Wild Chum Research Articles

Condition factor dependency of burst swimming ability between wild and hatchery-reared chum salmon fry (Oncorhynchus keta)

Condition factor dependency of burst swimming ability between wild and hatchery-reared chum salmon fry (Oncorhynchus keta)

Occurrence of wild chum salmon fry in the surf zone, and spawning and emergence timing in the adjacent nonstocked river in Niigata Prefecture, Japan

Occurrence of wild chum salmon fry in the surf zone, and spawning and emergence timing in the adjacent nonstocked river in Niigata Prefecture, Japan

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.

Is blood cortisol or vateritic otolith composition associated with natal dispersal or reproductive performance on the spawning grounds of straying and homing hatchery-produced chum salmon (Oncorhynchus keta) in Southeast Alaska?

ABSTRACTHoming with high fidelity to natal spawning grounds for reproduction is a hallmark of anadromous Pacific salmon biology, although low rates of dispersal (‘straying’) also occurs. Currently little is known about the proximate factors influencing straying, which limits our understanding of this fundamental biological phenomenon and impedes options for reducing straying-mediated interactions between wild and hatchery-produced individuals. We explored the potential role of stress experienced in captivity prior to intentional release to manifest in developmental irregularities and potentially influence rates of straying by adults. We compared two proxies for stress between groups of hatchery-produced individuals that had homed back to the hatchery or strayed to non-natal streams compared to wild individuals that were presumed to have homed to a wild spawning stream. Blood plasma cortisol was used to assess stress at the terminus of their migration, and percent frequency of vateritic otolith development within groups as a measure of stresses incurred during development. We found no evidence that either proxy for stress was associated with straying. No differences in cortisol concentrations were found between wild and hatchery-produced chum salmon that had homed or strayed, either in males (wild=95.9±175.7 ng/ml; stray=113.4±99.7 ng/ml; home=124.7±113.8 ng/ml) or females (wild=307.6±83.4 ng/ml; stray= 329.0±208.9 ng/ml; home=294.1±134.8 ng/ml); however, significant differences between males and females occurred in each group. The percent frequency of vaterite occurrence in otoliths of hatchery-produced chum salmon that either strayed (40% vaterite) or homed (45% vaterite) did not differ significantly, though rates of vaterite occurred less frequently in wild chum salmon (24%), which is consistent with other studies. Mass thermal marking of juvenile fish in hatcheries is unlikely to increase vateritic development as neither intensity (number of temperature changes) or complexity (number of temperature change sequences) of the mark was associated with frequency of vaterite occurrence. Though not associated with straying, cortisol concentrations were associated with shorter instream lifespan of both hatchery and wild individuals but did not appear to influence rates of egg retention in spawning females, suggesting an equivocal role in reproductive ecology. Our results are suggestive that stress induced during the early stages of rearing in a hatchery environment from marking or other causes may not increase straying later in life, though the higher rates of vaterite observed in hatchery-produced fish may come at a cost of increased marine mortality, due to the otoliths' role in navigation and hearing.

Density and body size of wild chum salmon Oncorhynchus keta fry in the lower reaches of a small stream on the Sanriku coast, northern Honshu, Japan

Density and body size of wild chum salmon <i>Oncorhynchus keta</i> fry in the lower reaches of a small stream on the Sanriku coast, northern Honshu, Japan

Differences in fitness-associated traits between hatchery and wild chum salmon despite long-term immigration by strays

Differences in fitness-associated traits between hatchery and wild chum salmon despite long-term immigration by strays

Epizootiology of the ectoparasitic protozoans Ichthyobodo salmonis and Trichodina truttae on wild chum salmon Oncorhynchus keta.

Infestations of the ectoparasitic flagellate Ichthyobodo salmonis and the ciliate Trichodina truttae have caused acute mortalities of hatchery-reared juvenile chum salmon Oncorhynchus keta in Hokkaido, northern Japan. This study examined the epizootiology of I. salmonis and T. truttae on wild chum salmon as a possible infection source of the 2 parasitic protozoans in hatcheries. Infestations by both ectoparasites were detected on freshwater-adapted adult and juvenile chum salmon in all 4 rivers examined. This is the first study of an anadromous Pacific salmonid to report infestation of I. salmonis and T. truttae in adults returning for spawning. Among the marine-inhabiting phase of chum salmon, infestation with I. salmonis, but not T. truttae, was observed on adults and juveniles. The 2 protozoans were experimentally transmitted at the same time from wild to hatchery-reared chum salmon juveniles, and caused a high rate of mortality in the hatchery fish. In freshwater, the proliferation rate of T. truttae was greater than that of I. salmonis. These observations show that the euryhaline ectoparasite I. salmonis can infest chum salmon throughout their life cycle, in both river and ocean habitats, whereas T. truttae is able to infest these salmonids only in freshwater. Furthermore, wild chum salmon were shown to be a potential infestation source for both T. truttae and I. salmonis in hatchery fish.

Структура возврата, численность и биологические характеристики заводской и дикой кеты в бассейне реки Паратунки (юго-восточная Камчатка) в 2010-2015 гг.

Структура возврата, численность и биологические характеристики заводской и дикой кеты в бассейне реки Паратунки (юго-восточная Камчатка) в 2010-2015 гг.

The Kuril Islands as a potential region for aquaculture: Trace elements in chum salmon

The Kuril Islands region is considered promising for development of salmon aquaculture. There are 41 salmon fish hatcheries in the Sakhalin Island and the Kuril Islands, 34 of them are hatcheries of the chum. Therefore, concentrations of six elements (Zn, Cu, Cd, Pb, As, and Hg) were determined in chum salmon were caught in this region. The contents of toxic elements (Cd, Pb, As, and Hg) don't exceed their maximum permissible concentrations (MPC) according to the Russian sanitary standards, but concentration of Pb are closely to MPC. Increased concentrations of Pb in wild chum have the natural origin. The unusual conditions of the Western Pacific are formed under the influence such factors as volcanism and upwelling.

Regional-Scale Declines in Productivity of Pink and Chum Salmon Stocks in Western North America.

Sockeye salmon (Oncorhynchus nerka) stocks throughout the southern part of their North American range have experienced declines in productivity over the past two decades. In this study, we tested the hypothesis that pink (O. gorbuscha) and chum (O. keta) salmon stocks have also experienced recent declines in productivity by investigating temporal and spatial trends in productivity of 99 wild North American pink and chum salmon stocks. We used a combination of population dynamics and time series models to quantify individual stock trends as well as common temporal trends in pink and chum salmon productivity across local, regional, and continental spatial scales. Our results indicated widespread declines in productivity of wild chum salmon stocks throughout Washington (WA) and British Columbia (BC) with 81% of stocks showing recent declines in productivity, although the exact form of the trends varied among regions. For pink salmon, the majority of stocks in WA and BC (65%) did not have strong temporal trends in productivity; however, all stocks that did have trends in productivity showed declining productivity since at least brood year 1996. We found weaker evidence of widespread declines in productivity for Alaska pink and chum salmon, with some regions and stocks showing declines in productivity (e.g., Kodiak chum salmon stocks) and others showing increases (e.g., Alaska Peninsula pink salmon stocks). We also found strong positive covariation between stock productivity series at the regional spatial scale for both pink and chum salmon, along with evidence that this regional-scale positive covariation has become stronger since the early 1990s in WA and BC. In general, our results suggest that common processes operating at the regional or multi-regional spatial scales drive productivity of pink and chum salmon stocks in western North America and that the effects of these process on productivity may change over time.

Space–time cluster analysis of sea lice infestation (Caligus clemensi and Lepeophtheirus salmonis) on wild juvenile Pacific salmon in the Broughton Archipelago of Canada

Sea lice infestation levels on wild chum and pink salmon in the Broughton Archipelago region are known to vary spatially and temporally; however, the locations of areas associated with a high infestation level had not been investigated yet. In the present study, the multivariate spatial scan statistic based on a Poisson model was used to assess spatial clustering of elevated sea lice (Caligus clemensi and Lepeophtheirus salmonis) infestation levels on wild chum and pink salmon sampled between March and July of 2004 to 2012 in the Broughton Archipelago and Knight Inlet regions of British Columbia, Canada. Three covariates, seine type (beach and purse seining), fish size, and year effect, were used to provide adjustment within the analyses. The analyses were carried out across the five months/datasets and between two fish species to assess the consistency of the identified clusters. Sea lice stages were explored separately for the early life stages (non-motile) and the late life stages of sea lice (motile). Spatial patterns in fish migration were also explored using monthly plots showing the average number of each fish species captured per sampling site. The results revealed three clusters for non-motile C. clemensi, two clusters for non-motile L. salmonis, and one cluster for the motile stage in each of the sea lice species. In general, the location and timing of clusters detected for both fish species were similar. Early in the season, the clusters of elevated sea lice infestation levels on wild fish are detected in areas closer to the rivers, with decreasing relative risks as the season progresses. Clusters were detected further from the estuaries later in the season, accompanied by increasing relative risks. In addition, the plots for fish migration exhibit similar patterns for both fish species in that, as expected, the juveniles move from the rivers toward the open ocean as the season progresses The identification of space–time clustering of infestation on wild fish from this study can help in targeting investigations of factors associated with these infestations and thereby support the development of more effective sea lice control measures.

Effects of hatchery chum salmon fry on density-dependent intra- and interspecific competition between wild chum and masu salmon fry

Stocking with hatchery fish is the principal method for harvest augmentation and, recently, restoring endangered populations. However, there is increasing concern about the negative effects of competition between hatchery and wild fish. In this study, enclosure experiments were conducted to evaluate the effects of hatchery chum salmon fry (Oncorhynchus keta) on wild masu (Oncorhynchus masou) and chum salmon fry through density-dependent competition. For masu and chum salmon, density-dependent performance (foraging rate and growth) varied depending on the presence or absence of competitor species. The negative effects on the foraging rate (evaluated by stomach content mass) and growth of wild masu salmon caused by wild conspecifics were greater than those exerted by wild and hatchery chum salmon. Wild chum salmon decreased foraging rate with increasing density of conspecifics and masu salmon and also in the presence of hatchery chum salmon. Although we could not evaluate growth under interspecific competition, wild chum salmon show body mass loss in the presence of hatchery chum salmon. These results suggest that the effects of stocking with hatchery chum salmon vary depending on the interacting species.

The Early Marine Biology of the Hatchery/Wild Juvenile Salmonid (Oncorhynchus sp.) Community in Barkley Sound, Canada

We conducted 11 purse seine/beachseine surveys over the summers of 2000 and 2001 to learn about the migration timing, distribution, and diet of hatchery chinook (Oncorhynchus tshawytscha) and coho (O. kisutch), and wild chinook, coho, sockeye (O. nerka) and chum (O. keta) juvenile salmon, in Barkley Sound, West Coast Vancouver Island. Juvenile salmon partitioned Barkley Sound by time and space, and by diet except for hatchery and wild coho. The analysis of migration timing included historic data for 1987-89, and results showed that timing differed between species and was consistent over years. Sockeye and chum dominated the juvenile salmon community until mid-June and hatchery and wild chinook dominated subsequently. Fish tended to be dispersed contagiously. Results of correlation analyses of catch suggested that fish of different origins and species did not co-occur. The euphausiid Thysanoessa spinifera was an important prey item but different fish species selected different sizes of T. spinifera at different times. The diet overlap between hatchery and wild coho did not affect return. Migration timing for sockeye and wild coho seems to reflect a strategy to enter the ocean when the biomass of the size fraction of T. spinifera that each species selects is likely to be maximal. Descriptions of migration timing, fish interactions, and diet provide information which appears to be useful for learning about the biological basis of salmon return variability.

人工ふ化放流河川におけるサケの成熟年齢・サイズの野生魚&amp;mdash;放流魚間比較

人工ふ化放流河川におけるサケの成熟年齢・サイズの野生魚&amp;mdash;放流魚間比較

Wild and hatchery reproduction of pink and chum salmon and their catches in the Sakhalin-Kuril region, Russia

In the Sakhalin-Kuril region hatchery culture of pink and chum salmon is of great importance compared to other regions of the Russian Far East. During the last 30 years the number of hatcheries increased two-fold, and significant advances were made in hatchery technologies. As a result, chum salmon capture in regions where hatcheries operate (southwestern and eastern Sakhalin coasts, and Iturup Island) was 9 times as high during 2006–2010 than during 1986–1990, whereas wild chum salmon harvest markedly declined. Recent dynamics in pink salmon catch appear to track trends in natural spawning in monitored index rivers, suggesting natural-origin pink salmon play a dominant role in supporting the commercial fishery. It remains uncertain as to whether hatcheries have substantially supplemented commercial catch of pink salmon in this region, and I recommend continued research (including implementing mass marking and recovery programs) before decisions are made regarding increasing pink salmon hatchery production. Location of hatcheries in spawning river basins poses problems for structuring a management system that treats hatchery and wild populations separately. Debate continues regarding the existence and importance of density-dependent processes operating in the ocean environment and the role hatcheries play in these processes. Loss of critical spawning habitat for chum salmon in the Sakhalin-Kuril region has lead to significant declines in their abundance. I conclude by recommending increases in releases of hatchery chum salmon numbers in the region to help recover depressed wild populations and provide greater commercial fishing benefits in the region.

Lack of trophic competition among wild and hatchery juvenile chum salmon during early marine residence in Taku Inlet, Southeast Alaska

Early marine trophic interactions of wild and hatchery chum salmon (Oncorhynchus keta) were examined as a potential cause for the decline in harvests of adult wild chum salmon in Taku Inlet, Southeast Alaska. In 2004 and 2005, outmigrating juvenile chum salmon were sampled in nearshore habitats of the inlet (spring) and in epipelagic habitat at Icy Strait (summer) as they approached the Gulf of Alaska. Fish were frozen for energy density determination or preserved for diet analyses, and hatchery stocks were identified from the presence of thermal marks on otoliths. We compared feeding intensity, diets, energy density, and size relationships of wild and hatchery stocks (n = 3123) across locations and weeks. Only hatchery fish feeding intensity was negatively correlated with fish abundance. In both years, hatchery chum salmon were initially larger and had greater energy density than wild fish, but lost condition in early weeks after release as they adapted to feeding on wild prey assemblages. Diets differed between the stocks at all inlet locations, but did not differ for hatchery salmon between littoral and neritic habitats in the outer inlet, where the stocks overlapped most. Both diets and energy density converged by late June. Therefore, if density-dependent interactions affect wild chum salmon, these effects must be very rapid because survivors in Icy Strait showed few differences. Our study also demonstrates that hatchery release strategies used near Taku Inlet successfully promote early spatial segregation and prey partitioning, which reduce the probability of competition between wild and hatchery chum salmon stocks.

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.

Magnitude and Trends in Abundance of Hatchery and Wild Pink Salmon, Chum Salmon, and Sockeye Salmon in the North Pacific Ocean

AbstractAbundance estimates of wild and hatchery Pacific salmon Oncorhynchus spp. are important for evaluation of stock status and density‐dependent interactions at sea. We assembled available salmon catch and spawning abundance data for both Asia and North America and reconstructed total abundances of pink salmon O. gorbuscha, chum salmon O. keta, and sockeye salmon O. nerka during 1952–2005. Abundance trends were evaluated with respect to species, regional stock groups, and climatic regimes. Wild adult pink salmon were the most numerous salmon species (average = 268 × 106 fish/year, or 70% of the total abundance of the three species), followed by sockeye salmon (63 × 106 fish/year, or 17%) and chum salmon (48 × 106 fish/year, or 13%). After the 1976–1977 ocean regime shift, abundances of wild pink salmon and sockeye salmon increased by more than 65% on average, whereas abundance of wild chum salmon was lower in recent decades. Although wild salmon abundances in most regions of North America increased in the late 1970s, abundances in Asia typically did not increase until the 1990s. Annual releases of juvenile salmon from hatcheries increased rapidly during the 1970s and 1980s and reached approximately 4.5 × 109 juveniles/year during the 1990s and early 2000s. During 1990–2005, annual production of hatchery‐origin adult salmon averaged 78 × 106 chum salmon, 54 × 106 pink salmon, and 3.2 × 106 sockeye salmon, or approximately 62, 13, and 4%, respectively, of the combined total wild and hatchery salmon abundance. The combined abundance of adult wild and hatchery salmon during 1990–2005 averaged 634 × 106 salmon/year (498 × 106 wild salmon/year), or approximately twice as many as during 1952–1975. The large and increasing abundances of hatchery salmon have important management implications in terms of density‐dependent processes and conservation of wild salmon populations; management agencies should improve estimates of hatchery salmon abundance in harvests and on the spawning grounds.

Real-time PCR for quantification of viable Renibacterium salmoninarum in chum salmon Oncorhynchus keta

Quantification of msa gene mRNA of Renibacterium salmoninarum, the causative agent of bacterial kidney disease (BKD), was investigated using reverse transcription followed by real-time PCR assay on R. salmoninarum in culture, and in experimentally challenged chum salmon Oncorhynchus keta fry kidney tissues (total of 70 samples) after intraperitoneal (i.p.) injection and bath infection. Correlations of msa gene mRNA concentrations with culturable cell concentrations (as colony forming units [CFU]), determined by drop-plate culture method on selective kidney disease medium (SKDM) agar through a 12 wk incubation time, and msa gene DNA concentrations by real-time PCR assay were examined. Furthermore, ovarian fluid samples from wild chum salmon adults with no clinical signs of disease were collected from 8 rivers and from clinically infected kokanee 0. nerka and masu salmon O. masou that were reared in 1 and 2 hatcheries, respectively (total of 414 samples). All samples were examined by nested PCR assay. Then, positive samples were examined by real-time PCR assays for mRNA and DNA; mRNA was detectable at 8 log units (5.0 x 101 to 5.0 x 10(9) copies p11(-1)) with high correlation (R2 = 0.999). The mRNA concentration correlated with CFU in kidney tissue from fish infected by i.p. injection (R2 = 0.924), by bath infection (R2 = 0.502) and in culture (R2 = 0.888). R. salmoninarum was detected and quantified by real-time PCR assay for mRNA in ovarian fluid samples in both subclinically infected chum salmon adults and clinically infected kokanee and masu salmon adults; detection rates ranged from 0 to 44.4% and concentrations ranged from 9.7 x 10(2) to 5.6 x 10(5) copies pl(-1). These results indicate that real-time PCR assay for the mRNA is a rapid, sensitive and reliable method to detect and quantify the viability of R. salmoninarum in kidney and ovarian fluid samples of salmonid fishes with both clinical and subclinical infection of the pathogen.

Diel Spawning Behavior of Chum Salmon in the Columbia River

AbstractWe conducted a study during 2003 in a side channel of the Columbia River downstream of Bonneville Dam to describe the diel spawning behavior of wild chum salmon Oncorhynchus keta. We collected observational data on 14 pairs of chum salmon using a dual‐frequency identification sonar. Spawners of both genders were observed chasing intruders during nighttime and daytime as nests were constructed. Regardless of diel period, females were engaged in digging to both construct nests and cover eggs, and courting males exhibited the prespawning behavior of tail‐crossing. We observed a total of 13 spawning events, of which 9 occurred at night and 4 occurred during the day. Once chum salmon begin nest construction, visual cues are apparently not required for courtship, nest defense, and spawning. To enhance successful spawning, flows from Bonneville Dam during the spawning season were reduced during the day but were sometimes increased at night to pass water and meet power demand (i.e., reverse loading), the assumption being that chum salmon are inactive at night. Our findings show that this assumption was violated. Therefore, reverse loading may disrupt the complex prespawning behavior that occurs both during the day and at night, as well as attract spawners to areas that were dewatered during the day.