Hydrological alteration has contributed to the global decline of stream frogs. Flows support stream frog reproduction, juvenile development, food resources, and maintain habitats for all life stages. At present, there is a lack of information regarding the specific water requirements necessary for the conservation of stream frogs. To address this gap, we developed a traits-based approach that serves as a valuable tool for grouping and prioritising water-dependent stream frog species to inform future research priorities and environmental flow design. In this study, we focussed on 53 Australian frog species and analysed eight species traits to develop water-dependent functional groups for stream frogs. We classified frogs based on their level of water dependency using an agglomerative hierarchical clustering analysis and a systematic review of water requirements and water management threats. The distinguishing traits that determined functional groups were: tadpole body type, egg clutch type, stream breeding habitat type, and documented association with flowing water and water permanence. Our study identified two distinct water-dependent groups: facultative stream spawners, capable of reproducing in both stream and non-stream habitats, and obligate stream spawners, restricted solely to stream habitats. Importantly, we highlight that the obligate stream spawners are the most sensitive group to within-channel flow alteration and should be prioritised for water management decisions in lotic environments. This study represents the first comprehensive overview of the importance of hydrology for stream frogs and identifies the critical need for additional research and validation to enhance our understanding of stream frog responses to flows regimes.

Anadromous Pacific salmon (Oncorhynchus spp.) are vulnerable to climate change in both freshwater and marine habitats. I use a qualitative model to assess the cumulative effects of climate change across life stages and generations of Fraser River sockeye salmon (Oncorhynchus nerka) and other salmon species. The effects of climate change most relevant to Fraser River sockeye include warming of freshwater and marine habitats, altered hydrology in spawning rivers, reduced productivity in nursery habitats, and changed distribution and phenology of predator and prey species. The weight of evidence indicates that these changes will negatively affect growth and survival of Fraser River sockeye at all life stages. Effects on one life stage will also carry forward to heighten adverse effects at subsequent life stages and across generations so that the cumulative impact is greater than the impact on individual stages. Salmon can adapt to climate change but probably not enough to sustain productivity. In the south, focus of policy and management on conserving and enhancing resilience is needed to retain some salmon production. At the same time, Arctic habitats are becoming accessible to salmon. Management in the Arctic should protect potentially productive habitats from development and facilitate their colonization by Pacific salmon.

A noninvasive biopsy protocol was used to sample plasma and gill tissue in individual sockeye salmon (Oncorhynchus nerka) during the critical life stage associated with spawning-arrival at a spawning channel through senescence to death several days later. Our main objective was to characterize the physiological changes associated with rapid senescence in terms of the physiological stress/cortisol hypersecretion model and the energy exhaustion model. Salmon lived an average of 5 d in the spawning channel, during which time there were three major physiological trends that were independent of sexual status: a large increase in plasma indicators of stress and exercise (i.e., lactate and cortisol), a decrease in the major plasma ions (i.e., Cl(-) and Na(+)) and osmolality, and a decrease in gross somatic energy reserves. Contrary to a generalized stress response, plasma glucose decreased in approximately 2/3 of the fish after arrival, as opposed to increasing. Furthermore, plasma cortisol levels at spawning-ground arrival were not correlated with the degree of ionoregulatory changes during rapid senescence. One mechanism of mortality in some fish may involve the exhaustion of energy reserves, resulting in the inability to mobilize plasma glucose. Sex had a significant modulating effect on the degree of physiological change. Females exhibited a greater magnitude of change for gross somatic energy, osmolality, and plasma concentrations of Cl(-), Na(+), cortisol, testosterone, 11-ketotestosterone, 17,20 beta-progesterone, and estradiol. The activity level of an individual on the spawning grounds appeared to influence the degree of some physiological changes during senescence. For example, males that received a greater frequency of attacks exhibited larger net decreases in plasma 11-ketotestosterone while on the spawning grounds. These results suggest that rapid senescence on spawning grounds is influenced by multiple physiological processes and perhaps behavior. This study provides some of the first data to look at sex differences in senescence in Pacific salmon.

Fraser River sockeye salmon have been the basis for a major commercial fishery shared by Canada and the United States, and an important cultural foundation for many aboriginal groups; they are also of huge ecological significance throughout the Fraser Basin. The potential for altered aquatic habitat and temperature regimes due to climate change is an important concern for Fraser River sockeye salmon. This paper characterizes the vulnerability of Fraser River sockeye salmon to future climate change using an approach that is novel on three counts. First, previous efforts to assess the vulnerability of salmon to climate change have largely focused on only part of the life cycle, whereas we consider climate vulnerability at all stages in the life cycle. Second, we use the available scientific literature to provide a basis for structuring and eliciting judgments from fisheries science and management experts who research and manage these systems. Third, we consider prospects for mitigating the effects of climate change on sockeye salmon. Tests showed that participants' judgments differentiated in statistically significant ways among questions that varied in terms of life stages, spawning regions and climate scenarios. The consensus among participants was that Fraser River sockeye are most vulnerable to climate change during the egg and returning adult stages of the life cycle. A high temperature scenario was seen as imposing the greatest risk on sockeye stocks, particularly those that migrate to the upper reaches of the Fraser River system and spawn earlier in the summer. The inability to alter water temperature and the highly constrained nature of sockeye management, with competing gear types and sequential fisheries over a long distance, suggest the potential to mitigate adverse effects is limited. Fraser River sockeye already demonstrate a great deal of adaptive capacity in utilizing heterogeneous habitats in different river sub-basins. This adaptability points to the potential value of policies to make stocks more resilient to uncertain futures.

We compared the effects of water resource development on migratory fish in two North American rivers using a descriptive approach based on four high-level indicators: (1) trends in abundance of Pacific salmon, (2) reliance on artificial production to maintain fisheries, (3) proportion of adult salmon that are wild- versus hatchery-origin, and (4) number of salmon populations needing federal protection to avoid extinction. The two rivers had similar biological and physical features but radically different levels of water resource development: the Fraser River has few dams and all are located in tributaries, whereas the Columbia River has more than 130 large mainstem and tributary dams. Not surprisingly, we found substantial effects of development on salmon in the Columbia River. We related the results to potential effects on migratory fish in the Mekong River where nearly 200 mainstem and tributary dams are installed, under construction, or planned and could have profound effects on its 135 migratory fish species. Impacts will vary with dam location due to differential fish production within the basin, with overall effects likely being greatest from 11 proposed mainstem dams. Minimizing impacts will require decades to design specialized fish passage facilities, dam operations, and artificial production, and is complicated by the Mekong’s high diversity and productivity. Prompt action is needed by governments and fisheries managers to plan Mekong water resource development wisely to prevent impacts to the world’s most productive inland fisheries, and food security and employment opportunities for millions of people in the region.

Salmon are inherently resilient species.However, this resiliency has been undermined in British Columbia by a century of centralized, command-and-control management focused initially on maximizing yield and, more recently, on economic efficiency.Community and cultural resiliency have also been undermined, especially by the recent emphasis on economic efficiency, which has concentrated access in the hands of a few and has disenfranchised fishery-dependent communities.Recent declines in both salmon stocks and salmon prices have revealed the systemic failure of the current management system.If salmon and their fisheries are to become viable again, radically new management policies are needed.For the salmon species, the emphasis must shift from maximizing yield to restoring resilience; for salmon fisheries, the emphasis must shift from maximizing economic efficiency to maximizing community and cultural resilience.For the species, an approach is needed that integrates harvest management, habitat management, and habitat enhancement to sustain and enhance resilience.This is best achieved by giving fishing and aboriginal communities greater responsibility and authority to manage the fisheries on which they depend.Co-management arrangements that involve cooperative ownership of major multistock resources like the Fraser River and Skeena River fisheries and community-based quota management of smaller fisheries provide ways to put species conservation much more directly in the hands of the communities most dependent on the well-being and resilience of these fisheries.

Animal migrations typically occur within a predictable time frame and sequence, but little is known about the triggers that initiate migration, despite their importance in animal ecology and for resource management. The migration of adult sockeye salmon (Oncorhynchus nerka) in the Fraser River, British Columbia, Canada, is an excellent model to study such triggers because for nearly a decade a segment of the late summer stocks has been proceeding into the river as much as 6 weeks earlier than the historic norm. In this study, late-run sockeye salmon (N = 146) were intercepted about 215 km from the mouth of the Fraser River and implanted with radio transmitters. These fish were biopsied, which included drawing blood from the caudal vessels, removing some gill filament tips, and quantifying energetic status using a microwave energy meter. Fish that entered the river without delaying in the estuary were in a more advanced state of reproductive maturation, as evidenced by hormone and energy levels. Indicators of osmoregulatory preparedness (i.e., plasma ions and gill Na+/K+-ATPase activity) provided little insight into migration timing aside from greater variation in Na+/K+-ATPase activity in fish that entered early relative to those that held in the ocean. Given the dissimilar reproductive hormone profiles for early arrival into the estuary and early entry into the Fraser River, it appears that only a subset of the population are early migrants and triggers for early migration may be related to a relatively advanced reproductive development and higher energetic status. These findings provide the first assessment of the physiological correlates of migration timing and provide a mechanistic understanding of the proximate factors associated with abnormal migration timing in late-run sockeye salmon.

Despite increasingly large investments, the potential ecological effects of river restoration programs are still small compared to the degree of human alterations to physical and ecological function. Thus, it is rarely possible to “restore” pre-disturbance conditions; rather restoration programs (even large, well-funded ones) will nearly always involve multiple small projects, each of which can make some modest change to selected ecosystem processes and habitats. At present, such projects are typically selected based on their attributes as individual projects (e.g., consistency with programmatic goals of the funders, scientific soundness, and acceptance by local communities), and ease of implementation. Projects are rarely prioritized (at least explicitly) based on how they will cumulatively affect ecosystem function over coming decades. Such projections require an understanding of the form of the restoration response curve, or at least that we assume some plausible relations and estimate cumulative effects based thereon. Drawing on our experience with the CALFED Bay-Delta Ecosystem Restoration Program in California, we consider potential cumulative system-wide benefits of a restoration activity extensively implemented in the region: isolating/filling abandoned floodplain gravel pits captured by rivers to reduce predation of outmigrating juvenile salmon by exotic warmwater species inhabiting the pits. We present a simple spreadsheet model to show how different assumptions about gravel pit bathymetry and predator behavior would affect the cumulative benefits of multiple pit-filling and isolation projects, and how these insights could help managers prioritize which pits to fill.

There has been little investigation into the physiological and energetic factors affecting reproductive success in free-swimming, spawning fish. One of the major impediments has been the lack of methods for nonlethally studying individual-specific energetics and physiological condition, as well as the lack of utilization of technologies for associating specific behaviors with energetics, condition, and fertilization success. Here we review three approaches (electromyogram [EMG] telemetry, nondestructive physiological sampling, and microsatellite analysis) that have recently been used to examine individual specific differences in behavior, energetics, and physiology in spawning sockeye salmon Oncorhynchus nerka. We also review major findings from other studies that have used these approaches in the context of how they were, or could have been, used to assess reproductive success in sockeye. Electromyogram telemetry can provide good estimates of individual specific energy expenditures during spawning and help identify energetic costs of specific reproductive behaviors. Nondestructive physiological sampling can provide information into pre- and postspawning levels of energy, hormones, and metabolites, enabling assessments of physiological stress, reproductive preparedness, and osmoregulatory function. Microsatellite analysis is a genetic marker technique that enables an assessment of parentage. We discuss several of the strengths of these research approaches and the value of integrating them with studies of fish behavior as a means of significantly advancing our understanding of individual variation in reproductive success of spawning salmonids.

Since 1995, large segments of the late-run sockeye salmon (Oncorhynchus nerka) stock complex from the Fraser River, British Columbia, Canada, have been initiating spawning migrations several weeks earlier than normal. Most aberrant migrants die before spawning. To evaluate the mechanisms underlying the mortality, we intercepted late-run sockeye salmon of the Adams–Shuswap stock complex halfway along their freshwater migration (i.e., in the Thompson River Canyon situated 270 km from the Fraser estuary), nonlethally assessed physiological and energetic status, and tracked individuals using gastrically inserted radio transmitters. Aberrant migrants that resumed their migration but failed to reach the spawning grounds had lower gross somatic energy, higher average migration ground speeds, higher plasma osmolality, and higher levels of plasma reproductive hormones than those that reached the spawning grounds. Fish surgically fitted with electromyogram radio transmitters did not continue their migration and fell downstream. These fish displayed excessive bleeding during transmitter implantation, an unusual phenomenon that likely contributed to the fish's inability to resume migration. Blood clotting time decreased steadily throughout the migration period. Collectively, these data implicate a combination of energy depletion, premature reproductive development, and blood loss from wounds as potential contributors to mortality in early migrating late-run sockeye.

Reproductive-based migration is a challenging period for many animals, but particularly for Pacific salmonids, which must navigate from the high seas to freshwater natal streams. For the first time, we attempt to answer the question as to why some migratory adult Pacific salmon die en route to spawning grounds. Summer-run sockeye salmon (Oncorhynchus nerka) were used as a model, and the migration behavior of 301 fish was followed by intercepting them in the ocean about 215 km from the mouth of the Fraser River, British Columbia, Canada, and implanting a gastric radio transmitter. Before release, telemetered fish were also bio-sampled, which included drawing a blood sample, collecting a gill biopsy, and quantifying energetic status with a microwave energy meter. We tested the predictions that the fish that died prematurely would be characterized by low energy reserves, advanced reproductive development, elevated indicators of stress, and low osmoregulatory preparedness compared with fish that completed their river migration. Just over half (52.3%) of the sockeye tagged were subsequently detected in the Fraser River. Salmon that failed to enter the river had exhibited indicators of stress (e.g., elevated plasma lactate, glucose, and cortisol). Contrary to our prediction, fish that failed to enter the river tended to have higher gross somatic energy and be larger at the time of sampling in the ocean than fish that successfully entered the river. Of the fish that were detected in the river (i.e., 134 fish excluding fishery removals), 9.7% did not migrate beyond the lower reaches (approximately 250 km from ocean), and a further 14.2% reached the upper reaches but failed to reach natal sub-watersheds, whereas the remainder (76.1%) reached natal sub-watersheds. Of these, fish unsuccessful in the lower reaches tended to have a high plasma osmolality in the ocean, whereas fish failing in the upper reaches had lower levels of reproductive hormones in the ocean.

Frogs are in decline worldwide, and are known to be sensitive indicators of environmental change. Floodplains of the Murray-Darling Basin in southeastern Australia have been altered in many ways by livestock grazing, by the introduction of exotic fish, and by changes to flooding regimes. These changes have led to declines in wetland condition and hence to the availability of habitat for wetland frogs. This study examined relationships between frogs, wetland condition and livestock grazing intensity at 26 wetlands on the floodplain of the Murrumbidgee River. Frog communities, species richness, and some individual species of frogs declined with increased grazing intensity. Wetland condition also declined with increased grazing intensity, particularly the aquatic vegetation and water quality components. There were clear relationships between frog communities and wetland condition, with several taxa responding to aquatic and fringing vegetation components of wetland condition. Thus, grazing intensity appeared to influence frog communities through changes in wetland habitat quality, particularly the vegetation. Reduced stocking rates may result in improved wetland condition and more diverse frog communities. River management to provide natural seasonal inundation of floodplain wetlands may also enhance wetland condition, frog activity and reproductive success.

Little is known about the behaviour patterns and swimming speed strategies of anadromous upriver migrating fish. We used electromyogram telemetry to estimate instantaneous swimming speeds for individual sockeye (Oncorhynchus nerka) and pink salmon (O. gorbuscha) during their spawning migrations through reaches which spanned a gradient in river hydraulic features in the Fraser River, British Columbia. Our main objectives were to describe patterns of individual-specific swim speeds and behaviours, identify swimming speed strategies and contrast these between sexes, species and reaches. Although mean swimming speeds did not differ between pink salmon (2.21 BL s−1) and sockeye salmon (1.60 BL s−1), sockeye salmon were over twice as variable (mean CV; 54.78) in swimming speeds as pink salmon (mean CV; 22.54). Using laboratory-derived criteria, we classified swimming speeds as sustained (<2.5 BL s−1), prolonged (2.5–3.2 BL s−1), or burst (>3.2 BL s−1). We found no differences between sexes or species in the proportion of total time swimming in these categories – sustained (0.76), prolonged (0.18), burst (0.06); numbers are based on species and sexes combined. Reaches with relatively complex hydraulics and fast surface currents had migrants with relatively high levels of swimming speed variation (e.g., high swimming speed CV, reduced proportions of sustained speeds, elevated proportions of burst speeds, and high rates of bursts) and high frequency of river crossings. We speculate that complex current patterns generated by river constrictions created confusing migration cues, which impeded a salmon's ability to locate appropriate pathways.

The Taiwan Endemic Species Research Institute hosted a workshop in April 2000 to explore options for conservation of the endangered Formosa landlocked salmon (Oncorhynchus masou formosanus). At the request of the institute, two representatives of the American Fisheries Society participated in this workshop. The Formosa salmon has suffered severe range restriction in recent years due to habitat loss and pollution and is now found only in the headwaters of Chichiawan Stream. Options to assist include restoration of in-stream and riparian habitat, removal of debris check dams on the Chichiawan Stream, artificial propagation, and establishment of satellite populations in other watersheds. Institutional arrangements to facilitate conservation and an action plan for conservation were also addressed.

In the US and Canada, a commitment to fairness leads to overly complex management regimes that contribute to overexploitation. We illustrate the pattern of increasing complexity in the Scotia/Fundy groundfish fishery in Atlantic Canada, the New England groundfish fishery and the Fraser River salmon fishery in British Columbia, all of which have collapsed or declined in r ecent years. Increasing complexity proceeds inexorably in publicly managed fisheries. However, the alternatives of transferring ownership to individual fishers or fishing communities appear not to be viable solutions. Rather, we suggest a co-management approach which may be unfair to some fishers but will greatly reduce the pressure to overfish.