Adult Chinook Salmon Research Articles

Migration depths of adult steelhead Oncorhynchus mykiss in relation to dissolved gas supersaturation in a regulated river system

Adult steelhead Oncorhynchus mykiss tagged with archival transmitters primarily migrated through a large river corridor at depths >2 m interspersed with frequent but short (<5 min) periods closer to the surface. The recorded swimming depths and behaviours probably provided adequate hydrostatic compensation for the supersaturated dissolved gas conditions encountered and probably limited development of gas bubble disease (GBD). Results parallel those from a concurrent adult Chinook salmon Oncorhynchus tshawytscha study, except O. mykiss experienced greater seasonal variability and were more likely to have depth uncompensated supersaturation exposure in some dam tailraces, perhaps explaining the higher incidence of GBD in this species.

The influence of hydrology and waterway distance on population structure of Chinook salmon Oncorhynchus tshawytscha in a large river

Adult Chinook salmon Oncorhynchus tshawytscha navigate in river systems using olfactory cues that may be influenced by hydrologic factors such as flow and the number, size and spatial distribution of tributaries. Thus, river hydrology may influence both homing success and the level of straying (gene flow), which in turn influences population structure. In this study, two methods of multivariate analysis were used to examine the extent to which four indicators of hydrology and waterway distance explained population structure of O. tshawytscha in the Yukon River. A partial Mantel test showed that the indicators of hydrology were positively associated with broad-scale (Yukon basin) population structure, when controlling for the influence of waterway distance. Multivariate multiple regression showed that waterway distance, supplemented with the number and flow of major drainage basins, explained more variation in broad-scale population structure than any single indicator. At an intermediate spatial scale, indicators of hydrology did not appear to influence population structure after accounting for waterway distance. These results suggest that habitat changes in the Yukon River, which alter hydrology, may influence the basin-wide pattern of population structure in O. tshawytscha. Further research is warranted on the role of hydrology in concert with waterway distance in influencing population structure in Pacific salmon.

Epizootic Ameloblastomas in Chinook Salmon (Oncorhynchus tshawytscha) of the Northwestern United States

Abnormal growths were observed on the lips and in the oral cavities of 2- and 3-year-old Chinook salmon (Oncorhynchus tshawytscha) maintained in one freshwater and one saltwater captive fish-rearing facility in the Columbia River (Pacific Northwest). Initially presenting as bilaterally symmetrical, red, irregular plaques on oral mucosal surfaces, the lesions developed progressively into large, disfiguring masses. Of the 502 natural parr collected for captive broodstock, 432 (86%) displayed these tumors, whereas cohort salmon (i.e., same year classes) in these same facilities remained unaffected. Morphologically similar neoplasms were collected occasionally from adult Chinook salmon that had returned to their natal streams. Histologic features of the tumors suggested that they were derived from the portion of dental lamina destined to form tooth root sulci; therefore, these neoplasms were diagnosed as ameloblastomas. The lesions also resembled archived specimens of Chinook salmon oral tumors, which had been described decades earlier. Etiologic investigations performed during the current outbreak included bacteriologic, virologic, genetic, ultrastructural analyses, and cohabitation exposure studies. Results of these efforts did not indicate an obvious genetic basis for this syndrome, attempts to isolate potentially causative viruses or bacteria were negative, and disease transmission to naïve fish was unsuccessful. A few intracytoplasmic hexagonal structures, possibly consistent with viral particles (approximately 100 nm), were observed ultrastructurally in a tumor cell from 1 of 6 specimens submitted for transmission electron microscopy. Although the presence of these particles does not constitute sufficient evidence for causality, an infectious or multifactorial etiology seems plausible.

Differential Gene Expression between Fall‐ and Spring‐Run Chinook Salmon Assessed by Long Serial Analysis of Gene Expression

AbstractOf all Pacific salmonids, Chinook salmon Oncorhynchus tshawytscha display the greatest variability in return times to freshwater. The molecular mechanisms of these differential return times have not been well described. Current methods, such as long serial analysis of gene expression (LongSAGE) and microarrays, allow gene expression to be analyzed for thousands of genes simultaneously. To investigate whether differential gene expression is observed between fall‐ and spring‐run Chinook salmon from California's Central Valley, LongSAGE libraries were constructed. Three libraries containing between 25,512 and 29,372 sequenced tags (21 base pairs/tag) were generated using messenger RNA from the brains of adult Chinook salmon returning in fall and spring and from one ocean‐caught Chinook salmon. Tags were annotated to genes using complementary DNA libraries from Atlantic salmon Salmo salar and rainbow trout O. mykiss. Differentially expressed genes, as estimated by differences in the number of sequence tags, were found in all pairwise comparisons of libraries (freshwater versus saltwater = 40 genes; fall versus spring = 11 genes; and spawning versus nonspawning = 51 genes). The gene for ependymin, an extracellular glycoprotein involved in behavioral plasticity in fish, exhibited the most differential expression among the three groupings. Reverse transcription polymerase chain reaction analysis verified the differential expression of ependymin between the fall‐ and spring‐run samples. These LongSAGE libraries, the first reported for Chinook salmon, provide a window of the transcriptional changes during Chinook salmon return migration to freshwater and spawning and increase the amount of expressed sequence data.

Migration Timing of Columbia River Spring Chinook Salmon: Effects of Temperature, River Discharge, and Ocean Environment

AbstractIn an effort to improve run timing forecasts for Columbia River spring Chinook salmonOncorhynchus tshawytscha, we examined relationships among regional ocean climate indices, in‐river environmental conditions, and full run and stock‐specific migration timing metrics. Results consistently indicated that adult Chinook salmon arrived earliest in years with low river discharge or warm water temperatures and arrived latest in years of cold water temperatures and high flows. As single predictors, in‐river conditions generally explained more interannual variability in salmon return timing than did air temperature, the Pacific Decadal Oscillation, or the North Pacific Index. However, best‐fit multiple‐regression models included a combination of in‐river and climate predictors. While spatial and temporal scales of the analyses were relatively coarse (i.e., monthly values were used for all predictors), clear patterns emerged that can be used to improve pre‐ and in‐season run timing forecasting models for Columbia River spring Chinook salmon. We recommend continued refinement of climate‐based and environmental predictive tools to help manage anadromous fish stocks, including the threatened and endangered populations of the Columbia River basin.

Non‐direct homing behaviours by adult Chinook salmon in a large, multi‐stock river system

Two non‐direct homing behaviours, overshoot of natal tributaries and temporary non‐natal tributary use, were evaluated for 5150 radio‐tagged spring–summer Chinook salmon Oncorhynchus tshawytscha from 40 populations in the large Columbia River system. Over 7 years, 2–44% (mean = 15%) of individuals within each group temporarily entered presumed non‐natal tributaries. In addition, many Chinook salmon from lower river tributaries initially travelled 3 to &gt;250 km upstream in the main‐stem river beyond confluences with presumed natal tributaries before returning to the natal sites (‘overshoot’). Both overshoot and temporary tributary use behaviours declined exponentially with increasing distance from the natal tributary. Non‐direct homing also increased later in the season as water temperatures rose and was associated with hatchery origin in some cases. The behaviours may reflect a mix of active searching for olfactory cues from natal sites, behavioural thermoregulation and orientation challenges in a large‐river migration corridor transformed by dams and reservoirs. While anadromous salmonid homing is generally accurate and precise, these results indicate that route finding can be non‐direct, potentially increasing energetic costs and harvest risks during migration.

Comparison of Methods Used to Age Spring–Summer Chinook Salmon in Idaho: Validation and Simulated Effects on Estimated Age Composition

AbstractValidation of aging methods with known‐age individuals is rarely done with wild fish. We used samples collected from carcasses of adult Chinook salmon Oncorhynchus tshawytscha that were tagged as juveniles to (1) compare accuracy and precision of ocean ages determined from scales and fin rays and (2) simulate the effects of aging errors on run reconstruction (assignment to migratory cohort) under two age composition scenarios. Scale age had an overall accuracy of 81.8% and was biased high (χ2 = 8.67; P = 0.014). Fin ray age had an overall accuracy of 98.6% and was unbiased (χ2 = 2.00; P = 0.34). Precision of fin ray readings was higher than that of scale readings (coefficient of variation = 2.1% versus 7.8%, respectively). Accuracy of fin ray ages was greater than that of scale ages (Z = 2.198; P = 0.03). For two age composition scenarios, age classification errors were greatest when using scales and least when using fin rays. Aging errors inflated the size of weak cohorts in simulated run reconstructions. We showed how this can cause large errors in estimates of smolt‐to‐adult return rate when run strength and age composition vary among years. The amount of error associated with scale aging then becomes problematic for tracking the status of both threatened and healthy salmon stocks. Data based on fin ray readings provided the most accurate, unbiased estimates of age structure. Correction for methodological bias is important if age data are to be used in rigorous analyses.

Estimating adult Chinook salmon exposure to dissolved gas supersaturation downstream of hydroelectric dams using telemetry and hydrodynamic models

AbstractGas bubble disease (GBD) has been recognized as a potential problem for fishes in the Columbia River basin. GBD results from exposure to gas supersaturated water created by discharge over dam spillways. Spill creates a downstream plume of water with high total dissolved gas supersaturation (TDGS) that may be positioned along either shore or mid‐channel, depending on dam operations. We obtained spatial data on fish migration paths and migration depths for adult spring and summer Chinook salmon, Oncorhynchus tshawytscha, during 2000. Migration paths were compared to output from a two‐dimensional (2‐dimensional) hydrodynamic and dissolved gas model to estimate the potential for GBD expression and to test for behavioural avoidance of the high TDGS plume. We observed salmon swam sufficiently deep in the water column to receive complete hydrostatic compensation 95.9% of the time spent in the Bonneville Dam tailrace and 88.1% of the time in the Ice Harbor Dam tailrace. The majority of depth uncompensated exposure occurred at TDGS levels &gt;115%. Adult Chinook salmon tended to migrate near the shoreline and they tended to remain in relatively deep water. Adults moved into the high dissolved‐gas plume as often as they moved out of it downstream of Bonneville Dam, providing no evidence that adults moved laterally to avoid areas with elevated dissolved gas levels. When water depths decreased due to reduced river discharge, adults tended to migrate in the deeper navigation channel downstream from Ice Harbor Dam. The strong influence of dam operations on the position of the high‐TDGS plume and shoreline‐orientation behaviours of adults suggest that exposure of adult salmonids to high‐TDGS conditions may be minimized using operational conditions that direct the spilled water mid‐channel. Our approach illustrates the potential for combined field and modelling efforts to estimate the fine‐scale environmental conditions encountered by fishes in natural and regulated rivers. Published in 2007 by John Wiley &amp; Sons, Ltd.

Slow dam passage in adult Columbia River salmonids associated with unsuccessful migration: delayed negative effects of passage obstacles or condition-dependent mortality?

The relationships among behavior, environment, and migration success in anadromous fishes are poorly understood. We monitored migration behavior at eight Columbia and Snake river dams for 18 286 adult Chinook salmon (Oncorhynchus tshawytscha) and steelhead (sea-run Oncorhynchus mykiss) over 7 years using radiotelemetry. When statistically controlling for variation in flow, temperature, fisheries take, and other environmental variables, we observed that unsuccessful individuals — those not observed to reach spawning areas — had longer passage times at nearly all dams than fish that eventually reached tributaries. In many cases, times were also longer for unsuccessful adults passing through a multiple-dam reach. Four ecological mechanisms may have contributed to these patterns: (i) environmental factors not accounted for in the analyses; (ii) inefficient responses by some fish to passage conditions at dams that resulted in slowed passage, energetic depletion, and unsuccessful migration; (iii) ongoing selection for traits needed to pass obstructions; and (or) (iv) passage rate was not directly linked to migration success, but rather, both resulted from relatively poor phenotypic condition upon river entry in unsuccessful migrants. Overall, these results illustrate the need for a mechanistic understanding of the factors that influence migration success and the need for fitness-based criteria to assess the effects of dams on anadromous fishes.

Genotypes and phylogeographical relationships of infectious hematopoietic necrosis virus in California, USA

Infectious hematopoietic necrosis virus (IHNV) contains 3 major genogroups in North America with discreet geographic ranges designated as upper (U), middle (M), and lower (L). A comprehensive genotyping of 237 IHNV isolates from hatchery and wild salmonids in California revealed 25 different sequence types (a to y) all in the L genogroup; specifically, the genogroup contained 14 sequence types that were unique to individual isolates as well as 11 sequence types representing 2 or more identical isolates. The most evident trend was the phylogenetic and geographical division of the L genogroup into 2 distinct subgroups designated as LI and LII. Isolates within Subgroup LI were primarily found within waterways linked to southern Oregon and northern California coastal rivers. Isolates in Subgroup LII were concentrated within inland valley watersheds that included the Sacramento River, San Joaquin River, and their tributaries. The temporal and spatial patterns of virus occurrence suggested that infections among adult Chinook salmon in the hatchery or that spawn in the river are a major source of virus potentially infecting other migrating or resident salmonids in California. Serum neutralization results of the California isolates of IHNV corroborated a temporal trend of sequence divergence; specifically, 2 progressive shifts in which more recent virus isolates represent new serotypes. A comparison of the estimates of divergence rates for Subgroup LI (1 x 10(-5) mutations per nucleotide site per year) indicated stasis similar to that observed in the U genogroup, while the Subgroup LII rate (1 x 10(-3) mutations per nucleotide site per year) suggested a more active evolution similar to that of the M genogroup.

Gross and Microscopic Pathology Associated with Large Cavernous Lesions in Muscle of Chinook Salmon from Lake Ontario

Since 1999, eight adult Chinook salmon (Onchorhynchus tshawytscha) from Lake Ontario with large, focal, cavernous, fluid-filled muscle lesions have been examined in our respective laboratories. Gross and microscopic examination, cytology, and bacteriology were performed. Microscopically the lesions were consistent with chronic abscesses. Cytologic evaluation revealed diplomonad flagellate Spironucleus within these lesions. We provide a description of the gross and microscopic pathology associated with the cavernous lesions.

Experimental evaluation of fishway modifications on the passage behaviour of adult Chinook salmon and steelhead at Lower Granite Dam, Snake River, USA

AbstractPrevious studies of Pacific salmonid passage over Snake River dams indicated slowed passage at transition pools, the transition area between the fishway entrance and the fish ladder. In 2001 and 2002, we conducted an experiment to determine if modified weirs affected adult salmon and steelhead passage times and route selection through the Lower Granite Dam transition pool. Fish attraction flows through the lower ladder weirs were experimentally increased using removable panels. During the experiment we monitored radio‐tagged adult Chinook salmon and steelhead to determine passage routes and times through the transition pool. The weir treatment increased the number of spring–summer Chinook salmon passing straight through the transition pool compared to those exiting the transition pool to the collection channel or tailrace. Mean passage times through the transition pool differed among routes and were significantly lower during treatment periods for the exit‐to‐collection channel route in spring‐summer Chinook salmon, but not for other routes. Passage times among routes differed in steelhead, but there was no evidence of treatment effects on route use or passage time. Fall Chinook exhibited similar trends in route use and passage time to spring–summer Chinook, but differences were not significant, perhaps because of relatively small sample size. Total dam passage times did not differ by treatment or route for any run. Fish depth during passage of the transition pool suggested that most fish passed through submerged orifices and supported the hypothesis that increased water velocity through these orifices caused the increase in straight‐through passage in spring–summer Chinook. Collectively, the results suggested the weir modifications provided improvement to passage through the transition pool for spring–summer Chinook and no evidence of negative effects on other runs. The results from this study were used to develop new design criteria and modifications of the Lower Granite Dam fishway. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Contrasting sex ratios in juvenile and adult chinook salmon Oncorhynchus tshawytscha (Walbaum) from south‐west Alaska: sex reversal or differential survival?

A sex‐specific genetic marker (growth hormone pseudogene) and age‐at‐maturation data were used to infer the cause of male‐biased phenotypic sex ratios in adult chinook salmon Oncorhynchus tshawytscha from the Kwethluk and Tuluksak Rivers, south‐west Alaska. The results showed that: (1) adult genetic and phenotypic sex ratios were similar and were male biased, (2) genetic sex ratios of pre‐smolts were not male biased and (3) the average age‐at‐maturation for males was significantly less than for females. These results suggest that the sex ratio distortion is due to gender bias in marine survival probably related to gender differences in marine life‐history strategies.

Performance of Passive Integrated Transponder Tags and Radio Tags in Determining Dam Passage Behavior of Adult Chinook Salmon and Steelhead

AbstractPassage of adult Pacific salmon Oncorhynchus spp. and steelhead O. mykiss at dams in the Columbia River basin has historically been determined by visual fish counts and radiotelemetry. Increasingly, however, passive integrated transponder (PIT) tags are being used for adult salmonid research and monitoring. Although both radiotelemetry and PIT tag technology provide accurate and cost‐effective data under certain circumstances, neither alone meets all needs, and managers need to understand the strengths, weaknesses, and biases of each method. To evaluate the two tagging methods, we tagged over 3,200 adult Chinook salmon O. tshawytscha and steelhead during 2002 and 2003 with both a radio transmitter and a PIT tag as the fish migrated upstream past Bonneville Dam. We compared their performance in measuring upstream passage and fallback (i.e., downstream passage) behavior at each of four main‐stem hydropower dams. Counts of fish passage at dams based on data from double‐tagged fish were similar between methods (largest difference was 5.1%), but the two methods produced less consistent results for fallback behavior. Visual count escapement estimates based on PIT tags were 1% higher on average than those based on radio tags, suggesting there would be little impact on the management of salmonid populations with a switch from radiotelemetry to PIT tag systems as the primary data source. We also analyzed a broader group of PIT‐tagged (but not radio‐tagged) fish to simulate the analysis one could expect from PIT tag data without radiotelemetry validation. When compared with PIT tag data from double‐tagged fish, data from the PIT tag‐only fish showed slight differences in the timing of peak passage. These differences were due, at least in part, to the fact that the fish in each group comprised differing proportions of fish from multiple populations, highlighting the importance of having representative stocks of fish PIT‐tagged as juveniles.

Route selection in a large river during the homing migration of Chinook salmon (Oncorhynchus tshawytscha)

Upstream-migrating adult salmon must make a series of correct navigation and route-selection decisions to successfully locate natal streams. In this field study, we examined factors influencing migration route selections early in the migration of 4361 radio-tagged adult Chinook salmon (Oncorhynchus tshawytscha) as they moved upstream past dams in the large (~1 km wide) Columbia River. Substantial behavioral differences were observed among 11 conspecific populations, despite largely concurrent migrations. At dams, Chinook salmon generally preferred ladder passage routes adjacent to the shoreline where their natal tributaries entered, and the degree of preference increased as salmon proximity to natal tributaries increased. Columbia River discharge also influenced route choices, explaining some route selection variability. We suggest that salmon detect lateral gradients in orientation cues across the Columbia River channel that are entrained within tributary plumes and that these gradients in cues can persist downstream for tens to hundreds of kilometres. Detection of tributary plumes in large river systems, using olfactory or other navigation cues, may facilitate efficient route selection and optimize energy conservation by long-distance migrants.

Long‐distance downstream movements by homing adult chinook salmon

Unusually long downstream movements totalling several hundred kilometres to &gt;1100 km were observed during upstream homing migrations of radio‐tagged spring chinook salmon Oncorhynchus tshawytscha in the Columbia and Snake Rivers, U.S.A. Downstream migrants, identified by their repeated ascension and fallback over a series of large hydroelectric dams within the migration corridor, were primarily hatchery‐origin males.

Effects of Water Temperature and Flow on Adult Salmon Migration Swim Speed and Delay

AbstractThe effects of temperature and flow on the migration of adult Chinook salmon Oncorhynchus tshawytscha and steelhead O. mykiss through the Columbia River hydrosystem were determined with a novel technique that fits a broken linear model of swim speed versus temperature and flow by partitioning data into speed ranks. Using the migration times of passive integrated transponder (PIT)–tagged adult Chinook salmon upstream between Bonneville and Lower Granite dams (462 km) over the years 1998–2002, we found that a maximum swim speed of about 1 body length/s occurred at 16.3°C. Speed was less above and below this optimum temperature. For PIT‐tagged steelhead, migration speed uniformly decreased with increasing temperature, suggesting that the fish migrated at temperatures above the optimum. Migration delay was also a unimodal function of temperature, the minimum delay occurring around 16–17°C. The broken linear model was compared with seven alternative models of unimodal and monotonic speed versus temperature and flow. The unimodal models fit the data better than the monotonic models (when ranked by the Akaike information criterion), and the broken linear model fit the data best. Flow was insignificant in all of the monotonic models and only marginally significant in the unimodal models. The findings of this study have significance in evaluating the effects of hydrosystem operations and climate change on salmon and steelhead fitness.

Migration Depths of Adult Spring and Summer Chinook Salmon in the Lower Columbia and Snake Rivers in Relation to Dissolved Gas Supersaturation

AbstractHigh spill volume at dams can create supersaturated dissolved gas conditions that may have negative effects on fish. Water spilling over Columbia and Snake River dams during the spring and summer creates plumes with high dissolved gas that extend downstream of dam spillways and throughout reservoirs and creates gas‐supersaturated conditions throughout the water column. During the spring and summer of 2000, 228 adult Chinook salmon Oncorhynchus tshawytscha were tagged at Bonneville Dam with archival radio data storage transmitters (RDSTs) that recorded depth and water temperature as the fish migrated through dams and reservoirs of the lower Columbia and Snake rivers. Swimming depths from 131 of the 228 adult spring and summer Chinook salmon tagged with RDSTs were used to estimate the potential for gas bubble formation given in‐river dissolved gas concentrations and hydrostatic compensation. We found that adult spring and summer Chinook salmon spent a majority of the time at depths that would have provided adequate hydrostatic compensation for in‐river dissolved gas conditions during this study, which were at or slightly below long‐term averages. Adult spring and summer Chinook salmon spent a majority of their time at depths deeper than 2 m, interspersed with periods lasting minutes at depths shallower than 2 m. Statistical associations were weak between the percent and duration of time fish occupied depths near the surface and dissolved gas concentrations, suggesting a lack of behavioral avoidance. Collectively, these data suggest little potential for negative effects of gas supersaturation on adult spring and summer Chinook salmon under average river conditions, despite the fact that fish tissues were probably supersaturated with dissolved gases. However, additional research over a broader range of dissolved gas conditions is needed to confirm that short, but frequent, exposure to conditions conducive to gas bubble formation does not affect survival and reproductive potential.

Escapement, harvest, and unknown loss of radio-tagged adult salmonids in the Columbia River – Snake River hydrosystem

Accurate estimates of escapement by adult anadromous salmonids are difficult, especially in large, multistock river systems. We used radiotelemetry and a fishery reward program to calculate escapement, harvest, and unaccounted for loss rates for 10 498 adult chinook salmon (Oncorhynchus tshawytscha) and 5324 steelhead (Oncorhynchus mykiss) during six return years in the Columbia River basin. Mean annual escapements to spawning sites, hatcheries, or the upper bounds of the monitored hydrosystem were 73.4% (spring–summer chinook salmon), 61.3% (fall chinook salmon), and 62.6% (steelhead). Mean reported harvest rates were 8.7% (spring–summer chinook), 22.0% (fall chinook), and 15.1% (steelhead) within the mainstem hydrosystem and 5.9%, 3.4%, and 5.7%, respectively, in lower hydrosystem tributaries. On average, 12%–17% of each run had unknown fates in the mainstem hydrosystem. Escapement, harvest, and loss varied significantly between runs and years, within runs between known-origin subbasin stocks, and between interdam river reaches. Multiyear quantitative assessments like this can reduce uncertainty, clarify inter- and intra-annual variability, and help managers better evaluate fisheries, identify conservation priorities, and help protect evolutionarily significant populations.

Determination of carotenoids and all- trans-retinol in fish eggs by liquid chromatography–electrospray ionization–tandem mass spectrometry

A novel method was developed for the combined determination of carotenoids and retinoids in fish eggs, which incorporates prior analyte isolation using liquid-liquid partitioning to minimize analyte degradation, and fraction analysis using high-performance liquid chromatography–electrospray (positive)–quadrupole mass spectrometry (LC–ESI(+)–MS; SIM or MRM modes). Eggs from Chinook salmon ( Oncorhynchus tshawytscha) were used as the model fish egg matrix. The methodology was assessed and validated for β-carotene, lutein, zeaxanthin, and β-cryptoxanthin (molecular ion radicals [ M] +), canthaxanthin and astaxanthin ([ M + Na] + adducts) and all- trans-retinol ([( M + H)–H 2O] +). Using replicate egg samples ( n = 5) spiked with β-cryptoxanthin and β-carotene before and after extraction, matrix-sourced ESI(+) enhancement was observed as evidenced by comparable %matrix effect and %process efficiency values for β-cryptoxanthin and β-carotene of 114–119%. In aquaculture-raised eggs from adult Chinook salmon astaxanthin, all- trans-retinol, lutein and canthaxanthin were identified and determined at concentrations of 4.12, 1.06, 0.12 and 0.45 μg/g (egg wet weight), respectively. To our knowledge, this is the first report on a method for LC–MS determination of carotenoids and retinoids in a fish egg matrix, and the first carotenoid-specific determination in any fish egg sample.