Cardiac arrest in the spawning chum salmon

1. Cardiac activities of male and female spawning chum salmon were recorded simultaneously by using a radio telemetry system in combination with a wired system. 2. Heart beat stopped during a spawning bout for about 10 sec in female and for 4-6 sec in male. 3. Just before and after the temporary cardiac arrest, heart rate increased from the usual rate, about 50 to about 60 beats per min. 4. It is suggested that the cessation of heart beat might be a reflex response of the cardiovascular system to the hypertension at spawning.     

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.     

Metabolic pathways of carotenoids in chum salmon Oncorhynchus keta during spawning migration

1. Based on the contents and individual composition of carotenoids in the muscle, serum and ovaries of chum salmon during spawning migration, the reductive metabolism of astaxanthin to zeaxanthin was presumed to take place in the muscle of both male and female. 2. The metabolic rates of zeaxanthin and 4-keto-zeaxanthin in female serum were much faster than those in male serum.     

Primary structure of chum salmon prolactins: occurrence of highly conserved regions

The complete amino acid sequence of prolactin from the pituitaries of salmon (Oncorhynchus keta) has been determined. Salmon prolactin comprised two variants, I and II, which were separated by reverse-phase high-performance liquid chromatography. Each variant was reduced, S-carboxymethylated, and then cleaved with cyanogen bromide and enzymes. The resulting fragments were separated by reverse-phase high-performance liquid chromatography, as well as gel filtration, and subjected to sequence analysis by the dansyl-Edman method. Both variants contain 187 amino acid residues with two disulfide linkages at residues 46-160 and 177-187, lack a linkage in the N-terminal portion of mammalian prolactins, and differ from each other by the replacement of only four amino acid residues. Salmon prolactin (sPRL) shows 31% sequence identify with ovine prolactin. Moreover, four restricted regions, i.e., sPRL (3-21), (46-60), (68-83), and (160-178), encompass this significant conservatism between the teleost and the mammalian hormone, with identities of 47, 87, 62, and 68%, respectively. Such considerable identity between these distant phylogenic species strongly suggests that these regions may be responsible for the biological activity of prolactin.     

Energy expenditures during spawning by chum salmon Oncorhynchus keta (Walbaum) in British Columbia

Physiological telemetry and proximate tissue analyses were used to assess energy expended by chum salmon Oncorhynchus keta on various behaviours during spawning in Kanaka Creek, British Columbia, Canada, and results were compared with published data on Fraser River sockeye salmon Oncorhynchus nerka , the only other species for which both types of measurements have been taken. Chum salmon arrived at the spawning grounds with body energy densities of 4·84 MJ kg⁻¹ in males and 4·62 MJ kg⁻¹ in females, lower than most sockeye salmon populations, and died with energy densities of c . 4 MJ kg⁻¹, similar to that observed in sockeye salmon and other salmonids. Moisture levels generally increased in body tissues over the spawning life, particularly in female gonads, and lipid levels decreased. Declines in protein observed over the spawning life of other Pacific salmon Oncorhynchus sp. were less evident in Kanaka Creek chum salmon. Holding behaviour constituted the dominant component of the activity schedule and energy budget of both sexes. After holding, the most expensive behaviours were nest digging in females and aggressive displays in males. Dominant males expended the most energy on behaviours each day, as indexed by oxygen consumption (3600 mgO₂ kg⁻¹), while satellite males expended nearly as much (3504 mgO₂ kg⁻¹) but females expended considerably less (2327 mgO₂ kg⁻¹). Kanaka chum salmon engaged more frequently in energetically expensive reproductive behaviours than Stuart River sockeye salmon.     

Use of ELISA to monitor bacterial kidney disease in naturally spawning chinook salmon

Bacterial kidney disease (BKD) caused by Renibacterium salmoninarum (Rs) is a serious problem among Pacific Northwest salmon hatcheries and has raised concerns that salmon reared in hatcheries may spread BKD to natural populations. In order to monitor the potential spread of this disease to salmon spawning in nature, a method must be available to collect and analyze tissues from naturally spawning salmon. Kidney tissue analyzed by enzyme-linked immunosorbent assay (ELISA) is the standard method to detect the presence of Rs in salmon sampled in hatcheries. In this study, we tested the validity of using ELISA on kidney tissue collected from intact carcasses recovered on the spawning grounds to monitor BKD in naturally spawning populations by comparing ELISA optical density (OD) values from kidney tissue that was subjected to conditions that simulated decomposition in a carcass and collection during a spawning ground survey with samples freshly collected from salmon at a hatchery. Mean ELISA OD levels were 1.060 for the samples prepared by the normal preparation and 1.115 for samples prepared by simulating spawning ground survey collection. There was no significant difference in mean ELISA OD between the 2 sample preparations and the relationship did not significantly differ from 1:1 (slope = 0.946). This demonstrates that BKD prevalence in natural populations can be monitored using ELISA conducted on samples from intact carcasses recovered on spawning ground surveys. This will be an important tool for monitoring the effect of hatchery supplementation on naturally spawning salmon populations.     

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.     

A comparison of cystatin activity in the various tissues of chum salmon Oncorhynchus keta between feeding and spawning migrations

• 1.1. Cystatin was found to be widely distributed in various tissues of chum salmon. Most of the cystatins in the salmon tissues appeared to have a molecular weight between 10,000 and 20,000. They were considered to belong to the low molecular weight form cystatin, the type 1 and/or type 2 cystatins.
• 2.2. The activity in the liver of the salmon in spawning migration was significantly higher than that of the fish in feeding migration, while the activities of the serum, kidney, intestine, stomach, gill, skin and white muscle in spawning migration were apparently lower than that of the fish in feeding migration.
• 3.3. Such differences in the cystatin activity were considered to relate closely to the physiological conditions such as sexual maturation and/or starvation during spawning migration of the fish.

     

Age composition of masu salmon smolts in northern Japan

Smolts of anadromous masu salmon Oncorhynchus masou aged 3+ years were found in a northern Japanese river. This is the first recording of 3+ year smolts in Japan. These fish appeared to originate in the cold upper river where 2+ year parr were found during autumn.     

Spatial and temporal variability of macroinvertebrates in spawning and non-spawning habitats during a salmon run in Southeast Alaska

Spawning salmon create patches of disturbance through redd digging which can reduce macroinvertebrate abundance and biomass in spawning habitat. We asked whether displaced invertebrates use non-spawning habitats as refugia in streams. Our study explored how the spatial and temporal distribution of macroinvertebrates changed during a pink salmon (Oncorhynchus gorbuscha) spawning run and compared macroinvertebrates in spawning (riffle) and non-spawning (refugia) habitats in an Alaskan stream. Potential refugia included: pools, stream margins and the hyporheic zone, and we also sampled invertebrate drift. We predicted that macroinvertebrates would decline in riffles and increase in drift and refugia habitats during salmon spawning. We observed a reduction in the density, biomass and taxonomic richness of macroinvertebrates in riffles during spawning. There was no change in pool and margin invertebrate communities, except insect biomass declined in pools during the spawning period. Macroinvertebrate density was greater in the hyporheic zone and macroinvertebrate density and richness increased in the drift during spawning. We observed significant invertebrate declines within spawning habitat; however in non-spawning habitat, there were less pronounced changes in invertebrate density and richness. The results observed may be due to spawning-related disturbances, insect phenology, or other variables. We propose that certain in-stream habitats could be important for the persistence of macroinvertebrates during salmon spawning in a Southeast Alaskan stream.     

Microsatellite variability in chum salmon of Primorye

In this study, 12 samples of chum salmon from the southern and central parts of Primorye were studied with ten microsatellite loci. All studied localities of chum salmon of Primorye formed three main genetically different groups: (1) the Narva–Barabashevka–Ryazanovka cluster of southern Primorye, (2) Kievka River, and (3) Avvakumovka River. The revealed genetic heterogeneity of chum salmon showed clear population structure in accordance with the geographical location of the samples. The study suggests that, for the purposes of artificial reproduction of chum salmon, it is desirable to perform egg planting with regard to the described population structure of chum salmon of Primorye.     

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.

     

Isolation and characterization of chum salmon growth hormone

Two molecular forms of salmon growth hormone (sGH), sGH I and II, have been isolated from the pituitary glands of the chum salmon (Oncorhynchus keta); a two-step extraction procedure, under alkaline (pH 10) conditions, subsequent to acid-acetone extraction was employed for extraction of the sGHs. They were then purified by iso-electric precipitation at pH 5.6, gel filtration on Sephadex G-100, and high-performance liquid chromatography on ODS. Intraperitoneal injection of sGH I and a combination of sGH I and II at doses of 0.01 microgram/g body wt at different intervals resulted in a significant increase in body weight and length of juvenile rainbow trout. The GH producing cells in the pituitary of mature chum salmon were identified in the proximal pars distalis immunocytochemically with a specific antiserum; no cross-reactivity was seen in the prolactin cells in the rostral pars distalis. A molecular weight of 22,000 was estimated for both sGHs by gel electrophoresis in sodium dodecyl sulfate. Isoelectric points, by gel electrofocusing, of 5.6 and 6.0 were estimated for sGH I and II, respectively, with differences present in the amino acid composition and the N-terminal residue, suggesting that they may be genetic variants coded on two separate genes. The partial amino acid sequences of sGH I at both terminal regions have been determined.     

Gene mapping of isozyme loci in chum salmon

Recombination values were used to calculate the gene-centromere map distances for four electrophoretically detected loci, Aat3, Idh1, Idh4, and Mpi, in chum salmon (Oncorhynchus keta). We also report the results from 39 pairwise examinations for joint segregation for 10 loci in nine testcross families. Only two loci assorted nonrandomly--either Aat1 or Aat2 with Gpt. Gene-centromere distances for Aat3 and Mpi differed significantly from those reported previously for rainbow trout (Salmo gairdneri), a closely related species. This difference indicates either the presence of chromosome rearrangements or a different rate of recombination between the species. These results contrast with the conservation of linkage distances previously reported within and between other salmonid genera.     

High activities of cathepsins B, D, H, and L in the white muscle of chum salmon in spawning migration

1. Activities of cathepsins, lysosomal hydrolytic enzymes and cysteine protease inhibitor in both the white and red muscles of chum salmon (Oncorhynchus keta) caught during spawning and feeding migrations were compared. 2. In the white muscle, cathepsins B, D, H and L activities were 3-7 times higher in the fish in spawning migration than those in feeding migration. However, in the red muscle, no such marked differences were observed between them. 3. Cysteine protease inhibitory activity and extractable protein content in the white muscle of the fish in spawning migration were about 40% lower than those in feeding migration. 4. The present study supports the conception that the cathepsins are related to protein catabolism of the fish during spawning migration.     

Detection of Renibacterium salmoninarum antigen in migrating adult chum salmon (Oncorhynchus keta) in Japan.

Renibacterium salmoninarum antigen was detected in the kidney of migrating chum salmon (Oncorhynchus keta) using the indirect dot blot assay and indirect fluorescent antibody test. The adult chum salmon had migrated into a bay in which cultured coho salmon infected with R. salmoninarum were present. Antigen was detected in 5% of the chum salmon although they did not have clinical signs of bacterial kidney disease (BKD). This report describes the first case of R. salmoninarum antigen detection among wild chum salmon populations in eastern Asia.     

Long‐term declines in body size and shifts in run timing of Atlantic salmon in Ireland

Records extending back from three to seven decades from Atlantic salmon Salmo salar fisheries on the Blackwater, Newport and Owenduff River systems in Ireland, were used to test the hypothesis that there have been progressive declines in size and associated shifts in run timing. They showed identical patterns in four respects: 1) peaks of catch, in spring (March to April) and summer (June to July), 2) the largest fish were caught in the spring, with declines in size over the summer and a slight increase in autumn, 3) marked declines over time in average size and in the proportion of the Atlantic salmon taken in spring and 4) reductions in size in most months at all three sites. Correlations were also detected in average fish mass among the rivers over time (especially the Owenduff and Newport systems), showing a slight rise from the late 1960s until the late 1970s, followed by a steep decline. Data from an electronic counter on the Blackwater showed a reduction in the abundance of early migrants. The early fish were apparently much more vulnerable to fishing than later migrants, so the catch records overstated the abundance of early fish. These long‐term declines in size, which have been noted elsewhere, may be due to other factors in addition to changes in marine productivity. Specifically, reduction in the abundance of large, spring‐running Atlantic salmon may be due to selection resulting from heavy angler exploitation.     

DNA homologies between the rainbow trout, chum salmon and coho salmon

The thermal stabilities of hybrid duplexes between the DNAs from three salmonid fish species were monitored as measures of DNA homology. The chum salmon, Oncorhynchus keta, and coho salmon, Oncorhynchus kisutch, had more DNA homology with each other than either had with the rainbow trout, Salmo gairdnerii. Morphological, ecological and protein similarities between the coho salmon and the rainbow trout may be due to parallel or convergent evolution.