Publications by authors named "Scott G Hinch"

67 Publications

Infected juvenile salmon can experience increased predation during freshwater migration.

R Soc Open Sci 2021 Mar 24;8(3):201522. Epub 2021 Mar 24.

Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, Canada.

Predation risk for animal migrants can be impacted by physical condition. Although size- or condition-based selection is often observed, observing infection-based predation is rare due to the difficulties in assessing infectious agents in predated samples. We examined predation of outmigrating sockeye salmon () smolts by bull trout () in south-central British Columbia, Canada. We used a high-throughput quantitative polymerase chain reaction (qPCR) platform to screen for the presence of 17 infectious agents found in salmon and assess 14 host genes associated with viral responses. In one (2014) of the two years assessed (2014 and 2015), the presence of infectious haematopoietic necrosis virus (IHNv) resulted in 15-26 times greater chance of predation; in 2015 IHNv was absent among all samples, predated or not. Thus, we provide further evidence that infection can impact predation risk in migrants. Some smolts with high IHNv loads also exhibited gene expression profiles consistent with a virus-induced disease state. Nine other infectious agents were observed between the two years, none of which were associated with increased selection by bull trout. In 2014, richness of infectious agents was also associated with greater predation risk. This is a rare demonstration of predator consumption resulting in selection for prey that carry infectious agents. The mechanism by which this selection occurs is not yet determined. By culling infectious agents from migrant populations, fish predators could provide an ecological benefit to prey.
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http://dx.doi.org/10.1098/rsos.201522DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8074935PMC
March 2021

Maxed Out: Optimizing Accuracy, Precision, and Power for Field Measures of Maximum Metabolic Rate in Fishes.

Physiol Biochem Zool 2020 May/Jun;93(3):243-254

Both laboratory and field respirometry are rapidly growing techniques to determine animal performance thresholds. However, replicating protocols to estimate maximum metabolic rate (MMR) between species, populations, and individuals can be difficult, especially in the field. We therefore evaluated seven different exercise treatments-four laboratory methods involving a swim tunnel (critical swim speed [], postswim fatigue, maximum swim speed [], and postswim fatigue) and three field-based chasing methods (3-min chase with 1-min air exposure, 3-min chase with no air exposure, and chase to exhaustion)-in adult coho salmon () as a case study to determine best general practices for measuring and quantifying MMR in fish. We found that all seven methods were highly comparable and that chase treatments represent a valuable field alternative to swim tunnels. Moreover, we caution that the type of test and duration of measurement windows used to calculate MMR can have significant effects on estimates of MMR and statistical power for each approach.
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http://dx.doi.org/10.1086/708673DOI Listing
April 2020

Erratum to: Simulated maternal stress reduces offspring aerobic swimming performance in Pacific salmon.

Conserv Physiol 2020;8(1):coaa004. Epub 2020 Feb 5.

Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.

[This corrects the article DOI: 10.1093/conphys/coz095.].
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http://dx.doi.org/10.1093/conphys/coaa004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7001111PMC
February 2020

Simulated maternal stress reduces offspring aerobic swimming performance in Pacific salmon.

Conserv Physiol 2019 18;7(1):coz095. Epub 2019 Dec 18.

Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada.

Pacific salmon routinely encounter stressors during their upriver spawning migration, which have the potential to influence offspring through hormonally-mediated maternal effects. To disentangle genetic vs. hormonal effects on offspring swimming performance, we collected gametes from three species of Pacific salmon (Chinook, pink and sockeye) at the end of migration and exposed a subset of eggs from each female to cortisol baths to simulate high levels of maternal stress. Fertilised eggs were reared to fry and put through a series of aerobic swim trials. Results show that exposure to cortisol early in development reduces maximum oxygen consumption while swimming, and decreases aerobic scope in all three species. Resting oxygen consumption did not differ between cortisol and control treatment groups. We also examined several metrics that could influence aerobic performance, and found no differences between treatment groups in haematocrit%, haemoglobin concentration, heart mass, citrate synthase activity or lactate dehydrogenase activity. Though it was not the focus of this study, an interesting discovery was that pink salmon had a higher MO and aerobic scope relative to the other species, which was supported by a greater haematocrit, haemoglobin, a larger heart and higher CS activity. Some management and conservation practices for Pacific salmon focus efforts primarily on facilitating adult spawning. However, if deleterious effects of maternal stress acquired prior to spawning persist into the next generation, consideration will need to be given to sub-lethal effects that could be imparted onto offspring from maternal stress.
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http://dx.doi.org/10.1093/conphys/coz095DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6919300PMC
December 2019

"Consulted to death": Personal stress as a major barrier to environmental co-management.

J Environ Manage 2020 Jan 13;254:109820. Epub 2019 Nov 13.

Norwegian Institute of Food, Fisheries and Aquaculture Research (Nofima AS), Muninbakken 9, 9019, Tromsø, Norway.

Co-management is widely seen as a way of improving environmental governance and empowering communities. When successful, co-management enhances the validity and legitimacy of decision-making, while providing stakeholders with influence over processes and outcomes that directly impact them. However, our research with participants in co-management across several cases leads us to argue that many of the individuals who contribute to co-management are subject to significant personal stress arising from both the logistical and social/emotional demands of participation in these processes. We argue that the literature on co-management has touched on this only indirectly, and that personal stress is a major challenge for participants that ought to be integrated into research agendas and addressed by policy-makers. In this article, we review the contours of the personal stress issue as it has appeared in our observations of co-management events and interviews with participants. While these findings are partial and preliminary, we argue that personal stress has theoretical and practical significance to the broader literature and process design. We conclude the article with recommendations for participants, researchers and policy-makers about how to consider and respond to problems of personal stress.
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http://dx.doi.org/10.1016/j.jenvman.2019.109820DOI Listing
January 2020

Linking environmental factors with reflex action mortality predictors, physiological stress, and post-release movement behaviour to evaluate the response of white sturgeon (Acipenser transmontanus Richardson, 1836) to catch-and-release angling.

Comp Biochem Physiol A Mol Integr Physiol 2020 02 12;240:110618. Epub 2019 Nov 12.

Evolutionary Physiology and Animal Ecology Laboratory, Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 1J8, Canada.

White sturgeon are the largest freshwater fish in North America and are the focus of an intense catch-and-release (C&R) fishery; the effects are largely unknown. We assessed the effect of fight and handling time, water temperature, river discharge rate, and fish size on physiological and reflex impairment responses of wild white sturgeon to angling. Sixty of these fish were tagged with acoustic transmitters to assess survival and post-release behaviour. Survival was high (100%). Water temperature and discharge influenced post-capture blood physiology. Specifically, lactate, chloride, and cortisol concentrations were elevated in individuals fought longer, and captured at higher water temperatures and river discharge. Cortisol was affected by fish size, with lower concentrations found in larger individuals. Only lactate and chloride were positively related to reflex impairment scores. Post-release movements were correlated with physiological state, fight characteristics and the environment. Specifically, higher blood lactate and chloride and those with longer fight times moved shorter distances after release. Contrastingly, higher levels of circulating glucose and potassium, as well as larger fish captured during periods of high discharge moved longer distances. Sturgeon tended to move shorter distances and at slower rates when reflex impairment was high, although reflex impairment in general did not explain a significant proportion of the variance in any movement metric. Our results show intriguing variance in the physiological and behavioural response of individual white sturgeon to C&R angling, with some degree of environmental dependence, and highlights the importance of understanding drivers of such variation when managing fisheries.
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http://dx.doi.org/10.1016/j.cbpa.2019.110618DOI Listing
February 2020

Discovery and validation of candidate smoltification gene expression biomarkers across multiple species and ecotypes of Pacific salmonids.

Conserv Physiol 2019 11;7(1):coz051. Epub 2019 Oct 11.

Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, V9T 6N7, Canada.

Early marine survival of juvenile salmon is intimately associated with their physiological condition during smoltification and ocean entry. Smoltification (parr-smolt transformation) is a developmental process that allows salmon to acquire seawater tolerance in preparation for marine living. Traditionally, this developmental process has been monitored using gill Na/K-ATPase (NKA) activity or plasma hormones, but gill gene expression offers the possibility of another method. Here, we describe the discovery of candidate genes from gill tissue for staging smoltification using comparisons of microarray studies with particular focus on the commonalities between anadromous Rainbow trout and Sockeye salmon datasets, as well as a literature comparison encompassing more species. A subset of 37 candidate genes mainly from the microarray analyses was used for TaqMan quantitative PCR assay design and their expression patterns were validated using gill samples from four groups, representing three species and two ecotypes: Coho salmon, Sockeye salmon, stream-type Chinook salmon and ocean-type Chinook salmon. The best smoltification biomarkers, as measured by consistent changes across these four groups, were genes involved in ion regulation, oxygen transport and immunity. Smoltification gene expression patterns (using the top 10 biomarkers) were confirmed by significant correlations with NKA activity and were associated with changes in body brightness, caudal fin darkness and caudal peduncle length. We incorporate gene expression patterns of pre-smolt, smolt and de-smolt trials from acute seawater transfers from a companion study to develop a preliminary seawater tolerance classification model for ocean-type Chinook salmon. This work demonstrates the potential of gene expression biomarkers to stage smoltification and classify juveniles as pre-smolt, smolt or de-smolt.
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http://dx.doi.org/10.1093/conphys/coz051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6788492PMC
October 2019

Salmonid gene expression biomarkers indicative of physiological responses to changes in salinity and temperature, but not dissolved oxygen.

J Exp Biol 2019 07 5;222(Pt 13). Epub 2019 Jul 5.

Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, BC, Canada, V9T 6N7

An organism's ability to respond effectively to environmental change is critical to its survival. Yet, life stage and overall condition can dictate tolerance thresholds to heightened environmental stressors, such that stress may not be equally felt across individuals and at all times. Also, the transcriptional responses induced by environmental changes can reflect both generalized responses as well as others that are highly specific to the type of change being experienced. Thus, if transcriptional biomarkers specific to a stressor, even under multi-stressor conditions, can be identified, the biomarkers could then be applied in natural environments to determine when and where an individual experiences such a stressor. Here, we experimentally challenged juvenile Chinook salmon () to validate candidate gill gene expression biomarkers. A sophisticated experimental design manipulated salinity (freshwater, brackish water and seawater), temperature (10, 14 and 18°C) and dissolved oxygen (normoxia and hypoxia) in all 18 possible combinations for 6 days using separate trials for three smolt statuses (pre-smolt, smolt and de-smolt). In addition, changes in juvenile behaviour, plasma variables, gill Na/K-ATPase activity, body size, body morphology and skin pigmentation supplemented the gene expression responses. We identified biomarkers specific to salinity and temperature that transcended the multiple stressors, smolt status and mortality (live, dead and moribund). Similar biomarkers for dissolved oxygen were not identified. This work demonstrates the unique power of gene expression biomarkers to identify a specific stressor even under multi-stressor conditions, and we discuss our next steps for hypoxia biomarkers using an RNA-seq study.
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http://dx.doi.org/10.1242/jeb.198036DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6633282PMC
July 2019

Migratory coupling between predators and prey.

Nat Ecol Evol 2018 12 22;2(12):1846-1853. Epub 2018 Nov 22.

Department of Forest and Conservation Sciences, Pacific Salmon Ecology and Conservation Laboratory, University of British Columbia, Vancouver, British Columbia, Canada.

Animal migrations act to couple ecosystems and are undertaken by some of the world's most endangered taxa. Predators often exploit migrant prey, but the movements taken by these consumers are rarely studied or understood. We define such movements, where migrant prey induce large-scale movements of predators, as migratory coupling. Migratory coupling can have ecological consequences for the participating prey, predators and the communities they traverse across the landscape. We review examples of migratory coupling in the literature and provide hypotheses regarding conditions favourable for their occurrence. We also provide a framework for interactions induced by migratory coupling and demonstrate their potential community-level impacts by examining other forms of spatial shifts in predators. Migratory coupling integrates the fields of landscape, movement, food web and community ecologies, and represents an understudied frontier in ecology.
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http://dx.doi.org/10.1038/s41559-018-0711-3DOI Listing
December 2018

Transcriptional shifts during juvenile Coho salmon (Oncorhynchus kisutch) life stage changes in freshwater and early marine environments.

Comp Biochem Physiol Part D Genomics Proteomics 2019 03 18;29:32-42. Epub 2018 Oct 18.

Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia V9T 6N7, Canada. Electronic address:

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.
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http://dx.doi.org/10.1016/j.cbd.2018.10.002DOI Listing
March 2019

Developing specific molecular biomarkers for thermal stress in salmonids.

BMC Genomics 2018 Oct 16;19(1):749. Epub 2018 Oct 16.

Fisheries and Oceans Canada, Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, BC, V9T 6N7, Canada.

Background: Pacific salmon (Oncorhynchus spp.) serve as good biological indicators of the breadth of climate warming effects on fish because their anadromous life cycle exposes them to environmental challenges in both marine and freshwater environments. Our study sought to mine the extensive functional genomic studies in fishes to identify robust thermally-responsive biomarkers that could monitor molecular physiological signatures of chronic thermal stress in fish using non-lethal sampling of gill tissue.

Results: Candidate thermal stress biomarkers for gill tissue were identified using comparisons among microarray datasets produced in the Molecular Genetics Laboratory, Pacific Biological Station, Nanaimo, BC, six external, published microarray studies on chronic and acute temperature stress in salmon, and a comparison of significant genes across published studies in multiple fishes using deep literature mining. Eighty-two microarray features related to 39 unique gene IDs were selected as candidate chronic thermal stress biomarkers. Most of these genes were identified both in the meta-analysis of salmon microarray data and in the literature mining for thermal stress markers in salmonids and other fishes. Quantitative reverse transcription PCR (qRT-PCR) assays for 32 unique genes with good efficiencies across salmon species were developed, and their activity in response to thermally challenged sockeye salmon (O. nerka) and Chinook salmon (O. tshawytscha) (cool, 13-14 °C and warm temperatures 18-19 °C) over 5-7 days was assessed. Eight genes, including two transcripts of each SERPINH1 and HSP90AA1, FKBP10, MAP3K14, SFRS2, and EEF2 showed strong and robust chronic temperature stress response consistently in the discovery analysis and both sockeye and Chinook salmon validation studies.

Conclusions: The results of both discovery analysis and gene expression showed that a panel of genes involved in chaperoning and protein rescue, oxidative stress, and protein biosynthesis were differentially activated in gill tissue of Pacific salmon in response to elevated temperatures. While individually, some of these biomarkers may also respond to other stressors or biological processes, when expressed in concert, we argue that a biomarker panel comprised of some or all of these genes could provide a reliable means to specifically detect thermal stress in field-caught salmon.
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http://dx.doi.org/10.1186/s12864-018-5108-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6192343PMC
October 2018

Dermal injuries caused by purse seine capture result in lasting physiological disturbances in coho salmon.

Comp Biochem Physiol A Mol Integr Physiol 2019 01 5;227:75-83. Epub 2018 Oct 5.

Department of Biology and Institute of Environmental Science, Carleton University, Ottawa, ON K1S 5B6, Canada.

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.
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http://dx.doi.org/10.1016/j.cbpa.2018.09.026DOI Listing
January 2019

Thiamine Levels in Muscle and Eggs of Adult Pacific Salmon from the Fraser River, British Columbia.

J Aquat Anim Health 2018 09 10;30(3):191-200. Epub 2018 Jul 10.

35 Honeyfield Lane, Peralta, New Mexico, 87042, USA.

Multiple species and stocks of Pacific salmon Oncorhynchus spp. have experienced large declines in the number of returning adults over a wide region of the Pacific Northwest due to poor marine survival (low smolt-to-adult survival rates). One possible explanation for reduced survival is thiamine deficiency. Thiamine (vitamin B ) is an essential vitamin with an integral role in many metabolic processes, and thiamine deficiency is an important cause of salmonid mortality in the Baltic Sea and in the Laurentian Great Lakes. To assess this possibility, we (1) compared muscle thiamine content over time in a holding experiment using Fraser River (British Columbia) Sockeye Salmon O. nerka to establish whether adults that died during the holding period had lower thiamine levels than survivors, (2) measured infectious loads of multiple pathogens in held fish, and (3) measured egg thiamine content from four species of Pacific salmon collected on Fraser River spawning grounds. Chinook Salmon O. tshawytscha had the lowest egg thiamine, followed by Sockeye Salmon; however, egg thiamine concentrations were above levels known to cause overt fry mortality. Thiamine vitamers in the muscle of Fraser River adult Sockeye Salmon shifted over a 13-d holding period, with a precipitous decline in thiamine pyrophosphate (the active form of thiamine used in enzyme reactions) in surviving fish. Survivors also carried lower loads of Flavobacterium psychrophilum than fish that died during in the holding period. Although there is no evidence of thiamine deficiency in the adults studied, questions remain about possible thiamine metabolism-fish pathogen relationships that influence survival.
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http://dx.doi.org/10.1002/aah.10024DOI Listing
September 2018

The influence of water temperature on sockeye salmon heart rate recovery following simulated fisheries interactions.

Conserv Physiol 2017 22;5(1):cox050. Epub 2017 Aug 22.

Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental Science, Carleton University, Ottawa K1S 5B6, Canada.

Selective harvest policies have been implemented in North America to enhance the conservation of Pacific salmon ( spp.) stocks, which has led to an increase in the capture and release of fish by all fishing sectors. Despite the immediate survival benefits, catch-and-release results in capture stress, particularly at high water temperatures, and this can result in delayed post-release mortality minutes to days later. The objective of this study was to evaluate how different water temperatures influenced heart rate disturbance and recovery of wild sockeye salmon () following fisheries interactions (i.e. exhaustive exercise). Heart rate loggers were implanted into Fraser River sockeye salmon prior to simulated catch-and-release events conducted at three water temperatures (16°C, 19°C and 21°C). The fisheries simulation involved chasing logger-implanted fish in tanks for 3 min, followed by a 1 min air exposure. Neither resting nor routine heart rate differed among temperature treatments. In response to the fisheries simulation, peak heart rate increased with temperature (16°C = 91.3 ± 1.3 beats min; 19°C = 104.9 ± 2.0 beats min and 21°C = 117 ± 1.3 beats min). Factorial heart rate and scope for heart rate were highest at 21°C and lowest at 16°C, but did not differ between 19°C and 21°C. Temperature affected the initial rate of cardiac recovery but not the overall duration (~10 h) such that the rate of energy expenditure during recovery increased with temperature. These findings support the notion that in the face of climate change, efforts to reduce stress at warmer temperatures will be necessary if catch-and-release practices are to be an effective conservation strategy.
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http://dx.doi.org/10.1093/conphys/cox050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5597901PMC
August 2017

Ecology of Exercise in Wild Fish: Integrating Concepts of Individual Physiological Capacity, Behavior, and Fitness Through Diverse Case Studies.

Integr Comp Biol 2017 08;57(2):281-292

Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada.

Synopsis: Wild animals maximize fitness through certain behaviors (e.g., foraging, mating, predator avoidance) that incur metabolic costs and often require high levels of locomotor activity. Consequently, the ability of animals to achieve high fitness often relies on their physiological capacity for exercise (aerobic scope) and/or their ability to acquire and utilize energy judiciously. Here, we explore how environmental factors and physiological limitations influence exercise and metabolism in fish while foraging, migrating to spawning grounds, and providing parental care. We do so with three case studies that use a number of approaches to studying exercise in wild fish using biologging and biotelemetry platforms. Bonefish (Albula vulpes) selectively use shallow water tropical marine environments to forage when temperatures are near optimal for aerobic scope and exercise capacity. Bonefish energy expenditure at upper thermal extremes is maximal while activity levels diminish, likely caused by reduced aerobic scope. Pacific salmon (Oncorhynchus spp.) reproductive migrations frequently involve passage through hydraulically challenging areas, and their ability to successfully pass these regions is constrained by their physiological capacity for exercise. Aerobic scope and swim performance are correlated with migration difficulty among sockeye salmon (O. nerka) populations; however, depletion of endogenous energy stores can also limit migration success. In another example, male smallmouth bass (Micropterus dolomieu) allocate a significant amount of energy to nest-guarding behaviors to protect their developing brood. Smallmouth bass body size, endogenous energy reserves, and physiological state influence nest-guarding behaviors and reproductive success. We suggest that in some scenarios (e.g., bonefish foraging, Pacific salmon dam passage) metabolic capacity for exercise may be the strongest determinant of biological fitness, while in others (e.g., long distance salmon migration, smallmouth bass parental care) energy stores may be more important. Interactions among environmental and ecological factors, fish behavior, and fish physiology offer important avenues of mechanistic inquiry to explain ecological dynamics and demonstrate how exercise is fundamental to the ecology of fish.
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http://dx.doi.org/10.1093/icb/icx012DOI Listing
August 2017

Capture severity, infectious disease processes and sex influence post-release mortality of sockeye salmon bycatch.

Conserv Physiol 2017 28;5(1):cox017. Epub 2017 Mar 28.

Department of Biology, University of Victoria, Victoria, BC V8P 5C2, Canada.

Bycatch is a common occurrence in heavily fished areas such as the Fraser River, British Columbia, where fisheries target returning adult Pacific salmon ( spp.) to spawning grounds. The extent to which these encounters reduce fish survival through injury and physiological impairment depends on multiple factors including capture severity, river temperature and infectious agents. In an effort to characterize the mechanisms of post-release mortality and address fishery and managerial concerns regarding specific regulations, wild-caught Early Stuart sockeye salmon () were exposed to either mild (20 s) or severe (20 min) gillnet entanglement and then held at ecologically relevant temperatures throughout their period of river migration (mid-late July) and spawning (early August). Individuals were biopsy sampled immediately after entanglement and at death to measure indicators of stress and immunity, and the infection intensity of 44 potential pathogens. Biopsy alone increased mortality (males: 33%, females: 60%) when compared with non-biopsied controls (males: 7%, females: 15%), indicating high sensitivity to any handling during river migration, especially among females. Mortality did not occur until 5-10 days after entanglement, with severe entanglement resulting in the greatest mortality (males: 62%, females: 90%), followed by mild entanglement (males: 44%, females: 70%). Infection intensities of and measured at death were greater in fish that died sooner. Physiological indicators of host stress and immunity also differed depending on longevity, and indicated anaerobic metabolism, osmoregulatory failure and altered immune gene regulation in premature mortalities. Together, these results implicate latent effects of entanglement, especially among females, resulting in mortality days or weeks after release. Although any entanglement is potentially detrimental, reducing entanglement durations can improve post-release survival.
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http://dx.doi.org/10.1093/conphys/cox017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5569998PMC
March 2017

A perspective on physiological studies supporting the provision of scientific advice for the management of Fraser River sockeye salmon ().

Conserv Physiol 2016 26;4(1):cow026. Epub 2016 Aug 26.

Fisheries and Oceans Canada, Science Branch, Pacific Biological Station, 3190 Hammond Bay Road , Nanaimo, BC , Canada V9T 6N7.

The inability of physiologists to effect change in fisheries management has been the source of frustration for many decades. Close collaboration between fisheries managers and researchers has afforded our interdisciplinary team an unusual opportunity to evaluate the emerging impact that physiology can have in providing relevant and credible scientific advice to assist in management decisions. We categorize the quality of scientific advice given to management into five levels based on the type of scientific activity and resulting advice (notions, observations, descriptions, predictions and prescriptions). We argue that, ideally, both managers and researchers have concomitant but separate responsibilities for increasing the level of scientific advice provided. The responsibility of managers involves clear communication of management objectives to researchers, including exact descriptions of knowledge needs and researchable problems. The role of the researcher is to provide scientific advice based on the current state of scientific information and the level of integration with management. The examples of scientific advice discussed herein relate to physiological research on the impact of high discharge and water temperature, pathogens, sex and fisheries interactions on in-river migration success of adult Fraser River sockeye salmon () and the increased understanding and quality of scientific advice that emerges. We submit that success in increasing the quality of scientific advice is a function of political motivation linked to funding, legal clarity in management objectives, collaborative structures in government and academia, personal relationships, access to interdisciplinary experts and scientific peer acceptance. The major challenges with advancing scientific advice include uncertainty in results, lack of integration with management needs and institutional caution in adopting new research. We hope that conservation physiologists can learn from our experiences of providing scientific advice to management to increase the potential for this growing field of research to have a positive influence on resource management.
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http://dx.doi.org/10.1093/conphys/cow026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5001150PMC
August 2016

Evidence of Olfactory Imprinting at an Early Life Stage in Pink Salmon (Oncorhynchus gorbuscha).

Sci Rep 2016 11 9;6:36393. Epub 2016 Nov 9.

University of British Columbia, Faculty of Land and Food Systems, 2357 Main Mall, Vancouver, BC, V6T 1Z4, Canada.

Pacific salmon (Oncorhynchus spp.) navigate towards spawning grounds using olfactory cues they imprinted on as juveniles. The timing at which imprinting occurs has been studied extensively, and there is strong evidence that salmon imprint on their natal water during the parr-smolt transformation (PST). Researchers have noted, however, that the life histories of some species of Pacific salmon could necessitate imprinting prior to the PST. Juvenile pink salmon (O. gorbuscha) spend less time in fresh water than any other species of Pacific salmon, and presumably must imprint on their natal water at a very young age. The time at which imprinting occurs in this species, however, has not been experimentally tested. We exposed juvenile pink salmon as alevins to phenethyl alcohol (PEA) or control water, reared these fish to adulthood, and then tested their behavioural responses to PEA to determine whether the fish successfully imprinted. We found that pink salmon exposed to PEA as alevins were attracted to the chemical as adults, suggesting that imprinting can occur during this stage. Our finding provides some of the first evidence to support the long-standing belief that imprinting can occur in pink salmon prior to the PST.
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http://dx.doi.org/10.1038/srep36393DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5101574PMC
November 2016

How do potential knowledge users evaluate new claims about a contested resource? Problems of power and politics in knowledge exchange and mobilization.

J Environ Manage 2016 Dec 10;184(Pt 2):380-388. Epub 2016 Oct 10.

Department of Forest and Conservation Sciences, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada.

This article examines how potential users of scientific and local/traditional/experiential knowledge evaluate new claims to knowing, using 67 interviews with government employees and non-governmental stakeholders involved in co-managing salmon fisheries in Canada's Fraser River. Research has consistently shown that there are major obstacles to moving new knowledge into policy, management, and public domains. New concepts such as Knowledge Exchange (KE) and Knowledge Mobilization (KMb) are being used to investigate these obstacles, but the processes by which potential users evaluate (sometimes competing) knowledge claims remain poorly understood. We use concepts from the sociology of science and find that potential users evaluate new knowledge claims based on three broad criteria: (1) the perceived merits of the claim, (2) perceptions of the character and motivation of the claimant, and (3) considerations of the social and political context of the claim. However, government employees and stakeholders have different interpretations of these criteria, leading to different knowledge preferences and normative expectations of scientists and other claimants. We draw both theoretical and practical lessons from these findings. With respect to theory, we argue that the sociology of science provides valuable insights into the political dimensions of knowledge and should be explicitly incorporated into KE/KMb research. With respect to practice, our findings underline the need for scientists and other claimants to make conscious decisions about whose expectations they hope to meet in their communications and engagement activities.
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http://dx.doi.org/10.1016/j.jenvman.2016.10.006DOI Listing
December 2016

Behavioural responses of Pacific salmon to chemical disturbance cues during the spawning migration.

Behav Processes 2016 Nov 5;132:76-84. Epub 2016 Oct 5.

Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.

Many fish that are exposed to a threat release disturbance cues, which are chemicals that alert conspecifics to the presence of the threat. The release of disturbance cues has been well demonstrated in various species of laboratory-reared fish. Migratory fish species often exhibit increased cortisol levels and are exposed to numerous stressors during their migrations, which could trigger the release of disturbance cues. We tested the responses of wild migrating sockeye salmon (Oncorhynchus nerka) and pink salmon (O. gorbuscha) to the odours of disturbed and undisturbed conspecifics to determine whether these fish release disturbance cues following exposure to a simulated stressor. Furthermore, we tested the responses of sockeye salmon to water-borne cortisol, following evidence from past studies that this chemical is excreted through the gills of stressed fish, and speculation that endogenous correlates of stress might function as disturbance cues. We found that sockeye salmon avoid the odour of disturbed conspecifics, whereas pink salmon do not. Avoidance occurred in both female and male sockeye salmon, and was associated with an increase in plasma cortisol levels in females, but not in males. We also found no behavioural response to water-borne cortisol, which suggests this chemical does not act as an exogenous disturbance cue in sockeye salmon. Avoidance of disturbed conspecifics could limit exposure to risks during the sockeye salmon spawning migration, but could also delay the rate of migration and thereby accrue reproductive costs.
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http://dx.doi.org/10.1016/j.beproc.2016.10.001DOI Listing
November 2016

Physiological stress response, reflex impairment and delayed mortality of white sturgeon exposed to simulated fisheries stressors.

Conserv Physiol 2016 26;4(1):cow031. Epub 2016 Aug 26.

Department of Biology , Dalhousie University , Halifax, Nova Scotia , Canada B3H 4R2.

White sturgeon () are the largest freshwater fish in North America and a species exposed to widespread fishing pressure. Despite the growing interest in recreational fishing for white sturgeon, little is known about the sublethal and lethal impacts of angling on released sturgeon. In summer (July 2014, mean water temperature 15.3°C) and winter (February 2015, mean water temperature 6.6°C), captive white sturgeon ( = 48) were exposed to a combination of exercise and air exposure as a method of simulating an angling event. After the stressor, sturgeon were assessed for a physiological stress response, and reflex impairments were quantified to determine overall fish vitality (i.e. capacity for survival). A physiological stress response occurred in all sturgeon exposed to a fishing-related stressor, with the magnitude of the response correlated with the duration of the stressor. Moreover, the stress from exercise was more pronounced in summer, leading to higher reflex impairment scores (mean ± SEM, 0.44 ± 0.07 and 0.25 ± 0.05 in summer and winter, respectively). Reflex impairment was also correlated with lactate concentrations (e.g. physiological stress measures related to exhaustive exercise;  = 0.53) and recovery time ( = 0.76). Two mortalities occurred >24 h after the cessation of treatment in the summer. Given that natural habitats for white sturgeon can reach much higher temperatures than those presented in our study, we caution the use of this mortality estimate for a summer season, because latent mortality could be much higher when temperatures exceed 16°C. This is the first experiment investigating the physiological disturbance and reflex impairment of capture and release at two temperatures on subadult/adult white sturgeon, and the results suggest that future research needs to examine the longer term and fitness consequences of extended play and air exposure times, because these are largely unknown for wild populations.
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http://dx.doi.org/10.1093/conphys/cow031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5070429PMC
August 2016

Tracking wild sockeye salmon smolts to the ocean reveals distinct regions of nocturnal movement and high mortality.

Ecol Appl 2016 Jun;26(4):959-78

Few estimates of migration rates or descriptions of behavior or survival exist for wild populations of out-migrating Pacific salmon smolts from natal freshwater rearing areas to the ocean. Using acoustic transmitters and fixed receiver arrays across four years (2010-2013), we tracked the migration of > 1850 wild sockeye salmon (Oncorhynchus nerka) smolts from Chilko Lake, British Columbia, to the coastal Pacific Ocean (> 1000 km distance). Cumulative survival to the ocean ranged 3-10% among years, although this may be slightly underestimated due to technical limitations at the final receiver array. Distinct spatial patterns in both behavior and survival were observed through all years. In small, clear, upper-river reaches, downstream migration largely occurred at night at speeds up to 50 km/d and coincided with poor survival. Among years, only 57-78% of smolts survived the first 80 km. Parallel laboratory experiments revealed excellent short-term survival and unhindered swimming performance of dummy-tagged smolts, suggesting that predators rather than tagging effects were responsible for the initial high mortality of acoustic-tagged smolts. Migration speeds increased in the Fraser River mainstem (~220 km/d in some years), diel movement patterns ceased, and smolt survival generally exceeded 90% in this segment. Marine movement rates and survival were variable across years, with among-year segment-specific survival being the most variable and lowest (19-61%) during the final (and longest, 240 km) marine migration segment. Osmoregulatory preparedness was not expected to influence marine survival, as smolts could maintain normal levels of plasma chloride when experimentally exposed to saltwater (30 ppt) immediately upon commencing their migration from Chilko Lake. Transportation of smolts downstream generally increased survival to the farthest marine array. The act of tagging may have affected smolts in the marine environment in some years as dummy-tagged fish had poorer survival than control fish when transitioned to saltwater in laboratory-based experiments. Current fisheries models for forecasting the number of adult sockeye returning to spawn have been inaccurate in recent years and generally do not incorporate juvenile or smolt survival information. Our results highlight significant potential for early migration conditions to influence adult recruitment.
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http://dx.doi.org/10.1890/15-0632DOI Listing
June 2016

Piscivorous fish exhibit temperature-influenced binge feeding during an annual prey pulse.

J Anim Ecol 2016 09 26;85(5):1307-17. Epub 2016 Jul 26.

U.S. Geological Survey, Washington Cooperative Fish and Wildlife Research Unit, School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, USA.

Understanding the limits of consumption is important for determining trophic influences on ecosystems and predator adaptations to inconsistent prey availability. Fishes have been observed to consume beyond what is sustainable (i.e. digested on a daily basis), but this phenomenon of hyperphagia (or binge-feeding) is largely overlooked. We expect hyperphagia to be a short-term (1-day) event that is facilitated by gut volume providing capacity to store consumed food during periods of high prey availability to be later digested. We define how temperature, body size and food availability influence the degree of binge-feeding by comparing field observations with laboratory experiments of bull trout (Salvelinus confluentus), a large freshwater piscivore that experiences highly variable prey pulses. We also simulated bull trout consumption and growth during salmon smolt outmigrations under two scenarios: 1) daily consumption being dependent upon bioenergetically sustainable rates and 2) daily consumption being dependent upon available gut volume (i.e. consumption is equal to gut volume when empty and otherwise 'topping off' based on sustainable digestion rates). One-day consumption by laboratory-held bull trout during the first day of feeding experiments after fasting exceeded bioenergetically sustainable rates by 12- to 87-fold at low temperatures (3 °C) and by  ˜1·3-fold at 20 °C. The degree of binge-feeding by bull trout in the field was slightly reduced but largely in agreement with laboratory estimates, especially when prey availability was extremely high [during a sockeye salmon (Oncorhynchus nerka) smolt outmigration and at a counting fence where smolts are funnelled into high densities]. Consumption by bull trout at other settings were lower and more variable, but still regularly hyperphagic. Simulations demonstrated the ability to binge-feed increased cumulative consumption (16-32%) and cumulative growth (19-110%) relative to only feeding at bioenergetically sustainable rates during the  ˜1-month smolt outmigration period. Our results indicate the ability for predators to maximize short-term consumption when prey are available can be extreme and is limited primarily by gut volume, then mediated by temperature; thus, predator-prey relationships may be more dependent upon prey availability than traditional bioenergetic models suggest. Binge-feeding has important implications for energy budgets of consumers as well as acute predation impacts on prey.
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http://dx.doi.org/10.1111/1365-2656.12565DOI Listing
September 2016

Examining the relationships between egg cortisol and oxidative stress in developing wild sockeye salmon (Oncorhynchus nerka).

Comp Biochem Physiol A Mol Integr Physiol 2016 10 15;200:87-93. Epub 2016 Jun 15.

Institute of Biochemistry and Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada.

Maternally-derived hormones in oocytes, such as glucocorticoids (GCs), play a crucial role in embryo development in oviparous taxa. In fishes, maternal stressor exposure increases circulating and egg cortisol levels, the primary GC in fishes, as well as induces oxidative stress. Elevated egg cortisol levels modify offspring traits but whether maternal oxidative stress correlates with circulating and egg cortisol levels, and whether maternal/egg cortisol levels correlate with offspring oxidative stress have yet to be determined. The objective of this study was to examine the relationships among maternal and egg cortisol, and maternal and offspring oxidative stress to provide insight into the potential intergenerational effects of stressor exposure in sockeye salmon (Oncorhynchus nerka). Antioxidant concentration and oxidative stress were measured in maternal tissues (plasma, brain, heart and liver) as well as offspring developmental stages (pre-fertilization, 24h post-fertilization, eyed, and hatch), and were compared to both naturally-occurring and experimentally-elevated (via cortisol egg bath) levels of cortisol in eggs. Oxygen radical absorptive capacity of tissues from maternal sockeye salmon was measured spectrophotometrically and was not correlated with maternal or egg cortisol concentrations. Also, naturally-occurring and experimentally-elevated cortisol levels in eggs (to mimic maternal stress) did not affect oxidative stress or antioxidant capacity of the offspring. We conclude that the metrics of maternal stress examined in sockeye salmon (i.e., maternal/egg cortisol, maternal oxidative stress) are independent of each other, and that egg cortisol content does not influence offspring oxidative stress.
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http://dx.doi.org/10.1016/j.cbpa.2016.06.012DOI Listing
October 2016

Predator swamping reduces predation risk during nocturnal migration of juvenile salmon in a high-mortality landscape.

J Anim Ecol 2016 07 9;85(4):948-59. Epub 2016 May 9.

Department of Forest and Conservation Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada.

Animal migrations are costly and are often characterized by high predation risk for individuals. Three of the most oft-assumed mechanisms for reducing risk for migrants are swamping predators with high densities, specific timing of migrations and increased body size. Assessing the relative importance of these mechanisms in reducing predation risk particularly for migrants is generally lacking due to the difficulties in tracking the fate of individuals and population-level characteristics simultaneously. We used acoustic telemetry to track migration behaviour and survival of juvenile sockeye salmon (Oncorhynchus nerka) smolts released over a wide range of conspecific outmigration densities in a river associated with poor survival. The landscape was indeed high risk; smolt survival was poor (˜68%) over 13·5 km of river examined even though migration was rapid (generally <48 h). Our results demonstrate that smolts largely employ swamping of predators to reduce predation risk. Increased densities of co-migrant conspecifics dramatically improved survival of smolts. The strong propensity for nocturnal migration resulted in smolts pausing downstream movements until the next nightfall, greatly increasing relative migration durations for smolts that could not traverse the study area in a single night. Smolt size did not appear to impact predation risk, potentially due to unique characteristics of the system or our inability to tag the entire size range of outmigrants. Movement behaviours were important in traversing this high-risk landscape and provide rare evidence for swamping to effectively reduce individual predation risk.
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http://dx.doi.org/10.1111/1365-2656.12528DOI Listing
July 2016

Remote bioenergetics measurements in wild fish: Opportunities and challenges.

Comp Biochem Physiol A Mol Integr Physiol 2016 12 6;202:23-37. Epub 2016 Apr 6.

Fisheries and Aquaculture Centre, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS 7001, Australia.

The generalized energy budget for fish (i.e., Energy Consumed=Metabolism+Waste+Growth) is as relevant today as when it was first proposed decades ago and serves as a foundational concept in fish biology. Yet, generating accurate measurements of components of the bioenergetics equation in wild fish is a major challenge. How often does a fish eat and what does it consume? How much energy is expended on locomotion? How do human-induced stressors influence energy acquisition and expenditure? Generating answers to these questions is important to fisheries management and to our understanding of adaptation and evolutionary processes. The advent of electronic tags (transmitters and data loggers) has provided biologists with improved opportunities to understand bioenergetics in wild fish. Here, we review the growing diversity of electronic tags with a focus on sensor-equipped devices that are commercially available (e.g., heart rate/electrocardiogram, electromyogram, acceleration, image capture). Next, we discuss each component of the bioenergetics model, recognizing that most research to date has focused on quantifying the activity component of metabolism, and identify ways in which the other, less studied components (e.g., consumption, specific dynamic action component of metabolism, somatic growth, reproductive investment, waste) could be estimated remotely. We conclude with a critical but forward-looking appraisal of the opportunities and challenges in using existing and emerging electronic sensor-tags for the study of fish energetics in the wild. Electronic tagging has become a central and widespread tool in fish ecology and fisheries management; the growing and increasingly affordable toolbox of sensor tags will ensure this trend continues, which will lead to major advances in our understanding of fish biology over the coming decades.
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http://dx.doi.org/10.1016/j.cbpa.2016.03.022DOI Listing
December 2016

Aerobic scope increases throughout an ecologically relevant temperature range in coho salmon.

J Exp Biol 2016 06 8;219(Pt 12):1922-31. Epub 2016 Apr 8.

Australian Institute of Marine Science, PMB 3, Townsville MC, Townsville, Queensland 4810, Australia.

Aerobic scope (AS) has been proposed as a functional measurement that can be used to make predictions about the thermal niche of aquatic ectotherms and hence potential fitness outcomes under future warming scenarios. Some salmonid species and populations, for example, have been reported to exhibit different thermal profiles for their AS curves such that AS peaks around the modal river temperature encountered during the upriver spawning migration, suggesting species- and population-level adaptations to river temperature regimes. Interestingly, some other salmonid species and populations have been reported to exhibit AS curves that maintain an upwards trajectory throughout the ecologically relevant temperature range rather than peaking at a modal temperature. To shed further light on this apparent dichotomy, we used adult coho salmon (Oncorhynchus kisutch) to test the prediction that peak AS coincides with population-specific, historically experienced river temperatures. We assessed AS at 10 and 15°C, which represent a typical river migration temperature and the upper limit of the historically experienced temperature range, respectively. We also examined published data on AS in juvenile coho salmon in relation to new temperature data measured from their freshwater rearing environments. In both cases, AS was either maintained or increased modestly throughout the range of ecologically relevant temperatures. In light of existing evidence and the new data presented here, we suggest that when attempting to understand thermal optima for Pacific salmon and other species across life stages, AS is a useful metric of oxygen transport capacity but other thermally sensitive physiological indices of performance and fitness should be considered in concert.
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http://dx.doi.org/10.1242/jeb.137166DOI Listing
June 2016

Getting past the blame game: Convergence and divergence in perceived threats to salmon resources among anglers and indigenous fishers in Canada's lower Fraser River.

Ambio 2016 Sep 20;45(5):591-601. Epub 2016 Feb 20.

Biology Department, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada.

This article examines threat perception as a potential dimension of inter-group conflict over salmon fisheries in Canada's Fraser River watershed. Environmental changes and the entry of new user groups are putting pressure on both the resource and regulators, as well as threatening to exacerbate conflicts, notably between First Nation (indigenous) fishers and non-indigenous recreational anglers. While resource conflicts are often superficially conceptualized as cases of competing interests, we build on recent studies suggesting that conflicts are associated with deeper cognitive and perceptual differences among user groups. We report findings from 422 riverbank interviews with First Nation fishers and recreational anglers focusing on perceptions of threat to the fisheries. Responses reveal both substantial agreement and disagreement in threat perceptions between the two groups. These patterns provide a potential roadmap for consensus building, and suggest possible avenues for policy-makers to defuse the "blame game" that often dominates this type of conflict.
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http://dx.doi.org/10.1007/s13280-016-0769-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4980314PMC
September 2016

Mechanisms to explain purse seine bycatch mortality of coho salmon.

Ecol Appl 2015 Oct;25(7):1757-75

Research on fisheries bycatch and discards frequently involves the assessment of reflex impairment, injury, or blood physiology as means of quantifying vitality and predicting post-release mortality, but exceptionally few studies have used all three metrics concurrently. We conducted an experimental purse seine fishery for Pacific salmon in the Juan de Fuca Strait, with a focus on understanding the relationships between different sublethal indicators and whether mortality could be predicted in coho salmon (Oncorhynchus kisutch) bycatch. We monitored mortality using a ~24-h net pen experiment (N = 118) and acoustic telemetry (N = 50), two approaches commonly used to assess bycatch mortality that have rarely been directly compared. Short-term mortality was 21% in the net pen experiment (~24 h) and estimated at 20% for telemetry-tagged fish (~48-96 h). Mortality was predicted by injury and reflex impairment, but only in the net pen experiment. Higher reflex impairment was mirrored by perturbations to plasma ions and lactate, supporting the notion that reflex impairment can be used as a proxy for departure from physiological homeostasis. Reflex impairment also significantly correlated with injury scores, while injury scores were significantly correlated with plasma ion concentrations. The higher time-specific mortality rate in the net pen and the fact that reflexes and injury corresponded with mortality in that experiment, but not in the telemetry-tagged fish released into the wild could be explained partly by confinement stress. While holding experiments offer the potential to provide insights into the underlying causes of mortality, chronic confinement stress can complicate the interpretation of patterns and ultimately affect mortality rates. Collectively, these results help refine our understanding of the different sublethal metrics used to assess bycatch and the mechanisms that can lead to mortality.
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http://dx.doi.org/10.1890/14-0798.1DOI Listing
October 2015

Variability in Migration Routes Influences Early Marine Survival of Juvenile Salmon Smolts.

PLoS One 2015 9;10(10):e0139269. Epub 2015 Oct 9.

Kintama Research Services Ltd., Nanaimo, British Columbia, Canada.

Variability in animal migratory behavior is expected to influence fitness, but few empirical examples demonstrating this relationship exist. The initial marine phase in the migration of juvenile salmon smolts has been identified as a potentially critical life history stage to overall population productivity, yet how fine-scale migration routes may influence survival are unknown. Large-scale acoustic telemetry studies have estimated survival rates of outmigrant Pacific salmon smolts through the Strait of Georgia (SOG) along the British Columbian coastline to the Pacific Ocean, but these data have not been used to identify and characterize fine-scale movements. Data collected on over 850 sockeye salmon (Oncorhynchus nerka) and steelhead (Oncorhynchus mykiss) smolts detected at an array in the Strait of Georgia in 2004-2008 and 2010-2013 were analyzed to characterize migration routes and link movements to subsequent survival at an array 250 km further along the marine migration pathway. Both species exhibited disproportionate use of the most eastern route in the Strait of Georgia (Malaspina Strait). While many smolts moved across the northern Strait of Georgia acoustic array with no indication of long-term milling or large-scale east-to-west movements, large proportions (20-40% of sockeye and 30-50% of steelhead) exhibited a different behavior, apparently moving in a westward or counterclockwise pattern. Variability in migratory behavior for both species was linked to subsequent survival through the Strait of Georgia. Survival for both species was influenced by initial east-to-west location, and sockeye were further influenced by migration timing and duration of time spent near the northern Strait of Georgia array. Westward movements result in a net transport of smolts from Malaspina Strait to the Strait of Georgia, particularly for steelhead. Counterclockwise movements may be due to the currents in this area during the time of outmigration, and the higher proportion of steelhead smolts exhibiting this counterclockwise behavior may reflect a greater exposure to wind-altered currents for the more surface-oriented steelhead. Our results provide an empirical example of how movements can affect migration survival, for which examples remain rare in movement ecology, confirming that variability in movements themselves are an important part of the migratory process.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0139269PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4599731PMC
June 2016