Chum Salmon Fry Research Articles

Scenario analysis of the effects of the Great East Japan Earthquake on the chum salmon population-enhancement system

The Great East Japan Earthquake may have resulted in increased mortality of artificially propagated chum salmon fry (2010 year class) from Iwate Prefecture (CSI), both in the hatchery and after release. Individuals from the 2010 year class will return in 2014–2015. To evaluate the potential for future issues associated with the effects of the earthquake, we simulated CSI population dynamics using a model that incorporated stratified earthquake-influenced survival rates λ l (l = 0.00−1.00 at intervals of 0.25) under various scenarios. Under laissez-faire scenarios (median exploitation rate E Med) under low post-release survival rate S Low and all λ l , the median number of hatchery-released fry $$H^{\prime }_{t}$$ did not reach the target H * in 2014 and 2015. The probability P j,t of not meeting the targets was 0.56−1.00 (2014) and 0.79−1.00 (2015). Meanwhile, with simulation of a low exploitation rate, S Low, and a higher λ l (0.50), the P j,t in 2014 and 2015 was 0.00−0.17 and 0.21−0.72, respectively. Under S Med and S High, $$H^{\prime }_{t}$$ reached H * at λ l (>0.50) regardless of E l , and the cumulative catch varied primarily with S l . Our results suggest that simulations can provide a method of predicting potential issues and can offer insight into strategies to minimize future problems.

サケ稚魚の脊椎骨数における地域差

サケ稚魚の脊椎骨数における地域差

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.

Microscale Environments along the Seaward Migration Route of Stocked Chum Salmon Fry

AbstractThe microscale environment (e.g., current velocity) along the migratory route of aquatic organisms may directly affect their performance (e.g., migration speed or survival). We used minnow traps to evaluate how stocked Chum Salmon Oncorhynchus keta fry use stream velocity to optimize seaward migration. We found that fry were primarily captured at night and the number of fry collected was higher in traps with faster velocity water at the entrance to the trap. We interpreted this to mean that the fry were optimizing their migration efficiency by using faster velocity areas, which promote more rapid downstream migration.

The Effects of Total Dissolved Gas on Chum Salmon Fry Survival, Growth, Gas Bubble Disease, and Seawater Tolerance

AbstractChum Salmon Oncorhynchus keta alevins developing in gravel downstream of Bonneville Dam on the Columbia River are exposed to elevated total dissolved gas (TDG) when water is spilled to move migrating salmon smolts to the ocean. We studied whether alevins that were exposed to six levels of dissolved gas ranging from 100% to 130% TDG at three development periods between hatch and emergence (hereafter, early, middle, and late stages) experienced differential mortality, growth, gas bubble disease, or seawater tolerance. Each life stage was exposed for 49 d (early stage), 28 d (middle stage), or 15 d (late stage) beginning at 13, 34, and 47 d posthatch, respectively, through emergence. Mortality for all stages was estimated to be 8% (95% confidence interval [CI] = 4–12%) when dissolved gas levels were less than 117% TDG. Mortality increased as dissolved gas levels rose above 117% TDG; the lethal concentration producing 50% mortality was 128.7% TDG (95% CI = 127.2–130.3% TDG) in the early and middle stages. There was no evidence that gas exposure affected growth. The proportion of fish with gas bubble disease increased with increasing gas concentrations, and bubbles occurred most commonly in the nares and gastrointestinal tract. Early stage fish exhibited higher ratios of filamental to lamellar gill chloride cells than late‐stage fish, and these ratios increased and decreased for early and late‐stage fish, respectively, as gas levels increased; however, there were no significant differences in mortality between life stages after 96 h in seawater. The study results suggest that water quality guidelines for dissolved gas (≤105% TDG) offer a conservative level of protection to Chum Salmon alevins incubating in gravel habitat downstream of Bonneville Dam.Received June 1, 2012; accepted November 13, 2012

Relationship Between Rearing Conditions and Health in Chum Salmon (Oncorhynchus keta) Fry

Relationship Between Rearing Conditions and Health in Chum Salmon (Oncorhynchus keta) Fry

Effects of Starvation on the Morphometric Characteristics and Histological Changes in Chum Salmon (Oncorhynchus keta) Fry

A 26 day experiment was conducted to determine the effects of feeding and starvation on the survival, morphology, and histology in chum salmon (Oncorhynchus keta) fry. We included three experimental groups: starved, fed, and initial. The survival and growth rates were lower in the starved group than in the fed group (P < 0.05). In the starved group, survival began to decline after 16 days, and all fish had died after 26 days. We determined the effects of starvation on the morphometric parameters using the truss and classical dimensions. The dimensions in the head region were larger in the starved group than in the initial and fed groups. In contrast, the truss dimensions of the fed group were larger than those of the initial and starved groups. Starvation reduced the heights of the hepatocyte nuclei and of the intestinal epithelium (P < 0.05). The starved group also showed atrophy of the digestive structures and shrinkage of the foregut and midgut. Starvation led to the degeneration and atrophy of the exocrine pancreas, in which the lumen was markedly diminished and the folds of mucosa were less apparent. The hepatocyte morphology in the starved group was abnormal compared with that of the initial and fed groups, with highly compact, irregularly shrunken nuclei. Melanomacrophages were randomly distributed in the kidneys of the starved group, and their abundance increased rapidly during the experiment. In contrast, neither the initial nor fed group had any melanomacrophages. These results suggest that the nutritional parameters used in this study are useful indices of nutritional status in chum salmon.

Chum salmon fry grow faster in seawater, exhibit greater activity of the GH/IGF axis, higher Na+, K+-ATPase activity, and greater gill chloride cell development

Chum salmon (Oncorhynchus keta) fry were reared in freshwater (FW), mimicking the hatchery enhancement program, and in seawater (SW) to determine the effect on growth. The fry groups in SW showed exponential growth, whereas those in FW grew in a linear manner in two experiments over 49 and 70days. Fry adapted to SW for 49days survived well after returning to FW for 7days. Gill Na+, K+-ATPase activity in the SW group was higher than that of the FW group. The chloride cells in gill filaments increased in number and developed larger in size in SW fry. Pituitary growth hormone (GH) mRNA levels increased 14days after transfer to SW. The mRNA levels of GH receptor (GHR) and insulin-like growth factor I (IGF-I) in the liver and gill increased in the fry reared in SW.

Inflexibility of vertebral number in chum salmon Oncorhynchus keta

Chum salmon Oncorhynchus keta eggs from the Chitose and Shiriuchi rivers in Hokkaido, northern Japan, were incubated under identical conditions with the aim of comparing vertebral number (VN) to that reported archived data from the 1950s. The comparison revealed that mean VN of salmon from the Shiriuchi River has remained unchanged for 50 years and is higher than that from the Chitose River. The VN in the Chitose River salmon was found to be significantly higher than that recorded in the archival data. The variation in the mean VN of chum salmon fry collected during different seasons and years in the Chitose River falls within a range that has remained constant, suggesting that the difference between the values obtained in our study and the archival data may be due to differences in the timing of egg collection. These results indicate that the mean VN of chum salmon has been stable for a long period. Incubation experiments under identical conditions are a useful tool for examining changes in genetic structure and detecting the essential properties of populations.

Juvenile Salmonid Use of Reconnected Tidal Freshwater Wetlands in Grays River, Lower Columbia River Basin

AbstractDegraded wetland systems with impaired hydraulic connections have resulted in diminished habitat opportunity for salmonid fishes and other native flora and fauna in the Pacific Northwest. Many of these lost habitats were once intertidal freshwater marshes and swamps. Restoration of these systems is effected in part by reestablishing tidal processes that promote connectivity, with a central goal of restoring rearing habitat for juvenile Pacific salmon Oncorhynchus spp. In the Grays River tidal freshwater system of Washington, we measured hydrologic changes that resulted from the removal of tide gates from diked pastureland and we determined the subsequent time series of salmonid abundance and size frequency in the restoring marshes. Dike breaching caused an immediate return of full semidiurnal tidal fluctuations to the pasturelands. Juvenile Pacific salmonids quickly expanded into this newly available habitat and used prey items that were presumably produced within the marshes. Habitat use varied by species and life history stage. Fry of chum salmon O. keta migrated rapidly through the system, whereas populations of Chinook salmon O. tshawytscha and coho salmon O. kisutch resided from March to at least July and were composed of fry, fingerlings, and (for coho salmon) yearlings. Based on salmon size at date and the timing of hatchery releases, we concluded that most salmon sampled in restored and reference sites were the progeny of natural spawners. However, the presence of adipose‐fin‐clipped Chinook salmon indicated that hatchery‐raised fish originating outside the Grays River system also used the restoring wetland habitat. Because of extensive mixing of stocks through hatchery practices, genetic analyses did not provide additional insight into the origins of the Chinook salmon but did reveal that out‐migrating juveniles were an admixed population composed of lower Columbia River ancestry and nonindigenous Rogue River stock. Restoration of tidal wetlands in the Columbia River estuary will improve overall ecosystem connectivity and reduce habitat fragmentation and may therefore increase survival of a variety of Pacific salmon stocks during migration.

Reciprocal Subsidies and Food Web Pathways Leading to Chum Salmon Fry in a Temperate Marine-Terrestrial Ecotone

Stable isotope analysis was used to determine the relative proportions of terrestrial and marine subsidies of carbon to invertebrates along a tidal gradient (low-intertidal, mid-intertidal, high-intertidal, supralittoral) and to determine the relative importance of terrestrial carbon in food web pathways leading to chum salmon fry Oncorhynchus keta (Walbaum) in Howe Sound, British Columbia. We found a clear gradient in the proportion of terrestrially derived carbon along the tidal gradient ranging from 68% across all invertebrate taxa in the supralittoral to 25% in the high-intertidal, 20% in the mid-intertidal, and 12% in the low-intertidal. Stable isotope values of chum salmon fry indicated carbon contributions from both terrestrial and marine sources, with terrestrially derived carbon ranging from 12.8 to 61.5% in the muscle tissue of chum salmon fry (mean 30%). Our results provide evidence for reciprocal subsidies of marine and terrestrially derived carbon on beaches in the estuary and suggest that the vegetated supralittoral is an important trophic link in supplying terrestrial carbon to nearshore food webs.

Food spectra of the farm juveniles of the Chum Salmon Oncorhynchus keta (Salmoniformes, Salmonidae) in the Ryazanovka River (Southern Primor’e)

Qualitative data are presented on the diet of juvenile chum salmon Oncorhynchus keta released from the Ryazanovka experimental fish hatchery farm situated in the south of Primor’e Territory. The stomach fullness, frequency of occurrence of food items, their average weight value, and selectivity are estimated. Food spectra of chum salmon juveniles during downstream migration comprised representatives of 51 taxa of bottom freshwater invertebrates and terrestrial insects. The bulk of the diet consisted of larvae of aquatic insects—chironomids, other Diptera, and mayflies. Their diversity increased with the growth of fry. Fry of chum salmon had a wide spectrum of feeding preference, favorite food items were larvae and pupae of chironomids.

Variable Effects of Biological and Environmental Processes on Coho Salmon Marine Survival in Southeast Alaska

AbstractCorrelation analyses, linear regression models, and multistock mixed effects models were used to examine the relationships between coho salmon Oncorhynchus kisutch marine survival and six biological and environmental covariates across 14 southeast Alaska (SEAK) stocks. A primary focus of the study was to investigate the influence of pink salmon O. gorbuscha and chum salmon O. keta fry abundances on coho salmon marine survival. The coho salmon stocks exhibited strong covariation; 88 of the 91 pairwise comparisons among the coho salmon stocks covaried positively and 54 of them were significant (P &lt; 0.05). Only one of the covariates, the North Pacific index, which is a measure of the Aleutian low pressure zone, had consistent relationships (positive) across all 14 stocks. The other covariates, including freshwater discharge, the Pacific decadal oscillation, sea‐surface temperature, and two indices of pink salmon and chum salmon fry abundances, all had inconsistent relationships with marine survival. The best‐fit linear regression models varied greatly among the 14 stocks, as did the R2 values, which ranged from 0.00 to 0.54. An index representing local hatchery pink salmon and chum salmon fry abundance was the most important variable in explaining the variation in marine survival, having a stronger estimated effect on survival than an index of local wild pink salmon fry abundance. The magnitude and sign of the hatchery pink salmon and chum salmon effect varied greatly among different localities. Our results suggest that (1) SEAK coho salmon stocks are not equally influenced by the same factors and (2) there are factors that appear to affect marine survival of SEAK coho salmon stocks at varying spatial scales. This study also provides evidence that coho salmon stocks throughout SEAK experience some degree of regional concordance in the marine environment but also that local stock‐specific conditions are important in fully understanding variation in marine survival.

Changing expression patterns: focus on “The transcription factor, glial cell missing 2, is involved in differentiation and functional regulation of H+-ATPase-rich cells in zebrafish (Danio rerio)”

euryhaline species of fish have a remarkable osmo- and ionoregulatory capacity. Some euryhaline species like the Mozambique tilapia can directly be transferred from freshwater to seawater and vice versa, i.e., osmolarity of the external fluid changes by ∼1,000 mOsm. Many others can tolerate this

Presence of Homologous DNAs to M Gene RNA of Infectious Hematopoietic Necrosis Virus in Chum Salmon Oncorhynchus keta

Homologous DNAs (M DNA) to the infectious hematopoietic necrosis virus (IHNV) M gene were detected in river-homing chum salmon Oncorhynchus keta sperm, eyed-egg embryos, alevins and fry collected from nine rivers and four hatcheries in Hokkaido Prefecture, Japan, in 1998-2002, although no virus titer was observed in the samples. Real-time PCR assay revealed M DNA at the highest number of 1.7 × 104 copies/mg of tissue. Nucleotide sequence similarities between the M DNA and the viral M genes were ≥97%. When CHSE-214 and RTG-2 cells were inoculated with IHNV, the cells contained 3.8 × 101 to 1.8 × 103 copies of M DNA/105 cells and showed cytopathic effects (CPE). Salmonid fish fry and yearlings infected with the virus contained 1.3 × 101 to 2.6 × 103 copies of M DNA/mg of tissue. CHSE-214 cells transfected with the viral RNA produced M DNA without showing CPE. Reverse transcriptase (RTase) activities in the fish cells and the fish tissues were equivalent to 86-578 pg HIV-1 RTase/106 cells and 2.1-12 pg HIV-1 RTase/mg of tissue, respectively. These results suggest that M DNA is produced from IHNV RNA and retained in the fish.

Central administration of growth hormone-releasing hormone triggers downstream movement and schooling behavior of chum salmon ( Oncorhynchus keta) fry in an artificial stream

Anadromous salmonids migrate downstream to the ocean (downstream migration). The neuroendocrine mechanism of triggering the onset of downstream migration is not well known. We investigated the effects of 14 chemicals, including neuropeptides, pineal hormones, neurotransmitters, and neuromodulators (growth hormone-releasing hormone: GHRH, thyrotropin-releasing hormone, corticotropin-releasing hormone: CRH, gonadotropin-releasing hormone, melatonin, N-acetyl serotonin, serotonin, β-endorphin, enkephalin, dopamine, norepinephrine, epinephrine, acetylcholine, and histamine) on the onset of downstream migration in chum salmon ( Oncorhynchus keta) fry. We defined downstream migration as a downstream movement (negative rheotaxis) with schooling behavior and counted the number of downstream movements and school size in experimental circulation tanks. An intracerebroventricular injection of GHRH, CRH, melatonin, N-acetyl serotonin, or serotonin stimulated the number of downstream movements. However, GHRH was the only chemical that also stimulated an increase in schooling behavior. These results suggest that CRH, melatonin, N-acetyl serotonin, and serotonin are involved in the stimulation of downstream movement in chum salmon, while GHRH stimulates both downstream movement and schooling behavior.

The relationship between thyroxine surge and onset of downstream migration in chum salmon Oncorhynchus keta fry

Downstream migration in chum salmon fry was initiated soon after the gate of a hatchery raceway was opened. The relationship between the onset of downstream movement and thyroxine (T4) surge was investigated. In experiment 1, the gates of the raceways were opened at 0930 in March and April, and l–3 million fry were discharged to a creek pool through a drain channel. The fish were sampled in the raceway (initial), the pool (staying: preparing for migration), and a lower creek (migrating). Peaks of the number of the fry migrating from the pool to the creek and T4 surge appeared 1 h and 4.5–7 h, respectively after the gates were opened. In experiment 2, treatments with fall stress from l-m high buckets, turbid water (200 mg/l), and exogenous T4 (1 mg/g diet) were conducted in the raceway to examine the effects on downstream locomotion and plasma T4 concentrations. Fall stress did not induce an increase in either plasma T4 concentration or the number of migrants, whereas turbid-water treatment induced 10 ng/ml T4 increase and a greater downstream locomotion than the other treatments. T4 treatment induced a continuous high level in plasma T4 but had less effect on locomotion. These results suggest that although thyroid hormones play a pivotal role in the preparation for downstream migration, they are not the sole factors responsible for the onset of their downstream migration.

Efficacy of green tea extract on removal of the ectoparasitic flagellate Ichthyobodo necator from chum salmon, Oncorhynchus keta, and masu salmon, O. masou

The efficacy of green tea extract (GTE) on removal of the ectoparasitic flagellate Ichthyobodo necator (Henneguy, 1883) from the fins and skin surface of infected chum salmon, Oncorhynchus keta, and masu salmon, O. masou, fry is reported. Immersion of infected fry (body weight 0.2–0.9 g) in 0.03% GTE for 30–60 min or 0.3–0.9% GTE for 1–5 min resulted in a decrease of 87.6–100% in chum salmon and 86.5–99.6% in masu salmon in the number of parasites on the dorsal and anal fins in comparison to untreated controls (statistically significant, p < 0.01). Scanning electron microscopy showed no parasite present on the skin surface of infected chum salmon fry after a 1 min bath in 0.9% GTE. To clarify the contribution of (−)-epigallocatechin gallate (EGCg), which comprises 14% of GTE, to the efficacy, a 60-min bath with 0.0042% EGCg, equivalent to 0.03% GTE, and a 5-min bath with 0.126% EGCg, equivalent to 0.9% GTE, was evaluated; the number of parasites on the fins decreased 78.3% and 83.5%, respectively. Neither the long (0.03% GTE for 60 min) or short bath treatments (0.3% GTE for 15 min, 0.6–0.9% GTE for 5 min, or 2.7% GTE for 3 min) resulted in any mortality in normal (parasite-free) alevin and fry (0.4–0.7 g) of either species, indicating the safety of the treatments. Moreover, seawater challenge tests of chum salmon fry indicated that the treatments had no effect on the seawater adaptability of normal fish and restored seawater adaptability to infected fish by removing the parasite. Large-scale application of the treatments to approximately 900,000 chum salmon fry (0.4–0.6 g) infected with the parasite in two hatcheries showed that baths in 0.03% GTE for 30 min or 0.6% GTE for 2.5 min resulted in statistically significant decreases of 76.2–90.7% or 98.8–99.4%, respectively ( p < 0.01), in the number of the parasites on the skin surface and fins in comparison to untreated controls. Cumulative mortalities for 48 h after the treatments were 0.08–0.14%. From our results, we conclude that treatment of I. necator-infected salmonids with GTE is safe, efficacious, and applicable to treatment of large numbers of fish in hatcheries, and that one of the efficacious constituents is EGCg.

A Classification of Habitat Types in a Large River and Their Use by Juvenile Salmonids

AbstractWe describe six habitat types for large rivers (&gt;100 m bank‐full width), including pools, riffles, and glides in midchannel and bank edges, bar edges, and backwaters along channel margins. Midchannel units were deeper and faster than edge units on average. Among edge habitat types, backwater units had the lowest velocities and contained complex cover consisting mainly of wood accumulations and aquatic plants. Banks and bars had similar velocity distributions, but banks had more complex cover such as rootwads and debris jams. Because sampling of juvenile salmonids was ineffective in the midchannel units (electrofishing capture efficiency was low, and the units were too deep and fast to snorkel), we focused our sampling efforts on juvenile salmonid use of edge habitats during winter, spring, and late summer. Densities of juvenile Chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch were highest in bank and backwater units in winter, whereas age‐0 and age‐1 or older steelhead densities were highest in bank units in winter. In summer, only coho salmon densities were significantly different among edge unit types, densities being highest in banks and backwaters. Microhabitat selection (velocity, depth, and cover type) by juvenile salmonids mirrored that in small streams, most fish occupying areas with a velocity less than 15 cm/s and wood cover. Among ocean‐type salmon, Chinook and chum salmon fry were captured in large numbers in all edge units and exhibited only slightly higher densities in low‐velocity areas (&lt;15 cm/s).

Stock Identification of Chum Salmon (Oncorhynchus keta) Using Trace Elements in Otoliths

The relationship between trace elements in chum salmon otoliths and in their rearing water was investigated to develop ways to distinguish chum salmon stocks in Korea. Rearing water and otoliths of hatchery-reared chum salmon fry were collected from three major hatcheries (Yangyang, Samchuk, and Uljin) on the east coast of Korea in spring 2001 and 2002. Trace elements in the otoliths and rearing water were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) at the Korea Basic Science Institute. The chemical composition of rearing water and otoliths of the salmon fry at specific sites did not vary significantly through the study period. The ratios of some trace elements to Ca in rearing water, such as Sr/Ca and Ba/Ca, was clearly reflected in the chemical composition of otoliths, although the absolute concentrations were different. These two elements may be useful in distinguishing between salmon hatcheries, which have different chemical environments. Discriminant analysis with the ratios of eight elements to Ca (Na/Ca, Mg/Ca, Al/Ca, Cu/Ca, Sr/Ca, Ba/ Ca, Mn/Ca, and Zn/Ca) revealed a distinct separation of natal area in stocks. The analysis of otolith chemistry may be an effective technique for identifying the origins of wild salmon caught at sea.