Chum Salmon Oncorhynchus Keta Research Articles

Temporal trends in geographic clines of chum salmon reproductive traits associated with global warming and hatchery programmes

Abstract Geographic clines in life‐history traits are often recognized as adaptations to the associated transitional environments. As life‐history traits evolve in response to anthropogenic processes, these geographic clines can change over time. The geographic and temporal trends of reproductive traits in Japanese chum salmon Oncorhynchus keta were analysed. Data were collected from 23 rivers located between 36° and 45° north latitude and 136° and 146° east longitude from 1994 to 2010. We confirmed the geographic clines of reproductive traits: relative gonad weight increased in more northeasterly locations, and females had fewer, but larger, eggs in more northeasterly locations after standardization by body size. The geographic clines changed over the years. The northeastward geographic trend of increasing gonad weight became more pronounced over time. Temporal trends towards smaller but more numerous eggs were evident, especially in northeasterly locations. Under natural and sexual selection, gonadal investment should be constrained by the energetic demands of the cost of migration, particularly in southwesterly locations (which are farthest from the feeding grounds), and by breeding competition during natural reproduction. In addition, females should have fewer but larger eggs owing to a constraint on growth opportunities for their offspring in more northeasterly regions of Japan, which are colder and have less available food. However, global warming may mitigate this constraint on growth opportunities in northeastern Japan by increasing river water temperatures. Moreover, we consider that relaxation of the effects of natural and sexual selection on intense breeding competition and early growth conditions has occurred through domestication selection by hatchery programmes. These may have caused temporal shifts in geographic clines. We should consider several co‐occurring anthropogenic impacts on natural and sexual selection when evaluating the life‐history traits of organisms. For the sustainable use of biological resources, maintaining geographically adapted life‐history traits during adaptation to climate change is essential. Therefore, the conservation of wild salmon populations formed by natural selection is preferable to the stocking of hatchery‐reared fry.

Population structure of chum salmon and selection on the markers collected for stock identification.

Genetic stock identification (GSI) is a major management tool of Pacific salmon (Oncorhynchus Spp.) that has provided rich genetic baseline data of allozymes, microsatellites, and single‐nucleotide polymorphisms (SNPs) across the Pacific Rim. Here, we analyzed published data sets for adult chum salmon (Oncorhynchus keta), namely 10 microsatellites, 53 SNPs, and a mitochondrial DNA locus (mtDNA3, control region, and NADH‐3 combined) in samples from 495 locations in the same distribution range (n = 61,813). TreeMix analysis of the microsatellite loci identified the greatest convergence toward Japanese/Korean populations and suggested two admixture events from Japan/Korea to Russia and the Alaskan Peninsula. The SNPs had been purposively collected from rapidly evolving genes to increase the power of GSI. The largest expected heterozygosity was observed in Japanese/Korean populations for microsatellites, whereas it was largest in Western Alaskan populations for SNPs, reflecting the SNP discovery process. A regression of SNP population structures on those of microsatellites indicated the selection of the SNP loci according to deviations from the predicted structures. Specifically, we matched the sampling locations of the SNPs with those of the microsatellites and performed regression analyses of SNP allele frequencies on a 2‐dimensional scaling (MDS) of matched locations obtained from microsatellite pairwise F ST values. The MDS first axis indicated a latitudinal cline in American and Russian populations, whereas the second axis showed differentiation of Japanese/Korean populations. The top five outlier SNPs included mtDNA3, U502241 (unknown), GnRH373, ras1362, and TCP178, which were identified by principal component analysis. We summarized the functions of 53 nuclear genes surrounding SNPs and the mtDNA3 locus by referring to a gene database system and propose how they may influence the fitness of chum salmon.

Relationships between maturational status and migration behavior of homing chum salmon Oncorhynchus keta in inner bays of the Sanriku coast

The correlations among gonad maturity and various homing behaviors of chum salmon, Oncorhynchus keta, were evaluated using acoustic tracking of tagged fish in Otsuchi Bay, Japan. There was a negative correlation between the time duration from release of tagged fish until river entry and the plasma 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) levels, an indicator of final maturation. Females with high DHP entered the rivers soon after the release, whereas females with low DHP (<10 ng/ml) took a few days to more than one week until river entry. Similar correlation was also found in males. A pattern of river entry correlated with maturational conditions was also observed in fish entering the rivers of neighboring bays. DHP concentrations of fish caught in the rivers were consistently higher. On the other hand, more than half of released salmon departed from the bay regardless of their plasma DHP level, suggesting that maturational status does not force homing adults to enter the most available nearest rivers. Fish entering the rivers experienced ambient temperatures less than 8 °C, which is approximately 5 °C lower than that of the bay. These results indicate that homing salmon hold their position in the bay until just before spawning, which may be attributable to low temperature avoidance. This characteristic type of river entry may be suitable to geographical features and thermal regimes of this region.

Puget Sound Chum Salmon Growth Linked to Competitor Abundance, Climate Indices, and Copepod Species Richness

AbstractAn improved understanding of the mechanisms influencing productivity of fish populations is critical for accurately determining harvest rates and identifying years of conservation concern. Here we reconstruct yearly scale growth of three Puget Sound (PS) Chum Salmon Oncorhynchus keta stocks over 16 brood years (1997–2012) to better understand how variation in marine growth may be related to environmental factors, intra‐ and interspecific competition, and stock productivity. Generalized additive mixed models identified copepod species richness in the northern California Current and the abundance of PS Pink Salmon O. gorbuscha and Chum Salmon as strong predictors of first‐year growth, the latter indicative of density‐dependent effects as the abundance of local competitors (Pink and Chum salmon) increased. Second‐year growth was negatively related to the Aleutian Low–Beaufort Sea Anticyclone (ALBSA), a recently defined metric of the Aleutian Low, and showed a nonlinear positive to negative relationship with sea surface temperature in the Gulf of Alaska. Puget Sound Chum and Pink Salmon abundances were also significantly related to second‐year growth but did not suggest density‐dependent effects like those observed in ocean year 1. Third‐year growth was closely related to large‐scale climate indicators, demonstrating a nonlinear negative to positive relationship with the North Pacific Gyre Oscillation, a negative relationship with ALBSA, and a negative relationship with North Pacific Pink Salmon abundance when catch statistics indicated that abundance was high. Models indicated that PS Chum Salmon stock productivity (recruits per spawner) was positively correlated with back‐calculated first‐year growth and negatively correlated with second‐ and third‐year growth, suggesting that for brood years whose surviving adults experienced rapid early marine growth, there were cohort survival benefits. As new relationships between large‐scale indicators and Pacific salmon stocks are identified, incorporating these indicators into forecasting efforts is paramount for effective and sustainable management of fishery resources.

Initial growth characteristics of poor-return stocks of chum salmon Oncorhynchus keta originating from the Okhotsk and Nemuro regions in Hokkaido on the basis of scale analysis

Initial growth characteristics of poor-return stocks of chum salmon Oncorhynchus keta originating from the Okhotsk and Nemuro regions in Hokkaido on the basis of scale analysis

Molecular characterization of transient receptor potential vanilloid 4 (TRPV4) gene transcript variant mRNA of chum salmon Oncorhynchus keta in response to salinity or temperature changes.

Transient receptor potential vanilloid 4 (TRPV4) is an osmosensory cation channel that respond to an increase in cell volume and participates in various physiological functions. Among organisms in aquatic environments, euryhaline teleost is are suitable experimental models to study ion channel proteins related to physiological functions involving osmosensing. Among the studies of various regulatory molecules that mediate osmotic regulation in fish, however, information is lacking, particularly on the TRP family. This study investigated the structural characteristics of theTRPV4 gene of chum salmon (Oncorhynchus keta) and their responses to changes in salinity and temperature. Interestingly, TRPV4 generates transcript variants of the intron-retention form through alternative splicing, resulting in a frameshift leading to the generation of transcripts of different structures. In particular, TRPV4 x1 and TRPV x2 mRNAs were predominant in the gill and skin including at the lateral line. The expression levels of chum salmon TRPV4 x1 were significantly increased with increase in salinity and temperature, whereas TRPV4 x2 mainly responded to temperature decrease. Overall, these results demonstrate for the first time the effects of salinity and temperature on the expression of two salmonid TRPV4 transcript variants, suggesting their contribution to the regulation of hydromineral balance.

Landscape attributes explain salmonid ecological neighbourhoods across a complex river network

Abstract Defining population neighbourhood boundaries provides a critical spatial framework for understanding ecological processes and informing species‐specific conservation and restoration planning. The population neighbourhood boundary demarcates the total quantity of available habitat across life stages where specific ecological processes (e.g., breeding, foraging, migration) occur for all individuals within a population. For mobile species within dendritic freshwater networks, the population neighbourhood boundary can be defined by the upper limit of occurrence (ULO) of an individual within a population. We sought to define contemporary neighbourhood boundaries across a complex river network in southwestern Washington State, U.S.A. by: (1) identifying ULOs for three anadromous fish (Oncorhynchus spp.); and (2) quantifying the relationship of the ULO with landscape attributes and local features for these species of profound social and ecological importance. Extensive field surveys covering 669 river km across 2 years documented the ULOs for coho salmon (Oncorhynchus kisutch), steelhead trout (Oncorhynchus mykiss), and chum salmon (Oncorhynchus keta) as well as any local features, such as natural barriers, that influenced the ULOs. Generalised linear mixed models quantified the relationships between the ULOs and landscape attributes derived from remote sensing data. We identified the ULO for 115 coho salmon terminal streams, 97 steelhead streams, and 57 chum salmon streams. Natural barriers determined the ULO in just 5%–16% of the terminal streams, depending on species. Landscape attributes associated with the ULOs varied among species; however, drainage area, elevation, and geology were important landscape predictors for all species. Models for each species had good to excellent predictive performance (percent correct classification: 78%–89%; AUC: 0.87–0.96). We demonstrated that large‐scale landscape attributes can accurately and consistently detect species‐specific differences in population neighbourhoods across broad and diverse habitats. In comparison, local scale features (e.g., natural barriers) played a minor role in determining the neighbourhood boundaries in our study catchment. The modelled relationships between landscape attributes and the population neighbourhood provide a framework to guide conservation planning and predict benefits of habitat reconnections.

High-resolution remote sensing and multistate occupancy estimation identify drivers of spawning site selection in fall chum salmon (Oncorhynchus keta) across a sub-Arctic riverscape

Groundwater upwellings provide warmer, stable overwinter temperatures for developing salmon embryos, which may be particularly important in cold, braided, gravel-bed sub-Arctic rivers. We used a three-year time series of aerial counts and remote sensing to estimate the distribution of low and high aggregations of spawning fall chum salmon (Oncorhynchus keta), classify approximately 0.5 km long river segments by geomorphic channel type, and map thermal variability along a 25.4 km stretch of the Teedriinjik River, Alaska. We used a dynamic multistate occupancy model to estimate detectability, occupancy, and the dynamics of spawning aggregations among river segments. Detectability was higher for large (&gt;150) relative to smaller aggregations. Unoccupied segments were likely to remain so from year to year; low abundance spawning segments were dynamic and rarely remained in that state for multiple years, while ∼20%–35% of high abundance segments remained stable, indicating the presence of high-quality spawning habitat. Spawning habitat use was associated with warmer water temperatures likely caused by groundwater upwellings. We identified spawning habitat characteristics and trends in usage by fall chum salmon, which will inform land management decisions and assist in evaluating impacts of shifting climate conditions and resource management on Arctic salmon populations.

Characteristics of roe of autumn chum salmon Oncorhynchus keta from the Amur River

Chemical composition and nutritional and biological value of roe are investigated for autumn chum salmon from the Amur River sampled during their run for spawning from the estuary to the area of Khabarovsk city. Color and strength of roe were examined, content of proteins, lipids and minerals was measured, amino acid and fatty acid composition was determined. Caloric capacity and biological value of the samples were usual for this species. Physical properties of the roe (strength, color intensity) practically did not change in dependence on distance from the river mouth. Stable quality of roe in the run of spawning migration in the lower Amur is concluded.

Ecogeographic Units and Management Units of Chum Salmon Oncorhynchus keta of the Amur Zoogeographic Province

—Using the example of chum salmon Oncorhynchus keta in the Amur zoogeographic province, we review the principle of subdividing the species into population groups. On the basis of zoogeographic zoning and biological boundaries of chum salmon groups defined by the spawning areas, taking into account the distribution, migration, and reproduction, as well as estimates of their differentiation using microsatellite DNA markers, we identified eight ecogeographic units in the Amur province. In the Amur zoogeographic region of this province, these included the summer chum salmon of the Amur-Amgun ecoregion and the autumn chum salmon of the Lower Amur (Amur-Amgun and Amur-Ussuri ecoregions); in the Shantar zoogeographic region of the province, the Uda-Tugur and Ulban groups; in the Sakhalin part of the Amur province, groups from the northwestern and northeastern Sakhalin, as well as summer and autumn chum salmon from the Poronai River. These ecogeographic units can be considered as basic spawning management units of chum salmon for this part of the species distribution range.

Flood-induced interspecific interactions in spring-fed tributary as an ecosystem function of heterogeneous river networks

Understanding the migratory community dynamics of river networks is important for maintaining lotic system integrity. River animals migrate to their preferred habitats in spatiotemporally heterogeneous river environments. Spring-fed habitats are uniquely characterized by stable temperature and flow regimes, which create suitable spawning habitats for the chum salmon Oncorhynchus keta. O. keta exhibits “run up” to its birthplace for spawning, especially during floods. Because the eggs deposited by this anadromous fish are nutritious and actively consumed by freshwater animals, the location and timing of O. keta spawning events affect the spatiotemporal accumulation of mobile consumers. In this study, we examined changes in temporal population density in spawning O. keta and a mobile consumer (juvenile O. masou masou) in a lowland, spring-fed tributary in northern Japan during a 48.5-mm autumn rainfall event. In both species, population density increased, and then decreased, after the rainfall event. In O. keta, these changes were closely associated with rainfall intensity, whereas in O. masou masou the peak was delayed until 3 days after the rainfall event. A comparison of the gut contents of O. masou masou sampled from a spring-fed tributary and an adjacent non-spring-fed tributary indicated greater consumption of O. keta eggs in the spring-fed tributary. These results suggested that preferential migration of O. keta into spring-fed tributaries for spawning induces subsequent accumulation of juvenile O. masou masou, in turn increasing O. keta egg consumption. These findings improve our understanding of community dynamics during floods in a heterogeneous river network environment.

Black bear colour polymorphism through a fragmented Snell’s window

Abstract The white colour morph of the black bear (Ursus americanus kermodei) occurring on islands on the coast of British Columbia, western Canada, captures more salmon (Oncorhynchus spp.) than does the black morph and is hypothesized to have reduced contrast against the sky from the visual perspective of the salmon. We tested this hypothesis in a natural salmon stream by recording the number and proximity of chum salmon (Oncorhynchus keta) approaches (N = 1617 fish, 91 trials) towards life-size bear models differing in body and leg coloration under a mixed forest-sky canopy. Although salmon approached the white models at a much higher rate than black models, consistent with camouflage, we found greater abrupt evasions to the black models, largely independent of their contrast against the above-surface or below-surface backgrounds. Upward-facing sub-surface video-imaging through the rippled water-air interface indicated major visual fragmentation of the model’s integrity. We suggest that increased evasiveness to black models reflects an evolutionary response due to 3+ million years of trophic interaction between salmon and bears, and that the major differences between calm vs. rippled conditions through the optical cone (Snell’s window) at the water-air interface remains a largely unexplored theme in assessing foraging preferences and adaptive coloration within and among species using the water-air interface.

Effects of fasting and water temperatures during transition from freshwater to seawater on juvenile chum salmon growth and metabolism

We examined the combined effects of fasting in freshwater and water temperature during the transition from freshwater to seawater on growth/metabolic parameters in juvenile chum salmon Oncorhynchus keta. Juveniles of 1 g in freshwater were first subjected to a 5-day fasting period at 10 or 5 °C, acclimated to either 10 or 5 °C seawater and fed ad libitum for 30 days. Control fish were transferred from 10 °C freshwater to 10 °C seawater and fed ad libitum throughout the experimental period. Serum insulin-like growth factor (IGF)-I was measured to evaluate growth status/potential and liver glycogen as an index of energy storage. Fasting in freshwater for 5 days negatively affected body size. Growth of juveniles kept at colder temperatures was retarded in seawater for at least 20 days, which may partly be explained by a lower feeding rate in cold seawater. Serum IGF-I levels were lower in fasted fish in freshwater at both temperatures and colder seawater had a negative effect on restoring serum IGF-I levels after refeeding for 20 days. Liver glycogen content was low in fish fasted in freshwater for 5 days. After refeeding in seawater for 10 days, liver glycogen content increased significantly in juveniles kept at colder temperatures. Colder water temperatures in both salinities positively affected glycogen content for 30 days after transfer to seawater, suggesting that juveniles allocated energy stores to the liver rather than growth under suboptimal feeding and temperature conditions. The findings of the present study suggested that relatively cold freshwater could negatively affect juvenile chum salmon growth soon after sea entry.

Proportions of Hatchery Fish in Escapements of Summer‐Run Chum Salmon in Southeast Alaska, 2013–2015

AbstractThe Alaska salmon hatchery program is intended to supplement salmon fisheries without supplanting wild stocks. Hatchery‐origin Chum Salmon Oncorhynchus keta spend most of their lives interacting with wild salmon, including some degree of straying to spawning streams. Our study was designed and implemented to measure the extent and annual variability of straying by hatchery‐produced, summer‐run Chum Salmon in Southeast Alaska from 2013 to 2015 by sampling in individual streams to estimate the proportion of hatchery strays. In the sampled index streams, the proportion ranged from 0.000 to 0.854 over the 3 years. Unbiased estimates of the proportions of hatchery‐origin fish spawning in each of the three management units ranged from 0.016 to 0.081, and the estimated hatchery proportions spawning across Southeast Alaska ranged from 0.032 to 0.060. The proportion of hatchery strays decreased as the distance from hatchery release sites increased; proportions were highest at streams located within 50 km of the nearest release site. The proportion of hatchery‐origin spawners was negatively related to the index of spawning escapement in a stream. A hatchery donor stray rate of 0.8–4.8% was estimated. Hatchery‐origin Chum Salmon occur at low levels in most Chum Salmon systems in Southeast Alaska and at higher levels in systems close to hatchery release sites.

DNA-based species identification of ancient salmonid remains provides new insight into pre-contact Coast Salish salmon fisheries in Burrard Inlet, British Columbia, Canada

This study uses ancient DNA analysis to identify the species of salmonids from a number of pre-contact Coast Salish settlements in Burrard Inlet, Canada dating from about 390 BCE to CE 1600. Our results indicate that chum salmon (Oncorhynchus keta) dominates all Burrard Inlet zooarchaeological assemblages through time, followed distantly by pink salmon (Oncorhynchus gorbuscha), sockeye (Oncorhynchus nerka), coho (Oncorhynchus kisutch), and Chinook (Oncorhynchus tshawytscha), indicative of very stable local fisheries. These results indicate that the four well-sampled sites appear to have been occupied during the fall and winter and perhaps during the spring.

The life history and populations of chum salmon (Oncorhynchus keta) in China: An otolith isotopic investigation

Stable isotope ratios of otoliths (δ13C and δ18O) can be used as a habitat index in anadromous fish, because there are marked differences between freshwater and marine settings. Here we report the results of 84 otoliths of chum salmon (Oncorhynchus keta) collected from three locations (Site-A, Site-B, and Site-C) in China, where all the estuaries for chum salmon ocean entry are located in Russia or North Korea and no biological observation data being obtained. In this study we adopted a blind-test protocol and applied stable isotope analyses in chum salmon otoliths. Two aragonite powder samples were taken from each otolith: one from the nucleus of otoliths; the other from the 2nd summer growth zones. Overall the δ13C values of chum salmon otoliths ranged from −10.9 to −4.0‰, whereas δ18O values of the same samples ranged from −6.4 to +1.9‰. Based on δ18O values at about −3.5‰ (the boundary line), two different spawning populations or stocks have been identified (p-value = 0.008). The Site-A samples were collected from the Amur River, while the Site-B samples were collected from the Tumen River. The Suifen River (Site-C) samples had some mixing with the Amur River chum salmon, but they were essentially classified into the Tumen River population. Comparison between our data and the previously reported sockeye salmon and chinook salmon data in North America indicated that the chum salmon in China are anadromous, and have the same life history from freshwater to marine as other populations over the world.

A comparison of avoidance to acoustic stimuli in fish with different auditory capabilities: juvenile chum salmon (Oncorhynchus keta) and common carp (Cyprinus carpio)

This study compared the repulsive effects of sound playbacks of intermittent 30, 150, 300, 600 and 900 Hz tones on two fish with different auditory capabilities: juvenile chum salmon (Oncorhynchus keta) and common carp (Cyprinus carpio). When 150 and 300 Hz tones were emitted from an underwater speaker, O. keta exhibited a moderate repulse reaction. Conversely, C. carpio exhibited a moderate repulse reaction to a tone with a frequency of 30 Hz, which indicates that a low-frequency component in complex broadband sound may be important for inducing a repulse reaction in cyprinids.

Detecting spawning of threatened chum salmon Oncorhynchus keta over a large spatial extent using eDNA sampling: Opportunities and considerations for monitoring recovery

AbstractOver the last century, anthropogenic activities have caused substantial declines in the abundance of chum salmon (Oncorhynchus keta) throughout their range in western North America. As a result, chum salmon were listed as threatened under the U.S. Endangered Species Act in 1999. Recovery strategies have been developed, but limited baseline data on distribution impedes implementation of these strategies. Traditional methods for identifying spawning distribution (e.g., spawning ground surveys) may be inadequate for rare species like chum salmon because of a low detection probability. In contrast, environmental DNA (eDNA) sampling is extremely sensitive to species presence and has the potential to supplement or replace existing methods for monitoring listed species. However, legal and administrative issues associated with accurately describing distribution of a listed species put a premium on understanding factors that influence detection of a species by eDNA sampling. In this study, we (a) developed and tested a quantitative PCR‐based eDNA assay for chum salmon, (b) collected eDNA samples to describe the spawning distribution of this species in Columbia River tributaries between Bonneville and The Dalles Dams, and (c) tested whether spawn surveyors could inadvertently transport chum salmon DNA between streams on their boots and waders. The newly developed assay was specific and sensitive to chum salmon DNA in both tissue and eDNA samples. Chum salmon DNA was detected in the positive control site and in four streams, which increased known contemporary spawning locations in the study area. In the contamination trial, surveyors successfully introduced chum salmon DNA into the study area but eDNA was only detected intermittently and locally over the next 11 days. The accuracy of eDNA sampling, combined with success in detecting a rare species at the population scale, makes this technique well‐suited for monitoring recolonization of chum salmon during the recovery process.

First results of acoustic tags using for studies of migrations of siberian taimen Huho taimen (Salmonidae) in the Tugur River basin (northwestern Okhotsk Sea)

Method of acoustic tagging of large-sized fish in a medium river is successfully tested for the case of siberian taimen Hucho taimen in the Tugur River. Algorithm of fish anesthesia and acoustic tag input into its body cavity is developed. For successful tagging, total duration of the process, including anesthesia, should not exceed 5 minutes. The best results of tagging are obtained for fish with a body length of 110–130 cm, which tolerate anesthesia easily. In 2017–2019, 25 out of 29 tagged fish were registered by acoustic equipment that indicates high efficiency of the method (86.2 %). Distance from the release point to the point of tag registration varied from 0.2 to 39.8 km. Some fish crossed almost completely the buoy-controlled section of the river that indicates a rather high migration potential of siberian taimen. On the background of high individual diversity of migration activity, two principally different behavioral strategies are distinguished — «residents» staying in one place up to 2 months and «nomads» migrating to a distance up to 30 km per day. The radius of taimen migration increases usually in May and September and decreases in August. The seasonal increasing is associated with feeding migrations: taimen feed on downstream juveniles of chum salmon Oncorhynchus keta and prespawning minnows Rhynchocypris lagowskii in May and on chum adults migrating to spawning grounds in September. During twilight and at night, the migrations are usually more active, but they are less visible and shorter in the morning and afternoon. Correspondingly, the main feeding of taimen is assumed in the twilight and dark time, whereas a supporting feeding in the daytime.

Dependence of number of chum salmon Oncorhynchus keta progeny in Okhotsky district on number of their parents and environments of reproduction

Dependence of chum salmon Oncorhynchus keta recruitment (number of mature adults) in Okhotsky district located on the Okhotsk Sea coast on a number of spawners is analyzed for the spawning years of 1983–2014. During this period, the progeny abundance increased, then stabilized on a high level, then decreased. Generally, the number of recruits depended poorly on the number of spawners because of clear environmental impact. Indeed, the recruitment variation could be simulated on the base of Ricker curve with addition of a variable responsible for environmental trend. Number of the year of spawning was used as such variable. So, the chum recruitment R is modeled as R = a. P. exp(–(P/b + ((X – c)/d)2 )) for the period of increasing and R = a. P. exp(–(P/b – ((X – c)/с)2 )) for the period of decreasing, where P — number of parents, X — year of spawning, and a, b, c, d — empirical coefficients. This model explains &gt; 80 % of the recruitment deviation. The environmental impact was weak in the period of stable recruitment, so the direct dependence of progeny abundance on spawners number (Ricker curve) can be used for these years, with similar determination (r2 &gt; 0.8). This approach is proposed as a possible compromise between hypotheses on climate-driven and autoregulating mechanisms of the salmons abundance variability.