Dworshak National Fish Hatchery Research Articles

Examining Life History Shifts and Genetic Composition in a Hatchery Steelhead Population, with Implications for Fishery and Ocean Selection

AbstractSteelhead Oncorhynchus mykiss exhibit significant variation in life histories. Dworshak National Fish Hatchery (NFH)‐stock steelhead exhibit a life history that is unique compared to other Columbia River basin hatchery summer steelhead stocks, as it is dominated by older and larger‐length fish relative to conspecifics. We evaluated changes within the Dworshak NFH stock's ocean age composition and length at age from run years 1978 to 2016 using samples collected from the commercial gill‐net fishery, the sport fishery, and the hatchery trap. In addition, we analyzed the genetic composition of the stock by comparing samples collected in 1969 from the wild founding stock to samples from recent returns. We found that Dworshak NFH steelhead became younger across the study, with fewer of the oldest, three‐ocean fish (i.e., rearing in the ocean for 3 years) and increases in the proportion of the population returning as one‐ocean fish (i.e., rearing in the ocean for 1 year). Length at ocean age decreased for all ocean ages; however, the decrease was not significant in one‐ocean fish. In general, samples collected from gill nets and the sport fishery contained fish with older ocean ages and larger sizes at age compared to samples collected from the hatchery trap. Neutral genetic diversity, as measured from a panel of single‐nucleotide polymorphic markers, showed no changes between the sample of fish representing the original founders and the present‐day population. Life history shifts observed in Dworshak NFH‐stock steelhead were likely influenced by a variety of factors, including gear selectivity and changing ocean conditions. Decreases in ocean age composition and length at age have implications for both fishery and broodstock management as well as generating concern that similar trends may be occurring within wild steelhead stocks.

Distribution and Movement of Steelhead and Anglers in the Clearwater River, Idaho

AbstractSteelhead Oncorhynchus mykiss is a species that is of high economic value that supports popular sport fisheries across the Pacific Northwest. The Clearwater River in Idaho provides a trophy steelhead fishery, and it is home to both wild‐ and hatchery‐origin steelhead. To manage the fishery effectively, information is needed about the spatial and temporal overlap of wild and hatchery steelhead in the Clearwater River, as well as the activity of anglers. We conducted a radiotelemetry study to describe the distribution of steelhead and their final fate in the Clearwater River, and creel surveys were used to describe the distribution of anglers. In total, 289 wild (Potlatch River and Lochsa River) and hatchery (from Dworshak National Fish Hatchery and South Fork Clearwater River) steelhead were radio‐tagged at Lower Granite Dam, 51 river kilometers (rkm) downstream from the mouth of the Clearwater River. Fish were monitored upon their entry into the Clearwater River by using mobile tracking surveys (boat and vehicle) and stationary antennas. The majority of wild and hatchery steelhead arrived in the Clearwater River in the fall with the exception of those from the Lochsa River, which arrived in the fall and following spring. Average daily movement of the fish was minimal (range = 0.3–4.7 km/d) and dependent on water temperature and flow. The fates of wild and hatchery steelhead varied. Fish returned to spawning grounds, were harvested by anglers (hatchery fish only), or had unknown fates. Both wild and hatchery steelhead returned at high rates to their natal tributaries and release locations. No straying was observed in either group; however, occasions when steelhead have overshot their natal tributaries and release locations were documented. Spatial and temporal overlap of the distributions of wild and hatchery steelhead was minimal. The distribution of anglers overlapped with that of hatchery steelhead in the fall, winter, and spring. The distributional overlap of anglers and wild steelhead was minimal and largely occurred in September in the lower Clearwater River. This suggests that the Clearwater River has a highly compartmentalized fishery and that current fishing regulations in the Clearwater River are providing for a diversity of angling opportunities while conserving wild steelhead and offering harvest of hatchery fish. The results from this study have important implications for the conservation and management of wild and hatchery steelhead.

Reproductive Performance and Energy Balance in Consecutive and Skip Repeat Spawning Female Steelhead Reconditioned in Captivity

AbstractSteelhead Oncorhynchus mykiss are known for their life history diversity, displaying a range of freshwater residence ages, maturation ages, and spawning intervals. Female maturation is thought to be condition dependent at critical periods, during which individuals falling below energetic thresholds remain reproductively inactive for the subsequent annual cycle. After their initial, or maiden, spawning, females may enter into another maturation cycle and spawn after 1 year (consecutive spawners) or 2 years (skip spawners). The purpose of this study was to quantify reproductive performance in maiden, consecutive, and skip spawning female steelhead, which differ in their energy availability schedules during ovarian development, in order to quantify the benefits that can be expected from kelt reconditioning programs. Hatchery origin female steelhead returning to Dworshak National Fish Hatchery for their maiden spawning (Clearwater River, Idaho, 2013–2016) were manually spawned, placed in tanks, and reconditioned. Size (somatic mass, FL) and reproductive performance (total, individual, and dry egg mass, fecundity, and fertilization success) were measured, and spawn date fidelity was determined. Repeat spawners had greater mass, length, and mass at length than did maiden spawners. In absolute terms, skip spawners had greater total, individual, and dry egg mass than maiden and consecutive spawners, and both consecutive and skip spawners had greater fecundity than did maiden spawners. When standardized for size, skip spawners had greater total, individual, and dry egg mass than maiden and consecutive spawners; size‐standardized consecutive spawners had lower individual egg mass than maiden spawners but higher fecundity. Our results suggest that egg size and reproductive investment are determined early in oogenesis based on an assessment of energy reserves, and do not increase when excess energy is available during the vitellogenic period of oogenesis. Instead, excess energy during the vitellogenic period is allocated to somatic growth. Increases in fecundity and egg size suggest that reconditioned kelts released to spawn naturally will be more productive than maiden spawners.

Comparison of hydraulics and particle removal efficiencies in a mixed cell raceway and Burrows pond rearing system

We compared the hydrodynamics of replicate experimental mixed cell and replicate standard Burrows pond rearing systems at the Dworshak National Fish Hatchery, ID, in an effort to identify methods for improved solids removal. We measured and compared the hydraulic residence time, particle removal efficiency, and measures of velocity using several tools. Computational fluid dynamics was used first to characterize hydraulics in the proposed retrofit that included removal of the traditional Burrows pond dividing wall and establishment of four counter rotating cells with appropriate drains and inlet water jets. Hydraulic residence time was subsequently established in the four full scale test tanks using measures of conductivity of a salt tracer introduced into the systems both with and without fish present. Vertical and horizontal velocities were also measured with acoustic Doppler velocimetry in transects across each of the rearing systems. Finally, we introduced ABS sinking beads that simulated fish solids then followed the kinetics of their removal via the drains to establish relative purge rates. The mixed cell raceway provided higher mean velocities and a more uniform velocity distribution than did the Burrows pond. Vectors revealed well-defined, counter-rotating cells in the mixed cell raceway, and were likely contributing factors in achieving a relatively high particle removal efficiency-88.6% versus 8.0% during the test period. We speculate retrofits of rearing ponds to mixed cell systems will improve both the rearing environments for the fish and solids removal, improving the efficiency and bio-security of fish culture. We recommend further testing in hatchery production trials to evaluate fish physiology and growth.

Successful mitigation of viral disease based on a delayed exposure rearing strategy at a large-scale steelhead trout conservation hatchery

In 2009, the largest steelhead trout conservation hatchery in the state of Idaho, Dworshak National Fish Hatchery (NFH), lost over 50% of the juvenile steelhead trout (Oncorhynchus mykiss) population being reared for release. The causative agent of this high mortality was the viral pathogen infectious hematopoietic necrosis virus (IHNV). This was neither the first nor the worst epidemic of IHNV to occur at the hatchery, but it was the worst in over a decade. Genetic analysis of IHNV isolates taken from juveniles suffering epidemic IHN disease in 2009 revealed that the virus was of the M group of IHNV viruses, known to have high virulence for trout. The water supply for steelhead trout rearing at Dworshak NFH is untreated water taken directly from the Clearwater River. Further genetic analysis of IHNV isolates from adults spawned in 2009 indicated that adult steelhead trout in the river (in the hatchery water supply) were the most probable transmission source for the epidemic IHN disease in the juvenile fish. Previously, Dworshak NFH had been able to gain access to reservoir water from behind the Dworshak Dam for nursery egg incubation and the earliest stage of fry rearing, which nearly eliminated incidence of IHN disease in that stage of rearing. Additionally, the nearby Clearwater State Fish Hatchery (SFH), which operates entirely with reservoir water, has never had a case of IHN disease in juvenile steelhead trout. Therefore, staff at Dworshak NFH sought and obtained access to a limited supply of reservoir water for the first few months of outdoor rearing of juvenile steelhead trout, beginning in 2010. This strategy delayed the exposure of juvenile steelhead trout to river water for several months. The effects of this program change were: drastic reduction in IHN disease in juvenile steelhead trout; interruption in the transmission of highly virulent M group IHNV from adult steelhead trout; no interruption in the transmission of low virulent U group IHNV from adult Chinook salmon; and a shift of IHNV types in adult fish spawned at Dworshak NFH in subsequent years from M to U group viruses. While juvenile steelhead trout may still be infected via exposure to IHNV in river water, the disruption of virulent M group IHNV has been successful in dramatically reducing IHN disease in steelhead trout every year since 2010.Statement of relevanceEffective reduction of severe mortality due to IHNV.

An Evaluation of the Influence of Stock Origin and Out‐migration History on the Disease Susceptibility and Survival of Juvenile Chinook Salmon

Various methods have been developed to mitigate the adverse effects of the Federal Columbia River Power System on juvenile Pacific salmon out-migrating through the Columbia River basin. In this study, we found that hatchery-reared spring Chinook salmon Oncorhynchus tshawytscha in the river are in varying degrees of health, which may affect delayed mortality and the assessment of the effectiveness of management actions to recover listed stocks (e.g., barging fish downstream versus leaving fish in the river). A laboratory disease challenge with Listonella anguillarum was completed on fish from Rapid River Hatchery and Dworshak National Fish Hatchery (NFH) with different out-migration histories: (1) transported by barge, (2) removed from the river before barging, or (3) left to travel in-river. Barged fish from Rapid River Hatchery experienced less mortality than fish from Dworshak NFH. No statistical differences were found between the hatcheries with fish that had in-river out-migration histories. We suggest that the stressors and low survival associated with out-migration through the hydropower system eliminated any differences that could have been present. However, 18-25% of the fish that were barged or collected before barging died in the laboratory before the disease challenge, compared with less than 2% of those that traveled in-river. Owing to disproportionate prechallenge mortality, the disease-challenged populations may have been biased; thus, they were also considered together with the prechallenge mortalities. The synthesis of prechallenge and disease-challenged mortalities and health characteristics evaluated during out-migration indicated that the benefit of barging was not consistent between the hatcheries. This finding agrees with adult survival and delayed mortality estimates for the individual hatcheries determined from adult returns. The results suggest that the health status of fish and their history before entering the hydropower system (hatchery of origin and out-migration path) are critical variables affecting the conclusions drawn from studies that evaluate mitigation strategies.

OZONE DISINFECTION OF FISH HATCHERY WATERS: PILOT PLANT RESULTS, PROTOTYPE DESIGN AND CONTROL CONSIDERATIONS

For over two years, ozone pilot plant studies have been conducted examining the efficacy of disinfecting makeup water entering the Dworshak National Fish Hatchery at Orofino, Idaho. The major pilot plant equipment consisted of a 1.12 kg/day Union Carbide Ozone Generator and contacting column. Plate counts for total bacteria were taken at various points in the pilot plant. Similar plate counts were taken from existing ultraviolet disinfection equipment. Also monitored were ozone residual levels entering and within the recycle system, ammonia, nitrate, nitrite, total organic nitrogen, suspended solids, turbidity and biochemical oxygen demand. Analysis of the plate counts shows ozone consistently provides more effective disinfection of the makeup water than the existing ultraviolet system. Nitrite levels after ozonation show a significant decrease, while nitrate levels increased. Ozone disinfection of recycle water was also satisfactorily demonstrated. Additionally, batch studies indicate ozone effectively destroyed algae. The pilot work established Dworshak ozone requirements to disinfect both makeup and recycle water. Experimental ozone demand, residual ozone removal rates, and ozone decay rates make it possible to design equipment and controls that will protect the fish from unsafe ozone concentrations. An ozone disinfection system preliminary design for a typical recycle fish hatchery is presented.

PEPA‐1* Genotype Affects Return Rate for Hatchery Steelhead

AbstractAllozymes continue to be useful as genetic markers in a variety of studies; however, their utility often hinges on the selective neutrality of the allelic variation. Our study tested for neutrality between the two most common alleles (*100 and *110) at the cytosol nonspecific dipeptidase locus (PEPA‐1*) in steelhead Oncorhynchus mykiss from Dworshak National Fish Hatchery in Idaho. We tested for differential growth and survival among fish with the *100/100, *100/ 110, and *110/110 genotypes rearing in a hatchery or a natural stream. We repeated the study for two year‐classes, using heterozygous (*100/110) adults to make the experimental crosses. This design avoided differences in family contribution among genotypes because each cross produced all three genotypes. We divided the progeny from each family into two groups. One group was reared in a hatchery for 1 year and then released for migration to the sea and subsequent return to the hatchery as adults. The other group was released into a natural stream and monitored for 3 years. We found no significant differences in size or survival among PEPA‐1* genotypes for either the naturally reared fish or the hatchery‐reared fish immediately prior to release as smolts. For females, survival to returning adult also was similar among genotypes; however, hatchery‐reared males with the *110/110 genotype returned at a higher rate than did males with the *100/ 100 genotype; heterozygous males were intermediate. These results indicate that selection occurs at the PEPA‐1* locus or at one or more loci tightly linked to it. The finding of nearly equal frequencies for these two alleles in the source population suggests that selection differentials among genotypes reverse or vary from year to year; otherwise, steady directional selection would drive the *100 allele to low frequencies or extinction. Locus PEPA‐1* seems inappropriate for genetic marks in studies of steelhead that span the full life cycle and probably should be avoided for any portion of the life cycle. Inferences about gene flow and population structure from studies that are substantially influenced by PEPA‐1* allele frequencies might be misleading.

Feeding Response by Northern Squawfish to a Hatchery Release of Juvenile Salmonids in the Clearwater River, Idaho

Abstract We collected gut contents from northern squawfish Ptychocheilus oregonensis captured in the Clearwater River, Idaho, 0–6 km from its confluence with the Snake River, following the release of 1.1 million yearling chinook salmon Oncorhynchus tshawytscha from the Dworshak National Fish Hatchery. Before the hatchery release, northern squawfish gut contents (by weight) in the study area were 38% crayfish Pacifastacus spp., 26% insects, 19% nonsalmonid fish, and 16% wheat kernels Triticum spp. Juvenile salmonids constituted 54% of gut contents about 24 h after the hatchery release, 78% after 5 d, and 86% after 7 d. The mean number of salmonids per gut (1.2) after release was higher than typically seen in guts from northern squawfish collected in mid-reservoir areas away from hydroelectric dams on the Snake and Columbia rivers. Length-frequency distributions of juvenile salmonids eaten and those captured in a scoop trap 4 km upstream of the study area indicated that northern squawfish were selectively f...

Detection of Infectious Hematopoietic Necrosis (IHN) Virus in Rearing Units for Steelhead before and during IHN Epizootics

Abstract Nursery tanks and Burrows ponds at Dworshak National Fish Hatchery, Ahsahka, Idaho, containing age-0 steelhead Oncorhynchus mykiss were sampled for IHN virus before and during epizootics of IHN. The hatchery water supply was also sampled weekly from March to September. By use of a precipitation method involving polyethylene glycol (PEG) to concentrate virus from water samples, IHN virus was detected in nursery tanks and Burrows ponds during the early stages of epizootics at concentrations ranging from 0.1 to 0.3 plaque-forming units (pfu)/mL. Peak virus concentrations were 1–5 pfu/mL in nursery tanks and exceeded 50 pfu/mL in Burrows ponds. When tangential flow filtration was used in conjunction with PEG precipitation, virus was detected in Burrows ponds at concentrations of 0.007–0.07 pfu/mL, 3–12 d before periods of rapidly increasing mortality. The results indicate that IHN epizootics begin with waterborne IHN virus at relatively low concentrations. Virus was not detected in the hatchery water...

Behavioral and physiological changes in yearling chinook salmon during hatchery residence and downstream migration

Swimming stamina, buoyancy, and gill Na +K + ATPase activity were measured in yearling spring chinook salmon before and after release from Dworshak National Fish Hatchery and Rapid River Hatchery from 1986 to 1988. Behavioral and physiological indices remained constant during the 3 months prior to release in early April. Following release, freeze-branded smolts were sampled at Lower Granite Dam, 118 and 279 km downstream from the respective hatcheries. These smolts exhibited swimming stamina and gill Na +K + ATPase levels that were significantly higher than those measured at the time of release. Buoyancy decreased among the same fish (significantly for one group). Migration rates to Lower Granite Dam were slow, but increased as smolts migrated further downstream. Experimental manipulation of water temperatures in the laboratory, using Little White Salmon National Fish Hatchery stock, produced smolts with behavioral and physiological responses similar in magnitude to those measured in actively migrating smolts from the Idaho hatcheries. The commonly held premise that, as a result of smoltification, migrating fish exhibit decreased swimming stamina and increased buoyancy during migration, is not supported by this study. Furthermore, the results indicate that the general hatchery population of yearling chinook salmon received insufficient environmental cues necessary for full smolt development, prior to release.

Accelerating smolt development and downstream movement in yearling chinook salmon with advanced photoperiod and increased temperature

To accelerate smolt development and downstream migration in yearling spring chinook salmon ( Oncorhynchus tshawytscha), treatment groups at Dworshak National Fish Hatchery (Idaho) were exposed to 3-month advanced photoperiod and ambient temperature (4–6°C). In each of 3 years, photoperiod treatment began in late December or January and continued for 13 to 18 weeks until release between 29 March and 5 April into the Clearwater River. Additional groups exposed to either the advanced photoperiod or ambient light were reared at an elevated water temperature (11–12°C) for 10 to 14 days preceding release. Downstream movement and recovery proportions were evaluated using passive-integrated-transponder (PIT) tags. Photoperiod treatment increased gill Na +K + ATPase levels significantly at the time of release in 2 of the 3 study years and in all 3 years resulted in significantly faster travel times to Lower Granite Dam, 117 km downstream. The combination of photoperiod and increased temperature treatment resulted in the highest gill Na +K + ATPase levels at release, the fastest downstream movement, and significantly higher recovery proportions downstream. Temperature treatment alone had no effect on gill Na +K + ATPase level or recovery proportion and resulted in significantly slower travel time to Lower Granite Dam. Treatment groups exhibiting faster travel time to Lower Granite Dam also passed McNary Dam (343 km downstream) sooner, although the differences were not as great.

Inactivation of Infectious Hematopoietic Necrosis Virus by Low Levels of Iodine

The fish rhabdovirus infectious hematopoietic necrosis virus (IHNV) was rapidly inactivated by extremely low concentrations of iodine in water. A 99.9% virus reduction was obtained in 7.5 s when virus (10 PFU/ml) and iodine (0.1 mg/liter, final concentration) were combined in distilled-deionized or hatchery water. Iodine efficacy decreased at pHs greater than 7.5 or when proteinaceous material was added to the water. Bovine serum albumin blocked iodine inactivation of the virus more effectively than did equal concentrations of fetal bovine serum or river sediment. Sodium thiosulfate effectively neutralized free iodine. Powder, iodophor, and crystalline iodine solutions inactivated IHNV equally. Iodine rapidly inactivated IHNV isolates representing each of the five electropherotypes. Under the conditions used in this study, inactivation was not affected by temperature, salinity, or water hardness. When Dworshak National Fish Hatchery water was continuously treated to provide a free iodine concentration of 0.14 mg/liter, a 7.5-s exposure to iodine was sufficient to inactivate 99.9% of the IHNV. Iodine added to water that contained IHNV prevented infection of rainbow trout (Oncorhynchus mykiss) fry. These results suggest that the waterborne route of IHNV transmission can be blocked by adding low iodine concentrations to the water supplies of hatcheries.

Cryopreservation of Sperm as a Means to Store Salmonid Germ Plasm and to Transfer Genes from Wild Fish to Hatchery Populations

Abstract The objective of this investigation was to determine if cryopreservation of salmonid sperm can be used successfully under normal field conditions. Sperm were collected from natural or wild steelhead (anadromous rainbow trout [Oncorhynchus mykiss]) trapped on two Lochsa River, Idaho, tributaries during spring 1987. Semen was frozen in liquid nitrogen and stored until spring 1988 (approximately 11 months), when it was thawed, and the sperm were used to fertilize eggs ofstock females from Dworshak National Fish Hatchery, Ahsahka, Idaho. Of the 44,676 eggs used from six females, 10,404 developed to the eyed stage and 10,254 embryos hatched.

Use of Self-Feeders for Rearing Steelhead Trout at Dworshak National Fish Hatchery

Use of Self-Feeders for Rearing Steelhead Trout at Dworshak National Fish Hatchery

Advanced Photoperiod and Water Temperature Effects on Gill Na+–K+ Adenosine Triphosphatase Activity and Migration of Juvenile Steelhead (Salmo gairdneri)

Under raceway conditions, an advanced photoperiod schedule caused migratory movements and elevation in gill Na+–K+ adenosine triphosphatase activity (Na+–K+ ATPase) to occur about 1 mo earlier than normal in yearling summer steelhead (Salmo gairdneri) from Dworshak National Fish Hatchery (Idaho). Exposure of migrants to 13 °C for 20 d resulted in serious impairment of continued migratory behavior and a reduction of gill Na+–K+ ATPase activity. Migrants outnumbered nonmigrants at fork lengths of 16 cm and longer. It is proposed that the potentially detrimental effects of warming river temperatures during the normal migratory season and delayed migration caused by dams and impoundments might be partially overcome by inducing early smolt transformation and migration with the use of advanced photoperiods.Key words: ATPase, steelhead, migration, temperature, photoperiod, smolts

ION EXCHANGE SYSTEMS FOR WATER RECIRCULATION

AbstractSince the Bozeman Study in 1972, several pilot plants have been investigated to evaluate the application of the ion exchange systems for water recirculation in fish hatcheries. Pioneering work was made at the biological research laboratory of Kramer, Chin and Mayo, Inc., followed by a pilot plant testing at the Oregon Aqua Fish Hatchery in Newport, Oregon. In 1976, two 50‐gallon per minute capacity ion exchange bed systems were installed and tested at Dworshak National Fish Hatchery in Orofino, Idaho. Recently, water reuse is accomplished by pumping approximately 120 gallons per minute from the raceway and filtering it through the pressure sand filter and the clinoptilolite filters for the removal of ammonia in the Seattle Aquarium.The paper will discuss the physical and chemical properties of ion exchange materials, pilot plant test results, engineering design criteria and application, and economics as compared to conventional biological ammonia removal systems. In addition, discussion will also be made in the area of pretreatment prior to ion exchange bed and regeneration as well as operational procedure adjustment. Further works needed to be conducted to provide optimum operating conditions will be discussed.

The Feasibility Of Ozone For Purification of Hatchery Waters

Abstract Ozone is feasible as a disinfectant of nursery tank makeup water in a planned recycle system at the Dworshak National Fish Hatchery. A dosage of 3 mg/L ozone to the makeup water should prevent disease carrying organisms and algae from entering the nursery tank system by way of the makeup water which is taken from the North Fork of the Clearwater River.