In situ egg incubators that retain fish embryos within gravel substrates are a valuable tool in salmonid research. Despite numerous designs, there have been few direct comparisons of the effectiveness of different incubator types. In this study, we compared the recovery, hatch, and survival rates of Chinook salmon (Oncorhynchus tshawytscha) embryos among three types of incubators: A, a modified Whitlock-Vibert box; B, a cylindrical “egg tube”; and C, an inverted dome-shaped kitchen strainer that mimicked natural egg pockets with embryos developing between gravels. To assess their performance, we stocked chinook embryos in these three different types of incubators and buried them in gravels of artificial redds in three outdoor experimental river mesocosms. All incubator types supported salmon development (>30% hatch and >20% survival), with incubator type C exhibiting the lowest recovery but highest mean hatch and survival rates, though differences among types showed only weak to moderate statistical evidence. Hatch and survival rates were lower in the most downstream redds. This comparison provides a better understanding of how incubator designs affect the success of in situ fish incubation in salmonid research.

Ecotoxicology offers a comprehensive overview of the science underpinning the recognition and management of environmental contamination. It describes the toxicology of environmental contaminants, the methods used for assessing their toxicity and ecological impacts, and approaches employed to mitigate pollution and ecological health risks globally. Chapters cover the latest advances in research, including genomics, natural toxins, endocrine disruption and the toxicology of radioactive substances. The second half of the book focuses on applications, such as cradle-to-grave effects of selected industries, legal and economic approaches to environmental regulation, ecological risk assessment, and contaminated site remediation. With short capsules written by invited experts, numerous case studies from around the world and further reading lists, this textbook is designed for advanced undergraduate and graduate one-semester courses. It is also a valuable reference for graduate students and professionals. Online resources for instructors and students are also available.

Ecotoxicology offers a comprehensive overview of the science underpinning the recognition and management of environmental contamination. It describes the toxicology of environmental contaminants, the methods used for assessing their toxicity and ecological impacts, and approaches employed to mitigate pollution and ecological health risks globally. Chapters cover the latest advances in research, including genomics, natural toxins, endocrine disruption and the toxicology of radioactive substances. The second half of the book focuses on applications, such as cradle-to-grave effects of selected industries, legal and economic approaches to environmental regulation, ecological risk assessment, and contaminated site remediation. With short capsules written by invited experts, numerous case studies from around the world and further reading lists, this textbook is designed for advanced undergraduate and graduate one-semester courses. It is also a valuable reference for graduate students and professionals. Online resources for instructors and students are also available.

Ecotoxicology offers a comprehensive overview of the science underpinning the recognition and management of environmental contamination. It describes the toxicology of environmental contaminants, the methods used for assessing their toxicity and ecological impacts, and approaches employed to mitigate pollution and ecological health risks globally. Chapters cover the latest advances in research, including genomics, natural toxins, endocrine disruption and the toxicology of radioactive substances. The second half of the book focuses on applications, such as cradle-to-grave effects of selected industries, legal and economic approaches to environmental regulation, ecological risk assessment, and contaminated site remediation. With short capsules written by invited experts, numerous case studies from around the world and further reading lists, this textbook is designed for advanced undergraduate and graduate one-semester courses. It is also a valuable reference for graduate students and professionals. Online resources for instructors and students are also available.

Polycyclic aromatic compounds (PACs) are ubiquitous across environmental media in Canada, including surface water, soil, sediment and snowpack. Information is presented according to pan-Canadian sources, and key geographical areas including the Great Lakes, the Alberta Oil Sands Region (AOSR) and the Canadian Arctic. Significant PAC releases result from exploitation of fossil fuels containing naturally-derived PACs, with anthropogenic sources related to production, upgrading and transport which also release alkylated PACs. Continued expansion of the oil and gas industry indicates contamination by PACs may increase. Monitoring networks should be expanded, and include petrogenic PACs in their analytical schema, particularly near fuel transportation routes. National-scale roll-ups of emission budgets may not expose important details for localized areas, and on local scales emissions can be substantial without significantly contributing to total Canadian emissions. Burning organic matter produces mainly parent or pyrogenic PACs, with forest fires and coal combustion to produce iron and steel being major sources of pyrogenic PACs in Canada. Another major source is the use of carbon electrodes at aluminum smelters in British Columbia and Quebec. Temporal trends in PAC levels across the Great Lakes basin have remained relatively consistent over the past four decades. Management actions to reduce PAC loadings have been countered by increased urbanization, vehicular emissions and areas of impervious surfaces. Major cities within the Great Lakes watershed act as diffuse sources of PACs, and result in coronas of contamination emanating from urban centres, highlighting the need for non-point source controls to reduce loadings.

The present study assessed the chronic toxicity of 2 chemically enhanced water accommodated fractions (CEWAFs) of diluted bitumens (dilbits), Access Western Blend (AWB) and Cold Lake Blend (CLB), to rainbow trout alevins. Chemical dispersion was used to overcome the resistance to dispersion of dilbits and to generate test solutions that contained more and smaller oil droplets for increased partitioning of petroleum hydrocarbons into water. Test solutions were characterized by fluorescence spectroscopy, a rapid and inexpensive analytical tool to compare toxicity endpoints measured by fluorescence (total petroleum hydrocarbons measured by fluorescence [TPH-F]). Cumulative mortality and the prevalence and severity of malformations increased following exposure of alevins to dispersed dilbits. Toxicity curves overlapped for AWB and CLB when expressed as TPH-F and 22- to 24-d median lethal and effect concentrations ranged from 0.36 to 1.5 mg/L. Gene expression in alevins was also altered following exposure to dispersed dilbit, with relative cytochrome P450-1A mRNA levels increasing up to 170-fold for AWB and up to 240-fold for CLB. Access Western Blend and CLB caused similar toxicity to rainbow trout alevins as light to medium conventional crude oils, and rainbow trout alevins were more sensitive than yellow perch, Japanese medaka, and fathead minnow embryos exposed to dispersed AWB and CLB. The present study is the first to assess the embryotoxicity of dilbits to a Canadian freshwater salmonid species. Environ Toxicol Chem 2020;39:1620-1633. © 2020 SETAC.

Little is known about the fate of oil spills in rivers. Hyporheic flows of water through river sediments exchange surface and groundwater and create upwelling and downwelling zones that are important for fish spawning and embryo development. Risk assessments of oil spills to rivers do not consider the potential for hyporheic flows to carry oil droplets into sediments and the potential for prolonged exposure of fish to trapped oil. This project assessed whether oil droplets in water flowing through gravel will be trapped and whether hydrocarbons partitioning from trapped oil droplets are bioavailable to fish. Columns packed with gravel were injected with oil-in-water dispersions prepared with light crude, medium crude, diluted bitumens, and heavy fuel oil to generate a series of oil droplet loadings. The concentrations of oil trapped in the gravel increased with oil loading and viscosity. When the columns were perfused with clean water, oil concentrations in column effluents decreased to the detection limit within the first week of water flow, with sporadically higher concentrations associated with oil droplet release. Despite the low concentrations of hydrocarbons measured in column effluent, hydrocarbons were bioavailable to juvenile rainbow trout (Oncorhynchus mykiss) for more than three weeks of water flow, as indicated by strong induction of liver ethoxyresorufin-o-deethylase activity. These findings indicate that ecological risk assessments and spill response should identify and protect areas in rivers sensitive to contaminant trapping.

Japanese medaka embryos were exposed to water accommodated fractions (WAF) and chemically-enhanced WAF of two types of diluted bitumen (dilbit) at concentrations bracketing the EC50s for developmental malformations. Within these treatments, fish were grouped based on the presence or absence of developmental malformations (e.g., blue sac disease (BSD)), and analyzed for novel transcriptomic responses. Microarray analyses identified novel biomarkers and gene networks in dilbit-exposed malformed embryos that were not evident in dilbit-exposed fish without BSD or in controls without dilbit. The top differentially expressed genes (DEGs) included cytochrome P450 transcripts (cyp1) in fish from all dilbit treatments (malformed and non-malformed fish), as well as: fibroblast growth factor (fgf7), AHR repressor (ahrr), and squalene monooxygenase (sqle). In dilbit-exposed fish that did not develop BSD, the only reported individual DEG was eukaryotic translation initiation factor 3 subunit D (eif3d). However, a number of other pathways were enriched, including melatonin effects on circadian clock and the antioxidant response, estrogen and androgen metabolism as well as many receptor signaling pathways. Pathways associated with hedgehog, steroid biosynthesis, and Wnt signaling were significantly altered between low and high concentrations of dilbit exposure. An effect of the dispersant control on swim bladder development was observed at concentrations 10-fold higher than those used to disperse dilbit, and a number of gene targets unique to fish in this comparison were affected. This suggests that the toxic effects of dispersant may involve alternative mechanisms to dilbit, but cause similar phenotypic responses. This study identified novel biomarkers in fish exposed to dilbit, with or without visual malformations, that can be used to assess the risks of dilbit to aquatic ecosystem health.

Polycyclic aromatic compounds (PACs) are ubiquitous in the environment. Wildlife (including fish) are chronically exposed to PACs through air, water, sediment, soil, and/or dietary routes. Exposures are highest near industrial or urban sites, such as aluminum smelters and oil sands mines, or near natural sources such as forest fires. This review assesses the exposure and toxicity of PACs to wildlife, with a focus on the Canadian environment. Most published field studies measured PAC concentrations in tissues of invertebrates, fish, and birds, with fewer studies of amphibians and mammals. In general, PAC concentrations measured in Canadian wildlife tissues were under the benzo[a]pyrene (BaP) guideline for human consumption. Health effects of PAC exposure include embryotoxicity, deformities, cardiotoxicity, DNA damage, changes to DNA methylation, oxidative stress, endocrine disruption, and impaired reproduction. Much of the toxicity of PACs can be attributed to their bioavailability, and the extent to which certain PACs are transformed into more toxic metabolites by cytochrome P450 enzymes. As most mechanistic studies are limited to individual polycyclic aromatic hydrocarbons (PAHs), particularly BaP, research on other PACs and PAC-containing complex mixtures is required to understand the environmental significance of PAC exposure and toxicity. Additional work on responses to PACs in amphibians, reptiles, and semi-aquatic mammals, and development of molecular markers for early detection of biological responses to PACs would provide a stronger biological and ecological justification for regulating PAC emissions to protect Canadian wildlife.

The toxicity of waterborne retene (7-isopropyl-1-methyl phenanthrene) to post-hatch embryos of rainbow trout (Oncorhynchus mykiss) was assessed at 5 and 11 degrees C. Survival times of retene-exposed embryos were 70 % longer at 5 degrees C than at 11 degrees C, but survival times and LC50 s did not vary when time was expressed as degree-days (thermal units), i.e., at a common stage of development. The size of survivors decreased with increasing retene concentrations, but not with temperature. Retene did not bioconcentrate to any extent (bioconcentration factors < 2) at either temperature, indicating effective biotransformation by embryos. However, concentrations of retene metabolites were slightly higher at 5 degrees C, suggesting slower excretion rates than at 11 degrees C. The relative expression of cytochrome P450 proteins (CYP1A) did not vary with temperature but increased with retene concentration, as indicated by cyp1a mRNA concentrations. The induction of CYP1A protein by retene exposure was evident in the vasculature of eye, brain, heart, kidney, liver, gill, mouth, intestine, muscle, and yolk-sac. However, immunohistochemical staining was greater at 5 than at 11 degrees C for all tissues except liver and muscle. Overall, temperature effects on retene toxicity disappeared when the duration of embryo development and retene exposure were expressed as thermal units (degree-days). Temperature controlled the rate of embryo development and the rate of toxicity (time to a toxic endpoint), but not the concentrations that were toxic.

Effects on trout alevins of chronic exposures to chemicallydispersed Access Western Blend and Cold Lake Blend dilbits Julie E. Adams, Barry N. Madison, Kelli Charbonneau, Marie Sereneo, Lucie Baillon, Valerie S. Langlois, R. Stephen Brown, and Peter V. Hodson a School of Environmental Studies, Queen’s University, Kingston, ON, Canada b Department of Biology, Queen’s University, Kingston, ON, Canada c Centre Eau Terre Environnement, Institut National de la Recherche Scientifique, Québec City, QC, Canada

Ecological risk assessments (ERAs) of polycyclic aromatic compounds (PACs), as single congeners or in mixtures, present technical challenges that raise concerns about their accuracy and validity for Canadian environments. Of more than 100,000 possible PAC structures, the toxicity of fewer than 1% have been tested as individual compounds, limiting the assessment of complex mixtures. Because of the diversity in modes of PAC action, the additivity of mixtures cannot be assumed, and mixture compositions change rapidly with weathering. In vertebrates, PACs are rapidly oxygenated by cytochrome P450 enzymes, often to metabolites that are more toxic than the parent compound. The ability to predict the ecological fate, distribution and effects of PACs is limited by toxicity data derived from tests of a few responses with a limited array of test species, under optimal laboratory conditions. Although several models are available to predict PAC toxicity and rank species sensitivity, they were developed with data biased by test methods, and the reported toxicities of many PACs exceed their solubility limits. As a result, Canadian Environmental Quality Guidelines for a few individual PACs provide little support for ERAs of complex mixtures in emissions and at contaminated sites. These issues are illustrated by reviews of three case studies of PAC-contaminated sites relevant to Canadian ecosystems. Interactions among ecosystem characteristics, the behaviour, fate and distribution of PACs, and non-chemical stresses on PAC-exposed species prevented clear associations between cause and effect. The uncertainties of ERAs can only be reduced by estimating the toxicity of a wider array of PACs to species typical of Canada's diverse geography and environmental conditions. Improvements are needed to models that predict toxicity, and more field studies of contaminated sites in Canada are needed to understand the ecological effects of PAC mixtures.

Multiple eel species of the genus Anguillidae are under anthropogenic pressure. This review presents strong evidence that chemical pollution is a driving force behind the catastrophic decline in recruitment and abundance of both the European (Anguilla anguilla) and the American eel (Anguilla rostrata). In response to this crisis, stock and habitat management policies have blindly focused on increasing the areas available for the recruitment and rearing of yellow eels, and increasing the numbers of silver eels escaping to spawn in the Sargasso Sea. No specific policies or regulations have been adopted to foster recruitment of yellow eels to uncontaminated watersheds, to monitor the quality and condition of silver eels, or to protect silver eels from contaminated environments. Research is needed to identify existing and emerging contaminant problems, to understand their potential impacts on eel reproduction, and to develop indicators of spawner quality and management actions that would increase the likelihood of successful eel reproduction and recruitment.

Increasing demand for diluted bitumen (dilbit) has led to the development of the oil sands industry and the expansion of transcontinental pipelines. Dilbit is an unresolved complex mixture with variable diluent and bitumen composition. Thus, it is important to understand the effects of the two most transported dilbits in Canada, Access Western Blend (AWB) and Cold Lake Blend (CLB) on a North America native and freshwater fish species, the yellow perch (Perca flavescens). Fertilized embryos were exposed to both dilbits for 16 days, from <24 h post-fertilization until hatch. The treatment regime was a static daily renewal of water accommodated fractions (WAF) and chemically-enhanced water accommodated fractions (CEWAF) at concentrations ranging from 0.01 to 21.3 mu g/L of total polycyclic aromatic compounds (TPACs). Hatched embryos were assessed for malformations and changes in the expression of genes associated with phase I and II detoxification and oxidative stress. The prevalence of developmental malformations increased significantly at the highest concentrations of all treatments, with WAF treatments yielding a higher prevalence than CEWAF. The EC50s for AWB and CLB WAF and CEWAF solutions ranged from 9.8 to 24 mu g/L TPACs, with the CEWAF of AWB being the least toxic. Relative mRNA levels of cyp1a showed induction by up to 18-fold inWAF and 50-fold in CEWAF treatments at similar concentrations of measured dilbit in solution. Complementary DNA methylation analysis was assessed and fish embryos exposed to AWB CEWAF and CLB WAF showed decreased DNA methylation profiles with increasing exposure to dilbit, suggesting that global gene expression is increasing in these treatments. With recent approvals of pipelines in North America, these data will support site-specific risk assessments and monitoring of Canadian ecosystems should a pipeline spill occur. (C) 2018 The Authors. Published by Elsevier B.V.