Search

A total of 122 coho salmon specimens were examined. The fish were caught in the coastal zone and in the rivers of Iturup Island (southern Kuril Islands) during their spawning migration in August–October 2021. Almost all females and males close to maturity in that year had spent 1 year at sea and were at ages of 1.1+ (66.7%) and 2.1+ (30.0%). Fish that had spent 2 years at sea were found singly: one specimen at an age of 1.2+ and three specimens at an age of 2.2+ (2.5%). Taking into account the age at maturity and the body weight (an average of 2.63 kg for females and 2.44 kg for males), an assumption can be made that the examined fish bred in short streams. The high value of the gonadosomatic index (up to 20–22% for some females) did not indicate that all the fish caught in the coastal waters would have run to other spawning grounds. At least a portion of them should have spawned in the water courses of Iturup Island, as was evidenced by the captures of a few coho salmon immediately in the rivers. Along with the fish running to the spawning grounds, two actively feeding coho females at an age of 0.0+ (0.55 kg) and 1.0+ (1.11 kg) were also caught with stake nets. [ABSTRACT FROM AUTHOR]

Climatic warming elevates mortality for many salmonid populations during their physically challenging up-river spawning migrations, yet, the mechanisms underlying the increased mortality remain elusive. One hypothesis posits that a cardiac oxygen insufficiency impairs the heart's capacity to pump sufficient oxygen to body tissues to sustain up-river swimming, especially in warm water when oxygen availability declines and cardiac and whole-animal oxygen demand increases. We tested this hypothesis by measuring cardiac and metabolic (cardiorespiratory) performance, and assessing the upper thermal tolerance of coho salmon (Oncorhynchus kisutch) during sustained swimming and acute warming. By surgically ligating the coronary artery, which naturally accumulates arteriosclerotic lesions in migrating salmon, we partially impaired oxygen supply to the heart. Coronary ligation caused drastic cardiac impairment during swimming, even at benign temperatures, and substantially constrained cardiorespiratory performance during swimming and progressive warming compared to sham-operated control fish. Furthermore, upper thermal tolerance during swimming was markedly reduced (by 4.4 °C) following ligation. While the cardiorespiratory capacity of female salmon was generally lower at higher temperatures compared to males, upper thermal tolerance during swimming was similar between sexes within treatment groups. Cardiac oxygen supply is a crucial determinant for the migratory capacity of salmon facing climatic environmental warming. [ABSTRACT FROM AUTHOR]

An analysis of the biological value of chum salmon showed that, in terms of the balance of the amino-acid composition of the protein, chum salmon with spawning changes is not inferior to chum salmon without spawning changes (silver chum salmon). A higher content of polyunsaturated fatty acids in total lipids, including omega-3, was noted in chum salmon with spawning changes compared to silver chum salmon. The metabolic profile of chum salmon samples obtained by NMR spectroscopy showed that the levels of Asp, Glu, and glucose markedly increase during spawning migration, which is explained by the limited feeding of fish. The calculated total taste index of silver chum salmon was 4.06 ± 0.11, and that of chum salmon with spawning changes was 3.46 ± 0.09. Therefore, according to taste sensations, the silver chum salmon has a richer taste compared to the chum salmon with spawning changes. The results of the analysis of the nutritional value and metabolic profile of chum salmon with spawning changes can be used in the manufacture of minced fish for the subsequent production of specialized food products by introducing functional additives that balance the consistency and color, as well as in production of functional food additives. [ABSTRACT FROM AUTHOR]

Antioxidants which are indispensable functional additives used in rubber tires, are released into aquatic habitats from tire wear particles (TWP), collected in water bodies, and threaten the aquatic ecosystem. This study aimed to design eco-friendly derivatives of 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) with increased antioxidant activity to use as tire antioxidants. Initially, seventy highly efficient derivatives of TMQ were designed by hydroxylation modifications at multiple sites. The antioxidant activity of hydroxyl derivatives was characterized based on DFT method and compared with TMQ. Twenty derivatives showing a significant (greater than 9%) increase in antioxidant activity compared to TMQ were selected for the next stage. The toxicity risk of these twenty TMQ derivatives was assessed using various toxicokinetic methods. Finally, six TMQ derivatives with significantly lower toxicity risk compared to that of TMQ were evaluated for potential developmental toxicity. They were characterized using molecular docking and molecular dynamics techniques to assess the developmental toxicity risk in silver salmon by absorption of their ROO·, HO·, O2·– and O3 derivatives. TMQ-6 and TMQ-48 showed the lowest toxicity among all TMQ derivatives by a rather large margin. The study throws light on the path of future endeavors to develop highly efficient and greener tire antioxidants. [ABSTRACT FROM AUTHOR]

There is tremendous variation in life-history strategies among anadromous salmonids. Species that enter the ocean environment at small sizes (< 20 g) are likely under more physiological pressure from pathogens; however, little data is available on responses at these early stages. With this in mind, we performed salmon louse challenges with Coho salmon either immediately after seawater entry (SW; ca. 10 g) or after 30 days in SW (ca. 20 g). Irrespective of size or time in SW, parasites were rapidly rejected by the host, with > 90% of all parasites lost by 16 days post-infection (dpi). Rejection was concomitant with host epithelial granulomatous infiltrations that initially targeted the embedded frontal filament (4 dpi) and the entire parasite by 10 dpi. Illumina sequencing, followed by functional enrichment analysis, revealed a concerted defense response in the fin within 1 dpi that included multiple innate and adaptive immunity components. Strikingly, early indications of an allergic-type inflammatory response were associated with chitin sensing pathways orchestrated by early overexpression of the IgE-receptor, fcer1g. Additionally, there was profound overexpression of several classes of c-type lectin receptors, including dectin-2, mincle, and dc-sign at 1 dpi onward. These profiles and upregulation of cellular effector markers were corroborated by histopathological evaluation, revealing the simultaneous presence of mast cell/eosinophilic granular cells, sacciform cells, macrophages/histiocytes, and granulocytes in fin. At 10 dpi and concurrent with parasite expulsion, there was evidence of immunoregulation in addition to tissue remodelling pathways. At 16 dpi, the response was effectively abrogated. Simultaneous profiling of the parasite transcriptome revealed early induction of chitin metabolism and immunomodulation, toxin production and ECM degradation; however, after 7 dpi, these were replaced with overexpression of stress and immune defense genes. These data present the first evidence for Coho salmon demonstrating chitin- and sugar moiety-sensing as key drivers of salmon louse rejection. [ABSTRACT FROM AUTHOR]

Estimating juvenile salmon habitat carrying capacities is a critical need for restoration planning. We assimilated more than 4500 unique estimates of published juvenile densities (e.g., fish/m2) in estuarine and floodplain habitats. These density data were categorized by species and life stage, habitat type, seasonal period, and geographic region to develop frequency statistics (e.g., 25th and 75th percentiles, or quartiles). These frequency statistics were then used in a habitat expansion approach to estimate carrying capacities based on habitat extent. We demonstrate the habitat expansion approach by applying the quantiles of observed juvenile Chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch) densities (fish/ha) to spatial data describing current, historical or potential, and predicted (based on seal level rise) habitat extents for 16 coastal Oregon estuaries to estimate carrying capacities. Current carrying capacities based on 75th percentile springtime (Apr–Jun) densities ranged from 2902 to 33,817 fish/delta for Chinook salmon and 2507 to 20,206 fish/delta for coho salmon. Historic carrying capacities during the peak rearing period (spring) ranged from 3869 to 71,844 fish/delta for Chinook salmon and 3201 to 38,337 fish/delta for coho salmon, representing a 3 to 72% loss in Chinook salmon capacity and 2 to 67% loss in coho salmon capacity. Estimated carrying capacities were predicted to decline by 2 to 54% with 1.4 m of sea level rise in systems that are projected to lose vegetated tidal wetland habitat, while a 1 to 320% increase in capacity was predicted for systems that are predicted to increase in area with sea level rise. Finally, we demonstrate how the carrying capacity estimates can be used to estimate changes in juvenile Chinook and coho salmon capacity following restoration, which can be used to both design and evaluate restoration projects. [ABSTRACT FROM AUTHOR]

Invasive species introductions in high latitudes are accelerating and elevating the need to address questions of their effects on Subarctic and Arctic ecosystems. As a driver of ecosystem function, submerged aquatic vegetation is one of the most deleterious biological invasions to aquatic food webs. The aquatic plant Elodea spp. has potential to be a widespread invader to Arctic and Subarctic ecosystems and is already established in 19 waterbodies in Alaska, USA. Elodea spp. has been found to alter ecosystem processes through multiple pathways; yet little is known about the impact of Elodea spp. on fish life history. A primary concern is the effect of Elodea spp. on juvenile Pacific salmon (Oncorhynchus spp.), because this invading plant can form dense stands in littoral zones, potentially impacting important freshwater rearing habitats used by juvenile fish for foraging and refuge from predators. We used a field experiment to test the effect of Elodea spp. on juvenile coho salmon (O. kisutch) growth in an infested lake near Cordova, Alaska, USA. We found that Elodea spp. stands result in reduced growth and a lower trophic position for juvenile coho salmon over the summer compared to habitats dominated by a native assemblage of aquatic plants. While infested sites were not associated with significant changes in water condition or primary productivity compared to sites dominated by native vegetation, zooplankton densities were reduced, and Elodea spp. height and vegetation richness increased macroinvertebrate densities. Combined, these results indicate that Elodea spp. may alter the flow of energy to juvenile salmon by restructuring space and affecting prey resources for rearing fish. Furthermore, these results suggest that widespread establishment of Elodea spp. may alter the quality of habitat for juvenile salmon and, by affecting juvenile fish growth, could lead to population-level impacts on salmon returns. [ABSTRACT FROM AUTHOR]

In the western US, freshwater mussels (Order Unionida) contribute valuable ecosystem functions to riverine systems, yet have declined across their range following widespread degradation of freshwater habitat and parallel declines in salmonids, host fish for larval western pearlshell mussels (Margaritifera falcata). The status of M. falcata populations is of particular conservation interest in isolated coastal watersheds given unique freshwater mussel-host fish relationships. To understand M. falcata population ecology in Oregon's coastal watersheds, we analyzed stream survey data on presence/absence of mussels collected over a recent eleven-year period, explored co-varying habitat characteristics, and summarized mussel distribution and host fish co-occurrence. We also collected M. falcata and compared condition indices among eight locations. Naïve occupancy in surveyed areas was 12.3%, about half of predicted occupancy (ψ = 0.24, CI 0.19–0.31) based on modeling repeated visits over a ten year assumed closed period. Mussel occupancy was correlated with reach-scale habitat variables, and the probability of mussel observations was positively correlated with presence of coho (Oncorhynchus kisutch) salmon. Condition varied significantly among locations. Spatial relationships between existing mussel distribution, host species, and habitat variables answer questions about coastal freshwater mussel populations, as well as serve to identify priorities for further research and population assessment. [ABSTRACT FROM AUTHOR]

A 12-week feeding trial was conducted to examine the effects of dietary protein concentrations on growth, whole-body chemical composition, and hepatic anti-oxidant enzyme activities of coho salmon Oncorhynchus kisutch (Walbaum, 1792) alevins. Five experimental diets were formulated with graded protein levels of 36.5%, 42.0%, 48.0%, 54.5%, and 60.0%, respectively, with each fed to triplicate groups of fish (0.36 ± 0.01 g). Stocked as groups of 50 individuals per tank (water volume of 240 L), fish were fed four times daily with the method of overfeeding (15–20% body weight). After the feeding trial, the specific growth rate (SGR) in groups fed diets with 48.0%, 54.5%, and 60.0% protein was significantly higher than that in the 36.5% protein group (P <.05). The feed conversion ratio (FCR) in 48.0%, 54.5%, and 60.0% dietary protein groups was significantly lower than that in the 36.5% protein group (P <.05). No significant differences were observed for hepatosomatic index (HSI), intestosomatic index (ISI), condition factor (CF), and whole-body composition, except the crude protein content, which increased significantly with the increment of dietary protein level up to 48.0% (P <.05) and then leveled off (P >.05). Dietary protein up to 48.0% significantly increased the activities of total superoxide dismutase (T-SOD) and catalase (CAT) and significantly decreased the malondialdehyde (MDA) contents in the liver (P <.05). The second-order polynomial regression analyses based on SGR indicated that the optimal protein requirement in diets of coho salmon alevins was 53.6%, which was concurrent with a protein to energy ratio of 25.8 g protein MJ−1. [ABSTRACT FROM AUTHOR]

Prompted by a recent report that 6PPD-quinone (6PPD-q), a by-product of a common tire manufacturing additive that is present in road runoff, is toxic to coho salmon (Oncorhynchus kisutch), extracts of water samples collected from an urban river were re-analyzed to determine if this compound was present in stormwater-influenced flows. In addition, extracts were analyzed for 1,3-diphenylguanidine (DPG), which is also used in tire manufacturing. Samples were originally collected in the fall of 2019 and winter of 2020 in the Greater Toronto Area of Canada from the Don River, a highly urbanized watershed in close proximity to several major multi-lane highways. These target compounds were analyzed using ultra-high pressure liquid chromatography with high resolution mass spectrometric detection with parallel reaction monitoring. Both 6PPD-q and DPG were detected above limits of quantification (i.e., 0.0098 µg/L) in all extracts. Maximum concentrations for 6PPD-quinone of 2.30 ± 0.05 µg/L observed in the river during storm events exceeded the LC50 for this compound for coho salmon (i.e., > 0.8 µg/L). In composite samples collected at intervals throughout one rain event, both compounds reached peak concentrations a few hours after initiation of the event (i.e., 0.52 µg/L for DPG and 2.85 µg/L for 6PPD-q), but the concentrations of 6PPD-q remained elevated above 2 µg/L for over 10-h in the middle of the event. Estimates of cumulative loads of these compounds in composite samples indicated that kg amounts of these compounds entered the Don River during each hydrological event, and the loads were proportional to the amounts of precipitation. This study contributes to the growing literature indicating that potentially toxic tire-wear compounds are present at elevated levels and are transported via road runoff into urban surface waters during rain events. [ABSTRACT FROM AUTHOR]

A 12-week feeding trial was conducted to determine the optimal dietary selenium requirement for coho salmon (Oncorhynchus kisutch W.) alevins. Six experimental diets (contained about 42.2% crude protein and 10.5% crude lipid) were formulated to contain selenium level of 0.07, 0.15, 0.24, 0.41, 0.75, and 1.38 mg/kg, respectively. Each diet was fed to triplicate groups of fish with initial mean body weight of 0.38 ± 0.01 g, which were randomly assigned to 18 plastic tanks (80 × 60 × 60 cm, length × width × height, water volume 240 L), and each tank was stocked initially with 50 fish. Fish were fed four times daily and used the method of overfeeding (15–20% body weight) to fish. The sampling procedure was implemented after 24 h of fasting. Results showed that specific growth rate (SGR) in 0.24, 0.41, and 0.75 mg Se/kg groups were significantly higher than those in 0.07 and 1.38 mg Se/kg groups (P <.05). There were no significant differences in hepatosomatic index (HIS), intestinal somatic index (ISI), condition factor (CF), and whole-body composition among dietary groups (P >.05). Hepatic malondialdehyde (MDA) content significantly declined with increasing dietary up to 0.41 mg Se/kg and increased as selenium further increased. The hepatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) significantly increased with increasing dietary selenium up to 0.41 mg/kg and decreased significantly as selenium further increased (P <.05). Fish fed diet with 0.75 mg Se/kg had the highest glutathione reductase (GR), which did not differ significantly with 0.41 and 1.38 mg Se/kg groups (P >.05) but significantly higher than those in 0.07, 0.15, and 0.24 mg Se/kg groups (P <.05). Broken-line regression analyses based on SGR, hepatic, and whole-body selenium contents indicated that the optimum dietary selenium requirements were in the range of 0.39–0.43 mg/kg for coho salmon alevins. [ABSTRACT FROM AUTHOR]

Piscirickettsiosis is the most important bacterial disease in the Chilean salmon industry, which has borne major economic losses due to failure to control it. Cells use extracellular vesicles (EVs) as an inter-cellular communicators to deliver several factors (e.g., microRNAs) that may regulate the responses of other cells. However, there is limited knowledge about the identification and characterization of EV-miRNAs in salmonids or the effect of infections on these. In this study, Illumina sequencing technology was used to identify Coho salmon plasma EV-miRNAs upon Piscirickettsia salmonis infection at four different time points. A total of 118 novels and 188 known EV-miRNAs, including key immune teleost miRNAs families (e.g., miR-146, miR-122), were identified. A total of 245 EV-miRNAs were detected as differentially expressed (FDR < 5%) in terms of control, with a clear down-regulation pattern throughout the disease. KEGG enrichment results of EV-miRNAs target genes showed that they were grouped mainly in cellular, stress, inflammation and immune responses. Therefore, it is hypothesized that P. salmonis could potentially benefit from unbalanced modulation response of Coho salmon EV-miRNAs in order to promote a hyper-inflammatory and compromised immune response through the suppression of different key immune host miRNAs during the course of the infection, as indicated by the results of this study. [ABSTRACT FROM AUTHOR]

Animal domestication and artificial selection give rise to gradual changes at the genomic level in populations. Subsequent footprints of selection, known as selection signatures or selective sweeps, have been traced in the genomes of many animal livestock species by exploiting variation in linkage disequilibrium patterns and/or reduction of genetic diversity. Domestication of most aquatic species is recent in comparison with land animals, and salmonids are one of the most important fish species in aquaculture. Coho salmon (Oncorhynchus kisutch), cultivated primarily in Chile, has been subjected to breeding programs to improve growth, disease resistance traits, and flesh color. This study aimed to identify selection signatures that may be involved in adaptation to culture conditions and traits of productive interest. To do so, individuals of two domestic populations cultured in Chile were genotyped with 200 thousand SNPs, and analyses were conducted using iHS, XP-EHH and CLR. Several signatures of selection on different chromosomal regions were detected across both populations. Some of the identified regions under selection contained genes such anapc2, alad, chp2 and myn, which have been previously associated with body weight in Atlantic salmon, or sec24d and robo1, which have been associated with resistance to Piscirickettsia salmonis in coho salmon. Findings in our study can contribute to an integrated genome-wide map of selection signatures, to help identify the genetic mechanisms of phenotypic diversity in coho salmon. [ABSTRACT FROM AUTHOR]

Urbanization-driven landscape changes are harmful to many species. Negative effects can be mitigated through habitat preservation and restoration, but it is often difficult to prioritize these conservation actions. This is due, in part, to the scarcity of species response data, which limit the predictive accuracy of modeling to estimate critical thresholds for biological decline and recovery. To address these challenges, we quantify effort required for restoration, in combination with a clear conservation objective and associated metric (e.g., habitat for focal organisms). We develop and apply this framework to coho salmon (Oncorhynchus kisutch), a highly migratory and culturally iconic species in western North America that is particularly sensitive to urbanization. We examine how uncertainty in biological parameters may alter locations prioritized for conservation action and compare this to the effect of shifting to a different conservation metric (e.g., a different focal salmon species). Our approach prioritized suburban areas (those with intermediate urbanization effects) for preservation and restoration action to benefit coho. We found that prioritization was most sensitive to the selected metric, rather than the level of uncertainty or critical threshold values. Our analyses highlight the importance of identifying metrics that are well-aligned with intended outcomes. [ABSTRACT FROM AUTHOR]

For species that have been extirpated from parts of their range, conservation managers often reintroduce individuals to these areas in hopes of restoring populations to pre-decline conditions. Coho salmon (Oncorhynchus kisutch) have been extirpated since the early 1900s in the interior reaches of the Columbia River watershed. Starting in the late 1990s, the Columbia River Treaty tribes were successful in starting a re-introduction program that has established an upper Columbia River Coho salmon stock. Fish are preferentially selected for broodstock to incorporate naturally occurring phenotypic characteristics to facilitate local adaptation. On the Wenatchee River in Washington, broodstock are preferentially selected at a lower and upper river dam, however, only ~ 32% of fish successfully ascend a 15 km high-gradient reach to the upper river dam. Fish that successfully ascend the reach generally arrive early in the season and have a better overall body condition. In other salmonids, phenotypic traits such as return timing has been shown to be under genetic control. To determine if there are genomic regions that underly the phenotypic traits found to impact migration success up a high-gradient reach, low-coverage whole genome re-sequencing (lcWGR) was performed on adult fish returning to the system. Genome-wide association tests revealed three genomic regions that are associated with fish return location. Results of the lcWGR suggest that candidate markers can be incorporated as a genetic screening tool during broodstock selection to preferentially breed fish that have the phenotypic characteristics that confer greater potential for steeper and longer migration distances. [ABSTRACT FROM AUTHOR]

Multiple Pleistocene glaciations significantly affected the gene pool of many species inhabiting the Northern part of the Pacific Rim, an area with a rich glacial history. This paper is devoted to the study of intraspecific polymorphism of the coho salmon and the routes of its settlement throughout the Asian part of its range. Such problems are traditionally solved by comparing parts of the mitochondrial genome. Here, two fragments of mtDNA, the control region (D-loop) and the cytochrome b gene (cytb), were investigated. It was shown that the settlement of the Asian Pacific coast by the coho salmon was preceded by a chain of successive migration events from the refugium located on the North American continent to the South of the ice sheet covering the area of modern Canada and southern Alaska. The low level of genetic polymorphism in Asian coho populations seems to be a result of a pronounced founder effect, rather than being characteristic of the species as a whole. [ABSTRACT FROM AUTHOR]

Biological reference materials (RMs) are essential for quality assurance, traceability of measurement results and for method validation. When addressing new measurement questions or emerging regulatory issues, rigorous large-scale CRM production may not be time efficient or economically practical using current production methods. By amending a relatively small matrix batch with a compound(s) of interest at the homogenization step, the National Institute of Standards and Technology (NIST) can create a custom material on an "as-needed" basis and circumvent the time delay inherent in large-batch production, thereby generating a fit-for-purpose, rapid-response RM. Here, Coho salmon (Oncorhynchus kisutch) was cryohomogenized and spiked with an aquaculture antibiotic and antibiotic metabolite. The resultant material was analyzed using liquid chromatography-high resolution tandem mass spectrometry (LC-HRMS/MS) to determine the effectiveness of the amendment technique in a fresh-frozen matrix by assessing homogeneity and accuracy to the target concentration (e.g. mass fraction). Target mass fractions were achieved for both spike components, with RSDs below 5% in replicate measurements of each compound (n = 8). The stability of the spiked compounds was assessed one year post-production and mass fractions were stable, within 1–6% of the initial measurement results, indicating minimal change to the amended analyte concentrations over time. The results support this method as a promising new technique for custom, small-batch RM generation. [ABSTRACT FROM AUTHOR]

Anadromous Pacific salmon are semelparous, and resource subsidies from spawning adults (marine-derived nutrients, or MDN) benefit juvenile salmonids rearing in freshwater. However, it remains unclear how MDN assimilation relates to spawner abundance within a watershed. To address this, we examined seasonal, watershed-scale patterns of MDN assimilation in rearing coho (Oncorhynchus kisutch) and Chinook (O. tshawytscha) salmon and compared it with spawner biomass and landscape features in a western Alaska watershed with contrasting structural complexity in two sub-drainages. Adult salmon biomass density was estimated from escapement and spawner distribution data, and MDN assimilation in juvenile salmon was estimated via stable isotopes. In the North River, MDN assimilation was lowest in early summer, prior to annual spawning migrations, increased after spawning, and peaked in late winter. In the more complex mainstem Unalakleet River, MDN assimilation was higher but varied minimally from summer through fall before increasing in late fall and winter. Summer MDN assimilation, prior to salmon spawning, was primarily a function of habitat complexity, where MDN was highest in sloughs and the more complex mainstem river. After salmon spawned, fall MDN assimilation was a function of adult pink and Chinook salmon biomass as well as MDN assimilation that occurred prior to spawning (that is, summer MDN), but unrelated to total summer biomass (all salmon species biomass combined). Thus, MDN assimilation by juvenile salmon in the fall was a function of species-specific adult spawner abundance but seasonal patterns of MDN assimilation were masked in complex habitat where summer MDN assimilation remained high. [ABSTRACT FROM AUTHOR]

Monitoring the growth of salmon during their early marine phase provides insights into prey availability, and growth rates may be linked to risks of size-dependent mortality. However, the measurement of growth rate is challenging for free-living salmon in the ocean. Insulin-like growth factor (IGF)-I is a growth-promoting hormone that is emerging as a useful index of growth in salmon. In addition, laboratory-based studies using coho salmon have shown that one of circulating IGF-binding proteins (IGFBPs), IGFBP-1b, is induced by fasting and thus could be used as an inverse index of growth and/or catabolic state in salmon. However, few studies have measured plasma levels of IGFBP-1b in salmon in the wild. We measured plasma IGFBP-1b levels for postsmolt coho salmon collected in the Strait of Georgia and surrounding waters, British Columbia, Canada, and compared regional differences in IGFBP-1b to ecological information such as seawater temperature and stomach fullness. Plasma IGFBP-1b levels were the highest in fish from Eastern Johnstone Strait and relatively high in Queen Charlotte Strait and Western Johnstone Strait, which was in good agreement with the poor ocean conditions for salmon hypothesized to occur in that region. The molar ratio of plasma IGF-I to IGFBP-1b, a theoretical parameter of IGF-I availability to the receptor, discriminated differences among regions better than IGF-I or IGFBP-1b alone. Our data suggest that plasma IGFBP-1b reflects catabolic status in postsmolt coho salmon, as highlighted in fish in Eastern Johnston Strait, and is a useful tool to monitor negative aspects of salmon growth in the ocean. [ABSTRACT FROM AUTHOR]

Placement of large wood is a common stream restoration technique in western North America and increasingly in other parts of the world. Considerable information exists on response of anadromous salmonids in small (< 15 m bankfull width) coastal streams of western North America, but limited information exists on anadromous fish response to wood placement in larger streams or in the more arid interior Columbia River Basin. An extensive post-treatment design was used to sample 29 large wood placement projects to determine their physical and biological effectiveness. We sampled paired treatment and control reaches that were approximately 20 times longer than bankfull width and quantified fish abundance and habitat attributes during summer. Proportion of pool area, number of pools, large wood (LW), and pool forming large wood were significantly higher in paired treatment than control reaches. Juvenile Chinook salmon (Oncorhynchus tshawytscha), steelhead (O. mykiss) coho salmon (O. kisutch), and cutthroat trout (O. clarkii) abundances were significantly higher in treatment than control reaches, but no significant responses were detected for mountain whitefish (Prosopium williamsoni) or dace (Rhinichthys spp.). Chinook and coho responses were positively correlated with LW and pool area suggesting wood placement produced reach-scale increases of juvenile salmonid abundance. [ABSTRACT FROM AUTHOR]

Dietary specialization has led to the origin of several ecotypes of killer whales (Orcinus orca). Comparing the feeding habits of different populations within an ecotype is valuable for understanding the evolution of foraging strategies. In this study we investigated the diet of fish-eating killer whales in the Northwest Pacific Ocean (Avacha Gulf, Kamchatka) and compared it to the published data on Northeast Pacific fish-eating killer whales. We collected prey fragments (N = 141) after hunting events in the summer seasons of 2011–2016 and determined the species of prey. Killer whales fed mainly on various species of Pacific salmon in Avacha Gulf. Coho salmon (Oncorhynchus kisutch) (56% of samples) and chum salmon (O. keta) (31% of samples) predominated in the diet. The results are comparable to the peculiarities of the fish-eating killer whale diet in the Northeast Pacific where killer whales prefer Chinook salmon (O. tshawytscha) most of the summer but shift toward coho and chum in late summer. Avacha Gulf could be an area where killer whales come to hunt coho similar to Prince William Sound in Alaska where killer whales prefer coho to other salmon species. We found significant differences in the diet between sex-age categories. Females (N = 42) and juveniles (N = 15) were more selective and hunted mainly coho while males (N = 53) hunted chum equally to coho. Like Chinook in British Columbia, coho in Kamchatka has a prolonged spawning period. Coho is the most nutritious after Chinook. Coho's prolonged abundance and nutritional value probably make it preferable to killer whales especially females. [ABSTRACT FROM AUTHOR]

For species of fish that spawn over a large geographic range, it is expected that populations will experience different water temperatures during early development. To gain a better understanding of water temperature regimes experienced by embryo and larvae among populations, we surveyed surface and intragravel temperatures at 10 locations where Coho Salmon (Oncorhynchus kisutch) spawn across British Columbia from mid-November to May. We chose coastal systems and interior systems at southern and northern latitudes to represent the range of potential conditions where fish spawn. Intragravel water temperatures varied significantly across study sites and were also significantly warmer than surface water temperatures – particularly during the coldest winter months. Northern interior populations experienced temperatures below 1 °C early in embryo development; less than a month after spawning and with fewer than 50 accumulated thermal units in some locations. Throughout the experimental period, temperature variability was less in intragravel water than surface water, but differences also existed among locations. Daily fluctuations in temperature were greatest for the southern-most coastal locations. Our results represent important findings when attempting to extrapolate incubation temperature from surface water temperature since even small differences in temperature have a cumulative effect in embryo and larval development. [ABSTRACT FROM AUTHOR]

A tension between cooperation and conflict characterizes the behavioral dynamics of many social species. The foraging benefits of group living include increased efficiency and reduced need for vigilance, but social foraging can also encourage theft of captured prey from conspecifics. The payoffs of stealing prey from others (scrounging) versus capturing prey (producing) may depend not only on the frequency of each foraging strategy in the group but also on an individual’s ability to steal. By observing the foraging behavior of juvenile coho salmon (Oncorhynchus kisutch), we found that, within a group, relatively smaller coho acted primarily as producers and took longer to handle prey, and were therefore more likely to be targeted by scroungers than relatively larger coho. Further, our observations suggest that the frequency of scrounging may be higher when groups contained individuals of different sizes. Based on these observations, we developed a model of phenotype-limited producer-scrounger dynamics, in which rates of stealing were structured by the relative size of producers and scroungers within the foraging group. Model simulations show that when the success of stealing is positively related to body size, relatively large predators should tend to be scroungers while smaller predators should be producers. Contrary to previous models, we also found that, under certain conditions, producer and scrounger strategies could coexist for both large and small phenotypes. Large scroungers tended to receive the highest payoff, suggesting that producer-scrounger dynamics may result in an uneven distribution of benefits among group members that—under the right conditions—could entrench social positions of dominance. [ABSTRACT FROM AUTHOR]

Fish are exposed to a wide variety of environmental stressors, such as chemicals and acute changes in temperature. Oxytetracycline (OTC) has been used as an antibiotic for many kinds of bacterial diseases in cultured fish, but excessive doses of OTC are known to cause side effects in fish and can have negative effects on their environment. In the present study, we examined stress-related biomarker expression in response to excessive doses of dietary OTC in coho salmon (Oncorhynchus kisutch). Fish received OTC (100 mg/kg body weight/day) orally for 2 weeks. The percentage of liver to body weight (hepatosomatic index; HSI) and plasma biochemical parameter, alanine aminotransferase (ALT) activity, of the group fed a diet containing OTC were observed to be significantly higher than those of the control group. The total glutathione (tGSH) levels in the liver of OTC-fed fish were four fold higher than those in control fish and double the control levels in muscle and stomach. Plasma tGSH levels in OTC-fed fish were also higher than those in control fish. Expression levels of heat shock protein 70 in the liver, muscle, and stomach decreased by OTC administration. Accordingly, OTC-induced stress might increase the metabolic turnover of GSH due to consumption by scavenging oxidants generated by stress. These results concerning the changing patterns of stress-related biomarkers indicate that excessive doses of OTC fed to coho salmon induce oxidative stress, which might enhance oxidation in the body and result in damage to tissues, especially in the liver. The present results also suggest that tissue-specific damage caused by OTC might already exist in fish. [ABSTRACT FROM AUTHOR]

Growth hormone (GH) transgenic (T) coho salmon consistently show remarkably enhanced growth associated with increased appetite and food consumption compared to non-transgenic wild-type (NT) coho salmon. To improve understanding of the mechanism by which GH overexpression mediates food intake and digestion in T fish, feed intake and gastric evacuation rate (over 7 days) were measured in size-matched T and NT coho salmon. T fish displayed greatly enhanced feed intake levels (~ 2.5-fold), and more than 3-fold increase in gastric evacuation rates relative to NT coho salmon. Despite the differences in feed intake, no differences were noted in the time taken from first ingestion of food to stomach evacuation between genotypes. These results indicate that enhanced feed intake is coupled with an overall increased processing rate to enhance energy intake by T fish. To further investigate the molecular basis of these responses, we examined the messenger RNA (mRNA) levels of several genes in appetite- and gastric-regulation pathways (Agrp1, Bbs, Cart, Cck, Glp, Ghrelin, Grp, Leptin, Mc4r, Npy, and Pomc) by qPCR analyses in the brain (hypothalamus, preoptic area) and pituitary, and in peripheral tissues associated with digestion (liver, stomach, intestine, and adipose tissue). Significant increases in mRNA levels were found for Agrp1 in the preoptic area (POA) of the brain, and Grp and Pomc in pituitary for T coho salmon relative to NT. Mch and Npy showed significantly lower mRNA levels than NT fish in all brain tissues examined across all time-points after feeding. Mc4r and Cart for T showed significantly lower mRNA levels than NT in the POA and hypothalamus, respectively. In the case of peripheral tissues, T fish had lower mRNA levels of Glp and Leptin than NT fish in the intestine and adipose tissue, respectively. Grp, Cck, Bbs, Glp, and Leptin in stomach, adipose tissue, and/or intestine showed significant differences across the time-points after feeding, but Ghrelin showed no significant difference between T and NT fish in all tested tissues. [ABSTRACT FROM AUTHOR]

We note the special features of the genetic structure of coho salmon Oncorhynchus kisutch (Walbaum) populations from the rivers of the mainland coast of the Sea of Okhotsk, eastern Kamchatka, and Chukotka. The evolutionary age of the mitochondrial gene pool of this species from the studied localities is estimated. It is shown that the most widespread haplotype K1 appeared in coho salmon populations at the border of Middle and Late Pleistocene. The primary structure of the coho salmon Cytb protein is investigated. Radical substitutions in the amino acid sequence of this polypeptide are detected, which confirms the influence of the positive vector of directional selection. [ABSTRACT FROM AUTHOR]

To understand the factors that regulate early marine survival of juvenile Chinook ( Oncorhynchus tshawytscha) and coho ( Oncorhynchus kisutch) salmon, it is necessary to characterize their prey availability, selectivity, and dietary niche widths. Currently, no sampling protocol exists that directly measures the salmonid prey field and quantifies dietary niche width via stable isotope analysis (SIA). The main goals of this study were to quantify the dietary niche widths of juvenile salmon and to compare environmental prey community compositions to juvenile salmon diets. Juvenile Chinook and coho salmon and their prey were collected in the northern California Current ecosystem via herring and Nordic trawls during 9-15 June 2010. The catch per unit effort of the salmonid prey field was compared to juvenile salmon stomach contents, and a Manly-Chesson index was used to quantify prey selectivity. Salmon and their prey were measured for δC and δN values and salmon were analyzed via Stable Isotope Bayesian Ellipses in R. Results indicated that there was no significant difference between juvenile Chinook and coho salmon diets and that they principally consumed rockfish juveniles ( Sebastes spp.) and Cancer megalopae. Juvenile salmon consumed somewhat different prey items compared to both herring and Nordic nets and these nets sampled different assemblages of similar prey communities. Though juvenile salmon were in isotopic disequilibrium with their marine prey, both species occupied similar isotopic niche widths. These results demonstrate that SIA provides complementary information to stomach content analysis. [ABSTRACT FROM AUTHOR]

Growth hormone (GH) transgenic salmon possesses markedly increased metabolic rate, appetite, and feed conversion efficiency, as well as an increased ability to compete for food resources. Thus, the ability of GH-transgenic fish to withstand periods of food deprivation as occurs in nature is potentially different than that of nontransgenic fish. However, the physiological and genetic effects of transgenic GH production over long periods of food deprivation remain largely unknown. Here, GH-transgenic coho salmon ( Oncorhynchus kisutch) and nontransgenic, wild-type coho salmon were subjected to a 3-month food deprivation trial, during which time performance characteristics related to growth were measured along with proximate compositions. To examine potential genetic effects of GH-transgenesis on long-term food deprivation, a group of genes related to muscle development and liver metabolism was selected for quantitative PCR analysis. Results showed that GH-transgenic fish lose weight at an increased rate compared to wild-type even though proximate compositions remained relatively similar between the groups. A total of nine genes related to muscle physiology (cathepsin, cee, insulin-like growth factor, myostatin, murf-1, myosin, myogenin, proteasome delta, tumor necrosis factor) and five genes related to liver metabolism (carnitine palmitoyltransferase, fatty acid synthase, glucose-6-phosphatase, glucose-6-phosphate dehydrogenase, glucokinase) were shown to be differentially regulated between GH-transgenic and wild-type coho salmon over time. These genetic and physiological responses assist in identifying differences between GH-transgenic and wild-type salmon in relation to fitness effects arising from elevated growth hormone during periods of long-term food shortage. [ABSTRACT FROM AUTHOR]

Fry of the coho salmon, Oncorhynchus kisutch (Walbaum, 1792), which were caught in the Kronotskaya River, were found to include six species of parasites belonging to four classes: Monogenea ( Salmonchus alaskensis), Cestoda ( Proteocephalus longicollis), Nematoda ( Sterliadochona ephemeridarum, Cucullanus truttae, Philonema oncorhynchi), and Acantocephala ( Neoechinorhynchus salmonis). The intensity of the parasitic invasion was not above three specimens per fish. [ABSTRACT FROM AUTHOR]

The use of techniques with low or inconsistent sampling efficiency may lead to erroneous estimates of abundance. Although an increase in sampling intensity can improve sampling efficiency and precision, its cost can limit a study's spatial extent. A low-effort approach may be preferred for landscape-scale studies of fish distribution and abundance; however, this requires information on whether the low-effort sampling is vulnerable to habitat-mediated bias and imprecision of the estimator. To determine how habitat features affected sampling efficiency of juvenile coho salmon Oncorhynchus kisutch in headwater streams of the Little Susitna drainage, Alaska, we validated single-pass backpack electrofishing methods with closed population mark-recapture sampling. We found that habitat features, such as stream size and density of wood debris, had no measurable or consistent effect on sampling efficiency within the range of conditions present in these headwater systems, and single-pass catch explained 94.8 % of the observed variation in log-transformed mark-recapture estimates. This suggests that low-effort methods in headwater streams of the Little Susitna River can approximate actual fish numbers without accounting for habitat covariates that may influence sampling efficiency, and the advantage of sampling a greater spatial extent may sufficiently offset any concerns over low estimator precision. [ABSTRACT FROM AUTHOR]

Re-introduction of large wood for expanding hydraulic variability is an increasingly common practice, yet it is not yet known what elements of hydraulic variability are most beneficial to fish. In an experiment designed to emphasize the minimization of energy expenditure through controlled predation and drift, we investigated whether juvenile coho, under winter conditions, discriminated between microhabitats based primarily on flow strength, depth, distance to wood, or based on temporal or spatial variability of the flow field, with the hypothesis that turbulence would be a strong factor in habitat selection. We conducted physical experiments in a 1:1 scale model of a large wood jam at the Oregon Hatchery Research Center in Alsea, Oregon. We conducted high resolution (0.1 m) mapping of the flow field using an acoustic Doppler velocimeter array and underwater videogrammetry of fish locations. Results indicated that discrimination of microhabitats by juvenile coho salmon in cold, low flows emphasized depth and distance to wood over any hydraulic measures of the flow field. Correlations between hydraulic parameters and distance to wood limited our ability to distinguish the importance of turbulence measures relative to velocities, but highlighted the positive relationships between velocity and turbulence measures and the negative relationships between hydraulics and distance from the roughness elements. Findings suggest areas of further study including potential thresholds of temperature and flow intensity on the importance of turbulence in habitat selection. [ABSTRACT FROM AUTHOR]

Estuaries are among the most productive ecosystems in the world and provide important rearing environments for a variety of fish species. Though generally considered important transitional habitats for smolting salmon, little is known about the role that estuaries serve for rearing and the environmental conditions important for salmon. We illustrate how juvenile coho salmon Oncorhynchus kisutch use a glacial river-fed estuary based on examination of spatial and seasonal variability in patterns of abundance, fish size, age structure, condition, and local habitat use. Fish abundance was greater in deeper channels with cooler and less variable temperatures, and these habitats were consistently occupied throughout the season. Variability in channel depth and water temperature was negatively associated with fish abundance. Fish size was negatively related to site distance from the upper extent of the tidal influence, while fish condition did not relate to channel location within the estuary ecotone. Our work demonstrates the potential this glacially-fed estuary serves as both transitional and rearing habitat for juvenile coho salmon during smolt emigration to the ocean, and patterns of fish distribution within the estuary correspond to environmental conditions. [ABSTRACT FROM AUTHOR]

Thirty years ago, Fausch (Can J Zool 62:441-451, ) proposed a simple model of optimal positions for drift-feeding salmonids in streams, whereby fish maximize their net energy intake (NEI) by selecting focal points in low water velocity near faster currents that deliver abundant drifting invertebrates. The theory was based on earlier observations in artificial and natural streams describing characteristics of salmonid positions and a conceptual model by Chapman (Am Nat 100:345-357, ). A test of this simple drift foraging model in a laboratory stream showed that the growth rate of juvenile trout and salmon increased with NEI, and that the rank of NEI at positions held by coho salmon ( Oncorhynchus kisutch) correlated nearly perfectly with their rank in the dominance hierarchy. Fausch () inferred from these findings that positions that optimize NEI, within the constraints of the dominance hierarchy, are the resource for which these stream salmonids compete. In turn, the model was used to test the effects of interspecific competition by coho salmon on the foraging positions held by brook trout ( Salvelinus fontinalis) and brown trout ( Salmo trutta), and these results were used to infer potential effects of the introduced salmon on resident trout in Lake Michigan tributaries. Though the goals for this model were originally modest, it was tested in the field and further refined by Hughes and Dill (Can J Fish Aquat Sci 47:2039-2048, ) and others. During the last 20 years, the general theory has been incorporated into other models, which have been applied widely to analyze salmonid distribution and abundance in streams and rivers and used for management and restoration of habitat and flow regimes to benefit these fishes. [ABSTRACT FROM AUTHOR]

Appraisal of hatchery-related effects on Pacific salmonids ( Oncorhynchus spp.) is a necessary component of species conservation. For example, hatchery supplementation can influence species viability by changing genetic, phenotypic and life-history diversity. We analyzed time series data for seven salmonid taxa from the Klamath River basin, California, to investigate trajectories of wild and hatchery adult populations. Linear regression coupled with randomized permutations ( n = 99,999), two- tailed t tests, and Bayesian change point analysis were used to detect trends over time. Cross correlation was also used to evaluate relationships between wild and hatchery populations. The taxa of interest were spring, fall, and late-fall Chinook Salmon ( O. tshawytscha); Coho Salmon ( O. kisutch); Coastal Cutthroat Trout ( O. clarki clarki); and summer and hybrid Steelhead Trout ( O. mykiss). Significant decreases were detected for summer and hybrid Steelhead Trout. The proportion of wild fall Chinook has also significantly decreased concurrently with increases in hatchery returns. In comparison, returns of most Chinook and coho runs to the hatcheries, and fall Chinook strays to wild spawning areas from Iron Gate Hatchery have significantly increased since the 1970s. Increases were also detected for wild late-fall Chinook and spring Chinook adults. However, both of these were significantly correlated with Chinook Salmon returns to Trinity River Hatchery, suggesting augmentation by hatchery strays. Changes in abundances appeared related to changing ocean habitat conditions and hatchery practices. Our results suggest that anadromous salmonid populations in the Klamath River basin are becoming increasingly dependent on hatchery propagation, a pattern that can threaten population persistence. [ABSTRACT FROM AUTHOR]

Phase I biotransformation enzymes are critically important in the disposition of xenobiotics within biota and are regulated by multiple environmental cues, particularly in anadromous fish species. Given the importance of these enzyme systems in xenobiotic/endogenous chemical bioactivation and detoxification, the current study was designed to better characterize the expression of Phase I biotransformation enzymes in coho salmon ( Oncorhynchus kisutch) and the effects of salinity acclimation on those enzymes. Livers, gills, and olfactory tissues were collected from coho salmon ( O. kisutch) after they had undergone acclimation from freshwater to various salinity regimes of seawater (8, 16 and 32 g/L). Using immunoblot techniques coupled with testosterone hydroxylase catalytic activities, 4 orthologs of cytochrome P450 (CYP1A, CYP2K1, CYP2M1, and CYP3A27) were measured in each tissue. Also, the expression of 2 transcripts of flavin-containing monooxygenases (FMO A and B) and associated activities were measured. With the exception of CYP1A, which was down-regulated in liver, protein expression of the other 3 enzymes was induced at higher salinity, with the greatest increase observed in CYP2M1 from olfactory tissues. In liver and gills, 6β- and 16β-hydroxylation of testosterone was also significantly increased after hypersaline acclimation. Similarly, FMO A was up-regulated in all 3 tissues in a salinity-dependent pattern, whereas FMO B mRNA was down-regulated. FMO-catalyzed benzydamine N-oxygenase and methyl p-tolyl sulfoxidation were significantly induced in liver and gills by hypersalinity, but was either unchanged or not detected in olfactory tissues. These data demonstrate that environmental conditions may significantly alter the toxicity of environmental chemicals in salmon during freshwater/saltwater acclimation. [ABSTRACT FROM AUTHOR]

The effect of a previous hydrostatic high-pressure (HHP) treatment on sensory and physical quality of chilled coho salmon ( Oncorhynchus kisutch) was investigated. As a first stage, a 2 factorial design based on the response surface methodology was used for optimization of HHP conditions; for it, the effects on color uniformity, white spots appearance, elasticity, and hardness were analyzed. In a second stage, optimized HHP conditions (135 MPa for 30 s, 170 MPa for 30 s, and 200 MPa for 30 s; treatments T-1, T-2, and T-3, respectively) were applied as previous treatment to chilling, being sampling carried out on salmon muscle at days 0, 6, 10, 15, and 20. A marked effect on sensory and physical parameters was detected after HHP treatment and throughout the chilled storage. According to odor (rancid, putrid), texture (elasticity, gaping, firmness), and color ( L* value) attributes, fish corresponding to T-1 condition was shown to have better-maintained quality throughout the chilled storage than fish belonging to T-2 and T-3 conditions; additionally, a quality enhancement (putrid odor, cohesivity, gaping) was found when compared with control samples. In agreement to the preliminary optimization study, it is concluded that T-1 condition can provide the most effective HHP pre-treatment to better maintain sensory and physical properties when salmon muscle is to be commercialized as a fresh product. Results obtained for the quality evolution of chilled fish attest the importance of establishing a judicious selection of previous HHP treatment parameters to minimize undesirable changes related to sensory and physical characteristics. [ABSTRACT FROM AUTHOR]

We monitored the movement of coho salmon ( Oncorhynchus kisutch) smolts with acoustic transmitters from freshwater, through the freshwater/estuary ecotone, through the estuary, and to ocean entry to determine residence time and habitat use in Humboldt Bay, California. Tagged fish were monitored with a fixed receiver network and mobile tracking conducted from a boat. Coho salmon observed during the two-year study resided in Humboldt Bay beginning at least as early as late April and resided through the beginning of July. Coho salmon smolts spent more time in the freshwater/estuary ecotone compared to the lower estuary and spent an average of 10-12 days migrating to Humboldt Bay. Coho salmon smolts resided in Humboldt Bay, a marine embayment, for an average of 15-22 days prior to leaving the bay for the open ocean. Coho salmon smolts, as observed from mobile tracking, used deep channels and channel margins more often than floating eelgrass mats, pilings, and docks. In addition, tagged fish were more often detected in the central portions of Humboldt Bay characterized by deep channels with narrow intertidal margins. There were fewer detections in other portions of the bay characterized by shallow channels with large intertidal mudflats and eelgrass meadows. Relatively short transmitter life (70 days) precluded determining the latest date of coho salmon smolt residency in Humboldt Bay. In addition, tag size limited use to the largest emigrating smolts and may not represent the behaviors of the smaller-sized smolts which were more abundant. [ABSTRACT FROM AUTHOR]

Coho salmon ( Oncorhynchus kisutch) of the Southern Oregon/Northern California Coast (SONCC) Evolutionarily Significant Unit (ESU) is federally listed as a threatened species. The Trinity River Restoration Program (TRRP) is rehabilitating the Trinity River to restore coho salmon (coho) and other salmonid populations. In order to evaluate the program's actions, several studies of movements and behavior of coho in the Trinity River were conducted from 2006 to 2009, including snorkel surveys and mark-recapture techniques based on Passive Integrated Transponder (PIT) tags, elastomer tags, and radio transmitters. Catch, recapture, and condition of natural sub-yearlings, along with site fidelity and emigration of hatchery-reared yearlings in rehabilitated and reference habitats, were studied. Location was important because coho were absent from the lower controlled and rehabilitated sites most of the time. However, rehabilitation did not have a significant effect on natural coho salmon at the site level. Apparent survival of radio-tagged, hatchery-reared yearling coho released downstream from Lewiston Dam was much lower in the first 10 km downstream from the release site than in other areas between Lewiston Dam and the Klamath River estuary. Estimated survival of yearling hatchery coho salmon per 100 km down to Blake's Riffle was estimated at 64 % over the distance of the 239 km study area. Migration primarily occurred at night in the upper Trinity River; however, as yearlings moved through the lower Trinity River towards the Klamath River, estuary nocturnal migration became less. Apparent survival was generally lowest in areas upstream from the North Fork of the Trinity River. [ABSTRACT FROM AUTHOR]

Early marine life is thought to be a critical period affecting recruitment of Pacific salmon populations, but movements and mortality patterns of juvenile salmon after ocean entry have been poorly documented. Transect surveys by boat with towed hydrophone and acoustic receiver, along with lines of stationary receivers, were used to quantify early ocean movement and mortality patterns of juvenile coho salmon ( Oncorhynchus kisutch) and steelhead trout ( O. mykiss) tagged with acoustic transmitters (>700 tagged). Salmon smolts showed no behavioural preference with respect to distance from shorelines while migrating through Howe Sound, a coastal fjord. There was no evidence of spatial bias in mortality locations in terms of distance either to shorelines or from the river mouth, suggesting that mortality locations were scattered soon after ocean entry rather than concentrated right at the river mouth. Movement patterns of some tags (annual estimates of 5-20% of smolts that survived the downstream migration) were suggestive of estuarine predation, with detected tags likely inside predator stomachs. Using only detection data from mobile transects, a distance-based mortality rate was estimated for coho smolts while accounting for imperfect detection efficiency of transect surveys. The estimate of 2.4% per km during the 40 km migration through the fjord was comparable to average annual mortality rates estimated using detection data from stationary acoustic receivers, but required pooling multiple years of data. This suggests that mobile transect surveys of tagged migrating fish are likely insufficient for estimating annual mortality rates, but mobile detection data can complement those from stationary receiver arrays to further refine mortality estimates and provide information about fish movement patterns between lines of stationary receivers. This work provides an important methodological comparison between biotelemetry approaches for migrating fishes as well as the most comprehensive description to date of spatial marine mortality patterns of juvenile coho salmon and steelhead trout. [ABSTRACT FROM AUTHOR]

The principal patterns of feeding of downstream-migrant and coastal young of the year of coho salmon are considered. The so-called potential downstream migrants and residents, which differ in size and feeding patterns, were distinguished among coastal fry. It is assumed that identification of particular coastal specimens to phenotypic groups of downstream migrants or nonmigrants of young of the year of coho salmon may be determined even in the daytime by such parameters as the body length, feeding intensity, and food spectrum. [ABSTRACT FROM AUTHOR]

A packaging system combining a polyphenol-rich film and vacuum (PPRF-VP) was applied to farmed coho salmon ( Oncorhynchus kisutch) muscle for an 18-month storage (−18 °C). For it, two different concentrations of polyphenol compounds (namely, p-coumaric and ferulic acids) obtained from a barley husk extract were applied (PPRF-VP conditions) and compared to vacuum packaging without polyphenol presence (vacuum control; VP condition) and to packaging in the absence of vacuum and polyphenols (control; CP condition). The study was addressed to lipid hydrolysis and oxidation development and to lipid changes related to nutritional value. Both PPRF-VP conditions provided an inhibitory effect ( p < 0.05) on conjugated diene and fluorescent compound formation in frozen salmon. Compared to CP condition, vacuum packaging (PPRF-VP and VP conditions) led to lower ( p < 0.05) peroxide and anisidine values and to an inhibitory effect ( p < 0.05) on α- and γ-tocopherol losses. No effect ( p > 0.05) of polyphenol presence and vacuum packaging could be inferred on free fatty acid formation (hydrolysis development) and on polyunsaturated fatty acid retention (polyene index assessment). A low rancid odour development was observed in all kinds of fish samples, this being lower ( p < 0.05) in fish kept under vacuum (PPRF-VP and VP) conditions. [ABSTRACT FROM AUTHOR]

Purpose: This paper analyses the presence of polychlorinated biphenyls (PCBs) in escaped: farmed and wild salmons in southern Chile, analysing their concentrations and congener profiles in two species ( Oncorhynchus kisutch and Oncorhynchus mykiss). Methods: Muscle samples from both farmed and escaped fish of two species, O. mykiss (rainbow trout) and O. kisutch (coho salmon), were analysed for PCBs (42 congeners). To differentiate between the wild salmon and the salmon that have escaped from fish farms, the astaxanthin content in the muscular tissue was analysed with a high-performance liquid chromatography -diode array detector method. PCBs were measured by gas chromatography with an electron capture detector. Results: The levels of astaxanthin can be used to differentiate between farmed, escaped and wild-borne salmons with statistically different concentrations. When comparing the total PCB concentrations for both trout and salmon samples, it can be determined that a separate analysis for farmed, escaped and wild-borne fish more accurately describes the real differences in the concentrations; these differences are hidden when separate analyses are not performed. The congener profiles are similar in both trout and coho salmon, where the tri-, tetra- and penta-CB congeners are the most abundant. Conclusion: This study is the first report of PCBs in wild-borne, farmed and escaped salmons for the Southern Hemisphere, considering that Chile is actually one of the principal world producers of salmon. [ABSTRACT FROM AUTHOR]

Growth rate is an ecologically important trait, affecting the energy acquisition from, and provisioning to, the surrounding community. One of many costs suggested to counteract the evolution of increased intrinsic growth rate is an associated reduction in tolerance to conditions of nutrient stress. Here we test this concept with individuals possessing experimentally increased intrinsic growth rates (growth hormone transgenic coho salmon, Oncorhynchus kisutch) relative to wild genotypes. Using a series of three experiments, survival and growth of both genotypes were assessed on a physiological and behavioral level while varying food abundance, social interactions, and predation risk. Only in complete absence of exogenous food in newly emerged fry did the high intrinsic growth rate appear costly with a shorter average survival time compared to wild-type (Exp. 1). In experiment 2, genotypes with elevated intrinsic growth showed equal or higher survival and growth than wild-type genotypes In a third experiment, adding very limited amounts of food and allowing for social interactions in a simulated natural environment benefited transgenic individuals relative to wild-types, but at similar magnitudes in both the absence and presence of predators. Populations with transgenic individuals present did not crash under these competitive conditions as previously reported when studied in simple environments where hiding and attack escape were not possible. Our data suggest that transgenic fish have a greater scope for growth under most conditions, but are not obligated to use this capability. Physiological (e.g. appetite and conversion efficiency) and behavioral traits (e.g. competitive ability and risk-taking) found previously to correlate positively with intrinsic growth rate in the transgenic strain likely aided in their survival and growth, even under food limited conditions. Hence, at least in coho salmon, intrinsic growth rate does not appear to strongly affect survival under nutrient stress. [ABSTRACT FROM AUTHOR]

We examined the assumption that landscape heterogeneity similarly influences the spatial distribution of genetic diversity in closely related and geographically overlapping species. Accordingly, we evaluated the influence of watershed affiliation and nine habitat variables from four categories (spatial isolation, habitat size, climate, and ecology) on population divergence in three species of Pacific salmon ( Oncorhynchus tshawytscha, O. kisutch, and O. keta) from three contiguous watersheds in subarctic North America. By incorporating spatial data we found that the three watersheds did not form the first level of hierarchical population structure as predicted. Instead, each species exhibited a broadly similar spatial pattern: a single coastal group with populations from all watersheds and one or more inland groups primarily in the largest watershed. These results imply that the spatial scale of conservation should extend across watersheds rather than at the watershed level which is the scale for fishery management. Three independent methods of multivariate analysis identified two variables as having influence on population divergence across all watersheds: precipitation in all species and subbasin area (SBA) in Chinook. Although we found general broad-scale congruence in the spatial patterns of population divergence and evidence that precipitation may influence population divergence in each species, we also found differences in the level of population divergence (coho > Chinook and chum) and evidence that SBA may influence population divergence only in Chinook. These differences among species support a species-specific approach to evaluating and planning for the influence of broad-scale impacts such as climate change. [ABSTRACT FROM AUTHOR]

In quantitative genetics, multivariate statistical approaches are increasingly used to describe genetic correlations in natural populations, yet the exact genetic relationship between phenotype and genotype is often unknown. Quantitative trait locus (QTL) analyses can be used to describe the molecular basis of this relationship. In salmonids, growth and development are important fitness traits that are phenotypically correlated with each other and with other life-history traits, and an understanding of the molecular basis of these relationships is valuable for future evolutionary studies. Here, a QTL analysis using an outbred cross was initiated to determine the molecular basis of phenotypic correlations between such growth traits in coho salmon (Oncorhynchus kisutch), an important fish species distributed throughout the North Pacific Ocean. Fifty-three QTL for growth rate, length and weight at eight time periods were located on seven linkage groups (OKI03, OKI06, OKI18, OKI19, OKI23, OKI24 and an unnamed linkage group) or associated with five unlinked markers (Omm1159, Omm1367/i, Omy325UoG, OmyRGT55TUF and OtsG422UCD). One QTL for hatch timing was associated with the marker, Omm1241. All QTL were of minor effect, explaining no more than 20% of the observed variation in phenotypic value. Several instances of colocalization of QTL weight, length and growth rate were observed, suggesting a genetic basis for phenotypic correlations observed between these traits. This study lays the foundation for future QTL mapping efforts, for detailed examinations of the genetic basis of phenotypic correlations between growth traits, and for exploring the adaptive significance of growth traits in natural populations. [ABSTRACT FROM AUTHOR]

Juvenile salmon exhibit high growth rates upon their arrival into the marine environment. Dietary changes from freshwater and estuarine habitats to those derived from the marine environment may play an important role in ultimate adult survival. We measured the total lipid and fatty acid (FA) composition of juvenile Chinook salmon ( Oncorhynchus tshawytscha), coho salmon ( O. kisutch), and 18 of their potential prey items sampled from coastal waters during their first few months at sea. Coho salmon had significant reductions in their lipid content (% wet weight) between May and June, likely due to early marine growth. We did not find a significant drop between May and June Chinook salmon lipid content, which may indicate an earlier ontogenetic selection to marine prey that are higher in lipids and essential fatty acids (EFAs). Juvenile salmon ate prey of both high and low lipids. Significant FA compositional changes occurred for both coho and Chinook salmon between May and June. In May, the FA profile of juvenile salmon, especially coho salmon, did not resemble their prey items; however, in June, there was a strong correlation between salmon and their common fish prey as determined by gut content analysis. Significant increases in the level of EFAs, especially docosahexaenoic acid (DHA, 22:6n-3) accounted for the majority of the monthly differences in salmon tissue FA composition. In order for juvenile salmon to adequately meet their physiological requirements, they may have adapted to select advantageous prey with higher levels of EFAs, especially DHA, in order to rapidly increase their growth and ultimate survival. [ABSTRACT FROM AUTHOR]

Juveniles of coho salmon Oncorhynchus kisutch and mykiss Parasalmo mykiss at the age 1 + (yearlings) are differentiated by the content of different fractions of lipids (the lipid status), feeding habits, and by size-weight characteristics even eight months prior to smoltification. The juveniles of coho salmon and mykiss with high lipid status consume more calorific food items and, as a rule, have higher (on average) body length and weight. The juveniles with low lipid status consume less calorific organisms and have lower body length and weight. It is supposed that a considerable part of juveniles with high lipid status will migrate seaward the next year. The role of feeding habits in formation of this differentiation and, accordingly, in determination of timing of smoltification are discussed. [ABSTRACT FROM AUTHOR]

Juvenile Coho Salmon undergo many physiological changes during their springtime transformation from a freshwater parr to a migratory, seawater-capable smolt. Although field observations indicate smolts moving towards the surface and across the breadth of their streams to either swim or drift downstream with the current, water-velocity preferences of these developing cohos are unknown. Using video analysis of their swimming patterns in a calibrated, laboratory flow table with a velocity gradient, groups of three cohos generally increased their preferred water velocity through the springtime study period, to a late-May peak (daytime data, change-point regression analysis, p < 0.05) and over the entire period (nighttime data, regression analysis, p < 0.05). Moving to swifter currents should facilitate the downstream movements of these young cohos, as they develop through the parr-smolt transformation period. This information should assist managers of regulated watersheds and salmon hatcheries in optimizing juvenile salmon survival (e.g., with timely, late-spring water releases producing 0.1–0.3 m s−1 downstream water velocities). [ABSTRACT FROM AUTHOR]

The young of the year mykiss Parasalmo mykiss and coho salmon Oncorhynchus kisutch which perform downstream migration and which stay in the coastal zone during the period of primary dispersion represent different phenotypic groups. They differ in weight, length, and lipid status. Such differentiation is a factor controlling the formation of intrapopulation diversity and of the life strategy of fish. It may determine the timing of smoltification in the future and, further on, of the return for spawning. There were found some analogies and differences in characteristics of lipid metabolism in the investigated species. The content of total lipids decreases by autumn in underyearlings of both species. Furthermore, changes in the content of particular lipid fractions are multidirectional and various scaled, seemingly being related to physiological preparation for the wintering. [ABSTRACT FROM AUTHOR]