Ceratonova shasta infection in Sacramento River Chinook salmon

Erythromycin is a therapeutic substance useful against bacterial kidney disease in salmon. In 1989 we began a multi year project to learn more about erythromycin applied to juvenile and adult salmon, with the goal of achieving registration of erythromycin with the US Food and Drug Administration. To begin the study, we studied the pharmacokinetics of erythromycin administered to both adult and juvenile chinook salmon. We monitored blood plasmas time curves from individual adult fish injected with two forms of injectable erythromycin using one of three routes of administration. In addition, we began experiments to evaluate hatchery applications of erythromycin to individually marked adult salmon, and we recovered blood tissues from these fish at the time of spawning. To determine how to use erythromycin in juvenile salmon, we evaluated the adsorption and elimination of erythromycin applied arterially and orally to individual juvenile fish. In feeding trials we determined the palatability to juvenile chinook salmon of feed made with one of two different carriers for erythromycin thiocyanate. 35 refs., 4 figs. , 3 tabs.

Variation in the recruitment of salmon is often found to be correlated with marine climate indices, but mechanisms behind environment–recruitment relationships remain unclear and correlations often break down over time. We used an ecosystem modeling approach to explore bottom‐up and top‐down mechanisms linking a variable environment to salmon recruitment variations. Our ecosystem model incorporates a regional ocean circulation submodel for hydrodynamics, a nutrient‐phytoplankton‐zooplankton submodel for producing planktonic prey fields, and an individual‐based model (IBM) representing juvenile Chinook salmon (Oncorhynchus tshawytscha), combined with observations of foraging distributions and diet of a seabird predator. The salmon IBM consists of modules, including a juvenile salmon growth module based on temperature and salmon–prey availability, a behavior‐based movement module, and a juvenile salmon predation mortality module based on juvenile salmon size distribution and predator–prey interaction probability. Seabird–salmon interactions depend on spatial overlap and juvenile salmon size, whereby salmon that grow past the size range of the prey distribution of the predator will escape predation. We used a 21‐year historical simulation to explore interannual variability in juvenile Chinook salmon growth and predation‐mediated survival under a range of ocean conditions for sized‐based mortality scenarios. We based a series of increasingly complex predation scenarios on seabird observational data to explore variability in predation mortality on juvenile Chinook salmon. We initially included information about the predator spatial distribution, then added population size, and finally the predator's diet percentage made up of juvenile salmon. Model agreement improves with added predator complexity, especially during periods when predator abundance is high. Overall, our model found that when the fraction of juvenile salmon in seabird diet increased relative to alternate prey (e.g., Northern anchovy Engraulis mordax, and juvenile rockfish Sebastes spp.), there was a concomitant decrease in salmon cohort survival during their first year at sea.

Abstract.—Size-selective mortality combined with longer winters at high-latitudes is expected to exert strong directional selection on size, growth, and energy use and storage capacity in northern fish populations. Here, we tested the hypotheses that juvenile Pacific salmon <em>Oncorhynchus </em>spp. grow faster, reach larger size, and accumulate higher energy reserves in the marine environment at northern latitudes using juvenile Chinook salmon <em>O. tshawystcha </em>and coho salmon <em>O. kisutch </em>collected on the continental shelf from the California coast to the Bering Sea. Size reached at the end of the growing season, the quantity of energy stored prior to the onset of winter, and summer growth of juvenile Chinook and coho salmon during their first year at sea varied significantly among regions of the continental shelf. Latitudinal trends were detected for the fall size of subyearling and yearling Chinook salmon and storage energy in yearling Chinook salmon. However, they were opposite to expectations, with values decreasing from southern to northern areas. Latitudinal trends were also apparent for summer growth in juvenile yearling Chinook salmon. However, in contrast to fall size and storage energy, higher growth rates were generally observed in northern rather than in southern regions. Similarly, summer growth generally decreased from northern to southern regions in juvenile coho salmon. Storage energy did not exhibit a consistent trend with latitude in juvenile subyearling Chinook salmon and coho salmon. The different response of juvenile Chinook salmon and coho salmon to a latitudinal cline in temperature and the length of the growing season suggest that both species utilize the marine environment differently. We suggest that regional variations in juvenile salmon growth and energy accumulation may result from differences in prey quality (i.e., lipids), diet, and interspecific competition for prey resources.

The Nez Perce Tribe Johnson Creek Artificial Propagation Enhancement Project (JCAPE) has conducted juvenile and adult monitoring and evaluation studies for its 10th consecutive year. Completion of adult and juvenile Chinook salmon studies were conducted for the purpose of evaluating a small-scale production initiative designed to increase the survival of a weak but recoverable spawning aggregate of summer Chinook salmon Oncorhynchus tshawytscha. The JCAPE program evaluates the life cycle of natural origin (NOR) and hatchery origin (HOR) supplementation fish to quantify the key performance measures: abundance, survival-productivity, distribution, genetics, life history, habitat, and in-hatchery metrics. Operation of a picket style weir and intensive multiple spawning ground surveys were completed to monitor adult Chinook salmon and a rotary screw trap was used to monitor migrating juvenile Chinook salmon in Johnson Creek. In 2007, spawning ground surveys were conducted on all available spawning habitat in Johnson Creek and one of its tributaries. A total of 63 redds were observed in the index reach and 11 redds for all other reaches for a combined count of 74 redds. Utilization of carcass recovery surveys and adult captures at an adult picket weir yielded a total estimated adult escapement to Johnson Creek of 438 Chinookmore » salmon. Upon deducting fish removed for broodstock (n=52), weir mortality/ known strays (n=12), and prespawning mortality (n=15), an estimated 359 summer Chinook salmon were available to spawn. Estimated total migration of brood year 2005 NOR juvenile Chinook salmon at the rotary screw trap was calculated for three seasons (summer, fall, and spring). The total estimated migration was 34,194 fish; 26,671 of the NOR migrants left in the summer (July 1 to August 31, 2005) as fry/parr, 5,852 left in the fall (September 1 to November 21, 2005) as presmolt, and only 1,671 NOR fish left in the spring (March 1 to June 30, 2006) as smolt. In addition, there were 120,415 HOR supplementation smolts released into Johnson Creek during the week of March 12, 2007. Life stage-specific juvenile survival from Johnson Creek to Lower Granite and McNary dams was calculated for brood year 2005 NOR and HOR supplementation juvenile Chinook salmon. Survival of NOR parr Chinook salmon migrating from Johnson Creek to Lower Granite and McNary dams was 28.2% and 16.2%. Survival of NOR presmolt Chinook salmon migrating from Johnson Creek to Lower Granite and McNary dams was 28.2% and 22.3%. Survival of NOR smolt Chinook salmon migrating from Johnson Creek to Lower Granite and McNary dams was 44.7% and 32.9%. Survival of HOR smolt Chinook salmon migrating from Johnson Creek to Lower Granite and McNary dams was 31.9% and 26.2%. Multi-year analysis on smolt to adult return rate's (SAR's) and progeny to parent ratio's (P:P's) were calculated for NOR and HOR supplementation Brood Year 2002 Chinook salmon. SAR's were calculated from Johnson Creek to Johnson Creek (JC to JC), Lower Granite Dam to Lower Granite (LGD to LGD), and Lower Granite Dam to Johnson Creek (LGD to JC); for NOR fish SAR's were 0.16%, 1.16% and 1.12%, while HOR supplementation SAR's from JC to JC, LGD to LGD and LGD to JC were 0.04%, 0.19% and 0.13%. P:P's for all returning NOR and HOR supplemented adults were under replacement levels at 0.13 and 0.65, respectively. Recruit per spawner estimates (R/S) for Brood Year 2005 adult Chinook salmon were also calculated for NOR and HOR supplemented Chinook salmon at JC and LGD. R/S estimates for NOR and HOR supplemented fish at JC were 231 and 1,745, while R/S estimates at LGD were 67 and 557. Management recommendations address (1) effectiveness of data collection methods, (2) sufficiency of data quality (statistical power) to enable management recommendations, (3) removal of uncertainty and subsequent cessation of M&E activities, and (4) sufficiency of findings for program modifications prior to five-year review.« less

Early marine life history of juvenile Pacific salmon in two regions of Puget Sound

Catching the prey: Sampling juvenile fish and invertebrate prey fields of juvenile coho and Chinook salmon during their early marine residence

Fine-scale spatiotemporal variation in juvenile Chinook Salmon distribution, diet and growth in an oceanographically heterogeneous region

The early marine period is a critical life history stage for growth and survival of anadromous juvenile Pacific salmon. The integrity of nearshore ecosystems where juvenile salmon reside and the capacity of these habitats to provide prey can thus influence overall salmon returns. Eelgrass Zostera marina beds in particular are considered critical nearshore habitat. By examining how juvenile salmon use this habitat during their early marine life, we gain insight into the trophic dynamics in these ecosystems and help gauge the effects of accelerating eelgrass loss and nearshore habitat development on juvenile salmon. This project investigated the role of eelgrass as juvenile salmon foraging habitat. We compared juvenile Chum Salmon Oncorhynchus keta and juvenile Chinook Salmon O. tshawytscha diets to prey availability in zooplankton tows and in epifaunal eelgrass samples across a gradient of eelgrass density in the Comox Estuary, British Columbia. Harpacticoid copepods dominated the diets of both juvenile Chum Salmon and Chinook Salmon and were found in abundance in eelgrass blades. We complemented diet analysis with carbon (δ13C) and nitrogen (δ15N) stable isotope analysis to examine the relative contribution of zooplankton, eelgrass epifaunal invertebrates, and terrestrial invertebrates to the diet of juvenile Chum Salmon. Juvenile Chum Salmon isotope ratios closely reflected those of eelgrass invertebrates, suggesting that eelgrass invertebrates made up approximately 80% of the diets of juvenile Chum Salmon. Our results highlight the value of eelgrass in providing nearshore foraging opportunities for juvenile salmon and suggest that eelgrass habitat protection and restoration may provide critical support for growth, thereby easing the transition of juvenile salmon from freshwater to the marine environment.

The Hylebos Waterway is an industrialized waterway ofCommencement Bay, Tacoma, Washington, that is severelycontaminated with aromatic and chlorinatedhydrocarbons in the sediment. Juvenile chinook (Oncorhynchus keta) and chum salmon (O.tshawytscha) inhabit this waterway for a few days orweeks during their outmigration from freshwaterstreams to saltwater. The purpose of thisinvestigation was to determine to what degree juvenilechum and chinook salmon captured from the HylebosWaterway might bioaccumulate organic contaminants. These levels of exposure will be compared to previousstudies where such exposures have been linked tobiological dysfunction in juvenile salmon. Theresults showed that juvenile chum and chinook salmonfrom the Hylebos Waterway take up a wide range ofchemical contaminants, compared to fish fromhatcheries or reference estuaries. These contaminantsinclude high and low molecular weight polycyclicaromatic hydrocarbons (PAHs), polychlorinatedbiphenyls (PCBs, including the toxic congeners 105 and118), hexachlorobutadiene (HCBD), hexachlorobenzene(HCB), DDTs, heptachlor, and several pesticides. Immunohistochemical examination of the gill and gut injuvenile chum salmon from the Hylebos Waterway showedthe induction of the P450 metabolizing enzyme. Moreover, concentrations of contaminants in juvenilechinook and chum salmon from the Hylebos Waterway arecomparable to levels previously shown to be associatedwith biological injury in juvenile chinook salmon,such as impaired growth, suppression of immunefunction as demonstrated by reduced B cell function,and increased mortality following pathogen exposure.

First posted January 26, 2023 For additional information, contact: Director, Western Fisheries Research CenterU.S. Geological Survey6505 NE 65th StreetSeattle, Washington 98115-5016 We conducted a field study during 2020–21 to describe habitat use patterns of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the mainstem Willamette, McKenzie, and Santiam Rivers and to evaluate how habitat suitability criteria affected the predictive accuracy of a hydraulic habitat model. Two approaches were used to collect habitat use data: a stratified sampling design was used to ensure that a representative sample of available habitats was included in our sampling; and a targeted sampling design was used to collect additional data in habitat cells where juvenile Chinook salmon were observed. Habitat attributes and fish presence data were collected in habitat cells that were approximately 2 square meters during April, June, and July. A total of 632 cells were sampled during the study and included habitat located in the main channel (373 cells), side channels (228 cells), and in alcoves (31 cells). Juvenile Chinook salmon were observed in 42 percent of the cells located in the main channel, 38 percent of the cells located in side channels, and 7 percent of the cells located in alcoves. We used logistic regression to develop resource selection functions for April, June, and July, which produced probability-based predictions of habitat use for juvenile Chinook salmon based on water velocity and water depth. The resource selection functions revealed a habitat shift by juvenile Chinook salmon to locations with higher water velocities and greater water depths from April to July as juvenile Chinook salmon size increased. The resource selection functions that we developed are an important addition to habitat modeling in the Willamette River basin because they were developed from in-basin data, capture seasonal differences in habitat use, and facilitate probability-based estimates of habitat use for juvenile Chinook salmon. These advancements will improve habitat modeling efforts for juvenile Chinook salmon during spring and summer months within the Willamette River.

Pesticide residues in juvenile Chinook salmon and prey items of the Sacramento River watershed, California – A comparison of riverine and floodplain habitats

Functions of restored wetlands for juvenile salmon in an industrialized estuary

Previous studies have shown that juvenile chinook salmon Oncorhynchus tshawytscha from a contaminated estuary of Puget Sound, Washington, are immunosuppressed. Immunosuppressed fish may be more susceptible to disease and ultimately experience an increase in mortality. To evaluate this possibility, differences in susceptibility to a marine pathogen in outmigrating juvenile chinook salmon from an urban estuary and a nonurban estuary in Puget Sound were assessed. Juvenile chinook salmon were sampled from hatcheries before their release and subsequently from their respective estuaries as the population outmigrated from freshwater to the saltwater environment during the springs of 1993 and 1994. The study was repeated during a 3-month period to assess the duration of the effect after the fish were removed from the source of contaminants and was replicated during a 2-year period to examine interannual variation. Bile, liver, and stomach contents were collected from fish after capture to determine exposure to organic chemical pollutants. Examination of these tissues demonstrated that juvenile salmon from the urban estuary were exposed to higher concentrations of polycyclic aromatic hydrocarbons and polychlorinated biphenyls than juveniles from the nonurban estuary or hatcheries. Juvenile salmon were challenged with serial doses of a marine pathogen, Vibrio anguillarum (serotype 1575), and mortality was measured daily for 7 d. In both years, salmon from the urban estuary challenged with V. anguillarum exhibited a higher cumulative mortality after exposure to the pathogen than salmon from the hatcheries or the nonurban estuary. Our results together with our previous findings support the hypothesisthat contaminant-associated immunodysfunction in juvenile chinook salmon may lead to increased susceptibility to infection by a virulent marine bacterium.

Alteration of thyroid hormone concentrations in juvenile Chinook salmon (Oncorhynchus tshawytscha) exposed to polybrominated diphenyl ethers, BDE-47 and BDE-99

Off-channel habitat has become increasingly recognized as key for migratory fishes such as juvenile Chinook salmon (Oncorhynchus tshawytscha). Hence, floodplain habitat has been identified as critical for the continued persistence of California’s Central Valley salmon, particularly the Yolo Bypass, the primary floodplain of the Sacramento River. To provide insight into factors supporting juvenile salmon use of this 240 km2, partially leveed floodplain, we examined inter- and intra-annual relationships between environmental correlates and residency time, apparent growth, emigration, migratory phenotype, and survival over more than a decade for natural-origin (“wild”) fish and experimentally-released hatchery fish. Flood duration was positively associated with hatchery juveniles residing longer and achieving larger size. Wild juveniles grew larger and emigrated later with cumulative temperature experience (accumulated thermal units) and warmer average annual temperatures during flood years. Within years, both wild and hatchery salmon departed the floodplain as flood waters receded. Parr-sized juveniles dominated outmigrant composition, though fry and smolt-sized juveniles were also consistently observed. Survival to the ocean fishery was not significantly different between hatchery fish that reared in the Yolo Bypass versus those that reared in the main stem Sacramento River. Our study indicates improved frequency and duration of connectivity between the Sacramento River and the Yolo Bypass could increase off-channel rearing opportunities that expand the life history diversity portfolio for Central Valley Chinook salmon.