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Energy depletion is a significant concern for animals that migrate long distances on fixed energy budgets. Migrating adult Fraser River sockeye salmon (Oncorhynchus nerka) cease feeding in the ocean and are entirely reliant on endogenous energy stores to successfully complete their subsequent freshwater migration and spawn. Most research on adult salmon energy use has focused on the riverine component of the migration, yet the coastal migration could be energetically costly, particularly in estuarine areas where temperatures can be warm and tidal currents turbulent. We compared the relative energetic costs of salmon migrations through coastal, estuarine, and riverine areas by tagging and tracking 38 adult sockeye salmon with acoustic tri-axial accelerometer transmitters for over 200 km along the British Columbian coast and through the Fraser River estuary. Accelerometer output was converted to temperature-specific rates of oxygen consumption. Oxygen consumption rates were twice as high in the riverine compared to coastal marine regions (including the estuary), driven largely by higher swim speeds. Oxygen consumption rates were also influenced by diel period, where energy use was higher during mid-day; however, we found no evidence that tidal cycles influenced energy use. Despite higher oxygen consumption rates in the Fraser River, cost of transport (kJ−1 kg−1 km) was highest in Seymour Narrows (a narrow coastal region with high tidal flushing), consistent with previous research showing this is a potentially challenging area for migrating salmon. Overall, we have demonstrated that coastal marine energy use is an important component of the spawning migration energy budget for Pacific salmon. [ABSTRACT FROM AUTHOR]

Adult sockeye salmon Oncorhynchus nerka destined for the Fraser River, British Columbia are some of the most economically important populations but changes in the timing of their homeward migration have led to management challenges and conservation concerns. After a directed migration from the open ocean to the coast, this group historically would mill just off shore for 3-6 weeks prior to migrating up the Fraser River. This milling behaviour changed abruptly in 1995 and thereafter, decreasing to only a few days in some years (termed early migration), with dramatic consequences that have necessitated risk-averse management strategies. Early migrating fish consistently suffer extremely high mortality (exceeding 90% in some years) during freshwater migration and on spawning grounds prior to spawning. This synthesis examines multidisciplinary, collaborative research aimed at understanding what triggers early migration, why it results in high mortality, and how fisheries managers can utilize these scientific results. Tissue analyses from thousands of O. nerka captured along their migration trajectory from ocean to spawning grounds, including hundreds that were tracked with biotelemetry, have revealed that early migrants are more reproductively advanced and ill-prepared for osmoregulatory transition upon their entry into fresh water. Gene array profiles indicate that many early migrants are also immunocompromised and stressed, carrying a genomic profile consistent with a viral infection. The causes of these physiological changes are still under investigation. Early migration brings O. nerka into the river when it is 3-6° C warmer than historical norms, which for some late-run populations approaches or exceeds their critical maxima leading to the collapse of metabolic and cardiac scope, and mortality. As peak spawning dates have not changed, the surviving early migrants tend to mill in warm lakes near to spawning areas. These results in the accumulation of many more thermal units and longer exposures to freshwater diseases and parasites compared to fish that delay freshwater entry by milling in the cool ocean environment. Experiments have confirmed that thermally driven processes are a primary cause of mortality for early-entry migrants. The Fraser River late-run O. nerka early migration phenomenon illustrates the complex links that exist between salmonid physiology, behaviour and environment and the pivotal role that water temperature can have on population-specific migration survival. [ABSTRACT FROM AUTHOR]

It is often recognized, but seldom addressed, that a quantitative assessment of the cumulative effects, both additive and non-additive, of multiple stressors on fish survival would provide a more realistic representation of the factors that influence fish migration. This review presents a compilation of analytical methods applied to a well-studied fish migration, a more general review of quantitative multivariable methods, and a synthesis on how to apply new analytical techniques in fish migration studies. A compilation of adult migration papers from Fraser River sockeye salmon Oncorhynchus nerka revealed a limited number of multivariable methods being applied and the sub-optimal reliance on univariable methods for multivariable problems. The literature review of fisheries science, general biology and medicine identified a large number of alternative methods for dealing with cumulative effects, with a limited number of techniques being used in fish migration studies. An evaluation of the different methods revealed that certain classes of multivariable analyses will probably prove useful in future assessments of cumulative effects on fish migration. This overview and evaluation of quantitative methods gathered from the disparate fields should serve as a primer for anyone seeking to quantify cumulative effects on fish migration survival. [ABSTRACT FROM AUTHOR]

We investigated the effect of changes in water discharge from the Seton River Dam, British Columbia, on the physiological condition, passage time, and passage success of adult migrant sockeye salmon Oncorhynchus nerka. Sockeye salmon were intercepted and nonlethally biopsied for blood plasma and energy status. A subset of these fish were fitted with radio transmitters and tracked under three different operational attraction flow levels. Indices of physiological stress and exhaustive exercise (e.g., plasma cortisol, glucose, lactate, osmolality. and hematocrit) did not differ among the attraction flow discharge levels that were examined, nor did they differ appreciably from those of other adult Fraser River sockeye salmon studied during upriver migrations in areas of natural, nonregulated flows. In fact, the fish appeared relatively unstressed after dam passage. Passage time was significantly longer (19.9 h) under intermediate discharge (12.7 m³/s) than under high (15.8 m³/s) ur low (11.0 m³/s) discharges (9.3 and 7.0 h, respectively) but did not differ between high- and low-discharge periods. No differences in passage success or fishway ascent lime were observed among the three discharges. Though we suspect that unique flow conditions were responsible for the longer passage time during intermediate discharge, a detailed hydraulic analysis is needed to further interpret our results. [ABSTRACT FROM AUTHOR]

Electromyogram (EMG) radio telemetry was used in conjunction with physiological biopsy to relate prior physiological condition and subsequent swimming energetics and behaviours to passage success of 13 wild adult sockeye salmon Oncorhynchus nerka at a vertical-slot fishway on the Seton River, British Columbia. At the time of capture, plasma lactate, glucose and cortisol levels indicated that fish were not exhibiting unusually high levels of physiological stress. Very few differences existed between successful and unsuccessful fish in body size, initial plasma physiology and energy state and mean swim speed and energy use during passage. Generally, fish did not employ burst swimming during successful or failed attempts at passage, indicating that failure was probably not related to metabolic acidosis. Plasma Na+ concentration was significantly lower in unsuccessful fish ( P < 0·05), which is suggestive of a depressed ionic state or a possible stress component, although values in all fish were within an expected range for migrant adult O. nerka. Nevertheless, six of 13 fish failed to reascend the fishway and remained in the tailrace of the dam for more than a day on average before moving downstream and away from the dam. During this time, fish were observed actively seeking a means of passage, suggesting that there may have been other, undetermined causes of passage failure. [ABSTRACT FROM AUTHOR]

Approximately 200 km from the mouth of the Fraser River, British Columbia, Canada, adult sockeye salmon Oncorhynchus nerka, were gastrically implanted with radio transmitters without anaesthetic. Subsets of the transmitter implanted fish were also biopsied which included drawing blood from the caudal peduncle (3 ml), removal of gill tissue (0·03 g) and quantification of energetic status using a microwave fat meter. Several experiments were used to test the hypothesis that the biopsy had a negligible effect on the subsequent survival and migratory behaviour of transmitter implanted fish. In the first experiment, no difference was found in the survival (both 100%) or tag retention (both 100%) between the two treatment groups (transmitter implanted with and without biopsy) when fish were held in pens for 24 h in the marine environment. Similarly, in other experiments where fish were released to the ocean to resume their migratory journey, no statistical differences were found in the travel times of fish in the two treatment groups, or in the proportion of fish that passed in-river telemetry checkpoints. These results indicated that the handling and biopsy methods produced similar levels of mortality and tag retention as the telemetry treatment alone and that any changes in behaviour between the two treatment groups did not adversely affect migration time. Based upon the evidence provided from the biotelemetry of >300 adult sockeye salmon, it was felt that this general type of approach could be applicable to other fish species. [ABSTRACT FROM AUTHOR]

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Pro-environmental behaviours (PEBs) are important for mitigation and restoration efforts in the Anthropocene. As recreationists are motivated to engage in leisure activities to increase their own personal wellbeing, we submit that threats to wellbeing (an egocentric motivator) predict engagement in PEBs amongst recreationists. We also predict that differences in experiences across groups of recreationists leads to differences in PEB engagement. Using an online survey, we test our two hypotheses (if recreationists perceive there is a threat to their wellbeing and that their behaviours can yield environmental successes, then they will be more likely to engage in PEBs, and if recreationists differ in recreational experiences then they will demonstrate differences in PEB engagement) amongst outdoor recreationists, specifically Canadian rainbow trout and steelhead anglers in British Columbia (n = 894 respondents). We define 'threat to wellbeing' as the interaction of environmental threat-perceptions of used environments for fishing, and level of centrality fishing has to one's lifestyle. To test our first hypothesis, we conducted three linear regressions corresponding to three different PEBs related to catch-and-release (C&R) fishing. Our egocentric predictor 'threat to wellbeing' was only significant for one out of the three PEBs tested, showing mixed support for our first hypothesis. It is of note that 'environmental threat perceptions' and one's belief in successes resulting from PEB engagement were found to be significant predictors for all three PEBs tested. These results suggest that predictors of PEB may not always be transferable across PEBs relating to recreational activities, and environmental threat perception and one's belief in successes resulting from PEB engagement are strong predictors of PEBs amongst recreationists. To test our second hypothesis, we conducted a Kruskal Wallis test to determine if there were significant differences across angler groups in PEB predictor scores and PEB engagement and conducted pairwise population Z-tests to determine proportional participation rates across angler groups for the three PEBs and PEB predictors investigated. Experiences were found to shape predictors of PEBs, as well as likelihood to engage in PEBs, as different angler groups targeting different fish (i.e., rainbow trout vs steelhead) and using different aquatic habitats (i.e., rivers vs. lakes) demonstrated significantly different scores for PEB predictors, as well as significantly different likelihood to engage in two of the three PEBs tested. These findings support the notion that recreationists are not a homogenous group, and that their beliefs and resulting behaviours during recreational activities are determined by their experiences in nature and can be influenced by the species with which they interact, and the habitats they use for recreation., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Movement estimates derived from sub-daily tracking of radio-tagged bull trout Salvelinus confluentus on the Columbia River, British Columbia, Canada, were used to test whether interindividual variation in behaviour was repeatable among contexts, both short- and long-term. Interindividual variation in S. confluentus behaviour was consistent across contexts. These findings emphasize the potential for telemetry as a tool in animal personality and temperament research., (© 2014 The Fisheries Society of the British Isles.)

The objective of this study was to determine whether fisheries-related stressors differently influence two populations of adult sockeye salmon (Oncorhynchus nerka) with shared migration timing and location but where one population (i.e., Harrison) spawns 1 mo after the other (i.e., Weaver). Four stressor treatments were used following beach seine capture: (1) immediate release, (2) release after 10-15 min in the beach seine, (3) an additional 3-min gill net entanglement and 1-min air exposure, and (4) an additional 3-min tangle net simulation and 1-min air exposure. A comprehensive acoustic telemetry array and manual tracking revealed that survival was low overall, with more Weaver fish (34.2% of 38 tagged) reaching spawning areas compared to Harrison fish (17.8% of 78 tagged). For the Harrison population but not the Weaver, the gill net treatment influenced immediate (i.e., survived treatment) and short-term (i.e., 5-d postrelease) survival as well as survival to reach spawning areas. Harrison fish were more likely to be injured by the treatment, and reflex impairment predicted their short-term and long-term survival. Physiological condition did not differ between populations at the time of release, although both populations showed signs of severe physiological disturbances from the gill and tangle net simulations. These results suggest that even short durations of gill or tangle net entanglement can result in profound population-specific physiological disturbances and mortality. The notion that there can be population-specific variation in response to fisheries encounters adds complexity to management and provides further evidence for intraspecific differences in migration success.

Maturing adult sockeye salmon Oncorhynchus nerka were intercepted while migrating in the ocean and upstream in freshwater over a combined distance of more than 1,300 km to determine physiological and endocrine changes associated with ionoregulation. Sockeye migrating through seawater and freshwater showed consistent declines in gill Na+/K+ -ATPase (NKA) activity, plasma osmolality and plasma chloride concentration. In contrast, plasma sodium concentration became elevated in seawater as fish approached the river mouth and was then restored after sockeye entered the river. Accompanying the movement from seawater to freshwater was a significant increase in mRNA for the NKA α1a subunit in the gill, with little change in the α1b subunit. Potential endocrine signals stimulating the physiological changes during migration were assessed by measuring plasma cortisol and prolactin (Prl) concentrations and quantifying mRNA extracted from the gill for glucocorticoid receptors 1 and 2 (GR1 and GR2), mineralocorticoid receptor (MR), growth hormone 1 receptor (GH1R), and prolactin receptor (PrlR). Plasma cortisol and prolactin concentrations were high in seawater suggesting a preparatory endocrine signal before freshwater entry. Generally, the mRNA expression for GR1, GR2 and MR declined during migration, most notably after fish entered freshwater. In contrast, PrlR mRNA increased throughout migration, particularly as sockeye approached the spawning grounds. A highly significant association existed between gill PrlR mRNA and gill NKA α1a mRNA. GH1R mRNA also increased significantly, but only after sockeye had migrated beyond tidal influence in the river and then again just before the fish reached the spawning grounds. These findings suggest that cortisol and prolactin stimulate ionoregulation in the gill as sockeye salmon adapt to freshwater.

Recently, a segment of the Adams-Shuswap sockeye salmon (Oncorhynchus nerka) population initiated freshwater migration several weeks earlier than historically recorded, resulting in high mortality rates. The comigrating Chilko population maintained their historic river entry timing and did not experience elevated mortality. To test the hypothesis that population-specific differences in physiological condition would differentially influence behavior and survival when exposed to fisheries capture stress, we physiologically sampled individuals from both populations at the onset of the freshwater phase of their reproductive migration and tracked the remainder of their migrations using radio telemetry. Adams-Shuswap individuals had slower migration rates and were less likely to reach natal subwatersheds relative to Chilko individuals. Metabolic and osmoregulatory impairment was related to mortality for Adams-Shuswap individuals but not for Chilko individuals. Similarly, physiological condition correlated with migration rate for Adams-Shuswap but not Chilko fish. Survival to natal subwatersheds was 1.9 times higher for Chilko relative to Adams-Shuswap, a result that did not emerge until individuals approached natal subwatersheds several days after the stressor was applied. We conclude that physiological condition differentially affects the behavior and survival of these two populations, which may be a consequence of the early-entry phenomenon by a segment of the Adams-Shuswap population.

We present the first data on changes in ionoregulatory physiology of maturing, migratory adult sockeye salmon Oncorhynchus nerka. Fraser River sockeye were intercepted in the ocean as far away as the Queen Charlotte Islands (approximately 850 km from the Fraser River) and during freshwater migration to the spawning grounds; for some populations this was a distance of over 700 km. Sockeye migrating in seawater toward the mouth of the Fraser River and upriver to spawning grounds showed a decline in gill Na+,K+-ATPase activity. As a result, gill Na+,K+-ATPase activity of fish arriving at the spawning grounds was significantly lower than values obtained from fish captured before entry into freshwater. Plasma osmolality and chloride levels also showed significant decreases from seawater values during the freshwater migration to spawning areas. Movement from seawater to freshwater increased mRNA expression of a freshwater-specific Na+,K+-ATPase isoform (alpha1a) while having no effect on the seawater-specific isoform (alpha1b). In addition, gill Na+,K+-ATPase activity generally increased in active spawners compared with unspawned fish on the spawning grounds and this was associated with a marked increase in Na+,K+-ATPase alpha1b mRNA. Increases in gill Na+,K+-ATPase activities observed in spawners suggests that the fish may be attempting to compensate for the osmotic perturbation associated with the decline in plasma chloride concentration and osmolality.