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Acoustic tag systems have been used for many years to study the behavior of fish in specific areas of interest. In particular tag systems are being used successfully to study the behavior of downstream migrating salmon smolts (Oncorhynchus spp.) as they approach hydro-electric dams. While field studies have demonstrated the potential for acoustic tag systems, little has been done to quantify their performance. This paper develops a method for predicting the accuracy of the “position estimates” provided by acoustic tag systems. General expressions are developed that can be applied to any particular deployment of a tag system which lead onto a method for the direct calculation of the “position error” as a function of hydrophone geometry, standard deviation of the signal arrival times, and the inaccuracies in the assumed sound velocities. This method is independent of the algorithm used to determine the position solution. Using the methods of analysis developed here some specific examples are presented that provide general guidelines that should be followed to achieve good performance when deploying an acoustic tag system. [Copyright &y& Elsevier]

The average adult size-at-return of North Pacific salmon (Oncorhynchus spp.) has decreased since the 1970s and several hypotheses regarding the cause of this decrease have been proposed. These have included fishing pressure, change of sea-surface temperature (SST) and density-dependence. This paper re-examines recent trends in the catch per unit effort (cpue) of chum salmon (Oncorhynchus keta), SST, sea surface salinity (SSS) and the Aleutian Low Pressure Index (ALPI), and compares them with trends in growth to determine if any of these factors related to the growth of chum salmon in the Sub-Arctic Domain of the Western North Pacific. From 1979 to 1998 chum salmon cpue increased, but fork length and back-calculated year-specific growth-increment size decreased significantly. SST showed no consistent pattern but SSS decreased significantly over time. Of total salmon cpue, chum salmon cpue, SST and SSS, only SSS was significantly correlated with growth-increment size; this relationship was positive. Residuals of the year-SSS relationship were also correlated with residuals of the year-growth increment-size relationship, indicating that SSS was consistently linked to growth-increment size. [ABSTRACT FROM PUBLISHER]

Global warming is changing the thermal habitat of cold-water freshwater fishes, which can lead to decreased fitness and survival and cause shifts in species distributions. The Alberta population of westslope cutthroat trout (Oncorhynchus clarkii lewisi) is listed as 'Threatened' under the Canadian Species at Risk Act. The major threats to the species are the alteration in habitat and water flow, competition and hybridization with non-native trout species and climate change. Here, we conducted (i) intermittent-flow respirometry experiments with adult native westslope cutthroat trout and non-native rainbow trout (Oncorhynchus mykiss) and (ii) critical thermal maximum experiments (CTmax) with adult westslope cutthroat trout to obtain valuable input data for species distribution models. For both species, standard metabolic rate (SMR) was lower at 10°C compared to 15°C and westslope cutthroat trout had higher SMR than rainbow trout. Although there were inter-specific differences in SMR, forced aerobic scope (using a standardized chase protocol) was different at 10°C, but no significant differences were observed at 15°C because of relative smaller differences in maximum metabolic rate between the species. CTmax of westslope cutthroat trout acclimated to 10°C was 27.0 ± 0.8°C and agitation temperature was 25.2 ± 1.0°C. The results from this study will inform and parametrize cumulative effects assessments and bioenergetics habitat modelling for the recovery planning of the species. [ABSTRACT FROM AUTHOR]

Pacific salmon (Oncorhynchus spp.) are at the center of social–ecological systems that have supported Indigenous peoples around the North Pacific Rim since time immemorial. Through generations of interdependence with salmon, Indigenous Peoples developed sophisticated systems of management involving cultural and spiritual beliefs, and stewardship practices. Colonization radically altered these social–ecological systems, disrupting Indigenous management, consolidating authority within colonial governments, and moving most harvest into mixed-stock fisheries. We review Indigenous management of salmon, including selective fishing technologies, harvest practices, and governance grounded in multigenerational place-based knowledge. These systems and practices showcase pathways for sustained productivity and resilience in contemporary salmon fisheries. Contrasting Indigenous systems with contemporary management, we document vulnerabilities of colonial governance and harvest management that have contributed to declining salmon fisheries in many locations. We suggest that revitalizing traditional systems of salmon management can improve prospects for sustainable fisheries and healthy fishing communities and identify opportunities for their resurgence. [ABSTRACT FROM AUTHOR]

Selective consumption of prey by predators, observed in many animals, is often attributed to optimal foraging. Consistent with this idea, brown bears (Ursus arctos) often exhibit partial consumption, feeding exclusively on lipid-rich tissues of Pacific salmon (Oncorhynchus spp.), and discarding remains. However, bears also kill and abandon salmon without consuming any tissue. These discarded fish may be consistent with optimal foraging choices if they are of poor quality and if bears have easy access to better prey, or may reveal nonadaptive surplus killing behavior if fish are killed and discarded at random or solely based on prey abundance. Using 21 consecutive years of data from sockeye salmon (O. nerka) carcass surveys in Alaska, we found that foraging to maximize energy intake best explained prey discarding behavior. Specifically, discarding was more common under high prey abundance, late in the salmon run, and with low-quality prey. Patterns of tissue consumption were consistent with these findings; bears were less likely to consume belly, body, and brain tissue when prey condition decreased. Other factors not quantified here (e.g. bear demography, alternative food resources) almost certainly influence prey discard and partial consumption, though the salmon-related factors explored here strongly influenced bear foraging decisions that were consistent with optimal foraging theory. We did not find clear evidence of surplus killing behavior in brown bears foraging on salmon, but prey selectivity manifested itself through both discarding and partial consumption, which contributes to our ability to predict transport of salmon nutrients by bears across ecosystem boundaries. [ABSTRACT FROM AUTHOR]

Behavioral decisions during periods of vulnerability to predation risk, such as migrations during the juvenile life-history stage, may strongly affect the probability of survival. Habitats through which animals migrate are heterogeneous, and risk-reducing behaviors may be more important in some habitats than others. Using biotelemetry data, diurnal and seasonal riverine migration patterns of >3800 juvenile salmon across 4 species, 12 watersheds, and 5 years were quantified to evaluate possible effects of migration timing on survival from lower river reaches to coastal waters. In small, clear rivers most salmon avoided migrating during daylight hours and average survival of fish migrating at night (55%; 95% confidence limits 50–61%) was twice that of fish migrating in daylight (24%; CL 17–31%). Conversely, in the large, heavily silted Fraser River neither preference for nocturnal travel nor effects of diurnal timing on survival were observed. Early ocean survival was also influenced by the timing of ocean entry, but in opposite directions for fish from the Fraser River and smaller rivers. In the Fraser River, average survival for later migrants (69%; CL 60–77%) was nearly twice that of earlier migrants (38%; CL 33–44%), likely related to seasonal increases in river flow. In contrast, in smaller rivers, average survival for earlier migrants (70%; CL 65–74%) was 3-fold greater than survival for later migrants (19%; 95% CL 14–25%). Together, these results demonstrate that timing decisions affecting survival of juvenile salmon during their migration are likely mediated by landscape characteristics that plausibly influence the risk of predation. [ABSTRACT FROM AUTHOR]

Aims: To develop probiotics for the control of vibriosis caused by Vibrio anguillarum and Vibrio ordalii in finfish. Methods and Results: Kocuria SM1, isolated from the digestive tract of rainbow trout, was administered orally to rainbow trout ( Oncorhynchus mykiss) for 2 weeks at a dose equivalent to c. 108 cells per g of feed and then challenged intraperitoneally with V. anguillarum and V. ordalii. Use of SM1 led to a reduction in mortalities to 15–20% compared to 74–80% mortalities in the controls. SM1 stimulated both cellular and humoral immune responses in rainbow trout, by elevation of leucocytes (5·5 ± 0·8 × 106 ml−1 from 3·7 ± 0·8 × 106 ml−1), erythrocytes (1·2 ± 0·1 × 108 ml−1 from 0·8 ± 0·1 × 108 ml−1), protein (23 ± 4·4 mg ml−1 from 16 ± 1·3 mg ml−1), globulin (15·7 ± 0·2 mg ml−1 from 9·9 ± 0·1 mg ml−1) and albumin (7·3 ± 0·2 mg ml−1 from 6·1 ± 0·1 mg ml−1) levels, upregulation of respiratory burst (0·05 ± 0·01 from 0·02 ± 0·01), complement (56 ± 7·2 units ml−1 from 40 ± 8·0 units ml−1), lysozyme (920 ± 128·8 units ml−1 from 760 ± 115·3 units ml−1) and bacterial killing activities. Conclusions: Kocuria SM1 successfully controlled vibriosis in rainbow trout, and the mode of action reflected stimulation of the host innate immune system. Significance and Impact of the Study: Probiotics can contribute a significant role in fish disease control strategies, and their use may replace some of the inhibitory chemicals currently used in fish farms. [ABSTRACT FROM AUTHOR]

We examine foraging behavior of coastal black bears (Ursus americanus kermodei) during different light regimes on a salmon stream in British Columbia, Canada (2000-2002). Bears (maximum 7 simultaneously) were primarily active during daylight near the onset of the salmon spawning run and shifted to twilight and darkness as the spawning run progressed. Overall time budget included search and pursuit (58%), handling and ingestion (38%), and agonistic interactions with other bears (4%). Scavenging was greatest during daylight (19%) and lowest during darkness (3%). Bears were most efficient at capturing live salmon when standing (35.4% success) followed by running (20.5%) and walking (15.2%). Highest capture efficiency occurred during twilight (33.6%) compared with daylight (26.5%) and darkness (24.7%). Capture rate ranged from 1 to 3 salmon per hour per bear. Our results suggest that bears increased their total salmon intake by alternate use of visual and auditory cues during daylight and darkness. [ABSTRACT FROM AUTHOR]

Little is known about actual mating systems in natural populations of parasites or about what constitutes the limits of a parasite deme. These parameters are interesting because they affect levels of genetic diversity, opportunities for local adaptation, and other evolutionary processes. We expect that transmission dynamics and the distribution of parasites among hosts should have a large effect on mating systems and demic structure, but currently we have mostly speculation and very few data. For example, infrapopulations (all the parasites in a single host) should behave as demes if parasite offspring are transmitted as a clump from host to host over several generations. However, if offspring are well mixed, then the parasite component population (all the parasites among a host population) would function as the deme. Similarly, low mean intensities or a high proportion of worms in single infections should increase the selfing rate. For species having an asexual amplification stage, transmission between intermediate and definitive (final) hosts will control the variance in clonal reproductive success, which in turn could have a large influence on effective sizes and rates of inbreeding. We examined demic structure, selling rates, and the variance in clonal reproductive success in natural populations of Plagioporus shawi, a hermaphroditic trematode that parasitizes salmon. Overall levels of genetic diversity were very high. An a posteriori inference of population structure overwhelmingly supports the component population as the deme, rather than individual infrapopulations. Only a single pair of 597 adult individuals was identified as clones. Thus, the variance in clonal reproductive success was almost zero. Despite being hermaphroditic, P. shawi appears to be almost entirely outcrossing. Genetic estimates of selfing (<5%) were in accordance with the proportion of parasites from single infections. Thus, it appears that individual flukes outcross whenever possible and only resort to selling when alone. Finally, our data support the hypothesis that aquatic transmission and the use of several intermediate hosts promotes high genetic diversity and well-mixed infrapopulations. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the genetic variation at several polymorphic allozyme loci and nuclear DNA loci and mitochondrial DNA in four spawning populations of sockeye salmon (Oncorhynchus nerka). Methodology of the study; Results and discussion on the study; Conclusions.

In assessing extinction risk for Pacific salmon (Oncorhynchus spp.), a variety of interacting risk factors are considered, some of which can be quantified but many of which are qualitative. In addition to the common measures of population abundance and trends for individual populations, these factors include ecological and genetic effects of hatchery fish, changes in life history traits, selective effects of harvest, trends in freshwater habitat condition, and climate variation. Combining such information into an assessment of the overall degree of risk facing populations and species relies heavily on scientific judgement rather than explicit quantitative criteria. To organize multifactor information and ensure consistency, a risk-matrix method has been implemented in which individual risk factors are scored on a 5-point scale, and then combined into an overall assessment of extinction risk. [ABSTRACT FROM PUBLISHER]

A salmon cystatin cDNA clone was isolated from a chum salmon cDNA library. The clone encoded a full-length extracellular-type cystatin and its signal peptide and included 5′- and 3′ -untranslated regions. The deduced amino acid sequence showed a high degree of sequence similarity to mammalian cystatin C, chicken egg cystatin, and chum salmon pituitary cystatin. By Northern blot analysis, the salmon cystatin was found to show apparently non-tissue specific expression. Because platyfish EHS cells transfected with a cystatin expression vector produced a 13 kDa mature cystatin in the culture medium, the salmon cystatin was considered to act as an extracellular type of cystatin in the fish cells. These findings indicate that the salmon cystatin is a homolog of mammalian cystatin C. [ABSTRACT FROM AUTHOR]

Pacific salmon have been fished extensively for at least a century and artificial production of Pacific salmon has been a management strategy to improve production for almost as long. Hatchery production is considered important because it is commonly believed that the carrying capacity for salmon in the ocean has remained more or less constant and is underutilized as a consequence of limited production of smolts in fresh water. Since the mid-1960s, there has been an increase in hatchery production, partly as a response to a desire to increase catch and partly because of improved hatchery techniques. Since the late 1970s there has been a dramatic increase in the total Pacific salmon catch. The increases in catch are now known to result from a large-scale shift in the productivity of the sub-arctic Pacific and management and enhancement actions. Environmental indices changed about 1989–1990 and may indicate that the productive regime of the 1980s has ended. This would imply that under natural conditions Pacific salmon abundance would decline. There are no clear indications of what to expect in the new regime, but it is apparent that the massive production of artificially reared Pacific salmon would not be necessary in a less productive regime. Of concern is the impact that the large numbers of artificially reared salmon will have on wild salmon stock levels. [ABSTRACT FROM PUBLISHER]

Horizontally scanning split-beam hydroacoustics was used to monitor downstream migrating juvenile salmon and steelhead trout smolts (Oncorhynchusspp.). The study was conducted in the reservoir of Rocky Reach Dam on the Columbia River (Washington, USA). The objective was to determine the movement patterns of smolts as they migrated through the reservoir. Scanning split-beam hydroacoustic techniques and three-dimensional target tracking were combined with remote multiplexing with the aim of investigating smolt movement patterns in the reservoir. The trajectory profiles, target strength distributions, and horizontal distributions of the smolts were estimated for each of six different aiming configurations utilizing six different elliptical split-beam transducers. The results of this study were used to determine the optimal location for installing a surface collector and bypass system. This system will be used to collect and bypass smolts past the dam, a safer alternative to passing through the turbines. The results showed that fish migrated downstream primarily along the east side of the reservoir, concentrated in the upper water column. Few fish were seen migrating down the western shoreline. At the southern end of the reservoir, there were areas where the fish congregated into relatively large schools before proceeding on their downstream migration. Following this study, a smolt bypass system has been installed and is currently being evaluated. [ABSTRACT FROM PUBLISHER]