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Piscirickettsiosis is the most important bacterial disease in the Chilean salmon industry, which has sorted several efforts to its control, generating enormous economic losses. Epigenetic alterations, such as DNA methylation, can play a relevant role in the modulation of the metazoans response to pathogens. Bacterial disease may activate global and local immune responses generating intricate responses with significant biological impact in the host. However, it is scarcely understood how bacterial infections influence fish epigenetic alterations. In the present study, we utilized Pacific salmon and Piscirickettsiosis as model, to gain understanding into the dynamics of DNA methylation among fish-bacterial infection interactions. A genome-wide analysis of DNA methylation patterns in female spleen tissue of Pacific salmon was achieved by reduced representation bisulphite sequencing from a time course design. We determined 2,251, 1,918, and 2,516 differentially methylated regions DMRs among infected and control Pacific salmon in 1 dpi, 5 dpi, and 15 dpi, respectively. The mean methylation difference per DMR among control and infected groups was of ~35%, with an oscillatory pattern of hypo, hyper, and hypomethylation across the disease. DMCs, among the control and infected group, showed that they were statistically enriched in intergenic regions and depleted in exons. Functional annotation of the DMR genes demonstrated three KEGG principal categories, associated directly with the host response to pathogens infections. Our results provide the first evidence of epigenetic variation in fish provoked by bacterial infection and demonstrate that this variation can be modulated across the disease. [ABSTRACT FROM AUTHOR]

The selection of salmon broodstock can enhance certain economically important biological traits over generations, via the use of genomic technologies. Information related to flesh quality, disease resistance, growth rate, and feed conversion ratio, has been collected for coho salmon (Onchorhynchus kisutch) and may be applied to breeding programs in British Columbia. Marker-assisted selection (MAS) and genomic selection (GS) are two technologies used to identify breeders based on genes directly controlling performance traits. This study aims to quantify the net present value of these technologies, applied to coho salmon broodstock in recirculating land-based systems. We compute the value of these genomic technologies by taking the difference in profits for farmed coho salmon production, when the biological traits mentioned above are enhanced through selective breeding. Results indicate the value of the genomic technologies is around $700 to $6,280 per tonne of coho salmon produced, depending on the targeted trait. Flesh quality yields the greatest change in net present value, followed by growth rate. Our findings may offer a means to meet part of the growing demand for seafood through increased production of coho salmon and reinforce the importance of an ecologically sustainable and economically viable aquaculture industry in British Columbia. [ABSTRACT FROM AUTHOR]

Stream fish rely on a mix of terrestrial and aquatic prey sources. While the importance of terrestrial invertebrates as a food source for stream fish is well documented, the role of aquatic insects that emerge from the stream as winged adult insects (aquatic winged adults) and return to the stream as prey is less understood. In this study we determined the proportion of total diet for stream-rearing juvenile Coho Salmon (Oncorhynchus kisutch) that is derived from terrestrial and aquatic winged adult invertebrates which enter the stream from riparian habitats and consider how those cross-ecosystem prey contributions vary based on riparian habitat type. Study reaches were identified in three streams within the Kenai River watershed of Alaska that were representative of habitats found throughout the region and riparian vegetation was classified into grass/sedge, shrub and tree types using LiDAR. Juvenile Coho Salmon stomach contents were sampled seasonally in study reaches over a two-year period and ingested invertebrates were identified by taxa, life stage and origin. Our results showed that aquatic winged adult prey contributions to juvenile salmon diet were significantly lower in the grass/sedge study reach, and cross-ecosystem invertebrate prey represented a significantly higher proportion of juvenile salmon diet in the tree study reach. Invertebrate prey in the grass/sedge reach were composed primarily of the larval life stage of aquatic winged adults. These results suggest that change in riparian vegetation from tree/shrub to grass/sedge along Kenai streams as projected by regional climate change models, or that results from anthropogenic modification, will likely lead to lower availability of cross-ecosystem prey for stream fish. Management of riparian buffers along streams to preserve or increase occurrence of trees and shrubs is likely to help mitigate impacts of those possible changes. [ABSTRACT FROM AUTHOR]

Resource competition between animals is influenced by a number of factors including the species, size and relative abundance of competing individuals. Stream-dwelling animals often experience variably available food resources, and some employ territorial behaviors to increase their access to food. We investigated the factors that affect dominance between resident, non-native brook trout and recolonizing juvenile coho salmon in the Elwha River, WA, USA, to see if brook trout are likely to disrupt coho salmon recolonization via interference competition. During dyadic laboratory feeding trials, we hypothesized that fish size, not species, would determine which individuals consumed the most food items, and that species would have no effect. We found that species, not size, played a significant role in dominance; coho salmon won 95% of trials, even when only 52% the length of their brook trout competitors. As the pairs of competing fish spent more time together during a trial sequence, coho salmon began to consume more food, and brook trout began to lose more, suggesting that the results of early trials influenced fish performance later. In group trials, we hypothesized that group composition and species would not influence fish foraging success. In single species groups, coho salmon consumed more than brook trout, but the ranges overlapped. Brook trout consumption remained constant through all treatments, but coho salmon consumed more food in treatments with fewer coho salmon, suggesting that coho salmon experienced more intra- than inter-specific competition and that brook trout do not pose a substantial challenge. Based on our results, we think it is unlikely that competition from brook trout will disrupt Elwha River recolonization by coho salmon. [ABSTRACT FROM AUTHOR]

This work focuses on changes in sensory and physical properties of coho salmon (Oncorhynchus kisutch) during chilled storage (24 days). A marked change (p< 0.05) in the results of sensory analysis was found in the flesh of raw chilled fish (fresh odor, elasticity, hardness, oxidized odor) and in the cooked flesh of the chill-stored fish (firmness, neutral flavor, oxidized flavor, oxidized odor) samples. Additionally, physical parameters (gaping, cooking loss) also showed changes (p< 0.05) during chilled storage. According to odor and flavor descriptors (fresh odor, oxidized odor, neutral flavor), salmon fish were not acceptable after 17 days of chilled storage. [ABSTRACT FROM PUBLISHER]

Clock genes are involved in generating a circadian rhythm that is integrated with the metabolic state of an organism and information from the environment. Growth hormone (GH) transgenic coho salmon, Oncorhynchus kisutch, show a large increase in growth rate, but also attenuated seasonal growth modulations, modified timing of physiological transformations (e.g. smoltification) and disruptions in pituitary gene expression compared with wild-type salmon. In several fishes, circadian rhythm gene expression has been found to oscillate in the suprachiasmatic nucleus of the hypothalamus, as well as in multiple peripheral tissues, but this control system has not been examined in the pituitary gland nor has the effect of transgenic growth modification been examined. Thus, the daily expression of 10 core clock genes has been examined in pituitary glands of GH transgenic (T) and wild-type coho salmon (NT) entrained on a regular photocycle (12L: 12D) and provided either with scheduled feeding or had food withheld for 60 h. Most clock genes in both genotypes showed oscillating patterns of mRNA levels with light and dark cycles. However, T showed different amplitudes and patterns of expression compared with wild salmon, both in fed and starved conditions. The results from this study indicate that constitutive expression of GH is associated with changes in clock gene regulation, which may play a role in the disrupted behavioural and physiological phenotypes observed in growth-modified transgenic strains. [ABSTRACT FROM AUTHOR]

Growth hormone (GH) transgenic fish have dramatically enhanced growth rates, increased oxygen demands and reactive oxygen species production. GH-transgenic coho salmon provide an opportunity to address effects of increased metabolism on physiological aging. The objective of this study was to compare oxidative stress in wild-type (WT) and GH-transgenic (T) coho salmon ( Oncorhynchus kisutch) of different ages (1 and 2 years). Antioxidant enzyme activity, protein carbonyls (PC) and glutathione (GSH, GSSG) were measured. PC correlated to growth rates in individual fish. T fish exhibited lower antioxidant enzyme activities and GSH levels compared to the WT, while levels of PC and GSSG were higher. Age affects were observed in both WT and T fish; enzyme activities and GSH decreased while PC and GSSG increased. Our results support the metabolic rate theory of aging. This study aims to be a platform for continued studies of the theories of aging using fish as model organisms. [ABSTRACT FROM AUTHOR]

Many populations of coho salmon Oncorhynchus kisutch and steelhead O. mykiss are listed under the U.S. Endangered Species Act. Until recently, the role of avian predation in limiting recovery of coho salmon and steelhead in central California coastal watersheds has been overlooked. We used recoveries of passive integrated transponder (PIT) tags from Año Nuevo Island (ANI), a breeding site for several species of piscivorous seabirds, to estimate predation rates on juvenile salmonids and identify susceptible life stages and species responsible for predation. A total of 34,485 PIT tags were deployed in coho salmon and steelhead in six watersheds in San Mateo and Santa Cruz counties. Tags were deposited on ANI by predators after ingestion of tagged fish. Because tags were not removed from the island and were detected on multiple sampling occasions, we were able to use mark-recapture models to generate a corrected minimum predation estimate. We used POPAN, a variation of the Jolly-Seber model, to generate an estimate of gross population abundance, which accounted for tags deposited on the island but not detected during surveys. Detections of 196 tags from surveys conducted between autumn 2006 and spring 2009 were incorporated into the model, producing a gross population estimate of 242 tags (SE = 9.8). Addition of tags detected between autumn 2009 and 2010 to the abundance estimate from POPAN produced a new minimum estimate of 362 tags on ANI. Western gulls Larus occidentalis probably were the primary predator depositing tags on ANI. Minimum predation estimates ranged from 0.1% (Soquel Creek) to 4.6% (Waddell Creek) of outmigrating coho salmon and steelhead smolts. Predation was potentially greater given still unquantified deposition of tags off-colony and destruction of tags during digestive processes of predators. Finally, avian predators targeted estuary-reared fish, which contributed disproportionately to adult populations, further impacting imperiled salmon populations. [ABSTRACT FROM AUTHOR]

A 4-year evaluation was conducted to determine the proportion of juvenile coho salmon Oncorhynchus kisutch passing Cowlitz Falls Dam, on the Cowlitz River, Washington, during winter. River and reservoir populations of coho salmon parr were monitored using radiotelemetry to determine if streamflow increases resulted in increased downstream movement and dam passage. This was of interest because fish that pass downstream of Cowlitz Falls Dam become landlocked in Riffe Lake and are lost to the anadromous population. Higher proportions of reservoir-released fish (0.391-0.480) passed Cowlitz Falls Dam than did river-released fish (0.037-0.119). Event-time analyses demonstrated that streamflow increases were important predictors of dam passage rates during the study. The estimated effect of increasing streamflows on the risk of dam passage varied annually and ranged from 9% to 75% for every 28.3 m³/s increase in streamflow. These results have current management implications because they demonstrate the significance of dam passage by juvenile coho salmon during winter months when juvenile fish collection facilities are typically not operating. The results also have future management implications because climate change predictions suggest that peak streamflow timing for many watersheds in the Pacific Northwest will shift from late spring and early summer to winter. Increased occurrence of intense winter flood events is also expected. Our results demonstrate that juvenile coho salmon respond readily to streamflow increases and initiate downstream movements during winter months, which could result in increased passage at dams during these periods if climate change predictions are realized in the coming decades. [ABSTRACT FROM AUTHOR]

Egg-to-fry survival of salmonids is tempered by habitat degradation, including increased sediment in streams. To best manage multiple salmon species and prioritize scarce habitat restoration funds for the benefit of fish recovery, many studies have described and predicted the relationship between fine sediment deposited in spawning gravels and salmonid egg-to-fry survival. In this article, we used published studies, agency reports, and university theses (N = 14) to create predictive relationships between percent fine sediment and egg-to-fry survival of Chinook (Oncorhynchus tshawytscha), coho (O. kisutch) and chum (O. keta) salmon, and steelhead trout (O. mykiss). In our analysis, coho survival tended to decline more rapidly per unit sediment increase and chum survival least rapidly. Threshold effects were observed, with survival dropping rapidly when percent fines less than 0.85 mm was greater than 10%. For other size classes of fines, a threshold was primarily observed only for eyed egg survival when fines exceeded 25-30%. Our predictive models combine both field and laboratorydata and take into account a variety of conditions; they include estimates of uncertainty in the impact of sediment on egg-to-fry survival. These models can be used to forecast effects of watershed management practices on salmonids and to make comparisons between predicted salmonid survival rates under alternative management strategies for conditions where fine sediment is the limiting factor for survival. [ABSTRACT FROM AUTHOR]

Potential feed ingredients with high lipid content were made by enzymatic digestion followed by centrifugation of eye tissue from dusky rockfish (Sebastes ciliatus), coho salmon (Oncorhynchus kisutch), and sockeye salmon (Oncorhynchus nerka), and brain tissue from sockeye salmon. Supernatant fractions contained significant levels of docosahexaenoic acid and eicosapentaenoic acid and were essentially pure triacyglycerides. For the digest of sockeye salmon brain tissue, the lipids were mainly composed of phospholipids (74%) and sterols (22%). Assays for amino acid profiles and mineral content of the precipitant layers were also performed. [ABSTRACT FROM AUTHOR]

Early mortality syndrome in fry of Great Lakes salmonines is linked to reduced levels of thiamine in eggs, which reflects maternal consumption of forage fishes such as alewife (Alosa pseudoharengus) that contain thiaminase, an enzyme that destroys thiamine. We assessed annual variations in abundance and condition of alewives and thiamine status of coho salmon (Oncorhynchus kisutch) in Lake Ontario. We analyzed total thiamine in eggs of 20 coho salmon collected annually between 2003 and 2006 at the Salmon River Hatchery on the Salmon River, New York. Alewife abundance was assessed annually in southern and eastern Lake Ontario with bottom trawis during late April and early May. Mean thiamine concentration in eggs varied annually, with those collected in 2003 (2.5 nmol/g) being significantly higher than those collected in 2004 to 2006 (1.5 to 1.7 nmol/g). Although we did not test survival of fry, if reported threshold levels of thiamine for preventing mortality of Lake Michigan coho salmon fry apply, then many or most Lake Ontario coho salmon produced fry were likely to incur thiamine-deficiency mortality, especially during years 2004 to 2006. Comparison to indices of annual abundance of alewife in Lake Ontario with thiamine concentration in coho salmon eggs failed to show any significant correlations (P> 0.05). However, total length of female spawning coho salmon was positively correlated (P <0.05) with increasing condition and estimated energy content of adult alewives in the previous spring. These results suggest that growth of coho salmon in Lake Ontario was first limited by energy intake, whereas the amount of thiamine provided by alewives was sufficient for growth (in length) but not for producing thiamine-adequate eggs. [ABSTRACT FROM AUTHOR]

Coho salmon (Oncorhynchus kisutch) fillets were processed using five different methods (smoking, canning, freezing, acidifying, and salting) to evaluate the effect of preservation choice on the quality of polyunsaturated fatty acids (PUFA). Salmon preserved by smoking, canning, or freezing retained higher values of total fatty acids, including n-3 PUFAs such as eicosapentaenoic acid and docosahexaenoic acid. Salting and acidifying (pickling) treatments resulted in a significant decrease in PUFAs. The results of this study are intended to provide direction for handling and storage of salmon to retain the maximum levels of high-value n-3 PUFAs. [ABSTRACT FROM AUTHOR]

Data‐logging exercises in science classrooms assume that with the proper scaffolding and provision of contexts by instructors, pupils are able to meaningfully comprehend the experimental variables under investigation. From a case study of knowing and learning in a fish hatchery using real‐time computer statistical software, we show that appreciating the distributions of fish weights and lengths were mediated by the practical understanding that comes from measuring and handling the animals over time. This prior knowledge was further mediated by the representations in mathematical forms where technology was central. Hence, as a fish culturist ‘played’ with the data logging‐like technology, expanded forms of learning were made possible during the process of analysis and reflection. Besides clarifying the process of learning when using educational media like data loggers, we present the computer as a self‐reflexive tool that constitutes—in a dialectical fashion—learning in the everyday world.Ordinateurs et développement cognitif à l’œuvreLes exercices d’enregistrement de données dans les cours de science partent du principe qu’avec les étais appropriés, et la fourniture de contextes par les enseignants, les élèves sont capables d’une compréhension significative des variables expérimentales objet de la recherche. En partant d’une étude de cas d’étude et d’apprentissage prise dans un alevinage en utilisant un logiciel statistique en temps réel, nous montrons qu’une compréhension de la distribution des poids et longueurs des poissons passait par le truchement de la connaissance pratique que l’on tire de la manipulation et de la mensuration des animaux pendant une certaine période de temps. Cette connaissance préalable passait en outre par la médiation d’une représentation en formes mathématiques dans laquelle la technologie jouait un rôle central. Par conséquent, lorsqu’un éleveur de poissons ≪ s’amusait ≫ avec une technologie de simulation d’enregistrement de données, des formes d’apprentissage étendues devenaient possibles dans le processus d’analyse et de réflexion. Outre l’éclairage sur le processus d’apprentissage lors de l’utilisation des medias éducatifs comme les enregistreurs de données, nous présentons l’ordinateur comme un outil d’auto‐réflexion qui reconstitue – sur le mode dialectique – l’apprentissage dans le monde réel.Computer und kognitive Entwicklung bei der ArbeitDas Aufzeichnen von Daten wissenschaftlicher Übungen wird in der Annahme, dass mit der Protokollierung des korrekten Verlaufs und der korrekten Zuordnung von Kontexten durch die Ausbilder Schüler in der Lage sind, die experimentell untersuchten Variablen richtig zu deuten. Wir werten eine Fallstudie an einem Fischbrutplatz, die unter Verwendung von statistischen Echtzeit‐Computerprogrammen erstellt wurde, aus und zeigen, dass das (korrekte, d.Ü.) Schätzen von Fischgewichten und Längen vom vorherigen praktischen Umgang und dem Messen der Tiere über längere Zeit abhängt. Dieses Vorwissen wurde weiter von den Repräsentanten in den mathematischen Formeln beeinflusst, die technikzentriert waren. Daher war es möglich, ausgedehnt mit den Daten während des Prozesses von Analyse und Reflexion zu ‘spielen’ und dabei zu lernen. Neben der Klärung des Lernprozesses durch den Gebrauch von Bildungsmedien wie Datenregistrationsprogrammen konnten wir den Computer als ein selbstreflexives Werkzeug vorstellen, das – in einer dialektischen Art – das Lernen in unserer täglichen Welt bestimmt. [ABSTRACT FROM AUTHOR]

Wild salmon stocks in the Pacific Northwest are imperiled by a variety of anthropogenic environmental modifications, not the least of which is increasing maximum water temperatures. While many reports have been written on physiological or population-level influences of temperature in terms of the decline of wild salmon, synthesis of these diverse sources is needed for evaluation of numeric temperature criteria and their potential in salmon recovery planning. Various sensitive life stages and biological processes are impacted differently for different salmon species. This article reviews the literature for chinook, coho, chum, and steelhead, which are currently listed in the Columbia River Basin under the Endangered Species Act. Spawning, incubation and early fry development, juvenile rearing and growth, smoltification, and migration are considered. Swimming speed, disease susceptibility, chemical considerations, and lethality are also reviewed. Regional population growth and climate change will exacerbate the difficulties of recovering Northwestern salmon beyond remnant runs. Ethical analysis of the assumptions underlying recovery policy decisions, proposals for regime-based water quality standards, and a systems level vulnerability analysis are components of the recovery planning discussions. Specific numeric maximum temperature criteria that can be integrated into a broader recovery planning process are described for sensitive life stages of three species of Pacific Northwest salmon and steelhead. [ABSTRACT FROM AUTHOR]

A neuroendocrine peptide can induce sex-reversal in protogynous labrid teleosts, similar to androgenic and antiestrogenic steroids. Culture water containing metabolites of 17á-methyltestosterone (MT), when recirculated, are more potent to induce sex-reversal than dietary supplemented MT; human estrogens present in sewage water, or other pollutants derail the normal course of sex differentiation. Steroid administration by immersion is 200-1,000 times cheaper than dietary supplementation; discrete immersion for 2-8 hours per day for 1-3 weeks after hatching induces maximal sex-reversal in salmonids like coho salmon, Oncorhynchus kisutch, while others like chinook salmon, O. tshawytscha, require dietary supplementation. Studies on uptake, disposition in the organs, and elimination of unlabeled or labeled steroids have indicated that the androgen is absorbed within one hour after intake, and selectively retained it in gall bladder, pyloric caeca and liver at higher concentrations for a longer time; however, 90-95% of the steroid is eliminated within 1-2 weeks. Estimated residual steroid of < 5 ng/g fish is too low to be a hazard to human health. Steroid delivered through water can be absorbed and retained by egg yolk of salmonids and is gradually released into the developing embryos. Temperature and autosomal gene(s) alter the process of sex differentiation in hormonally sex-reversing fish. Suboptimal treatment of steroids results in the production of hermaphroditic and intersex individuals. Hormonally sex-reversed fish also suffers from low survival and functional deficiences. The Indian scenario on the use of hormones for monosex aquaculture is described. [ABSTRACT FROM PUBLISHER]

The diets of coho fry in Baker Creek, Bellingham, Washington, and anadjacent pond were examined in November through January, 1988-89. Fry in both habitats had the larger numbers of prey in early December after heavy rain, when springtails comprised more than 70% of their food items in both habitats. In January, when rainfall was low, both populations fed more on benthic invertebrates, such as taeniopterygid nymphs and simuliid larvae in the creek, and chironomid larvae in bothhabitats. High rainfall and flooding played an important role in making available food for juvenile coho salmon in both off-channel and creek habitats in late fall and early winter. [ABSTRACT FROM AUTHOR]