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.     

Genetic differentiation among chum salmon, Oncorhynchus keta (Walbaum), from Primorye and Sakhalin

Mitochondrial DNA (mtDNA) was examined in six wild populations of chum salmon ( Oncorhynchus keta Walbaum) distributed over the Primorye Region which extends approximately 1000 km along the Sea of Japan coast, and six populations from Sakhalin, using restriction enzyme analysis. By means of two restriction enzymes ( Bam HI and Eco 81I) eight mtDNA clonal lines were revealed in the 346 chum salmon studied. Mitochondrial DNA variants grouped the fish into two major clusters representing the Primorye and Sakhalin regions. Analysis of different chum salmon generations showed stability in the temporal population genetic structure in the three Primorye populations studied, but instability in the Sakhalin population of the Naiba River. We succeeded in detecting four major mtDNA clonal variants in Primorye chum salmon. The geographic distribution of clonal frequencies in Primorye populations has a clinal U-shape associated with the north-south axis of the Primorye region. On the whole, Sakhalin populations are less heterogeneous than Primorye ones. Two hatchery-seeded stocks from south west Sakhalin showed no mtDNA clonal variation.     

Carotenoids in fish. XIX. Carotenoids in the eggs of Oncorhynchus keta (Walbaum)

The author investigated the presence of various carotenoids in the eggs of Oncorhynchus keta by means of columnar and thin-layer chromatography. The investigations revealed the presence of the following carotenoids: canthaxanthin, lutein-epoxide, 4-hydroxy-4-keto-ß-carotene, tunaxanthin, astaxanthin ester and asterin acid. Astaxanthin ester comprised the greatest part, 67.8% of, all carotenoids.     

Introductions of distinct stocks of chum salmon, Oncorhynchus keta (Walbaum), into natural populations of the species

Populations of chum salmon, Oncorhynchus keta , are recognizable by the allelic frequencies of allozyme loci. Identification of these was used to assess the return of spawning adults to alien rivers into which they were introduced via hatchery-reared, artificially-fertilized eggs obtained from populations elsewhere in the Soviet Far East. Coefficients of return to spawn in the alien rivers were much lower than returns for the native fish, and in succeeding generations the alien fish disappeared from the spawning runs. It is concluded that transplanting salmonid eggs between populations is ineffective as a means of establishing new stock in territory already occupied by another stock, and the practice is deplored on grounds of conserving unique gene pools within species.     

Effect of hypo-osmotic environmental changes on the expression of gonadotropin-releasing hormone,its receptor,and gonadotropin hormone subunit mRNA in adult chum salmon (Oncorhynchus keta)

Migrating fish such as salmonids are affected by external environmental factors and salinity changes are particularly important, influencing spawning migration. The aim of this study was to test whether changes in salinity would affect the expression of the hypothalamic-pituitary-gonadal (HPG) axis hormones (gonadotropin-releasing hormones (GnRHs) [salmon GnRH and chicken GnRH-II], GnRH receptors [GnRHR1 and GnRHR5], and mRNA of the gonadotropin hormone [GTH] subunits [GTHα, follicle stimulating hormone β, and luteinizing hormone β]) in chum salmon (Oncorhynchus keta). Fish were progressively transferred from seawater (SW) through 50% SW to freshwater (FW), and the relationship between the osmoregulatory hormone prolactin (PRL) and sexual maturation was determined. The expression and activity of HPG hormones and their receptors, and levels of estradiol-17β and PRL increased after fish were transferred to FW, demonstrating that changes in salinity stimulate the HPG axis and PRL production in migrating chum salmon. These findings reveal details about the role of the endocrine system in maintaining homeostasis and stimulating sexual maturation and reproduction in response to salinity changes in this species.     

大麻哈鱼卵黄囊期仔鱼异速生长及其生态学意义

运用实验生态学的方法, 对大麻哈鱼(Oncorhynchus keta Walbaum)卵黄囊期仔鱼的异速生长及器官优先发育在早期生存和环境适应上的生态学意义进行了研究。结果表明, 大麻哈鱼卵黄囊期仔鱼的感觉、摄食, 呼吸和游泳等器官快速分化, 许多关键器官均存在异速生长现象。在身体各部分中, 头部和尾部为正异速生长, 躯干部为负异速生长, 体高有先增大后减小的趋势; 在头部器官中, 眼径、口宽、吻长和眼后头长均为正异速生长; 在游泳器官中, 胸鳍、腹鳍、背鳍、臀鳍、背鳍基、臀鳍基和尾鳍均为正异速生长, 脂鳍为负异速生长, 其中, 腹鳍在全长25.31 mm、12日龄出现生长拐点, 但拐点前后均为正异速生长。大麻哈鱼卵黄囊期仔鱼感觉、摄食, 呼吸和游泳等器官的快速发育, 使出膜后的仔鱼在最短的时间内获得了与早期生存密切相关的各种能力, 对适应复杂多变的外界环境具有重要的生态学意义。       

Embryonic origin and development of the corpuscles of Stannius in chum salmon (Oncorhynchus keta)

Summary An immunocytochemical technique was used to follow the embryological origin and development of the corpuscles of Stannius (CS) in the chum salmon, Oncorhynchus keta. Stanniocalcin immunoreactive (ir-) cells can be observed as early as 13 days before hatching. The ir-CS cells appear in clusters of variable size in close association with nephric ducts. In addition, individual ir-cells also occur at this stage amoung epithelial cells of the nephric ducts. these individual cells may give rise to clusters which subsequently increase in size, the largest reaching 100 m in diameter by the time of hatching. During this period, dispersed CS cells become evident and develop into secondary clusters in the vicinity of the primary clusters. These clusters appear to fuse to form larger clusters with a lobular structure. Transfer of the larvae (20 days after hatching) from fresh water to 50% seawater, accelerates the development of the CS tissue, suggesting an important role of the CS in seawater adaptation.     

Deterioration of chum salmon muscle during spawning migration--VI. Changes in serum protease inhibitory activity during spawning migration of chum salmon (oncorhynchus keta)

A relation between muscle protease activity and serum protease inhibitory activity of chum salmon during spawning migration was studied with regard to their physiological states. The autolytic activity of chum salmon muscle significantly increased, while the trypsin inhibitory activity in serum significantly decreased during spawning migration. Serum trypsin inhibitor was inactivated following treatment with androgen. It was consequently proved that androgen was trigger to the inactivation of serum protease inhibitor, resulting in high levels of muscle protease activity during spawning migration.     

Swimming patterns and behaviour of upriver-migrating adult pink (Oncorhynchus gorbuscha) and sockeye (O. nerka) salmon as assessed by EMG telemetry in the Fraser River,British Columbia,Canada

Little is known about the behaviour patterns and swimming speed strategies of anadromous upriver migrating fish. We used electromyogram telemetry to estimate instantaneous swimming speeds for individual sockeye (Oncorhynchus nerka) and pink salmon (O. gorbuscha) during their spawning migrations through reaches which spanned a gradient in river hydraulic features in the Fraser River, British Columbia. Our main objectives were to describe patterns of individual-specific swim speeds and behaviours, identify swimming speed strategies and contrast these between sexes, species and reaches. Although mean swimming speeds did not differ between pink salmon (2.21 BL s^–1) and sockeye salmon (1.60 BL s^–1), sockeye salmon were over twice as variable (mean CV; 54.78) in swimming speeds as pink salmon (mean CV; 22.54). Using laboratory-derived criteria, we classified swimming speeds as sustained (<2.5 BL s^–1), prolonged (2.5–3.2 BL s^–1), or burst (>3.2 BL s^–1). We found no differences between sexes or species in the proportion of total time swimming in these categories – sustained (0.76), prolonged (0.18), burst (0.06); numbers are based on species and sexes combined. Reaches with relatively complex hydraulics and fast surface currents had migrants with relatively high levels of swimming speed variation (e.g., high swimming speed CV, reduced proportions of sustained speeds, elevated proportions of burst speeds, and high rates of bursts) and high frequency of river crossings. We speculate that complex current patterns generated by river constrictions created confusing migration cues, which impeded a salmon's ability to locate appropriate pathways.     

Phylogenic and geographic analysis of chum salmon Oncorhynchus keta (Walbaum) in Asian populations based on mitochondrial DNA variation

We used restriction length polymorphism (RFLP) analysis of PCR-amplified fragments of mtDNA to study the genetic structure of chum salmon populations sampled in 1993-2000 during a spawning run in five rivers: Narva (Southern Primorye), Naiba (Sakhalin Island), Sernovodnaya (Kunashir Island, Southern Kuril Islands), Ola (northwestern coast of the Sea of Okhotsk), and Anadyr' (Chukotka Peninsula). In total, 49 haplotypes were identified in 193 fish. Heterogeneity tests showed highly significant (P = 0) differences among all sample pairs. The estimated time of independent divergence of the populations or population groups is in good agreement with the time of Pleistocene glaciations. This result suggests that it is cyclic global changes during this time period that were crucial in determining the within-species divergence in chum salmon. The types of mtDNA genetic variability and mismatch distribution between haplotypes in the populations indicate that the southern regions of the Sea of Okhotsk and Sea of Japan served as refugia for chum salmon during glaciation periods.     

An enzyme-inhibitor complex of cathepsin L in the white muscle of chum salmon (Oncorhynchus keta) in spawning migration

• 1.1. A cathepsin L-inhibitor complex was purified from the white muscle of chum salmon (Oncorhynchus keta) by a series of chromatographies on DEAE-Sephadex, con A-Sepharose and Sephadex G-150.
• 2.2. The mol. wt of the complex was estimated to be 50,000 by gel filtration. The complex per se showed little activity of cathepsin L, but it became active when incubated at an acidic pH.
• 3.3. SDS-PAGE analysis and an experiment of activation by acidification indicated that the complex consisted of the 37 or 30 kDA-form of cathepsin L and the 15 kDa-endogenous cysteine protease inhibitor.
• 4.4. The enzyme-inhibitor complex was considered to be formed when cathepsin L leaks out of the lysosome in vivo or is freed from the lysosome when the tissue is artificially destroyed.

     

Mitochondrial DNA variation in populations of the chum salmon Oncorhynchus keta (Walbaum) from rivers of the Prymorye and Sakhalin

Mitochondrial DNA (mtDNA) variation was studied using restriction fragment length polymorphism (RFLP) in chum salmon populations from three rivers in southern Primorye and one river in Sakhalin Island. Significant differences were detected between the samples from Primorye and Sakhalin Island. No differences were found between the samples from the rivers of Primorye, which can be explained by a high rate of gene flow due to transplantation of spawn from one river to another. The effect of fish breeding on the chum salmon populations correlated with the indices of haplotype and nucleotide diversity (h and pi, respectively). The lowest diversity was found in the completely artificial population from the Ryazanovka River; the highest, in natural populations from the Narva and Naiba rivers. Frequencies of haplotypes in consecutive generations were significantly different, which confirms the effects of genetic drift on the small-size chum salmon populations of Primorye.     

Genetic stock structure of odd-year pink salmon, Oncorhynchus gorbuscha (Walbaum), from Washington and British Columbia and potential mixed-stock fisheries applications

We used electrophoresis to determine the number and characteristics of genetically distinct stocks of odd-year pink salmon in Washington and southern British Columbia. We analysed 5128 fish from 52 collections (taken in 1985, 1987 and 1989). We observed genetic variation at 53 enzyme-coding loci, 19 of which were polymorphic at the P_o-95 level in at least one stock. Genotypic proportions conformed to Hardy-Weinberg expectations in nearly all cases. The genetic profiles of individual populations were generally stable over the three cycle years studied. Significant differences in allele frequencies at sAAT-3* , PEP-LT* and PGDH* for several stocks were, however, noted between this study and previously reported data for pink salmon. We used G-tests and cluster analysis of genetic distances to evaluate genetic interrelationships among collections and to define genetically distinct stocks. Differentiation among stocks exhibited a clear geographic pattern with three major clusters of stocks recognizable: (1) Hood Canal and Washington Strait of Juan de Fuca stocks, (2) Puget Sound, Fraser River, and southern Canada South Coast stocks, and (3) northern Canada South Coast stocks and Canada North Coast stocks. Computer simulations using 14 and 28 loci, and sample sizes of 15C600, demonstrated that accurate estimates of stock-group composition could be obtained for pink salmon fisheries having a considerable range of stock compositions. The simulations revealed that approximately 50% fewer fish were required to obtain a given level of precision of stock group composition estimates with 28 loci as with the set of 14 loci used in previous investigations.     

The abundance and distribution of Lepeophtheirus salmonis (Copepoda: Caligidae) on pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon in coastal British Columbia

In total, 23,750 specimens of the salmon louse, Lepeophtheirus salmonis, were collected from 3,907 juvenile pink and 3,941 chum salmon caught within the Broughton Archipelago during a 2-yr survey. The prevalence on pink salmon was significantly higher than on chum salmon in 2004 (62.3% and 58.6%, respectively) and in 2005 (26.4% and 23.1%, respectively). The mean abundance on chum salmon was significantly higher than on pink salmon in 2004 (7.0 +/- 0.3 and 2.8 +/- 0.2, respectively), whereas in 2005 the mean abundance did not differ between species (0.6 +/- 0.1 and 0.5 +/- 0.0, respectively). The mean intensity on chum salmon was significantly higher than on pink salmon in 2004 (12.0 +/- 0.4 and 4.5 +/- 0.2, respectively) and in 2005 (2.5 +/- 0.2 and 1.7 +/- 0.1, respectively). The prevalence, intensity, and abundance of L. salmonis were significantly higher on salmon belonging to both host species in 2004 compared with 2005. In both years, a majority of pink and chum salmon had 2 or fewer lice. In general, a decline in abundance of L. salmonis over the 3 collection periods in each year coincided with an increased percentage of motile developmental stages. The abundance was lowest on fish collected from zones in which the seawater surface salinity was also lowest. Seawater surface temperature was higher and salinity was lower in 2004 compared with 2005. The spatial and temporal trends in the abundance of L. salmonis in relation to host size, infestation rates, and seawater salinity and temperature, evident in both years, must be considered in future studies assessing the role of farmed salmon in the epizootiology of this parasite on juvenile salmon in this area.     

The variability in chum salmon Oncorhynchus keta (Walbaum) mitochondrial DNA and its connection with the paleogeological events in the northwest Pacific

The results of examining mtDNA variability in populations of chum salmon Oncorhynchus keta from the rivers of the basins of the seas of Japan and Okhotsk and in the chum salmon seasonal races of the Amur River are presented. A significant level of polymorphism between the majority of the populations studied was detected. The groups of chum salmon from the seas of Japan and Okhotsk displayed the most pronounced differences. Analysis of genetic variability demonstrated that periodic paleontologic and climatic changes in the past of this region were the most probable factor that caused the divergence of these populations. The advances and retreats of glaciers and the accompanying regressions and transgressions of the ocean level caused isolation of chum salmon in the refugia belonging hypothetically to the paleo-Shuifen and paleo-Amur regions. These population groups diverged presumably 350–450 thousand years ago. Differences between the seasonal races of the Amur chum salmon are insignificant, and their emergence dates back to the period of the last Wisconsinian glaciation. Probably, the main isolation factor now is the genetically determined time of spawning.     

The variation in chum salmon Oncorhynchus keta (Walbaum) mitochondrial DNA and its connection with the paleogeographic events in the Northwest Pacific

The results of examining mtDNA variation in populations of chum salmon Oncorhynchus keta from the rivers of the basins of the seas of Japan and Okhotsk and in the chum salmon seasonal races of the Amur River are presented. A significant level of polymorphism between the majority of the populations studied was detected. The groups of chum salmon from the Japan and Okhotsk Seas displayed the most pronounced differences. Analysis of genetic variation demonstrated that periodic paleontologic and climatic changes in the past of this region were the most probable factor that caused the divergence of these populations. The advances and retreats of glaciers and the accompanying regressions and transgressions of the ocean level caused isolation of chum salmon in the refugia belonging hypothetically to the paleo-Suifun and paleo-Amur regions. These population groups diverged presumably 350-450 thousand years ago. Differences between the seasonal races of the Amur chum salmon are insignificant, and their emergence dates back to the period of the last Wisconsin glaciation. Probably, the main isolation factor now is the genetically determined time of spawning.     

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.     

Discriminating coho salmon (Oncorhynchus kisutch) populations within the Fraser River, British Columbia, using microsatellite DNA markers

Three microsatellite loci were used to examine genetic variation among 16 coho salmon ( Oncorhynchus kisutch ) populations within the Fraser River drainage system, in British Columbia, Canada. Each locus was highly polymorphic with 30 alleles at the Ots 101 locus, 15 alleles at the Ots 3 locus and 38 alleles at the Ots 103 locus. Average observed heterozygosities were 86.1%, 70%, and 56.1%, respectively. With the exception of the Dunn and Lemieux River populations, Chi-square tests and F _ST values indicated that all populations had significantly different allele frequencies. Two distinct population groups within the Fraser River drainage were observed. Lower Fraser River populations were strongly differentiated from populations spawning in the upper Fraser River, which includes the Thompson River (a tributary flowing into the upper Fraser) and the portion of the Fraser River beyond the precipitous Fraser River canyon. This regional population structure may have resulted from colonization of the upper and lower Fraser River regions by different founder populations following Pleistocene glaciation, and be maintained by adaptive differences between the two groups of coho salmon. Coho salmon populations in the upper Fraser and Thompson River drainages form an evolutionarily significant unit (ESU) of importance for conservation of biodiversity in coho salmon. Microsatellite DNA loci show promise as technically simple and highly informative genetic markers for coho salmon population management.     

Environmental correlates of life-history variation in juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum)

Throughout its native North Pacific, the chinook salmon, Oncorhynchus tshawytscha (Walbaum), exists as twolife-history types that aredistinguished by the age at which juvenile salmon migrate to sea as smolts. 'Stream-type' chinook migrate seaward after I or more years of feeding in fresh water, whereas 'ocean-type' fish migrate to sea as newly emerged fry or after 2–3 months in fresh water. Stream-type chinook predominate in populations distant from the sea south of 56° N, and in both inland and coastal populations north of this point. By contrast, ocean-type chinook predominate in coastal populations south of 56° N, but are rare in populations in more northerly latitudes. Stream-type populations are associated with areas of low 'growth opportunity' (as measured by temperature and photoperiod regimes) and/or areas distant from the sea compared to ocean-type. Geographic variability in juvenile life history is suggested to result, in part, from environmental modulation of smolting timing via differences in growth opportunity among geo-graphic areas. In addition, differences in migration distance and temperature regime may result in selection for different sizes at migration among populations which, through differences in growth opportunity, might promote geographic variability in age at seaward migration.     

Sub-surface drift feeding by coho salmon (Oncorhynchus kisutch, Walbaum): a model and test

The results of a test of a mechanistic encounter model that predicts the size-frequency composition of the diet of drift-feeding coho salmon ( Oncorhynchus kisulch , Walbaum) are described. When all taxa in the drift were included in the model the predicted and actual diets differed significantly, although the model explained most of the variance between the diet and the predictions of a null model. When non-consumed taxa, including the distasteful and aposematic taxon Hydracarina, were excluded from the drift composition there was no significant difference between predicted and actual diets. The model's goodness of fit increased when it was modified to predict the biomass size-frequency diet composition, explaining 99% of the weighted sum of squared deviations between the diet and a null model. A number of alternate models are tested and a potentially useful simplification of the model is identified.