRESTLE XXXXXXX KILPATRICK BRIDGE XXXXXXX IRRIGATION CANAL X X BIG WOOD RIVER XX X EXPOSURE SITES

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Gannett Bellevue Loving Creek Stalker Creek Hayspur Hatchery Silver Creek 5 km Big Wood River N S WE Gaver Lagoon Kilpatrick Bridge Railroad Trestle Brood Pond Intake Irrigation Canal Big Wood River 7 exposures; 0/217 fish 2 exposures; 80/81 fish (99%) 3 exposures; 64/112 fish (57%) 7 exposures; 0/197 fish 4 exposures; 0/133 fish 4 exposures; 0/101 fish 4 exposures; 0/122 fish Hayspur Hatchery sites

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Gannett Bellevue Loving Creek Stalker Creek Hayspur Hatchery Silver Creek 5 km Big Wood River N S WE Kilpatrick Bridge Railroad Trestle Intake Irrigation Canal 2 exposures; 0/86 fish 1 exposure; 47/47 fish (100%) 2 exposures; 1/84 fish 2 exposures; 0/88 fish 2 exposures; 0/75 fish 2006 Heavy snowpack = extended runoff Loving Creek Diversion

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Conclusions from the Hayspur Hatchery Exposures: M. cerebralis detections at Hayspur H. during the 88- 93 period was sporadic and low in prevalence (

CDOW 09 Hofer X CRR RBT Hybrid Evaluations Hybrids and CRR controls stocked in two river systems for four years Hybrids had higher survival than CRR controls Post-stocking survival was best when stocked at >9 TL to avoid predation by BNT Some natural reproduction has been detected in both rivers Hofer genetic markers have exceeded CRR markers in natural fry CDOW will continue stocking hybrids and monitoring natural production of hybrids vs controls

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So now I get to speculate on why whirling disease does not cause levels of impact in Idaho as reported in MT and CO. Habitats within the shaded area in which population impacts are suspected are all: Volcanic tuft soils, easily eroded Abundant groundwater, stable water temperature Eutrophic, highly productive High level of grazing impacts Low gradient river bottoms Tubifex habitat and lineages are important to examine

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HOST ENVIRONMENTPARASITE HOST PARASITE ENVIRONMENT ? Shaded drainages have aquatic habitats conducive to amplification: Pahsimeroi, Lemhi, Big & Little Lost, Birch Creek, and Teton R on a bad year Drainages outside of the shaded area are basaltic and granitic origin, lack amplification after parasite was introduced

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PLANS FOR THE FUTURE Expand knowledge on distribution and epidemiology of M. cerebralis: Upper Salmon River and role of carcasses Cooperate with ISDA and industry to reduce WD range and intensity through Invasive Species legislation Administer private pond stocking to reduce risk of parasite spread Monitor Hofer RBT resistance research and explore application for Idaho Educate regional biologists, conservation officers and anglers about whirling disease

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Thanks to Idaho Power Company for this $12 M investment!