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• DGT was applied for the first time to monitor 6PPD-Q in urban waters. • HLB-DGT performance was independent of multiple environmental factors. • 6PPD-Q concentrations were 3 to 6.5 times higher in snowmelt than in surface runoff. • 6PPD-Q in urban waters posed high risks to migratory fish. The occurrence and risk of N-(1,3-dimethylbutyl)-N′-phenyl- p -phenylenediamine-quinone (6PPD-Q), derived from the oxidation of the tire antidegradant 6PPD, has raised significant concern since it was found to cause acute mortality in coho salmon when exposed to urban runoff. Given the short half-life period and low solubility of 6PPD-Q, reliable in situ measurement techniques are required to accurately understand its occurrence and behaviour in aquatic environments. Here, using the diffusive gradients in thin-films (DGT) method with HLB as a binding agent, we developed a new methodology to measure 6PPD-Q in urban waters. 6PPD-Q was rapidly and strongly adsorbed on the HLB-binding gel and was efficiently extracted using organic solvents. The HLB-DGT accumulated 6PPD-Q linearly for >7 d and its performance was not significantly affected by pH (6.5–8.5), ionic strength (0.0001–0.5 M) or dissolved organic matter (0–20 mg L−1). Field evaluation of the DGT method demonstrated its effectiveness in urban runoff, detecting 6PPD-Q levels of 15.8–39.5 ng L−1 in rivers. In snowmelt, DGT detected 6PPD-Q levels of 210 ng L−1 which is two times higher than the value obtained by grab sampling. 6PPD-Q levels were much higher in snowmelt than those in rivers. This indicates that snowfall constitutes an important transport pathway for 6PPD-Q and that DGT effectively captured the fraction continuously released from dust particles in the snow samples. 6PPD-Q posed a substantial risk to migratory fish in urban waters, and its release from tire wear particles requires further investigation. This study is the first to develop a DGT-based method for 6PPD-Q determination in urban waters, and the method can ensure an accurate measurement of the release of 6PPD-Q to the environment, particularly in rainfall or snowmelt, important pathways for its entry into the aquatic environment. [Display omitted] [ABSTRACT FROM AUTHOR]

The extensive use of synthetic antioxidants, notably N-(1,3-dimethylbutyl)-N′-phenyl- p -phenylenediamine (6-PPD), in rubber-related products, particularly in tire manufacturing, has induced concerns regarding their environmental impact and potential health hazards. Despite the identification of 6-PPD and its derivative, 6-PPD quinone (6-PPDQ), in various water samples and their lethal effects on certain aquatic species (e.g. , coho salmon, rainbow trout and brook trout), the levels of airborne 6-PPD/6-PPDQ and their respiratory toxicity remain relatively unexplored. In this study, we aimed to evaluate the respiratory toxicity potential of 6-PPD and its derivatives, with a specific focus on detecting these compounds in airborne particulates and assessing their toxic effects on lung cells. Characterization of four airborne fine particulate (FP) samples revealed spherical morphologies with diameters ranging from 17.7 to 225.7 nm, displaying slight agglomeration and negative surface charge. methanol/acetonitrile extraction followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis confirmed the presence of both 6-PPD and 6-PPDQ on the surfaces of FPs, with significant variations (0.26–1.05 μg g−1) in loading capacity observed among the samples. Subsequent exposure of lung cells (THP-1, BEAS-2B, and A549) to 6-PPD and 6-PPDQ revealed dose-dependent declines in mitochondrial metabolic activity induced by 6-PPD, along with severe membrane damage, ATP depletion, and pro-inflammatory cytokine release. Conversely, 6-PPDQ exhibited negligible toxicity in all tested parameters. These findings underscore the potential health risks associated with airborne 6-PPD exposure and emphasize the importance of further research into the respiratory toxicity of 6-PPD derivatives. [Display omitted] • 6-PPD and 6-PPDQ were identified on the surfaces of airborne fine particulates. • Contents of 6-PPD and 6-PPDQ varied with distances from urban central traffic sites. • 6-PPD induced toxicity in lung cells by damaging metabolism, membrane and ATP level. • 6-PPD induced release of pro-inflammatory cytokine in lung macrophages. [ABSTRACT FROM AUTHOR]

Salmons are crucial to ecosystems and economic activities like commercial fishing and aquaculture, while also serving as an important source of nutrients, underscoring their ecological significance and the need for sustainable management. To better understand the toxicity and biological interactions between the salmon and industrial chemicals in the aquatic environment, we utilized the ToxValDB database to develop first ever computational toxicity models for six salmon subspecies (covering Atlantic and Pacific salmon) across two genera, employing Quantitative Structure-Activity Relationship (QSAR) and quantitative Read-Across Structure-Activity Relationship (q-RASAR) methods. For three smaller datasets (Oncorhynchus nerka , Oncorhynchus keta , and Oncorhynchus gorbuscha), we created mathematical models using the entire datasets where QSAR models demonstrated superior statistical quality compared to q-RASAR. Conversely, the three larger datasets (Oncorhynchus kisutch , Oncorhynchus tshawytscha , and Salmon salar) were divided into training and test sets, the q-RASAR models yielded better results compared to QSAR models. Mechanistic interpretations of these models revealed that descriptors such as Burden eigenvalues (BCUT), autocorrelation of topological structure (ATSC), and molecular polarizability were significant predictors of toxicity. For instance, higher polarizability and certain topological features were associated with increased toxicity as per the developed models. Statistically superior models for each subspecies were used to predict the aquatic toxicity of 1085 untested organic chemicals for toxicity data gap filling and risk assessment considering the applicability domain (AD). These insights are pivotal for designing safer chemicals and emphasize the need for sustainable management of salmon populations. [Display omitted] • First-ever QSAR and q-RASAR models for six salmon subspecies. • Identified ten most and least toxic chemicals for each species employing 1085 chemicals. • Highlighted the unique chemical features responsible for toxicity across different species. • Emphasized sustainable salmon management for chemicals risk assessment. [ABSTRACT FROM AUTHOR]

The environmental ubiquity of tire and road wear particles (TRWP) underscores the need to understand the occurrence, persistence, and environmental effects of tire-related chemicals in aquatic ecosystems. One such chemical is 6PPD-quinone (6PPD-Q), a transformation product of the tire antioxidant 6PPD. In urban stormwater runoff 6PPD-Q can exceed acute toxicity thresholds for several salmonid species and is being implicated in significant coho salmon losses in the Pacific Northwest. There is a critical need to understand the prevalence of 6PPD-Q across watersheds to identify habitats heavily affected by TRWPs. We conducted a reconnaissance of 6PPD and 6PPD-Q in surface waters across the United States from sites (N = 94) with varying land use (urban, agricultural, and forested) and streamflow to better understand stream exposures. A rapid, low-volume direct-inject, liquid chromatography mass spectrometry method was developed for the quantitation of 6PPD-Q and screening for 6PPD. Laboratory holding times, bottle material, headspace, and filter materials were investigated to inform best practices for 6PPD-Q sampling and analysis. Glass bottles with PTFE-lined caps minimized sorption and borosilicate glass fiber filters provided the highest recovery. 6PPD-Q was stable for at least 5 months in pure laboratory solutions and for 75 days at 5 °C with minimal headspace in the investigated surface water and stormwaters. Results also indicated samples can be frozen to extend holding times. 6PPD was not detected in any of the 526 analyzed samples and there were no detections of 6PPD-Q at agricultural or forested sites. 6PPD-Q was frequently detected in stormwater (57%, N = 90) and from urban impacted sites (45%, N = 276) with concentrations ranging from 0.002 to 0.29 μg/L. The highest concentrations, above the lethal level for coho salmon, occurred during stormwater runoff events. This highlights the importance of capturing episodic runoff events in urban areas near ecologically relevant habitat or nursery grounds for sensitive species. [Display omitted] • With a short half-life, 6PPD has a low aqueous detection frequency. • Urban-impacted stormwater has the highest observed aqueous concentrations of 6PPD-Q. • 6PPD-Q stream exposures are transient pulse(s) at concentrations toxic to coho salmon. • Sampling protocols and monitoring should account for the episodic nature of exposure. • Glass containers minimize sorption of 6PPD-Q. [ABSTRACT FROM AUTHOR]

N-1,3-Dimethylbutyl-N′-phenyl-p-quinone diamine (6PPDQ) is a derivative of 6PPD, a synthetic antioxidant used in tire manufacturing to control the degradation caused by oxidation and heat aging. Its discovery in 2020 has raised important environmental concern, particularly regarding its association with acute mortality in coho salmon, prompting surge in research on its occurrence, fate, and transport in aquatic ecosystems. Despite this attention, there remain notable gaps in grasping the knowledge, demanding an in depth overview. Thus, this review consolidates recent studies to offer a thorough investigation of 6PPDQ's environmental dynamics, pathways into aquatic ecosystems, toxicity to aquatic organisms, and human health implications. Various aquatic species exhibit differential susceptibility to 6PPDQ toxicity, manifesting in acute mortalities, disruption of metabolic pathways, oxidative stress, behavioral responses, and developmental abnormalities. Whereas, understanding the species-specific responses, molecular mechanisms, and broader ecological implications requires further investigation across disciplines such as ecotoxicology, molecular biology, and environmental chemistry. Integration of findings emphasizes the complexity of 6PPDQ toxicity and its potential risks to human health. However, urgent priorities should be given to the measures like long-term monitoring studies to evaluate the chronic effects on aquatic ecosystems and the establishment of standardized toxicity testing protocols to ensure the result comparability and reproducibility. This review serves as a vital resource for researchers, policymakers, and environmental professionals seeking appraisals into the impacts of 6PPDQ contamination on aquatic ecosystems and human health. [Display omitted] • Prevalence of 6PPDQ is an emerging challenge for environmental health. • 6PPDQ toxic effects linked to the organismal tolerances. • Inhalation, ingestion, and dermal contact pose human health hazards. • Interdisciplinary approach is essential for tackling 6PPDQ chemical challenges. • Urgent calls for standardized testing, epidemiological studies, and mitigation strategies required. [ABSTRACT FROM AUTHOR]

The increasing concern over tire pollution, exacerbated by the improper disposal of waste tires, serves as the backdrop for this research, which aims to explore the efficacy of incorporating ground tire rubber (GTR) into asphalt mixtures enhanced with a stress-absorbing membrane interlayer (SAMI). In this study, three variations of Hot Mix Asphalt (HMA) were evaluated: a conventional mix, a rubber-modified asphalt mixture (RMA), and a trans-polyoctenamer rubber (TOR) modified asphalt mixture in the laboratory. The assessment focused on the high and low-temperature performance of the asphalt mix and binder. Key findings from the laboratory tests indicate that the integration of a SAMI layer and GTR as additives markedly boosts the crack resistance of the asphalt mixture. Despite a reduction in fracture energy across all three HMA types following long-term aging, the GTR-modified HMA maintained superior fracture energy relative to the conventional mix. Initially, the inclusion of GTR adversely affected the mixture's rutting resistance. However, after undergoing long-term aging, both the conventional and GTR-modified HMAs exhibited exceptional rutting and moisture damage resistance. Field noise assessments further demonstrated that GTR-enhanced pavements produced noise levels approximately 2 dB lower than those of standard asphalt pavements. Additionally, pavements lacking a SAMI layer manifested low-severity cracking, with an average cracking frequency occurring every 2 ∼ 6 m, whereas pavements equipped with a SAMI layer exhibited no cracking following two winter seasons. The rubber asphalt overlay may increase the leaching of 6PPD-quinone, but the SAMI layer helps reduce tire wear particle generation by preventing road cracking. Rubber asphalt overlay leaching tests resulted in 6PPD-quinone concentrations lower than currently available toxicity data (LC50 for Coho Salmon, 0.095 ug/L). In conclusion, the utilization of dry-processed rubber asphalt mixes alongside a SAMI layer in pavement construction not only has the potential to extend the service life of pavements but also contributes to the production of quieter road surfaces. This study underscores the environmental and functional benefits of incorporating rubber modifications into asphalt pavements, presenting a viable strategy for mitigating tire pollution through the reuse of waste tires in infrastructure. • Recycled rubber and stress-absorbing membrane interlayer in asphalt pavement. • Rubber particle into the asphalt binder improved its resistance to both rutting，cracking and fatigue performance. • Recycled rubber + SAMI asphalt mixture increases 85.6 % fracture energy. • Recycled rubber in asphalt mixture showed noise reduction on the road. • The recycled rubber and SAMI pavement exhibited no cracking. [ABSTRACT FROM AUTHOR]

Although many coho salmon (Oncorhynchus kisutch) caught in recreational fisheries are harvested, a substantial number of salmon are released after capture. Mortality rates of coho salmon released from recreational fisheries are largely unknown in the marine environment. This two-year study investigated factors associated with post-release mortality and travel rate of coho salmon in a marine recreational fishery in British Columbia, Canada. Adult coho salmon were recreationally angled in the marine environment, affixed with acoustic tags, and tracked during their return migration to natal spawning streams using a network of acoustic receivers. We found post-release mortality to the first point of detection (∼50 km from release) was 31.5% (95% CI: 26.1 – 37.4%; n = 279). Scale loss, eye damage, bleeding, and smaller body size of coho salmon were associated with increased odds of mortality. Scale loss and smaller body size were also associated with slower migration rate post-release. Air exposure up to five minutes was not found to be a driving factor in mortality or travel rate. These fishing-related injuries can cause immediate physiological and behavioural disturbances, increase vulnerability to predation, infection, and disease, and delay migration as the fish recovers. Smaller coho salmon may also be less capable of overcoming capture stress. Our study highlights the importance of quantifying mortality of wild fish in their natural environment, and we suggest that small changes to fishing practices (e.g., smaller hook sizes, less handling, etc.) could make large differences in release survival thus encouraging a more sustainable recreational fishery. [ABSTRACT FROM AUTHOR]

Recent toxicity studies of stormwater runoff implicated N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPD-quinone) as the contaminant responsible for the mass mortality of coho salmon (Oncorhynchus kisutch). In the wake of this discovery, 6PPD-quinone has been measured in waterways around urban centers, along with other tire wear leachates like hexamethoxymethylmelamine (HMMM). The limited data available for 6PPD-quinone have shown toxicity can vary depending on the species. In this study we compared the acute toxicity of 6PPD-quinone and HMMM to Brook trout (Salvelinus fontinalis) fry and fingerlings. Our results show that fry are ∼3 times more sensitive to 6PPD-quinone than fingerlings. Exposure to HMMM ≤6.6 mg/L had no impact on fry survival. These results highlight the importance of conducting toxicity tests on multiple life stages of fish species, and that relying on fingerling life stages for species-based risk assessment may underestimate the impacts of exposure. 6PPD-quinone also had many sublethal effects on Brook trout fingerlings, such as increased interlamellar cell mass (ILCM) size, hematocrit, blood glucose, total CO 2 , and decreased blood sodium and chloride concentrations. Linear relationships between ILCM size and select blood parameters support the conclusion that 6PPD-quinone toxicity is an outcome of osmorespiratory challenges imposed by gill impairment. [Display omitted] • Brook trout fry and fingerlings were exposed to 2 different tire-wear contaminants. • No effects were observed in HMMM fry exposures. • Fry were 2-3x more sensitive to 6PPDq than the fingerling life stage. • 6PPDq exposure resulted in concentration dependent changes in blood chemistry. • 6PPDq changed the gill morphology, resulting in osmorespiratory compromise. [ABSTRACT FROM AUTHOR]

• 6PPDQ in the runoff readily reacts with hypochlorite and chlorine dioxide. • The quinone moiety of 6PPDQ is the reactive site toward the disinfectants. • A number of chlorinated products of 6PPDQ form from disinfection. • Disinfection enhances the toxicity of 6PPDQ towards zebrafish embryos. N -phenyl- N '-(1,3-dimethyl butyl)- p -phenylenediamine-quinone (6PPDQ) currently arouses broad concerns because of its acute lethality to coho salmon and rainbow trout at environmentally relevant concentrations and the wide occurrence in runoff-impacted water. Investigation on the fate and transformation of 6PPDQ in various treatment processes is necessary for its risk assessment and control. Here, we explored the transformation of 6PPDQ during disinfection with its precursor 6PPD as a reference, focusing on kinetics, products, and toxicity variation. 6PPDQ readily reacted with hypochlorite and chlorine dioxide with second-order rate constants of 2580 ± 143 M−1 s−1 and 614 ± 52 M−1 s−1 (pH 7.0 and 25 °C), which are slightly lower than the reactions of 6PPD. We tentatively identified thirteen transformation products for 6PPDQ and eight for 6PPD in reaction with the two disinfectants. It seems that the quinone ring of 6PPDQ and the p -phenylenediamine moiety of 6PPD are reactive sites. The transformation of these compounds probably proceeds through Cl-substitution, ring cleavage, hydroxylation, and amine oxidation and hydrolysis. Tests with zebrafish embryos revealed that the transformation products of 6PPDQ could have higher eco-toxicity than the parent compound, while the toxicity of the 6PPD products remained nearly unchanged. The increased toxicity of 6PPDQ during disinfection highlights the necessity to substantially reduce its content before the disinfection of runoff-impacted water. [Display omitted] [ABSTRACT FROM AUTHOR]

Efforts to recover depressed stocks of salmon and steelhead trout in North America include implementation of mark-selective recreational fisheries, whereby anglers are allowed to harvest hatchery-origin fish but must release natural-origin fish. Catch and release angling (C&R) is generally thought to be an effective tool for conservation relative to traditional retention fisheries due to high survival of released adult salmon and steelhead in freshwater. Studies designed to estimate C&R mortality have produced highly variable results among species and size classes of fish, gear types, and environmental conditions. Therefore, crude approximations of C&R mortality are commonly used to quantify impacts to natural-origin salmon and steelhead. In addition, managers often restrict use of certain angling methods and terminal tackle that are assumed to result in higher mortality, leading to a multiplicity of different regulatory requirements with limited empirical support. We conducted a novel three-year mark-recapture study in the Cowlitz River, Washington to estimate effects of a variety of factors hypothesized to influence salmon and steelhead C&R survival using a control-treatment design. Three species of anadromous salmonids were captured and released as treatments using various angling techniques and terminal tackle. Fight time, handling time, and water temperature were recorded during each capture event. Non-angled fish were captured in a trap and released back into the fishery to serve as controls. Recovery rates of Coho Salmon differed less than a percent between angled and non-angled fish across multiple gear types, indicating negligible effects of C&R. Angled Spring Chinook Salmon experienced 3.6–10.2 % C&R mortality relative to non-angled control fish, depending on terminal tackle. Barbless hooks were associated with higher survival than barbed hooks for both Chinook and Coho Salmon, although differences were small for Chinook and negligible for Coho. In contrast, steelhead trout angled on barbed hooks were recovered at slightly higher rates than those caught on barbless hooks. We also found evidence for a reduction in landing rates when angling using barbless hooks. Finally, use of bait increased the probability that salmon would be hooked in a critical location such as the esophagus or stomach. Our findings are useful for assessing trade-offs between conservation measures and harvest opportunity when defining fishing regulations in mark-selective salmon and steelhead fisheries. [ABSTRACT FROM AUTHOR]

Microplastics are increasingly prevalent in marine systems and are a growing concern as a marine pollutant and contaminant with consequences for high trophic level consumers, including humans. Given evidence that links plastics to degraded ecosystem functioning and organismal health, there is increased interest in understanding the prevalence, fate and consequences of marine plastics. Microplastics contain and absorb harmful chemicals which may serve as endocrine disruptors and have negative implications for growth, reproductive health, and longevity. To expand current knowledge on microplastics in coastal marine ecosystems and the potential for biomagnification in marine food webs, we conducted stomach analyses of microplastics in Pacific salmon (Oncorhynchus spp.) and Pacific sand lance (Ammodytes personatus), an important prey for salmon. Prevalence of microplastics was substantial; 77 % of all salmon and 25 % of all sand lance stomachs contained at least one microplastic. Fish were sampled at multiple sites throughout the inland Salish Sea, including beaches and sediment bedforms for Pacific sand lance and open-water pelagic habitat for Pacific salmon. Pacific sand lance sampled at beach sites had more microplastics compared to those sampled in subtidal sediments and there were more plastics in sand lance at a protected beach site as compared to an exposed beach site. Prevalence of plastics in salmon differed according to species and included analyses of pink salmon (Oncorhynchus gorbuscha), Chinook (Oncorhynchus tshawytscha), and Coho salmon (Oncorhynchus kisutch); plastics were predominantly fibers in all species, though there were relatively higher rates of ingestion of films and particles in Chinook. Comparisons between plastic concentrations and stomach fullness indicated a slight negative trend, suggesting that plastics may be retained. Further investigation is needed to develop a more thorough understanding of the prevalence and fate of microplastics in coastal marine systems such as the Salish Sea, their concentration within marine food webs, and the implications for species targeted in fisheries. • Microplastics are increasingly prevalent in marine systems and a concern as a marine pollutant • Microplastics – especially fibers – were common in Pacific salmon and sand lance • Spatial variation was evident in prevalence of microplastics – elevated in protected and reduced in high flow areas • Prevalence and type of plastics differed among Pacific salmon species • Results suggest potential for bioaccumulation [ABSTRACT FROM AUTHOR]

• Recent downward trend in the number of academic publications referring to coho. • Large variation of missing data in commercial and recreational fisheries. • Low survival of wild coho likely due to mixed-stock fishing and habitat degradation. • More research needed on enhancement practices and impacts on the physiology of the released salmon. • Genomic technologies offer cost-effective alternative to coded-wire tagging system. Coho salmon (Oncorhynchus kisutch) were once a thriving species in southern British Columbia, acting as a source of food, livelihood, and recreation. Research on the survival and status of coho salmon in British Columbia has been critical since an unprecedented moratorium on Interior Fraser River stocks was put in place in 1998, leading to its designation as an endangered species. Since then, no comprehensive literature review has been undertaken on coho salmon. The present paper outlines current publication trends since the early 1990s, covering research areas that include the management and regulation of wild-capture coho salmon fisheries, hatchery enhancement efforts, as well as the pertinent factors that resulted in low returns. A complementary analysis did reveal a progressive downward shift in the total publication records pertaining, but not limited to, coho salmon in British Columbia. This review process identifies future steps and guidelines that policy makers and fisheries managers should take into account to improve the conservation outlook of coho salmon. Emerging technologies such as the use of genomic identification tools, more consistent and thorough data gathering processes, as well as reformed hatchery rearing practices, have all been identified as decisive action items. [ABSTRACT FROM AUTHOR]

The aquaculture industry has many problems associated with bacteria, viruses, and parasites, and the stress caused by these infections can modulate the physiological response in fish. In Chile, the sea lice Caligus rogercresseyi constitutes a major problem affecting the Chilean salmonid industry, having a strong negative effect on salmon production. For this reason, the aim of this study was to investigate the neuroendocrine and stress response of the most commonly cultured salmonid species in Chile, the Atlantic salmon (Salmo salar) and the Coho salmon (Oncorynchus kisutch), which were experimentally infested with the sea lice Caligus rogercresseyi. We analyzed the monoamine response in the telencephalon, optic tectum, and hypothalamus, as well as cortisol levels in plasma. In the liver and muscle we analyzed the cellular response by measuring heat shock proteins (60, 70, 90) and glucocorticoid mRNA transcription. After 14 days post infection C. rogercresseyi infestation modified the neuroendocrine and stress response in Atlantic and Coho salmon, with Coho salmon presenting a faster and higher response than the Atlantic salmon. • The infestation of ectoparasites can be modulating the physiological response in fish • In Chile the sea lice Caligus rogercresseyi constitutes a major problem affecting the Chilean salmonids industry. • The neuroendocrine response produced by the infestation of sea lice fluctuates in relation to the post-infestation period • The infestation modified differentially the neuroendocrine stress response in the Atlantic salmon and Coho salmon • The Coho salmon (Oncorynchus kisutch) is presenting a quicker and higher response than the Atlantic salmon. [ABSTRACT FROM AUTHOR]

In salmonids, exposure to elevated temperature impairs oogenesis. As such, there is a need to understand the molecular mechanisms that underpin this process, and develop mitigation strategies that maintain or rescue reproductive development in broodstock. In this study, follicle stimulating hormone (Fsh) and/or insulin-like growth factor 1 (Igf1) treatment were assessed for their ability to promote reproductive function at 14 and 22 °C in ovarian follicles from coho salmon in vitro. Maintenance at 22 °C resulted in the downregulation of fsh receptor , 17α -hydroxylase/C17,20-lyase and p450 aromatase a (cyp19a1a), and connexin 34.3 (cx34.3). While combined treatment with Fsh and Igf1 stimulated the expression of cyp19a1a at 14 °C, this treatment was not effective at 22 °C. Upregulation of cx34.3 occurred in response to treatments that contained Igf1 regardless of temperature, and there is evidence to suggest that apoptosis was inhibited to some extent at 22 °C following combined treatment with Fsh and Igf1. This study demonstrates the thermal impairment of key reproductive genes, and highlights the potential for novel hormone treatments to rescue oogenesis in salmonids. • High temperature downregulates ovarian steroidogenic and gap junction genes. • Hormonal treatment stimulated aromatase expression at low, but not high temperature. • Expression of apoptotic genes was lowered by hormonal treatment at high temperature. [ABSTRACT FROM AUTHOR]

Abstract Land-based recirculating aquaculture systems (RAS) have been used to rear salmon from smolt to market-sized adults, but high operating costs have limited their wide spread adoption. One clear advantage of using RAS for salmon aquaculture over open net pens is that fish can be reared under optimal conditions in an attempt to maximize growth and physiological performance and reduce overall production costs. However, few studies have attempted to define the optimal conditions for the long-term rearing of salmon. Thus, the goal of this study is to determine the effects of salinity and photoperiod, two factors that can be easily manipulated in RAS, on the physiological performance of coho salmon (Oncorhynchus kisutch) during long-term rearing. To address this goal, post-smolt coho salmon were reared for 150 days in replicate RAS at 2.5, 5, 10 and 30 ppt under either 12:12 and 24:0 (light:dark) photoperiods. Routine metabolic rate, maximum metabolic rate, aerobic scope and hypoxia tolerance were measured at 60 and 120 days of rearing, while swimming performance was assessed at 60 and 150 days of rearing. There were no effects of salinity or photoperiod on metabolic rate measurements, hypoxia tolerance or swimming performance at any sampling time. There were, however, significant effects of salinity and photoperiod on post-swimming hematology. The results suggest that physiological disturbances continue to manifest due to different environmental conditions, despite acclimation, but do not hinder the animal's ability to cope with physiological stressors. Overall, rearing salinity and photoperiod had very few measurable effects on the physiology and performance of coho salmon except the ionoregulatory disturbances following swimming at salinities of 2.5 and 30 ppt. Highlights In coho salmon reared in RAS at 2.5, 5, 10 or 30 ppt in either 12:12 and 24:0 photoperiods for 150 days we found: • No effect on resting and maximal metabolic rate, or aerobic scope on days 60 or 120 of continuous rearing. • No effect on hypoxia tolerance on days 60 or 120 of continuous rearing. • No effect on repeat swimming performance on days 60 or 150 of continuous rearing despite some ionoregulatory disturbances. • Few physiological disturbances indicating coho salmon seem to acclimate well to these conditions in RAS. [ABSTRACT FROM AUTHOR]

Abstract Land-based, closed containment salmon aquaculture involves rearing salmon from smolt to adult in recirculating aquaculture systems (RAS). Unlike in open-net pen aquaculture, rearing conditions can be specified in RAS in order to optimize growth and physiological stress tolerance. The environmental conditions that yield optimal stress tolerance in salmon are, however, unknown. To address this knowledge gap, we reared Atlantic (Salmo salar) and coho (Oncorhynchus kisutch) salmon in 7 separate RASs for 400 days post-smoltification under 2 photoperiods (24:0 or 12:12, light:dark) and 4 salinities (2.5, 5, 10 or 30 ppt.) and assessed the effects of these conditions on thermal tolerance. We found that over the first 120 days post-smoltification, rearing coho under a 24:0 photoperiod resulted in a ~2 °C lower critical thermal maxima (CT max) than in coho reared under a 12:12 photoperiod. This photoperiod effect did not persist at 200 and 400 days, which was coincident with an overall decrease in CTmax in coho. Finally, Atlantic salmon had a higher CT max (~28 °C) compared to coho (~26 °C) at 400 days post-smoltification. Overall, these findings are important for the future implications of RAS and for the aquaculture industry to help identify physiologically sensitive time stages. Highlights • In coho salmon, a 24:0 photoperiod significantly reduced CT max relative to a 12:12 photoperiod on days 60 and 120. • CT max decreased over time in coho salmon from approximately 29 °C at 60 days to 26 °C at 400 days post-smoltification. • Salinity had no effect on CTmax in coho or Atlantic salmon. • Atlantic salmon had a higher CT max (28 °C) than coho salmon (26 °C). • This information is important for the aquaculture industry when considering the conditions under which salmon are reared in RAS. [ABSTRACT FROM AUTHOR]

Abstract In this study, we propose a novel framework combining spatially explicit population viability analysis and optimization for prioritizing fish passage barrier mitigation decisions. Our model aims to maximize the equilibrium population size, or alternatively minimize the extinction risk, of a target fish species subject to a budget on the total cost of barrier mitigation. A case study involving a wild coho salmon (Oncorhynchus kisutch) population from the Tillamook basin, Oregon, USA is used to illustrate the benefits of our approach. We consider two different spawning adult dispersal patterns, river and reach level homing, as well as straying. Under density dependent population growth, we find that homing behavior type has a significant effect on barrier mitigation decisions. In particular, with reach homing, our model produces virtually the same population sizes as a more traditional barrier prioritization procedure designed to maximize accessible habitat. With river homing, however, we find that it is not necessary to remove all barriers in order to maximize equilibrium population size. Indeed, a stochastic version of our model reveals that removing all barriers actually results in a marginal increase in quasi-extinction risk. We hypothesize that this is due to a population thinning effect of barriers, resulting in a surplus of recruits in areas of low spawner density. Our findings highlights the importance of considering spatiotemporal fish population dynamics in river connectivity restoration planning. By adding greater biological realism, models such as ours can help conservation managers to more strategically allocate limited resources, resulting in both cost savings and improved population status for a focal species. Highlights • A model is developed for optimizing river barrier mitigation actions. • Density dependent growth and dispersal dynamics are incorporated. • The model is applied to a wild coho population from the Oregon Coast. • Degree of homing fidelity has a strong impact on optimal decision making. • Leaving some barriers in place may help to decrease quasi-extinction risk. [ABSTRACT FROM AUTHOR]

Abstract There is a paucity of information on the physiological changes that occur over the course of salmon early marine migration. Here we aim to provide insight on juvenile Coho salmon (Oncorhynchus kisutch) physiology using the changes in gene expression (cGRASP 44K microarray) of four tissues (brain, gill, muscle, and liver) across the parr to smolt transition in freshwater and through the first eight months of ocean residence. We also examined transcriptome changes with body size as a covariate. The strongest shift in the transcriptome for brain, gill, and muscle occurred between summer and fall in the ocean, representing physiological changes that we speculate may be associated with migration preparation to feeding areas. Metabolic processes in the liver were positively associated with body length, generally consistent with enhanced feeding opportunities. However, a notable exception to this metabolic pattern was for spring post-smolts sampled soon after entry into the ocean, which showed a pattern of gene expression more likely associated with depressed feeding or recent fasting. Overall, this study has revealed life stages that may be the most critical developmentally (fall post-smolt) and for survival (spring post-smolt) in the early marine environment. These life stages may warrant further investigation. [ABSTRACT FROM AUTHOR]

Abstract In fish used for food production and scientific research, fast growth can be achieved via selective breeding or induced instantaneously via growth hormone (GH) transgenesis (GHT). The proteomic basis for these distinct routes towards a similar higher phenotype remains uncharacterized, as are associated implications for health parameters. We addressed this knowledge gap using skeletal muscle proteomics in coho salmon (Oncorhynchus kisutch), hypothesising that i) selective breeding and GHT are underpinned by both parallel and unique changes in growth systems, and ii) rapidly-growing fish strains have lowered scope to allocate resources towards immune function. Quantitative profiling of GHT and growth-selected strains was done in comparison to wild-type after injection with PBS (control) or Poly I:C (to mimic infection). We identified remodelling of the muscle proteome in each growth-enhanced strain that was strikingly non-overlapping. GHT was characterized by focal upregulation of systems driving protein synthesis, while the growth-selected fish presented a larger and more diverse set of changes, consistent with complex alterations to many metabolic and cellular pathways. Poly I:C had little detectable effect on the muscle proteome. This study demonstrates that distinct proteome profiles can explain outwardly similar enhanced growth phenotypes, improving our understanding of growth mechanisms in anthropogenic animal strains. Significance This work provides the first proteomic insights into mechanisms underpinning different anthropogenic routes to rapid growth in salmon. High-throughput proteomic profiling was used to reveal changes supporting enhanced growth, comparing skeletal muscle of growth hormone transgenic (GHT) and selectively-bred salmon strains with their wild-type counterparts. Contrasting past mRNA-level comparisons of the same fish strains, our data reveals a surprisingly substantial proteomic divergence between the GHT and selectively bred strains. The findings demonstrate that many unique molecular mechanisms underlie growth-enhanced phenotypes in different types of fish strain used for food production and scientific research. Graphical abstract Unlabelled Image Highlights • Mechanistic basis for rapid growth poorly understood in fish. • Comparative proteomic profiling done in fish strains showing highly enhanced growth. • Distinct basis for enhanced growth comparing transgenic and domesticated fish strains. • Highly distinct proteome profiles may explain outwardly similar growth phenotypes. • Study enhances understanding of how rapid growth is achieved in anthropogenic animal strains. [ABSTRACT FROM AUTHOR]

Abstract Fish vitality can be measured by classifying reflex impairments (i.e., a visual impression of the ability to respond to induced stimuli) and visible injuries. These metrics can predict survival probability following release from fisheries, and monitoring physiological disturbances following capture can help understand mechanisms of mortality. To test the hypothesis that severity of injury and reflex impairment influences the time course of physiological recovery, coho salmon (Oncorhynchus kisutch) were held for up to 84-h following capture by purse seine. We classified reflex impairments and visible dermal injuries, and through repeated blood sampling, assessed metrics indicative of stress, exhaustion, and osmoregulatory disturbances. Reflex-impairments and blood lactate levels suggested fish were exhausted upon capture but recovered after 48 h. Conversely, fish with dermal injuries showed disruptions to ion homeostasis that were greater in more severely injured fish and increased over time. While reflex impairments may predict short term post-release mortality, the prolonged physiological disturbances caused by dermal injuries are likely to be responsible for delayed mortality; our results suggest that disruptions to ion homeostasis is a possible mechanism of post-release mortality. Highlights • Effects of injury and reflex impairment on physiological recovery were assessed in coho salmon captured by purse seine. • Reflex-impairments and blood lactate levels suggested fish were exhausted upon capture but recovered after 48 hours. • Fish with dermal injuries showed disruptions to ion homeostasis that increased over time and with injury severity. • While impairment may predict short-term mortality, injuries may cause latent mortality given prolonged chemical disturbances. • Results suggest a possible mechanism by which capture-induced injury leads to mortality. [ABSTRACT FROM AUTHOR]

The antioxidant N-(1,3-Dimethylbutyl)-N′-phenyl-p- phenylenediamine (6PPD) is used to protect the rubber in tires from oxidation, which extends the life of the tire. When oxidized, 6PPD is transformed into 6PPD-quinone (6PPDQ). 6PPDQ, along with other tire ingredients, can enter aquatic ecosystems through the transport of tire wear particles in runoff during a precipitation event. The mass mortality of coho salmon following precipitation events in urban areas lead to the discovery that 6PPDQ is the likely cause due to coho salmon's relatively high sensitivity to 6PPDQ. The assessment of 6PPDQ toxicity to other aquatic species has expanded, but it has focused on fish. This study investigated the toxicity of 6PPDQ to four freshwater invertebrate species, larval burrowing mayfly (Hexagenia spp.), juvenile cladoceran (Daphnia magna) , file ramshorn snail embryo (Planorbella pilsbryi) , and adult washboard mussel (Megalonaias nervosa). For all four species, the highest concentration of 6PPDQ tested did not result in significant mortality. This translated into the determination of the highest concentration that did not cause significant mortality (NOEC) for Hexagenia spp., D. magna , P. pilsbryi , and M. nervosa of 232.0, 42.0, 11.7, and 17.9 μg/L, respectively. The data from this study indicate that freshwater invertebrates are not as sensitive to 6PPDQ as some salmonid species (e.g., coho salmon Oncorhynchus kisutch). This study also analyzed 6PPDQ in road runoff from around the city of Guelph in Ontario, Canada. 6PPQ was detected in all samples but the concentration was two orders of magnitude lower than the NOECs for the four tested species of freshwater invertebrate. [Display omitted] • Investigated toxicity of 6PPD-quinone to four freshwater invertebrate species • First study to investigate toxicity to freshwater insect and mollusk species • No adverse effects on survival, growth, and embryo development • Highest concentration with no effect are below concentrations in runoff [ABSTRACT FROM AUTHOR]

The antioxidant 6-PPD has been widely used to prevent cracking and thermal oxidative degradation and to extend the service life of tire rubber. 6-PPD quinone (6-PPDQ) is formed via the reaction of 6-PPD with O 3. Due to its acute lethality in coho salmon, 6-PPDQ has become an emerging pollutant of increasing concern. In this review, we provide a critical overview of the generation, environmental distribution, bioavailability, and potential toxicity of 6-PPDQ. The transformation pathways from 6-PPD to 6-PPDQ include the N -1,3-dimethylbutyl- N -phenyl quinone diamine (QDI), intermediate phenol, and semiquinone radical pathways. 6-PPDQ has been frequently detected in water, dust, air particles, soil, and sediments, indicating its large-scale and potentially global pollution trend. 6-PPDQ is bioavailable to both aquatic animals and mammals and acute exposure to 6-PPDQ can be lethal to some organisms. Exposure to 6-PPDQ at environmentally relevant concentrations could induce several types of toxicity, including neurotoxicity, intestinal toxicity, and reproductive toxicity. This review also identifies and discusses knowledge gaps and research needs for the study of 6-PPDQ. This review facilitates a better understanding of the environmental occurrence and exposure risk of 6-PPDQ. [Display omitted] • Three transformation pathways from 6-PPD to 6-PPDQ were summarized. • 6-PPDQ is widely distributed in water, dust, air particles, soil, and sediment environments. • 6-PPDQ can be bioavailable and accumulated in organisms. • Exposure to 6-PPDQ can cause several aspects of toxicity in organisms. • Physiochemical property, ecological risk, and health risk of 6-PPDQ can be predicted. [ABSTRACT FROM AUTHOR]

Piscine orthoreovirus (PRV) is associated with heart and skeletal muscle inflammation (HSMI) and circulatory disorders in salmonid species. In Chile, PRV affects the coho salmon industry most, as this virus correlates with both HSMI disease and jaundice syndrome. However, the causality of the latter has not been proven. In this study, we characterize nucleotide codifying and amino acid sequences of the PRV-3 detected in coho salmon with clinical signs and macroscopic evidence of jaundice syndrome in the seawater phase. The results support the diversification of the PRV-3 into two variants, PRV-3a and PRV-3b. The PRV-3a has been predominantly detected in coho salmon in the last five years. In addition, the new molecular sequences are characterized by polymorphisms exclusive to Chile in the σ3, p13 proteins encoded by the S1 segment and the μ1 protein encoded by the M2 segment. Additionally, we detected positive selection within the nucleotide sequence corresponding to the σ3 outer capsid protein. So far, PRV-3a has not been reported in other hosts in Chile, such as Atlantic salmon or rainbow trout. These findings highlight the diversification of PRV-3 in Chile and demonstrate a strong host-pathogen relationship which warrants further research to establish a link between PRV and jaundice syndrome in coho salmon. • Piscine orthoreovirus is detected in coho salmon with jaundice syndrome. • PRV variants detected in Chile are characterized by polymorphisms detected in the sigma 3 and p13 viral proteins. • Nucleotide sequences corresponding to the sigma 3 outer capsid protein displays positive selection. [ABSTRACT FROM AUTHOR]

N-(1,3-dimethylbutyl)- N ′-phenyl- p -phenylenediamine-quinone (6PPD-quinone) is an emerging contaminant of concern that is generated through the environmental oxidation of the rubber tire anti-degradant 6PPD. Since the initial report of 6PPD-quinone being the cause of urban runoff mortality syndrome of Coho salmon, numerous species have been identified as either sensitive or insensitive to acute lethality caused by 6PPD-quinone. In sensitive species, acute lethality might be caused by uncoupling of mitochondrial respiration in gills. However, little is known about effects of 6PPD-quinone on insensitive species. Here we demonstrate that embryos of fathead minnows (Pimephales promelas) are insensitive to exposure to concentrations as great as 39.97 μg/L for 168 h, and adult fathead minnows are insensitive to exposure to concentrations as great as 9.4 μg/L for 96 h. A multi-omics approach using a targeted transcriptomics array, (EcoToxChips), and proton nuclear magnetic resonance (1H NMR) was used to assess responses of the transcriptomes and metabolomes of gills and livers from adult fathead minnows exposed to 6PPD-quinone for 96 h to begin to identify sublethal effects of 6PPD-quinone. There was little agreement between results of the EcoToxChip and metabolomics analyses, likely because genes present on the EcoToxChip were not representative of pathways suggested to be perturbed by metabolomic analysis. Changes in abundances of transcripts and metabolites in livers and gills suggest that disruption of one‑carbon metabolism and induction of oxidative stress might be occurring in gills and livers, but that tissues differ in their sensitivity or responsiveness to 6PPD-quinone. Overall, several pathways impacted by 6PPD-quinone were identified as candidates for future studies of potential sublethal effects of this chemical. [Display omitted] • Fathead minnow embryos and adults are insensitive to 6PPD-quinone induced acute lethality. • 6PPD-quinone did not cause malformations of embryos. • 6PPD-quinone caused changes consistent with oxidative stress. • 6PPD-quinone caused changes consistent with one-carbon metabolism disruption. • Livers and gills of fathead minnows have different responses to 6PPD-quinone. [ABSTRACT FROM AUTHOR]

The increasing capacity of transcriptomic analysis by high throughput sequencing has highlighted the presence of a large proportion of transcripts that do not encode proteins. In particular, long non-coding RNAs (lncRNAs) are sequences with low coding potential and conservation among species. Moreover, cumulative evidence has revealed important roles in post-transcriptional gene modulation in several taxa. In fish, the role of lncRNAs has been scarcely studied and even less so during the immune response against sea lice. In the present study we mined for lncRNAs in Atlantic salmon ( Salmo salar ) and Coho salmon ( Oncorhynkus kisutch ), which are affected by the sea louse Caligus rogercresseyi , evaluating the degree of sequence conservation between these two fish species and their putative roles during the infection process. Herein, Atlantic and Coho salmon were infected with 35 lice/fish and evaluated after 7 and 14 days post-infestation (dpi). For RNA sequencing, samples from skin and head kidney were collected. A total of 5658/4140 and 3678/2123 lncRNAs were identified in uninfected/infected Atlantic and Coho salmon transcriptomes, respectively. Species-specific transcription patterns were observed in exclusive lncRNAs according to the tissue analyzed. Furthermore, neighbor gene GO enrichment analysis of the top 100 highly regulated lncRNAs in Atlantic salmon showed that lncRNAs were localized near genes related to the immune response. On the other hand, in Coho salmon the highly regulated lncRNAs were localized near genes involved in tissue repair processes. This study revealed high regulation of lncRNAs closely localized to immune and tissue repair-related genes in Atlantic and Coho salmon, respectively, suggesting putative roles for lncRNAs in salmon against sea lice infestation . [ABSTRACT FROM AUTHOR]

Interleukin-1 receptor-like 1 (Il1rl1 or ST2), a member of the interleukin-1 receptor family, has pleiotropic roles including tissue homeostasis, inflammation, immune polarization, and disease resistance in mammals. A single orthologue was previously described in salmonid fish; however, a recently improved genome assembly of rainbow trout ( Oncorhynchus mykiss ) revealed three adjacent, tandem il1rl1 orthologues on chromosome Omy 03. Here, we report the genomic organization and evolution of the three il1rl1 genes ( il1rl1α, il1rl1β, il1rl1γ ), and use both RNA-seq and gene-specific qPCR methods to quantify expression patterns. Nucleotide sequence homology between the three genes is >95% and each predicted protein contains three IG/IG-like domains, a transmembrane region and a TIR domain. The amino acid sequence homology of the rainbow trout il1rl1 genes are highly related to two functional copies in Atlantic and Coho salmon (∼94%) but relatively low (22–26%) with avian and mammalian species. Transcript abundance measured by RNA-seq in 15 tissues of healthy adult rainbow trout indicate constitutive expression of each gene. In whole body lysates, il1rl1α was shown to have >20 fold mRNA expression compared to il1rl1β and il1rl1γ as measured by qPCR assays specific to il1rl1α or il1rl1γ , as well as a multi-gene qPCR assay ( il1rl1α,β,γ ). Unrooted phylogenetic trees grouped the rainbow trout il1rl1 genes apart from other interleukin-1 receptor family genes and genomic comparisons identify preserved synteny between mammals, birds and salmonids albeit a pseudogene is present in both Atlantic salmon and Coho salmon. Phylogenetic analyses suggest that the three genes arose by tandem duplication but are inconclusive whether these events occurred prior-to or after salmonid speciation. These findings further the understanding of interleukin receptor family evolution and their contribution to teleost immune function. [ABSTRACT FROM AUTHOR]

This study aims to compare results obtained by mate selection accounting for different components in the objective function (OF), including functions related to genetic variability of the future progeny, using Nile tilapia and coho salmon real datasets. A total of 8782 Nile tilapias (NP) from five generations and 79,144 coho salmon (CS) from eight generations were used to optimize different OF accounting for coancestry of parents, expected genetic merit, inbreeding and components associated to genetic variability of the progeny. The candidates for selection were the superior animals of the last generation, corresponding to 281 males for NP population and 328 males for CS population, to be mated with 179 and 440 superior females, respectively. Candidate males were allowed to be mated with a maximum of four females. Different functions related to genetic variability of the progeny were tested in the mate selection and we observed that it was possible to increase the genetic variability or produce more uniform progeny, for both species studied. In addition, some OFs also allowed increasing the number of outstanding superior progeny. The tested OF were effective in optimizing the genetic gain and keeping the coancestry and inbreeding at controlled rates, while reducing or increasing the genetic variability of progeny, depending on the purpose of production. [ABSTRACT FROM AUTHOR]

Adult coho salmon ( Oncorhynchus kisutch ) prematurely die when they return from the ocean to spawn in urban watersheds throughout northwestern North America. The available evidence suggests the annual mortality events are caused by toxic stormwater runoff. The underlying pathophysiology of the urban spawner mortality syndrome is not known, and it is unclear whether closely related species of Pacific salmon are similarly at risk. The present study co-exposed adult coho and chum ( O. keta ) salmon to runoff from a high traffic volume urban arterial roadway. The spawners were monitored for the familiar symptoms of the mortality syndrome, including surface swimming, loss of orientation, and loss of equilibrium. Moreover, the hematology of both species was profiled by measuring arterial pH, blood gases, lactate, plasma electrolytes, hematocrit, and glucose. Adult coho developed behavioral symptoms within a few hours of exposure to stormwater. Various measured hematological parameters were significantly altered compared to coho controls, indicating a blood acidosis and ionoregulatory disturbance. By contrast, runoff-exposed chum spawners showed essentially no indications of the mortality syndrome, and measured blood hematological parameters were similar to unexposed chum controls. We conclude that contaminant(s) in urban runoff are the likely cause of the disruption of ion balance and pH in coho but not chum salmon. Among the thousands of chemicals in stormwater, future forensic analyses should focus on the gill or cardiovascular system of coho salmon. Because of their distinctive sensitivity to urban runoff, adult coho remain an important vertebrate indicator species for degraded water quality in freshwater habitats under pressure from human population growth and urbanization. [ABSTRACT FROM AUTHOR]

Expanding human population and urbanization alters freshwater systems through structural changes to habitat, temperature effects from increased runoff and reduced canopy cover, altered flows, and increased toxicants. Current stream assessments stop short of measuring health or condition of species utilizing these freshwater habitats and fail to link specific stressors mechanistically to the health of organisms in the stream. Juvenile fish growth integrates both external and internal conditions providing a useful indicator of habitat quality and ecosystem health. Thus, there is a need to account for ecological and environmental influences on fish growth accurately. Bioenergetics models can simulate changes in growth and consumption in response to environmental conditions and food availability to account for interactions between an organism's environmental experience and utilization of available resources. The bioenergetics approach accounts for how thermal regime, food supply, and food quality affect fish growth. This study used a bioenergetics modeling approach to evaluate the environmental factors influencing juvenile coho salmon growth among ten Pacific Northwest streams spanning an urban gradient. Urban streams tended to be warmer, have earlier emergence dates and stronger early season growth. However, fish in urban streams experienced increased stress through lower growth efficiencies, especially later in the summer as temperatures warmed, with as much as a 16.6% reduction when compared to fish from other streams. Bioenergetics modeling successfully characterized salmonid growth in small perennial streams as part of a more extensive monitoring program and provides a powerful assessment tool for characterizing mixed life-stage specific responses in urban streams. [ABSTRACT FROM AUTHOR]

Detecting the effectiveness of management actions intended to increase the abundance of threatened or exploited species can help resolve uncertainties about cost-effective management tactics. However, the complexity of ecological systems can make it difficult to identify important factors causing change in population abundance. This difficulty extends from detecting naturally-caused ecosystem regime shifts to management-induced regime shifts and the attendant change in population dynamics parameters. The adult abundance of naturally-produced coho salmon ( Oncorhynchus kisutch ) on the Oregon Coast generally declined until these fish were listed as threatened under the Endangered Species Act in 1998. The subsequent rebuilding of Oregon coastal coho adult abundance is coincident with increased habitat restoration, reduced hatchery production, and reduced harvest. Importantly, ocean survival also improved, thereby complicating the assessment of management effectiveness at the adult life stage. Our objective was to assess change in the freshwater production of juveniles (smolts) through time in order to determine if recent increases in adult abundance could be related to management affecting the freshwater juvenile production. We combined 46 years of data associated with 18 populations of Oregon coastal coho. Spawner-to-smolt relationships were modeled with Bayesian hierarchical state-space implementations of the logistic hockey stick recruitment function. We also develop a method of estimating the relative reproductive success of hatchery spawners. We found more evidence for decline than increase in productivity in the spawner-to-smolt life stage, suggesting that changes in physical oceanographic conditions are responsible for recent increases in adult abundance. The reproductive success of hatchery-origin fish relative to natural-origin fish was 0.51 with a 95% credible interval from 0.19 to 0.89. While some management effects may unfold on longer time-scales than we observed, we nonetheless contend that carefully tailored models of non-stationary population dynamics are needed to understand and the effectiveness of management actions intended to recover populations. [ABSTRACT FROM AUTHOR]

Although Caligus rogercresseyi negatively impacts Chilean salmon farming, the metabolic effects of infection by this sea louse have never been completely characterized. Therefore, this study analyzed lactate responses in the plasma, as well as the liver/muscle lactate dehydrogenase (LDH) activity and gene expression, in Salmo salar and Oncorhynchus kisutch infested by C. rogercresseyi . The lactate responses of Atlantic and Coho salmon were modified by the ectoparasite. Both salmon species showed increasing in plasma levels, whereas enzymatic activity increased in the muscle but decreased in the liver. Gene expression was overexpressed in both Coho salmon tissues but only in the liver for Atlantic salmon. These results suggest that salmonids need more energy to adapt to infection, resulting in increased gene expression, plasma levels, and enzyme activity in the muscles. The responses differed between both salmon species and over the course of infection, suggesting potential species-specific responses to sea-lice infection. [ABSTRACT FROM AUTHOR]

Female coho salmon, Oncorhynchus kisutch, were fed one of two experimental feeds containing lipids with markedly different stable 13 C isotope signatures during the late cortical alveolus, lipid droplet, and vitellogenesis stages of secondary oocyte growth. Ovarian and muscle lipids fatty acid concentrations were significantly affected by treatment during all three stages of development. Stable 13 C isotope analyses confirmed that dietary lipids were incorporated into both ovarian and muscle lipids during all three stages and revealed that ovarian lipids were more affected than muscle lipids during vitellogenesis. Arachidonic acid (ARA) was incorporated into ovarian lipids at the highest rate of all fatty acids examined with the greatest uptake observed during the cortical alveolus and lipid droplet stages of development. Docosahexaenoic acid (DHA) was incorporated into ovarian lipids at the next highest rate with the greatest uptake observed during the lipid droplet stage of development. The presence of an ovary specific, fatty acid transfer mechanism is proposed. Results from this study demonstrate the ability to greatly alter the fatty acid composition of ovarian lipids through a dietary change during secondary oocyte growth and may be of great interest to producers of farmed salmon and salmon broodstock programs. [ABSTRACT FROM AUTHOR]

• Coho salmon smolts were exposed to marine diesel seawater accommodated fractions. • Cyp1a1 transcripts were more elevated in caudal fin than liver regardless of sex. • Smolts were subsequently moved to clean seawater to monitor depuration over 8 days. • Cyp1a1 elevation returned to basal levels by two days of depuration. • Non-lethal biomonitoring of oil spills and remediation with caudal fin is viable. Oil spills that occur in high traffic coastal environments can have profound consequences for the health of marine ecosystems and the commercial and social interests that are dependent upon these habitats. Given that the global reliance on marine fuels is not abating, it is imperative to develop sensitive and robust tools to monitor oil contamination and remediation in a timely manner. Such tools are increasingly important for ascertaining the immediate and long-term effects of oil contamination on species of interest and local habitats as water-soluble components of oils, such as polycyclic aromatic hydrocarbons (PAHs), can persist post-remediation. We previously demonstrated that 3-methylcholanthrene responsive cytochrome P450–1a (cyp1a1) transcript abundance in the liver and caudal fin of coho salmon smolts (Onchorhynchus kisutch) was sensitive to exposure to low sulfur marine diesel (LSMD) seawater accommodated fractions (seaWAF) in cold water. We expanded upon this paradigm by assessing the utility of the cyp1a1 transcript to track both exposure to LSMD seaWAF and recovery from exposure by measuring cyp1a1 abundance in coho smolts using quantitative polymerase chain reaction (qPCR). Smolts were exposed to either 100 mg/L LSMD seaWAF or clean seawater (control) for 4 days. Fish were then transferred to clean seawater for depuration and tissues sampled at 0, 1, 2, 4, and 8 days from both treatments. Livers and caudal fins were dissected from 40 smolts per group (n total = 400 smolts). The LSMD seaWAF-induced cyp1a1 transcript levels significantly decreased one day after depuration in the liver and caudal fin in a sex-independent manner in genotyped females and males. After four days of depuration, cyp1a1 transcript abundance decreased to baseline control levels, regardless of tissue or sex. The present study demonstrates the value of using the caudal fin as a reliable, sensitive, and non-lethal sampling and monitoring tool. [ABSTRACT FROM AUTHOR]

Growth hormone transgenic coho salmon experience increased growth rates, driven primarily through elevated feed intake and feed conversion. However, neuropeptides that signal appetite stimulation have been shown to exhibit variable responses across fed states, suggesting a more complex system mediating growth in these fish. Studies have proposed that growth hormone may have a modulatory role on the energy reserves of fish, possibly through AMP-activated protein kinase (AMPK) activation. AMPK, an energy sensor in cells, has previously been shown to be upregulated in growth hormone transgenic salmon when compared to wild type, however, whether this effect is seen across fed states is unknown. Here, we tested the hypothesis that growth hormone induces an energetic deficit in metabolic tissues, leading to constitutive AMPK activation in growth hormone transgenic salmon. This study compared AMPK activity, ATP, and glycogen, of the liver, heart, and muscle of wild-type, and growth hormone transgenic salmon either fed to satiation or a wild-type ration. The results suggest that white muscle ATP levels in growth hormone salmon are elevated in satiation and rationed conditions. In the liver, growth hormone transgenic salmon fed a rationed wild-type diet experience reductions in ATP level and glycogen. In none of the tissues examined, did AMPK activity change. Taken together, these results indicate that growth hormone transgenic salmon experience metabolic duress when not fed to satiation. [Display omitted] • ATP levels in liver and muscle tissue are altered by fed state in GH transgenic salmon. • No change in AMPK activity is seen in key metabolic tissues. • Liver glycogen is depleted in rationed GH transgenic salmon. • Growth hormone transgenic salmon experience metabolic duress in conditions of limited food resources. [ABSTRACT FROM AUTHOR]

We quantified the bias and accuracy of U.S. West Coast Chinook and coho salmon abundance forecasts using lognormal distributions fitted to annual ratios between postseason abundance estimates and preseason forecasts, or constrained to assume unbiased forecasts. Accuracy was modest to low, with CVs exceeding 50% for 8/19 Chinook and 17/17 coho stocks. We evaluated the fitted median as a bias correction, and uncertainty buffers based on quantiles below the median. We tested whether retrospective application of bias corrections and/or buffers brought forecasts closer on average to postseason estimates; and performed retrospective and prospective analyses of consequences for stock status, harvest, and escapement for Sacramento River Fall Chinook (SRFC), a key fishery stock. Bias corrections and/or buffers improved most forecasts, with buffers providing improvement more often. For SRFC, bias correction alone could have led to one less year of overfished status, while buffers could have further shortened or avoided overfished status and reduced the frequency of under-escapement. Reductions in mean annual harvest resulting from applying bias corrections and/or moderate buffers were predicted to be smaller than the increases in harvest resulting from forecast and implementation error. Prospective simulations showed buffers could reduce risks of overfished status and under-escapement, at small costs to long-term mean harvests. However, this metric misses substantial harvest reductions in some years, since mean harvest is most sensitive to harvest at high abundance; though our analyses also neglected benefits of increased escapement for future production. Future work should incorporate observation error and nonstationarity, and the combined effects of forecast and implementation error on the probability of missing escapement goals. • Uncertainty in salmon abundance forecasts can be modeled based on past performance. • Bias corrections and/or buffers often bring forecasts closer to postseason estimates. • Buffers were predicted to reduce risks of under-escapement and overfished status. • Harvest reductions from buffers often smaller than recent management error overages. [ABSTRACT FROM AUTHOR]

Commercial fish traps were recently implemented at a limited scale in the lower Columbia River in efforts to selectively harvest hatchery-origin fishes with minimal mortality of wild-origin salmonids listed under the U.S. Endangered Species Act. Prior studies of a modified passive trapping technique demonstrated nearly 100 % survival among adult salmonids released as bycatch. Building upon this research, additional survival studies for adult coho salmon, spring-run Chinook salmon, and summer-run Chinook salmon were conducted between 2019 and 2021 at two separate fish trap sites in the lower Columbia River. Over three years of study, we used mark-recapture and net pen holding methodologies to estimate post-release survival of Chinook salmon and coho salmon, respectively. Evaluating detections of Chinook salmon tagged and released from a passively operated fish trap in 2019, detection at Bonneville Dam over a mean 6.5 d upriver migration (167 km) was 1.000 (95 % CI: S ≥ 0.970) for the sample genetically assigned to populations originating upriver of Bonneville Dam. Through two separate net pen holding studies, post-release survival of coho salmon was estimated at 1.000 (95 % CI: S ≥ 0.975) over 4 d in 2020 and 0.965 (95 % CI: 0.948 ≤ S ≤ 0.969) over 6 d in 2021. Given that these analyses lacked control groups to adjust survival estimates for confounding mortality effects, study results are inherently conservative. Ultimately, the findings of our research support the conclusions of prior studies and further suggest that passively operated fish traps may allow for selective harvesting of targeted fish stocks with little to no mortality of adult salmonid bycatch. • Modifications to salmon trap operations have improved bycatch survival. • Release survival of adult salmonids from passively operated fish traps neared 100 %. • Survival results validated the findings of prior studies for salmon traps. • Salmon traps allow for selective harvesting and bycatch mortality reduction. [ABSTRACT FROM AUTHOR]

N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) is a globally ubiquitous tire rubber antioxidant. Its transformation product, 6PPD-quinone, has been identified as a potent toxicant responsible for the acute mortality of coho salmon in Pacific Northwest during storm events, a phenomenon called "urban runoff mortality syndrome" that persists for decades. As a consequence, there has been mounting interest in understanding the occurrence, environmental fate and biotoxicity of this emerging contaminant. In this article, we review the current status of mass spectrometry (MS) as a preeminent analytical tool for analysis of 6PPD-quinone across multiple environmental compartments, including urban road runoff and watersheds, dust, and fine particulate matters. Novel strategies and refinements for MS data acquisition and the synergistic use of chromatographic techniques for enhanced identification and quantification are introduced. Concurrently, we summary the technical dissimilarities between currently available methods regarding their instrumental settings, data acquisition modes, and analytical performance. In addition, we highlight the utility of MS-based methodologies for interrogation of toxicological effects of 6PPD-quinone in living organisms, especially aquatic species. Finally, we comment on the foreseen applications of MS-based techniques for better understanding the environmental relevance, ecological toxicity, and human exposure risks of this emerging contaminant. [Display omitted] • The use of mass spectrometry (MS) sheds light on an emerging contaminant of 6PPD-quinone. • Different MS strategies and refinements allow efficient detection of 6PPD-quinone in the environment. • MS being the technique for interrogating the ecological consequences of 6PPD-quinone. • More rapid and accurate MS-based methods for detection of 6PPD-quinone are still needed. [ABSTRACT FROM AUTHOR]

• Diluted bitumen exposure impairs growth of coho fry and parr. • Cardiorespiratory performance was similarly impaired in both life-stages. • Baseline phase I biotransformation levels are greater in unexposed fry than parr. • Phase I biotransformation response to exposure was distinct for fry and parr. Millions of liters of diluted bitumen (dilbit), a crude oil product from Canada's oil sands region, is transported through critical Pacific salmon habitat each day. While the toxicity of the water-soluble fraction of dilbit (WSFd) to early life-stages of salmon is known, quantitative data on life-stage differences in sensitivity to WSFd is missing. To fill this knowledge gap, we exposed two juvenile life-stages of coho salmon (O. kisutch) in parallel to very low (parts per billion), environmentally-relevant concentrations of WSFd for acute (48 h) and sub-chronic (4 wk) durations. The relative sensitivities of the two life-stages (fry and parr) were assessed by comparing the timing and magnitude of biological responses using common organismal and molecular endpoints of crude oil exposure. A significant reduction in body condition occurred in both fry and parr after 4 wk exposure to WSFd. Both life-stages also experienced a concentration-dependent decrease in time-to-loss-of-equilibrium during a hypoxia challenge test at both 48 h and 4 wk of exposure. Although organismal responses were similar, molecular responses were distinct between life-stages. In general, unexposed fry had higher baseline values of hepatic phase I biotransformation indicators than unexposed parr, but induction of EROD activity and cyp1a mRNA expression in response to WSFd exposure was greater in parr than in fry. Neither gst nor hsp70 mRNA expression, markers of phase II biotransformation and cell stress, respectively, were reliably altered by WSFd exposure in either life-stage. Taken together, results of this study do not support differential sensitivities of coho fry and parr to WSFd. All the same, the potential for ontogenic differences in the expression and induction of phase I biotransformation need to be considered because age does matter for these endpoints if they are used as bioindicators of exposure in post-spill impact assessments. [ABSTRACT FROM AUTHOR]

Molecular processes that either regulate ovarian atresia or are consequences of atresia are poorly understood in teleost fishes. We hypothesized that feed restriction that perturbs normal ovarian growth and induces follicular atresia would alter ovarian gene expression patterns. Previtellogenic, two-year old coho salmon ( Oncorhynchus kisutch ) were subjected to prolonged fasting to induce atresia or maintained on a normal feeding schedule that would promote continued ovarian development. To identify genes that were specifically up- or down-regulated during oocyte growth in healthy, growing fish compared to fasted fish, reciprocal suppression subtractive hybridization (SSH) cDNA libraries were generated using ovaries from fed and fasted animals. Differential expression of genes identified by SSH was confirmed with quantitative PCR. The SSH library representing genes elevated in ovaries of fed fish relative to those of fasted fish contained steroidogenesis-related genes (e.g., hydroxy-delta-5-steroid dehydrogenase ), Tgf-beta superfamily members (e.g., anti-Mullerian hormone ) and cytoskeletal intermediate filament proteins (e.g., type I keratin s8 ). Overall, these genes were associated with steroid production, cell proliferation and differentiation, and ovarian epithelialization. The library representing genes elevated in ovaries of fasted fish relative to fed fish contained genes associated with apoptosis (e.g., programmed cell death protein 4 ), cortical alveoli (e.g., alveolin ), the zona pellucida (e.g., zona pellucida protein c ), and microtubules (e.g., microtubule associated protein tau ). Elevated expression of this suite of genes was likely associated with the initiation of atresia and/or a reduced rate of follicle development in response to fasting. This study revealed ovarian genes involved in normal early secondary oocyte growth and potential early markers of atresia. [ABSTRACT FROM AUTHOR]

Caligus rogercresseyi sea lice negatively impact Chilean salmonid farming, but no complete characterization for the metabolic effects of Caligus infestation currently exists. Therefore, the aim of this study was to analyze the effects of C. rogercresseyi infestation on the metabolic responses of Salmo salar and Oncorhynchus kisutch . Energy metabolism responses to C. rogercresseyi were examined over a time-course infestation of both salmonid species. Plasma metabolite levels and enzymatic activities related to intermediate metabolisms of carbohydrate, amino acid, and lipid were evaluated in the liver and muscle. Plasma glucose levels changed in both salmonid species, increasing at 1–3 days post-infestation. In turn, triglyceride levels increased at days 3 and 7 in O. kisutch and S. salar , respectively, while protein and total α-amino acids increased in O. kisutch but decreased in S. salar during infestation. Amino acid intermediate catabolic metabolism in the liver and muscle of O. kisutch increased during infestation, indicating a higher use of the gluconeogenic pathway than S. salar . Lipid intermediate anabolic metabolism increased in O. kisutch liver, remained unchanged in S. salar liver, and increased 1 day post-infestation in the muscle of both salmonids. Liver and muscle carbohydrate intermediate anabolic metabolism in O. kisutch increased during infestation, suggesting that this species preferentially uses the glycogenolytic-glucolytic pathway, in contrast with S. salar . In conclusion, amino acid and carbohydrate catabolism enzymes in O. kisutch activated soon after initial sea lice infestation, which would allow this species to dispose of energy substrates earlier than S. salar . This physiological data contributes towards the ability of O. kisutch to more adeptly cope with the increased energy demand imposed by C. rogercresseyi infestation. [ABSTRACT FROM AUTHOR]

It is well known that endocrine disrupting compounds (EDCs) present in wastewater treatment plant (WWTP) effluents interfere with reproduction in fish, including altered gonad development and induction of vitellogenin (Vtg), a female-specific egg yolk protein precursor produced in the liver. As a result, studies have focused on the effects of EDC exposure on the gonad and liver. However, impacts of environmental EDC exposure at higher levels of the hypothalamic-pituitary-gonad axis are less well understood. The pituitary gonadotropins, follicle-stimulating hormone (Fsh) and luteinizing hormone (Lh) are involved in all aspects of gonad development and are subject to feedback from gonadal steroids making them a likely target of endocrine disruption. In this study, the effects of WWTP effluent exposure on pituitary gonadotropin mRNA expression were investigated to assess the utility of Lh beta-subunit ( lhb ) as a biomarker of estrogen exposure in juvenile coho salmon ( Oncorhynchus kisutch ). First, a controlled 72-h exposure to 17α-ethynylestradiol (EE2) and 17β-trenbolone (TREN) was performed to evaluate the response of juvenile coho salmon to EDC exposure. Second, juvenile coho salmon were exposed to 0, 20 or 100% effluent from eight WWTPs from the Puget Sound, WA region for 72 h. Juvenile coho salmon exposed to 2 and 10 ng EE2 L −1 had 17-fold and 215-fold higher lhb mRNA levels relative to control fish. Hepatic vtg mRNA levels were dramatically increased 6670-fold, but only in response to 10 ng EE2 L −1 and Fsh beta-subunit ( fshb ) mRNA levels were not altered by any of the treatments. In the WWTP effluent exposures, lhb mRNA levels were significantly elevated in fish exposed to five of the WWTP effluents. In contrast, transcript levels of vtg were not affected by any of the WWTP effluent exposures. Mean levels of natural and synthetic estrogens in fish bile were consistent with pituitary lhb expression, suggesting that the observed lhb induction may be due to estrogenic activity of the WWTP effluents. These results suggest that lhb gene expression may be a sensitive index of acute exposure to estrogenic chemicals in juvenile coho salmon. Further work is needed to determine the kinetics and specificity of lhb induction to evaluate its utility as a potential indicator of estrogen exposure in immature fish. [ABSTRACT FROM AUTHOR]

Restoration of Atlantic salmon ( Salmo salar ) in Lake Ontario could potentially be negatively affected by the presence of non-native salmonids that are naturalized in the basin. Coho salmon ( Oncorhynchus kisutch ) have been spawning successfully in Lake Ontario tributaries for over 40 years and their juveniles will reside in streams with juvenile Atlantic salmon for one year. This study sought to examine interspecific diet associations between these species, and to compare diets to the composition of the benthos and drift in three Lake Ontario tributaries. Aquatic insects, mainly ephemeropterans and chironomids were the major prey consumed by subyearling Atlantic salmon whereas terrestrial invertebrates made up only 3.7% of the diet. Ephemeropterans and chironomids were the primary aquatic taxa consumed by subyearling coho salmon but, as a group, terrestrial invertebrates (41.8%) were the major prey. In sympatry, Atlantic salmon fed more actively from the benthos whereas the diet of coho salmon was more similar to the drift. The different feeding pattern of each species resulted in low interspecific diet similarity. There is likely little competition between these species for food in Lake Ontario tributaries as juveniles. [ABSTRACT FROM AUTHOR]

One of the major infectious diseases affecting coho salmon ( Oncorhynchus kisutch ) aquaculture is the Salmon Rickettsial Syndrome caused by Piscirickettsia salmonis . Conventional control measures such as antibiotics and vaccines have shown inconsistent results in production conditions. Thus, genetic improvement for P. salmonis resistance represents an alternative for the prevention of outbreaks. In the present study we aimed to determine both the levels of genetic variation for P. salmonis resistance (PSR) and genetic co-variation between PSR and harvest weight (HW) in coho salmon. A total of 2606 siblings from 108 maternal full-sib families (60 paternal half-sib families) were challenged against P. salmonis. The cumulative mortality rates among families ranged from 5% to 82%, with an average of 39%, indicating considerable phenotypic variation. For the genetic analyses PSR was defined as the day of death for each fish. We also recorded HW in 41,597 genetically related individuals of the challenged fish from the same breeding population. A linear bivariate animal model was used to estimate (co)variance components and to calculate genetic parameters. Estimated heritabilities for PSR and HW were 0.16 ± 0.04 and 0.41 ± 0.03, respectively. The genetic correlation between PSR and HW was − 0.50 ± 0.13. The levels of genetic variation detected in the present study indicate that selective breeding for these traits is feasible. However, the magnitude and direction of the genetic correlation between PSR and HW must be taken into account when selecting both traits simultaneously. Statement of relevance Negative relationship between resistance and growth in coho. [ABSTRACT FROM AUTHOR]

Salmonids are an important family of fish both from economic and basic research perspectives, and have been subjected to extensive research at whole-animal and molecular levels. Most research to date has been conducted on Atlantic salmon ( Salmo salar ) and rainbow trout ( Oncorhynchus mykiss ), but more recently other salmonids have become a focus of study due to their interesting life histories and because of their potential for use in commercial aquaculture. However, molecular biology and genetic analyses for these emerging species are currently hampered due to the lack of extensive genomic resources. To overcome some of these limitations, we have constructed a 43,228 sequence transcriptome from 13 tissues from coho salmon, Oncorhynchus kisutch using de novo transcriptome assembly methods. The transcriptome profiling analysis has provided data distinguishing allelic variation from paralogues that arose during the recent whole-genome duplication event in this family, thus allowing simplified analysis of gene-specific expression. Additionally, 1599 novel coho sequences have been identified through comparison with transcriptomes from two other salmonids species (Atlantic salmon and rainbow trout), and with northern pike. The transcriptome presented here will be useful for genomic analysis of coho salmon and other closely related salmonid species. [ABSTRACT FROM AUTHOR]

The environmental effects of fish culture operations are important issues in Michigan as well as many other parts of the world. The State of Michigan Department of Natural Resources operates the Platte River State Fish Hatchery (PRSFH) located near Honor, Michigan (USA). This facility has a restrictive discharge permit that limits the input of phosphorus into the Platte River that subsequently drains into a downstream oligotrophic lake (Platte Lake). The permit has been violated on occasion in recent years. Hatchery managers and operators need to understand the cause of these violations and prevent them in the future; and at the same time meet production goals to satisfy fishery management objectives. This paper describes the development and application of models designed to quantitatively analyze these issues. First, a bioenergetic growth and consumption model is developed for juvenile coho ( Oncorhynchus kisutch ) and Chinook ( Oncorhynchus tshawytscha ) salmon to quantify the relationship between fish production and by-product phosphorus loads. Next, phosphorus mass balance equations are used to calculate the phosphorus discharge from the facility as a function of the by-product phosphorus load and the efficiency of various phosphorus removal equipment and processes. The accuracy and consistency of the energy and mass balance equations are verified using extensive measurements. The ability of the model to successfully match various aspects of system performance supports the contention that the bioenergetic modeling approach developed here can provide reliable estimates of salmonid growth and feed requirements for a variety of food compositions, rations, and temperatures. This capability, along with knowledge of the effectiveness of phosphorus removal equipment, forms the basis of a practical operational and management tool. An example of model utility is presented that analyzes the PRSFH phosphorus discharge and provides insights into why permit violations occurred in 2009 but not in 2010. The model demonstrates how to avoid food waste caused by over feeding, lower the food conversion ratio, and evaluate the effectiveness of phosphorus removal treatment processes. A steady-state version of the model can be used by managers to establish production goals that avoid future violations of the phosphorus discharge limits. Statement of relevance The environmental effects of fish culture operations are important issues in many parts of the world. This paper describes the development and application of models designed to quantitatively analyze the relationships among fish production, by-product phosphorus loads, and the phosphorus concentration of the discharge following treatment. The ability of the model to successfully match various aspects of system performance supports the contention that the bioenergetic modeling approach developed here can provide reliable estimates of salmonid growth and feed requirements for a variety of food compositions, rations, and temperatures. This capability, along with knowledge of the effectiveness of phosphorus removal equipment, forms the basis of a practical operational and management tool. The model demonstrates how to avoid food waste caused by over feeding, lower the food conversion ratio, and evaluate the effectiveness of phosphorus removal treatment processes. A steady-state version of the model can be used by managers to establish production goals that avoid future violations of the phosphorus discharge limits. [ABSTRACT FROM AUTHOR]

A ten-week feeding trail was conducted to determine the dietary vitamin A (VA) requirement of coho salmon Oncorhynchus kisutch (Walbaum, 1792) post-smolts by formulating seven experimental diets containing graded VA levels of 367, 1060, 1823, 3482, 6715, 9984 and 22,935 IU/kg, respectively. Each diet was fed to triplicate groups of fish with the initial mean body weight of 185.86 ± 1.14 g. Stocked as groups of 10 individuals per cage (water volume 1000-L), fish were fed three times daily. After the feeding trail, the orthogonal polynomial contrasts showed that the specific growth rate (SGR) was linearly, quadratically and cubically increased with increasing dietary VA levels (P <.05). No significant differences were observed for hepatosomatic index (HSI), intestosomatic index (ISI), condition factor (CF) and muscle composition among dietary groups (P >.05). The muscle moisture, ash and crude protein were not significantly affected (P >.05), whereas the crude lipid was cubically affected (P <.05) by graded dietary VA levels. Serum alkaline phosphatase (AKP) activity and albumin (ALB) content were linearly, quadratically and cubically increased, whereas the serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were linearly, quadratically and cubically decreased with increasing dietary VA levels (P <.05). The increasing VA levels led to significantly linear, quadratic and cubic increase of hepatic SOD, CAT activities and serum SOD activity, and quadratic and cubic increase of serum T-AOC activity (P <.05). Increasing dietary VA levels quadratically and cubically decreased the hepatic MDA content (P <.05). The cubic regression analysis based on SGR indicated that the optimal dietary VA requirement was estimated to be 6422 IU/kg for coho salmon post-smolts. • Optimal dietary vitamin A (VA) level enhanced the growth and feed utilization of coho salmon post-smolts. • Adequate dietary VA requirement improved anti-oxidative enzymes activities and serum biochemical parameters. • Based on SGR, the optimal dietary VA level was estimated to be 6422 IU/kg. [ABSTRACT FROM AUTHOR]

Organisms must carefully regulate energy intake and expenditure to balance growth and trade-offs with other physiological processes. This regulation is influenced by key pathways controlling appetite, feeding behaviour and energy homeostasis. Growth hormone (GH) transgenesis provides a model where food intake can be elevated, and is associated with dramatic modifications of growth, metabolism, and feeding behaviour, particularly in fish. RNA-Seq and qPCR analyses were used to compare the expression of multiple genes important in appetite regulation within brain regions and the pituitary gland (PIT) of GH transgenic (fed fully to satiation or restricted to a wild-type ration throughout their lifetime) and wild-type coho salmon ( Oncorhynchus kisutch ). RNA-Seq results showed that differences in both genotype and ration levels resulted in differentially expressed genes associated with appetite regulation in transgenic fish, including elevated Agrp1 in hypothalamus (HYP) and reduced Mch in PIT. Altered mRNA levels for Agrp1 , Npy , Gh , Ghr , Igf1 , Mch and Pomc were also assessed using qPCR analysis. Levels of mRNA for Agrp1 , Gh , and Ghr were higher in transgenic than wild-type fish in HYP and in the preoptic area (POA), with Agrp1 more than 7-fold higher in POA and 12-fold higher in HYP of transgenic salmon compared to wild-type fish. These data are consistent with the known roles of orexigenic factors on foraging behaviour acting via GH and through MC4R receptor-mediated signalling. Igf1 mRNA was elevated in fully-fed transgenic fish in HYP and POA, but not in ration-restricted fish, yet both of these types of transgenic animals have very pronounced feeding behaviour relative to wild-type fish, suggesting IGF1 is not playing a direct role in appetite stimulation acting via paracrine or autocrine mechanisms. The present findings provide new insights on mechanisms ruling altered appetite regulation in response to chronically elevated GH, and on potential pathways by which elevated feeding response is controlled, independently of food availability and growth. [ABSTRACT FROM AUTHOR]

This study assessed the flesh proximate and lipid composition of two year classes and sizes of non-transgenic (NT) and transgenic (T) coho salmon ( Oncorhynchus kisutch ) that were grown to market size in the same rearing environment and on similar commercial feeds. The data also assessed land-based commercially raised farmed coho salmon, as well as two other species of ocean-raised farmed salmonids, and four species of wild Pacific salmon. The largest differences in nutritional content were seen between wild and farmed salmon. Farmed salmon contained higher muscle lipid levels and had higher levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) relative to wild counterparts. Moreover, the farmed fish also contained higher levels of n-6 poly-unsaturated fatty acids (PUFAs) and a lower omega-3 to omega-6 ratios (n-3/n-6). There were small differences in nutritional content between NT and T coho salmon, but most of these differences were due to the lower body weight and consequently lower lipid content in the small T coho salmon group. The larger NT coho salmon were very similar in nutritional content to their T counterparts. Overall, fish diet composition and rearing location (commercial feeds in culture vs. natural prey in the wild) had a much larger influence on the flesh nutritional content than did effects of the transgene, and all salmon, regardless of source, were found to be rich sources of EPA and DHA. [ABSTRACT FROM AUTHOR]

[Display omitted] • Products 6PPD-Q, 4-DBAP and 4-HDPA were detected in 6PPD water solutions. • 6PPD-Q hydrolysis half-lives (12.8–16.3 d) were longer than 6PPD (4.83–64.1 h). • For chiral 6PPD and 6PPD-Q, no enantioselective hydrolysis and conversion occurred. • 6PPD was highly toxic to G. rarus , and 6PPD-Q was "very highly toxic" to O. mykiss. • S -6PPD-Q toxicity was 2.6 times higher than R -6PPD-Q to O. mykiss. As a ubiquitous tire antidegradant, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) is persistently released into the environment. It is highly toxic to aquatic organisms, and its transformation product 6PPD-quinone (6PPD-Q), is "very highly toxic" to Oncorhynchus kisutch at a median lethal concentration (LC 50) of < 0.1 ng/mL. Notably, 6PPD and 6PPD-Q are chiral compounds. Here, enantioselective evaluations, including hydrolysis and acute toxicity were conducted after preparing the enantiomer, confirming the enantiomer absolute configuration and establishing enantioseparation methods. In the 6PPD hydrolysis experiments, the products 6PPD-Q, phenol, 4-[(1,3-dimethylbutyl)amino]- (4-DBAP) and 4-hydroxydiphenylamine (4-HDPA) were detected. In different water solutions, the hydrolysis of 4-DBAP and 4-HDPA was very fast (0.87–107 h), while the 6PPD-Q hydrolysis half-lives (12.8–16.3 d) were significantly longer than 6PPD (4.83–64.1 h). At the enantiomeric level, no enantioselective hydrolysis and conversion occurred. R -6PPD generated R -6PPD-Q, and S -6PPD generated S -6PPD-Q, and the formation rate of S -6PPD-Q was 1.77 times faster than R -6PPD-Q. In terms of the enantioselective toxicity, the 6PPD enantiomer was highly toxic to China-specific Gobiocypris rarus (LC 50 , 162–201 ng/mL), and it had no enantioselective difference. 6PPD-Q was "very highly toxic" (LC 50 , 1.66–4.31 ng/mL) to Oncorhynchus mykiss , which is of commercial importance, and the toxicities of rac -6PPD-Q and S -6PPD-Q were 1.9 and 2.6 times higher than R -6PPD-Q. Furthermore, the formation concentrations of S -6PPD-Q and R -6PPD-Q in 6PPD water solutions were higher than the LC 50 values of O. kisutch and O. mykiss , and the toxicity of 6PPD-Q was highly species-specific, which should raise concern. These results provide important information for environmental risk assessments of 6PPD and 6PPD-Q, especially from the perspective of enantiomers. [ABSTRACT FROM AUTHOR]

A recently identified chemical, 2-((4-Methylpentan-2-yl)amino)-5-(phenylamino)cyclohexa-2,5-diene-1,4-dione (6PPD-quinone; 6PPD-Q), is a transformation product of an additive used in the manufacture of tire rubber and causes acute lethality in coho salmon (Oncorhynchus kisutch) in urban watersheds. Despite its potential presence and ecotoxicity in receiving waters worldwide, information on the occurrence and fate of 6PPD-Q is limited. Here, we investigated the concentrations of 6PPD-Q and its parent chemical, 6PPD, in road dust collected from arterial and residential roads in Tokyo, Japan from May to October 2021. 6PPD-Q concentrations were highest from May to June, when atmospheric ozone concentrations are the highest in Japan; a correlation between 6PPD-Q and photochemical oxidants, as an alternative to ozone, corroborated this finding. We also found that 6PPD-Q concentrations at photochemical oxidant concentrations ranging from 35 to 47 ppbv were higher in dust collected from roads with high traffic volumes (i.e., arterial roads; median: 8.6 μg/g- OC) than in dust collected from roads with lower traffic volumes (i.e., residential roads; median: 6.3 μg/g- OC), indicating that 6PPD-Q is generated from traffic-related sources. We also found that 6PPD-Q was leached from dust particles within a few hours, with a log partitioning coefficient between organic carbon and water (K OC) of 3.2–3.5. The present results will help to understand the environmental occurrence, fate, and behavior of 6PPD-Q. [Display omitted] • 6PPD and 6PPD-Q were detected in road dust samples collected from May to October. • 6PPD-Q concentrations were highest from May to June. • Higher concentrations of 6PPD-Q could be due to higher ozone concentrations. • 6PPD-Q concentrations were higher for roads with higher traffic volumes. [ABSTRACT FROM AUTHOR]