Abundance Of Chum Salmon Research Articles

International Variability of Japanese Chum Salmon Abundance in the Summer Bering Sea during a Long Monitoring Survey in 2007–2019

International Variability of Japanese Chum Salmon Abundance in the Summer Bering Sea during a Long Monitoring Survey in 2007–2019

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.

Density‐dependent effects of eastern Kamchatka pink salmon (Oncorhynchus gorbuscha) and Japanese chum salmon (O. keta) on age‐specific growth of western Alaska chum salmon

AbstractHatcheries release >4.5 billion juvenile Pacific salmon (Oncorhynchus spp.) into the North Pacific Ocean annually, raising concerns about competition with wild salmon populations. We used retrospective scale analysis to investigate how the growth of chum salmon (O. keta) from western Alaska is affected by the abundance of chum salmon from Japanese hatcheries and wild pink salmon (O. gorbuscha) from the Russian Far East. Over nearly five decades, the growth of Kuskokwim River chum salmon was negatively correlated with the abundance of Japanese hatchery chum salmon after accounting for the effects of sex and spring/summer sea‐surface temperature in the Bering Sea. An effect of wild eastern Kamchatka pink salmon abundance on the growth of Kuskokwim River salmon was detectable but modest compared to the intraspecific competitive effect. A decrease in Japanese hatchery chum salmon releases in 2011–2013 was not associated with increased growth of Bering Sea chum salmon. However, the abundance of wild chum salmon from the Russian Far East increased during that time, possibly obscuring reduced competition with hatchery chum salmon. Our results support previous evidence that chum salmon are affected by intraspecific competition, and to a lesser extent interspecific competition, in the North Pacific, underscoring that the effects of salmon hatchery production transcend national boundaries.

Прогнозирование численности кеты на Южных Курильских островах

Прогнозирование численности кеты на Южных Курильских островах

Multi‐timescale interactions between pink and chum salmon catch per unit effort in the Bering Sea

AbstractBased on generalized linear models, interspecific interactions were identified between chum and pink salmon. In addition, the effects of sea surface temperature and location on the variability of catch per unit effort (CPUE) of chum salmon from gill‐net surveys carried out between 1972 and 2010 were investigated. In the optimal model, interspecific interactions between CPUEs of chum and pink salmon on a year scale were positive for approximately half of all years in the central Bering Sea. In addition, interspecific interactions on a multi‐year scale were positive in even‐numbered years. The effects of location on the CPUE of chum salmon were significant variables in the optimal model. The CPUEs of chum salmon located near the continental shelf in the Bering Sea were higher than those of other locations. This study provides new evidence of positive interspecific interactions between the CPUEs of chum and pink salmon. The results also suggest that the standardized CPUE of chum salmon from the gill‐net surveys reflects relative chum salmon abundance in the North Pacific Ocean in the following year.

Stock-Specific Abundance of Chum Salmon in the Central Gulf of Alaska during Winter

Stock-Specific Abundance of Chum Salmon in the Central Gulf of Alaska during Winter

Stock-Specific Abundance of Chum Salmon in the Central Gulf of Alaska during Winter

Stock-Specific Abundance of Chum Salmon in the Central Gulf of Alaska during Winter

Abundance of Skeena River Chum Salmon during the Early Rise of Commercial Fishing

AbstractWe used reported commercial catch data and historical information to estimate the abundance of Skeena River Chum Salmon Oncorhynchus keta during the early rise (1916–1919) in the commercial fishery to provide historical perspective for recovery plans. We applied a Bayesian analysis to address the uncertainties associated with the estimation process. Based on the historical catch of 204,000 in 1919 and an estimated harvest rate of 0.32–0.58, the estimated return of Skeena Chum Salmon ranged from 355,000 to 619,000, with the most probable single estimate being 431,000. The estimated return of Chum Salmon based on the 1916–1919 geometric mean catch of 154,000 ranged from 268,000 to 471,000, with the most probable single estimate being 325,000. Our posterior modal historical estimates are 8–11 times larger than the estimates for the contemporary period 1982–2010 and 39–52 times larger than those for the most recent period of 2007–2010. Intense harvest pressure is the single most probable factor explaining the sustained decline in Chum Salmon abundance, but other interactive factors, notably natural variations in survival, the loss of spawning and rearing habitat, and poor data quality, also are important considerations. Nonetheless, the Skeena catchment is largely pristine today, and our robust estimates of historical abundance should be of value to contemporary management and conservation agencies for the rebuilding of such severely diminished populations.

Historical growth of Bristol Bay and Yukon River, Alaska chum salmon (Oncorhynchus keta) in relation to climate and inter- and intraspecific competition

We examined Bristol Bay and Yukon River adult chum salmon scales to determine whether climate variability, such as changes in sea surface temperature and climate indices, and high pink and Asian chum salmon abundance reduced chum salmon growth. Annual marine growth increments for 1965–2006 were estimated from scale growth measurements and were modeled as a function of potential explanatory variables using a generalized least squares regression approach. First-year growth of salmon originating from Bristol Bay and the Yukon River showed increased growth in association with higher regional ocean temperatures and was negatively affected by wind mixing and ice cover. Third-year growth was lower when Asian chum salmon were more abundant. Contrary to our hypothesis, warmer large-scale sea surface temperatures in the Gulf of Alaska were also associated with reduced third-year growth. Negative effects of high abundances of Russian pink salmon on third-year growth provided some evidence for interspecific interactions, but the effects were smaller than the effects of Asian chum salmon abundance and Gulf of Alaska sea surface temperature. Although the relative effects of Asian chum salmon and sea surface temperature on the growth of Yukon and Bristol Bay chum salmon were difficult to untangle, we found consistent evidence that high abundances of Asian chum salmon contributed to a reduction in the growth of western Alaska chum salmon.

Evidence for competition at sea between Norton Sound chum salmon and Asian hatchery chum salmon

Increasing production of hatchery salmon over the past four decades has led to concerns about possible density-dependent effects on wild Pacific salmon populations in the North Pacific Ocean. The concern arises because salmon from distant regions overlap in the ocean, and wild salmon populations having low productivity may compete for food with abundant hatchery populations. We tested the hypothesis that adult length-at-age, age-at-maturation, productivity, and abundance of a Norton Sound, Alaska, chum salmon population were influenced by Asian hatchery chum salmon, which have become exceptionally abundant and surpassed the abundance of wild chum salmon in the North Pacific beginning in the early 1980s. We found that smaller adult length-at-age, delayed age-at-maturation, and reduced productivity and abundance of the Norton Sound salmon population were associated with greater production of Asian hatchery chum salmon since 1965. Modeling of the density-dependent relationship, while controlling for other influential variables, indicated that an increase in adult hatchery chum salmon abundance from 10 million to 80 million adult fish led to a 72% reduction in the abundance of the wild chum salmon population. These findings indicate that competition with hatchery chum salmon contributed to the low productivity and abundance of Norton Sound chum salmon, which includes several stocks that are classified as Stocks of Concern by the State of Alaska. This study provides new evidence indicating that large-scale hatchery production may influence body size, age-at-maturation, productivity and abundance of a distant wild salmon population.

Body size trends along vertical and thermal gradients of chum salmon in the Bering Sea during summer

Relationships between the vertical distribution and thermal habitat, and body size of chum salmon Oncorhynchus keta were studied in the Bering Sea in summer using trawl surveys at various depths. Chum salmon abundance decreased with increasing depth, but the patterns of decrease differed between size groups. The abundance of small salmon fell rapidly with depth, whereas that of large salmon decreased gradually to 40 m depth, and abruptly below that. The average fork length of chum salmon collected from each trawl correlated positively with trawl net depth and negatively with water temperature. Since the optimal temperature for growth decreases with body size in this species, the observed body size-related vertical habitat use by chum salmon may indicate size-dependent thermal preferences.

Estimating Indices of Abundance and Escapement of Pacific Salmon for Data‐Limited Situations

AbstractWe demonstrate the process of synchronously combining multiple sources of available fishery information to estimate total abundance in data‐limited situations. The application is specific to semelparous populations, such as Pacific salmon, where only data for spawners and recruits are necessary to describe the dynamics of these populations. We apply this technique to summer chum salmon Oncorhynchus keta of the Kuskokwim and Yukon rivers of Alaska. Since 1997, low numbers of returning chum salmon to these rivers have resulted in low harvests, with significant negative economic and social impacts to rural residents of the region. The existing programs for assessing salmon stock in these river basins are inadequate for conventional estimates of total run abundance and the modeling of stock dynamics necessary to derive a quantitative assessment of the returns. Our approach was to utilize the pattern extraction qualities of principal components analysis (PCA) to estimate the underlying trend in escapement. We then combined this index with other available fishery data in a maximum likelihood statistical framework, weighting the data sets according to their quality. Using this methodology, we derived indices of chum salmon abundance and escapement for the Kuskokwim and Yukon rivers. Data sources included commercial catch and effort, escapement surveys, test fishery catch rates, and whole‐river sonar counts. Error estimates of the time series of abundance and escapement as well as of the model parameters were generated by bootstrap methods. We found that several parameters of the model were confounded without some independent measure of total abundance or escapement. We also determined that the escapement trend estimated by PCA was consistent over a large geographic area, suggesting that survival was predominantly influenced by conditions where the fish share a common environment. We suggest that our methodology may be appropriate to other regions and different semelparous species.

Competition between juvenile pink (Oncorhynchus gorbuscha) and chum salmon (Oncorhynchus keta) and its effect on growth and survival

Pink (Oncorhynchus gorbuscha) and chum salmon (Oncorhynchus keta) fry have the potential for significant interactions in estuarine and nearshore waters of the Fraser River. Potential competitive effects were investigated by rearing both species for 60 d from fry emergence in monoculture and five duoculture environments (0, 10, 25, 50, 75, 90, and 100% pink salmon, and 100, 90, 75, 50, 25, 10, and 0% chum salmon, respectively), with the total number of fish in each environment constant. As the relative abundance of chum salmon increased, the mean weight of both pink and chum salmon declined, and reduced phenotypic variation in weight was observed. No marked trends in survival were observed in either species, but there was some indication that pink salmon survival was higher at intermediate relative densities of pink and chum salmon. Pink salmon biomass increased from 0.8 to 1.8%/d depending on the environment, and chum salmon biomass increased from 3.2 to 3.8%/d.

Relation between size‐at‐maturity and survival of progeny in chum salmon, Oncorhynchus keta (Walbaum)

Data on age‐ and size‐at‐maturity, growth, and abundance of chum salmon were collected from 1959 to 1977 at Olsen Creek in Prince William Sound, Alaska. Age composition of spawners (3 to 6‐year‐olds) varied from year to year: 4‐year‐old fish were the dominant age group in most (16 out of 19) years and 6‐year‐old fish usually represented less than 1 % of the returns. Mean size of older spawners was significantly larger than that of younger spawners. Size‐at‐maturity was similar among fish from different broods maturing at different ages in the same year. Size‐at‐maturity and survival of progeny were significantly related. The larger the mean size of spawners, the higher the survival rate to adulthood of their progeny. Possible reasons for this relationship are discussed.

Estimation of catch efficiency and chum salmon abundance by parallel gillnet experiment.

Parallel gillnet experiments were carried out in order to estimate catch efficiency of gillnet and abundance of chum salmon in the central Bering Sea in July, 1984. In the experiment, two gillnets were simultaneously set in parallel configuration at a distance of about 2km, and the catch in number of salmon by each side of each gillnet was recorded. Release and recovery ex-periments were also conducted to estimate the moving speed of salmon. In order to estimate catch efficiency and density of fish, data were analyzed based on a model that takes into account the moving speed of fish and the catch interaction between two parallel gillnets. A relationship between CPUE (number/tan) and density (number/km2) was constructed, and CPUE at each station was converted into density. The density was weighted by the size of the survey area, and the abundance of chum salmon was calculated.