Plasma insulin levels during the spawning migration of the pink salmon, Oncorhynchus gorbuscha

Plasma insulin concentration was measured by homologous radioimmunoassay in male and female pink salmon. Oncorhynchus gorbuscha , during spawning migration in the Fraser and Thompson Rivers, British Columbia. Although the fish ceased feeding prior to entering fresh water, plasma levels of insulin remained stable (males) or even elevated (females) during the final stages of oogenesis and spermatogenesis, decreasing thereafter. Mean concentrations ranged from 0–69 to 1.24 ng ml⁻¹ in males and from 0.33 to 0.88 ng ml⁻¹ in females. At all stages in the anadromous migration where a significant difference in plasma insulin levels between the sexes was observed, males had higher concentrations than females.     

Changes in structure of tissues and in plasma cortisol during the spawning migration of pink salmon, Oncorhynchus gorbucha (Walbaum)

Changes in the structure of the gonad, skin, interrenal, liver, kidney, stomach, gill and pituitary gland, as well as blood cortisol and haematocrit values were investigated in adult pink salmon during their migration through the Fraser and Thompson Rivers to the spawning grounds. At the commencement of their freshwater migration the gonads of both males and females were in an advanced state of development, the pituitary contained a large complement of well-granulated gonadotrops, and hypertrophy was evident in the interrenal tissue and in the epidermis of the skin. At this time, no change from the normal sexually immature salmon was evident in the structure of the gill, liver or stomach. Sclerosis of the glomeruli was noted in the kidney. The plasma cortisol level was consistent with concentrations in unstressed salmon.
Migration of the fish through a turbulent section of the Fraser River evoked a marked increase in both blood cortisol concentration and in interrenal nuclear diameters.
On arrival at the spawning grounds, 10–15 days after entry into fresh water, a general but not marked deterioration of the tissues was evident. The results are discussed in relation to the spawning migration of other species of Pacific salmon.     

Changes in plasma thyroid hormone levels in pink salmon, Oncorhynchus gorbuscha, during their spawning migration in the Fraser River (Canada)

Plasma thyroid hormone levels were measured in pink salmon, Oncorhynchus gorbuscha , during their spawning migration in the Fraser River, British Columbia. The plasma levels of both l-thyroxine (T₄) and triiodo-l-thyronine (T₃) were significantly higher in males than in females. In both sexes the hormone levels were maintained, or increased somewhat, during the early stages of migration, but fell thereafter. In females the plasma T₄ and T₃ levels of salmon collected on the spawning grounds were at or below detectable levels of the assays. The changes in thyroid hormone levels are correlated with changes in plasma insulin, gonadotropin, gonadal steroid hormones, cortisol and vitellogenin levels measured in the same specimens.     

Changes in the North Channel fish community,with emphasis on pink salmon (Oncorhynchus gorbuscha Walbaum)

Historical trends in commercial fishery yields were examined for evidence of structural changes in the North Channel fish community. Significant declines in the abundance of indigenous species occurred primarily as a result of man's activities. Lake sturgeon (Acipenser fulvescens Rafinesque) were harvested down to low levels by 1900. Introductions of exotics to the fish community were associated with major changes. Rainbow smelt (Osmerus mordax Mitchill) and sea lamprey (Petromyzon marinus Linnaeus) colonized the channel in the late 1930s. Concurrently, lake trout (Salvelinus namaycush Walbaum) and burbot (Lota lota Linnaeus), the top deepwater predators, declined to near extinction. Lake whitefish (Coregonus clupeaformis Mitchill) and shallow-water cisco (Coregonus artedii Lesueur) also declined. Without predation pressure, smelt abundance increased to high levels in the 1950s and alewife (Alosa pseudoharengus Wilson), another exotic, peaked during the 1960s. Both species equilibrated at lower levels in the 1970s, perhaps favouring colonization by pink salmon (Oncorhynchus gorbuscha Walbaum). Pink salmon which are larger and more fecund in Lake Huron than in Lake Superior, are increasing rapidly in numbers and are expanding their range in the channel. Certain whitefish stocks have increased sufficiently to support fishery yields greater than those of the 1930s, despite considerable exploitation pressure. This success is partially in response to the control of sea lamprey since 1961. However both lake whitefish and walleye (Stizostedion vitreum Mitchill) are now rare in the east end of the channel, possibly due to environmental factors such as acid precipitation and metal contaminants. Community stability will not likely be attained until a suitable climax predator becomes reestablished.     

Heavy metal contents in the pink salmon Oncorhynchus gorbuscha Walbaum, 1792 from Kuril oceanic waters during anadromous migration

The contents of trace elements, viz., Hg, As, Pb, Cd, Zn, and Cu, in a common species of Pacific salmon, viz., the pink salmon, which were caught in early July 2012 and 2013 in the vicinity of Kuril Islands, were examined. It was found that the contents of toxic elements, Cd, Pb, As, and Hg, in the salmon meet human-health consumption guidelines for seafood by the sanitary standards and regulations of the Russian Federation. The contents of all of the metals (except zinc) in pink salmon from the geochemically extreme Kuril area were higher than that in pink salmon from the Sea of Japan. The greatest difference was recorded for lead, whose concentrations in organs and tissues (liver, gonads, and muscle) of fish from Kuril oceanic waters was one and a half order of magnitude higher than that of pink salmon from the Sea of Japan.     

Genetic changes in pink salmon Oncorhynchus gorbuscha Walbaum during acclimatization in the White sea basin

Genetic parameters of pink salmon introduced into the White Sea basin in 1985 and 1998 were compared to the corresponding parameters of the donor population from the Ola River (Magadan oblast). The detected genetic differences indicate that colonization of a new area is accompanied by impoverishment of the gene pool of the native population. This effect was particularly marked in the odd-year line of pink salmon introduced in 1985. The probable causes of these genetic changes are discussed.     

Dorsal hump morphology in pink salmon (Oncorhynchus gorbuscha)

Mature male Pacific salmon (Genus Oncorhynchus) develop a dorsal hump, as a secondary male sexual characteristic, during the spawning period. Previous gross anatomical studies have indicated that the dorsal humps of salmon are mainly composed of cartilaginous tissue (Davidson [1935] J Morphol 57:169–183.) However, the histological and biochemical characteristics of such humps are poorly understood. In this study, the detailed microstructures and components of the dorsal humps of pink salmon were analyzed using histochemical techniques and electrophoresis. In mature males, free interneural spines and neural spines were located in a line near to the median septum of the dorsal hump. No cartilaginous tissue was detected within the dorsal hump. Fibrous and mucous connective tissues were mainly found in three regions of the dorsal hump: i) the median septum, ii) the distal region, and iii) the crescent‐shaped region. Both the median septum and distal region consisted of connective tissue with a high water content, which contained elastic fibers and hyaluronic acid. It was also demonstrated that the lipid content of the dorsal hump connective tissue was markedly decreased in the mature males compared with the immature and maturing males. Although, the crescent‐shaped region of the hump consisted of connective tissue, it did not contain elastic fibers, hyaluronic acid, or lipids. In an ultrastructural examination, it was found that all of the connective tissues in the dorsal hump were composed of collagen fibers. Gel electrophoresis of collagen extracts from these tissues found that the collagen in the dorsal hump is composed of Type I collagen, as is the case in salmon skin. These results indicate that in male pink salmon the dorsal hump is formed as a result of an increase in the amount of connective tissue, rather than cartilage, and the growth of free interneural spines and neural spines. J. Morphol. 275:514–527, 2014. © 2013 Wiley Periodicals, Inc.     

Migration and capture of pink salmon, Oncorhynchus gorbuscha Walbaum in Finnmark, North Norway

Pink salmon transplanted to the north Atlantic coast from the Soviet Union reached a peak in 1973, both in the Soviet Union and in Finnmark. Pink salmon catch statistics were compiled in 1977 for the inshore coastal and fjord areas of Finnmark from the atlantic salmon fisheries conducted locally and outside the coastal limits of Finnmark. The survey indicated a total sea catch of 12 800 specimens or 18 450 kg in Finnmark in 1977. The pink salmon reached the coast in the western regions of Finnmark during the first half of July, after which the main migration continued eastwards along the coast. The migrations into the western fjords were few, with half the total inshore catch captured in the most eastern fjord, Varangerfjord.     

Genetic differentiation of pink salmon Oncorhynchus gorbuscha Walbaum in the Asian part of the range

Genetic variation at 19 enzyme (including 11 polymorphic) and 10 microsatellite loci was examined in the population samples of odd-and even-broodline pink salmon from the southern part of Sakhalin Island, Southern Kuril Islands, and the northern coast of the Sea of Okhotsk. The estimates of relative interpopulation component of genetic variation for the allozyme loci, per broodline, were on average 0.43% (G _ST), while over the microsatellite loci it was 0.26% (the ?_ST coefficient, F-statistics based on the allele frequency variance), and 0.90% (the ρ_ST coefficient, R-statistics based on the allele size variance). The values of interlinear component constituted 2.34, 0.31, and 1.05% of the total variation, respectively. Using the allozyme loci, statistically significant intralinear heterogeneity was demonstrated among the regions, as well as among the populations of southern Sakhalin. Multidimensional scaling based on the allozyme data demonstrated regional clustering of the sample groups, representing certain populations during the spawning run or in different years. Most of the microsatellite loci examined were found to be highly polymorphic (mean heterozygosity > 0.880). The estimates of interlinear, interregional, and interpopulation variation over these loci in terms of ?_ST values were substantially lower than in terms of ρ_ST values. Regional genetic differentiation, mostly expressed at the allozyme loci between the populations from the northern Sea of Okhotsk and the Sakhalin and Kuril group of populations, was less expressed at the microsatellite loci. The differentiation between these regions observed can be considered as the evidence in favor of a large-scale isolation by distance characterizing Asian pink salmon. It is suggested that in pink salmon, low genetic differentiation at neutral microsatellite loci can be explained by extremely high heterozygosity of the loci themselves, as well as by the migration gene exchange among the populations (the estimate of the gene migration coefficient inferred from the “private” allele data constituted 2.6 to 3.4%), specifically, by the ancient migration exchange, which occurred during postglacial colonization of the range     

Allozyme heterozygosity and morphological homeostasis in pink salmon,Oncorhynchus gorbuscha (Walbaum): evidences from family analysis*

In the families produced by diallel 2 × 2 crosses there were positive relationships in two experimental groups between individual heterozygosity (H₀) at four allozyme loci (PGM*, G3PDH*, sMEP*, sMDH?3,4*) and the size of the fish, their morphological variability (10 traits) and the viability among families. An integrative H₀ influence on complexes of morphological traits was also obtained. On the basis of factor and discriminant analysis it was shown that H₀ correlated with morphological homeostasis at least within one experimental group.     

Identification of the sex chromosome pair in chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha)

Fluorescence in situ hybridization (FISH) using a probe to the male-specific GH-Y (growth hormone pseudogene) was used to identify the Y chromosome in the karyotypes of chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha). The sex chromosome pair is a small acrocentric chromosome pair in chum salmon and the smallest metacentric chromosome pair in pink salmon. Both of these chromosome pairs are morphologically different from the sex chromosome pairs in chinook salmon (Oncorhynchus tshawytscha) and coho salmon (Oncorhynchus kisutch). The 5S rRNA genes are on multiple chromosome pairs including the sex chromosome pair in chum salmon, but at the centromeres of two autosomal metacentric pairs in pink salmon. The sex chromosome pairs and the chromosomal locations of the 5S rDNA appear to be different in all five of the North American Pacific salmon species and rainbow trout. The implications of these results for evolution of sex chromosomes in salmonids are discussed.     

Effect of hunger on the daily pattern of feeding rates in juvenile pink salmon, Oncorhynchus gorbuscha Walbaum

Juvenile pink salmon, Oncorhynchus gorbuscha , in two test groups of differing hunger level fed continuously on live copepods, maintained at high densities, throughout 12 h feeding periods in the laboratory. Analysis of video films showed that mean feeding rates were initially (first 10 min) between 51.5 and 63.8 prey-capture attempts (snaps) fish^-1 10 min^-1, but declined abruptly with increasing satiation to relatively constant levels of about 5.0 and 8.0 snaps fish^-1 10 min^-1, which were maintained during the subsequent 11 h of feeding. The data suggests that after the initial filling of their stomachs with food, juvenile pink salmon keep their stomachs full by feeding at a rate that balances the gastric evacuation rate of 18.6 mg prey h^-1 at 11° C. Less than 15% of the fish's stomach contents need be evacuated apparently for spontaneous feeding to resume or occur. Increased hunger level (by increasing a pre-test food deprivation period from 24 to 72 h) resulted in fish increasing their average feeding rate and thus their ration consumed from 23.6 to 39.8% dry body weight per 12 h.     

Genetic analysis of growth and maturity in pink salmon (Oncorhynchus gorbuscha)

Variation in growth and sexual maturity was examined for five stocks of pink salmon (Oncorhynchus gorbuscha) spawning at different times in British Columbia. In each stock, four males were mated with eight females in a nested breeding design, and the juveniles were reared for 500 d after fry emergence. Adults in early-spawning northern stocks were smaller than those in late-spawning southern ones, but pink salmon from northern stocks had faster growth rates than those from southern ones. The relative ranking within stocks of family weight remained constant after late winter in the year of maturity. Heritability of weight based upon sire variance components was usually greater than 0.9 after 150 d of rearing. Pink salmon from the earlier-spawning stocks were in a more advanced state of sexual maturity when the experiment was terminated than were those from later-spawning stocks, indicative of a significant genetic component in timing of sexual maturity.     

Behavior of juvenile pink salmon (Oncorhynchus gorbuscha Walbaum) toward novel prey: influence of ontogeny and experience

Synopsis The behavior of individual, juvenile pink salmon toward novel prey (Artemia salina) under laboratory conditions is described. Two aspects of predatory behavior, namely latency time to initial prey-capture attempt and prey-capture success, are quantified in relation to chronological age and feeding experience. Initially, mean latency time declined slightly with increasing age up to Day 19 (post-emergence from gravel), but increased sharply to an asymptote with further aging. Mean percentage capture success gradually increased from 7.88% on Day 1 to 92.9% on Day 45. Prior feeding experience on the prey resulted in a decline (to a stable level) in mean latency time in experienced fish compared to control fish. Mean percentage capture success was not significantly altered by prior feeding experience on the prey.     

A genetic analysis of body size in pink salmon (Oncorhynchus gorbuscha)

Two small-sized and two large-sized male pink salmon (Oncorhynchus gorbuscha) were mated to each of four females, producing eight families sired by small males and eight sired by large males. The juveniles were reared for 500 d after fry emergence. Juvenile weight in the two male size classes was similar until the spring of the year of maturity, when juveniles sired by large males grew faster than those sired by small ones. Heritability estimates of weight based upon the dam component of variance increased during 500 d of rearing from 0.4 to 0.8. Heritability of weight based upon the sire component of variance generally ranged between 0.1 and 0.3. The large variation in male body size in spawning pink salmon populations may have resulted from different male breeding strategies.     

Widespread occurrence of pink salmon (Oncorhynchus gorbuscha) throughout Greenland coastal waters

Using social media, the Greenland Institute of Natural Resources collected data on the occurrence of pink salmon (Oncorhynchus gorbuscha) in 2019. Eighty-four pink salmon were reported from 22 locations across Greenland. This comprised 76 specimens from 2019 and 8 specimens from 2013 to 2018. Of these, 12 were caught in fresh water, and a single pink salmon was from the bottom of the Nuuk Fjord near the Kapisillit River – the only known river in Greenland where the Atlantic salmon (Salmo salar) spawn. It is unknown if pink salmon have reproduced in Greenland waters.