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.-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 m 3 /s) than under high (15.8 m 3 /s) or low (11.0 m 3 /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 time 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.

In 2005 and 2006, adult sockeye salmon (Oncorhynchus nerka) were captured en route to spawning grounds and placed in either a slow (∼ 0.1 m·s −1 ) or fast (∼0.4 m·s −1 ) water velocity treatment for 18 days in order to assess how migrational energy depletion during the final stages of maturation affected physiological condition and survival. Fish in the fast treatment utilized more energy than the slow treatment in 2005 (0.91 MJ kg −1 vs. 0.43 MJ kg −1 ; P=0.010), and 2006 (0.72 MJ kg −1 vs. 0.37 MJ kg −1 ; P=0.021). Non-treatment fish captured upon arrival at spawning grounds showed energy levels intermediate to the two treatments in 2005 and lower than both in 2006, suggesting that energy use during the treatments were within levels normally experienced by this population. No differences in survival were found between treatments (P>0.05), although females had lower survival than males in both years (both P<0.01). After 18 days, surviving fish from the fast treatment showed signs of elevated physiological stress relative to fish from the slow treatment. Specifically, plasma osmolality was lower in fast fish in 2005 (P<0.001), as was plasma chloride in both years (both P<0.02). In 2006, plasma lactate was higher (P=0.014) in fast fish. Within the ranges of energetic depletion that were examined here, a more energy-intensive migration can have a substantial influence on the physiological condition and stress of adult sockeye salmon, but not on survival.

We raised two populations of sockeye salmon fry from fertilized eggs in the laboratory and tested the hypothesis that outlet fry populations, fish which must migrate upstream to reach rearing lakes after yolk-sac absorption, have better swimming ability and morphological characteristics conducive to enhanced swimming performance than inlet fry populations, fish which migrate downstream to rearing lakes. Despite being of identical age, fry from the outlet population were larger (approx. 6.7% longer,~5 mm on average) and more laterally compressed than inlet fry at the time of our initial experiments.Using an open-top box flume, we found that the burst-swimming performance (in cm s -1 ) of the outlet population was 31% better. We found no differences between populations in prolongedswimming performance. We were unable to find any direct relationships between measures of swimming performance and size or shape variables, suggesting that the larger, more robust morphology of outlet fry was not responsible for the superior burst ability. Recent biochemical studies indicate outlet fry may be metabolically better provisioned for burst swimming than inlet fry. It is possible that the morphological differences between the populations of fry reflect adaptations needed by adults during their migration and spawning.

Sockeye salmon Oncorhynchus nerka were used as a model in an artificial fertilization experiment to investigate the relationships between individual adult O. nerka and their offspring. Survival, size and burst swimming ability were assessed in fry of known parentage (adult spawners from the Weaver Creek population, British Columbia, Canada). Maternal identity significantly affected the survival rate of eggs at hatch time, though this effect did not extend to fry life stages. The results were also suggestive of a paternal effect on both egg and fry survival, though this could not be separated from the experimental block design. After 4 months of exogenous feeding, fry mass remained under significant maternal influence, though fork length did not, despite having a high correlation with mass. Burst swimming performance was highly variable among individuals, and was not significantly influenced by maternal identity or individual fry size. Collectively, the findings presented here suggest that maternal, and possibly paternal, effects can be integral components of population dynamics in the early life stages of O. nerka. A good understanding of these factors will be essential for scientists and fisheries managers in developing a more holistic view of population-level spawning success and fry survival.

We captured 196 adult Fraser River sockeye salmon (Oncorhynchus nerka) in the Gulf of Alaska and collected blood and tissue samples to describe their energetics and physiology at an early stage of homeward migration. Somatic energy concentrations differed significantly among population (run-timing) groups, with the earliest entering group (the Early Summerruns) possessing less energy than Summer-run and Late Summer-run sockeye. Conversely, Early Summer-run fish had invested significantly more in testicular development relative to the other run-timing groups (76.1 AE 9.8 g vs. 47.0 AE 8.0 g and 39.0 AE 5.4 g). Egg production followed a similar trend but was only marginally significant. Plasma testosterone was also nearly twice as high in Early Summer sockeye relative to Late Summerrun sockeye (89.01 AE 13.12 ng mL À1 vs. 38.69 AE 5.61 ng mL À1 ). To test the pleiotropic effect of reproductive hormones on migratory behaviour, we implanted these same 196 sockeye with gonadotropin-releasing hormone and/or testosterone and examined travel times via acoustic telemetry. Relative to controls, there was no significant relationship between hormonal treatment and travel times, which suggests that exogenous treatment had little effect though sample size was small (N ¼ 13). Nonetheless, pre-treatment levels of testosterone correlated significantly with travel times (r ¼ À0.813), irrespective of treatment.

To date, few studies have evaluated sub-organismal responses (e.g., physiological or energetic consequences) of individual fish to hydropower infrastructure (e.g., fishways, turbines) or operations (e.g., fluctuating flows, low flows). The field of “conservation physiology” (i.e., the use of physiological information to enhance conservation) is expanding rapidly and has great promise for hydropower research. However, there is a need to both expand the “toolbox” available to practitioners and to validate these tools for use in this context. This synthetic report details the behavioural, energetic, genomic, molecular, forensic, isotopic, and physiological tools available for studying sub-organismal responses of fish to hydropower infrastructure and operating procedures with a critical assessment of their benefits and limitations. Furthermore, this paper provides two case studies where behavioural, energetic, and physiological tools have been used in hydropower settings. Progressive and interdisciplinary approaches to hydropower research are needed to advance the science of sustainable river regulation and hydropower development. The expanded toolbox could be used by practitioners to assess fishway performance, migration delays, and fish responses to fluctuating flows through a more mechanistic approach than can be offered by only focusing on population metrics or indices of community structure. These tools are also relevant for the evaluation of other anthropogenic impacts such as water withdrawal for irrigation or drinking water, habitat alteration, and fisheries interactions.

Beyond assessing passage efficiency of fishway structures, there is a need to examine the sublethal impacts of passage on the physiological condition of fish. Muscle and plasma samples were collected from pink salmon (Oncorhynchus gorbuscha) at four sites along a fishway and were compared in order to assess the effectiveness of these methods as they apply to fishway studies. Both plasma and muscle tissue revealed changes consistent with anaerobic activity when fish sampled from within the fishway were compared with field baseline estimates taken from fish sampled 50 m downstream of the fishway entrance. Plasma Cl−, osmolality and haematocrit increased significantly (all p < 0.01) during ascent, whereas muscle glycogen and phosphocreatine declined (both p < 0.03). Both plasma and muscle tissue collected from fish sampled at a site just upstream of the fishway showed physiological profiles that were consistent with metabolic recovery relative to physiological conditions during passage: plasma lactate, haematocrit and muscle lactate had decreased (all p < 0.01), and muscle phosphocreatine increased (p = 0.01). When examining the physiological changes that specifically occurred between the two sites within the fishway structure, we found no differences in plasma samples, but muscle lactate and water content both showed significant changes (both p < 0.05). These results are consistent with the greater sensitivity of muscle tissue than of blood to exercise‐related physiological changes and highlight the usefulness of sampling muscle tissue for assessing fishways that ascended in a short time. Fishway studies could benefit from greater inclusion of physiological tools and approaches to identify the costs of passage and areas of difficulty within a fishway. Copyright © 2011 John Wiley & Sons, Ltd.