Shuswap Lake Research Articles

Evaluation of Resistance to Rhabdocline Needlecast in Douglas Fir Variety Shuswap, with Quantitative Polymerase Chain Reaction

A quantitative polymerase chain reaction assay was developed that could detect DNA of Rhabdocline pseudotsugae and R. oblonga among DNA of Douglas fir needles to a limit as low as three copies of target DNA. Differential infection rates of two varieties (seed sources) of Douglas fir interplanted in a field were studied in relation to staggered bud breaks. Infection of Douglas fir var. San Isabel corresponded to ascospore release times for Rhabdocline spp., whereas infection of var. Shuswap Lake did not occur throughout the spore release period during 2 years of study, despite abundant inoculum and adequate moisture during bud break. Rhabdocline spp. DNA was never detected in Shuswap Lake and disease symptoms were not observed in any year. We provide evidence that Shuswap Lake is resistant and probably immune to Rhabdocline spp. infection and Rhabdocline needlecast under Michigan conditions.

Extensional shear zones, granitic melts, and linkage of overstepping normal faults bounding the Shuswap metamorphic core complex, British Columbia

An investigation of a normal-fault system in the southern Canadian Cordillera documents extensional shear zones exhumed from the middle crust, including the root of a transfer zone between overstepping fault segments in which shearing was enhanced by leucogranitic melts. The western margin of the Shuswap metamorphic core complex is delimited by west-dipping, ductile-brittle normal faults of the Eocene Okanagan Valley fault system. Migmatites with gently dipping mylonitic fabrics have been exhumed in the footwalls of the Okanagan-Eagle River and Adams-North Thompson fault segments. The mylonitic fabrics formed in upper amphibolite facies, continued to evolve in greenschist facies, and display asymmetric features that consistently indicate westward movement of the hanging wall. The Shuswap Lake transfer zone is a 45-km-wide left stepover between the two fault segments where a domed mylonitic shear zone has been exhumed and cut by high-angle brittle faults. Mylonites in the transfer zone display the same sense of shear as the mylonites that are associated with the overstepping fault segments. All of these mylonites are interpreted as having formed in a mid-crustal shear zone in which the fault system was rooted. The mylonites in the transfer zone are distinct, however, in that they formed in leucogranite (the Pukeashun granite). Structural relationships imply that the leucogranitic melts were emplaced during extensional shearing and that their distribution may have been influenced by preexisting structures in both the footwall and the hanging wall of the system. The melts in turn controlled the evolution of the transfer zone, facilitating the processes of heterogeneous extension, footwall doming, and differential exhumation.

Genotypic and Phenotypic Divergence of Sockeye Salmon in New Zealand from Their Ancestral British Columbia Populations

Abstract Embryos of sockeye salmon Oncorhynchus nerka were transplanted from Shuswap Lake, British Columbia (BC), to tributaries of Lake Ohau in the South Island of New Zealand (NZ) in 1901. This single shipment gave rise to a self-sustaining freshwater resident population that spawns primarily in Larch Stream north of Lake Ohau. We compared the genotypic (using protein electrophoresis) and phenotypic traits of the NZ O. nerka with anadromous (sockeye salmon) and nonanadromous (kokanee) populations of the species in the Shuswap Lake system. Genetic analysis confirmed that the transplanted fish had been sockeye salmon, not kokanee, and allele frequencies in the current NZ population were not significantly different from those in anadromous sockeye salmon from Scotch Creek, BC. The NZ O. nerka developed two life history patterns: some spent their entire rearing period in Lake Ohau, whereas others migrated downstream from Lake Ohau after 1 year to mature in Lake Benmore. These latter “migrants” grew faster a...

Long-term changes in parasites of sockeye salmon (Oncorhynchus nerka) smolts

Parasites were examined in 41 annual samples of sockeye salmon (Oncorhynchus nerka) juveniles originating from lakes in British Columbia: Chilko and Shuswap. Nine species of parasitic helminths and two species of parasitic Crustacea were recovered from various organs. The number of species ranged from three to nine per year. Most (94%) parasites belonged to three tapeworm species, identified as core to the parasite community because they also infected the most hosts. Two of these cestode species are probably maintained by resident freshwater hosts in the lakes. Positive numerical associations were observed between four parasite species pairs. Parasite communities in both lakes were composed of similar species, with the exception of three rare Chilko Lake species that were never recovered from Shuswap Lake. Parasites were often as variable within stock (temporally) as between stocks (geographically), except for the prevalence of Eubothrium sp. and Neoechinorhynchus sp. and mean annual intensity of Proteocephalus sp. and encysted digenetic metacercariae, which were greater at Chilko Lake than at Shuswap Lake. Discrimination between the two lakes based on their parasite community is possible only in extreme cases of infection and thus is of limited use to fisheries officers attempting to distinguish between these stocks.

Cycles of abundance among Fraser River sockeye salmon (Oncorhynchus nerka)

In some but not all populations of sockeye salmon (Oncorhynchus nerka) that mature mainly at age 4, there has been a persistently ``dominant'' line, a ``subdominant'' line about 10-25% as large, and two weak lines having less than 1% as many fish as the dominant one. Suggested causes of this phenomenon that have been shown to be wrong or inadequate are the presence of a few sockeye of ages 3 and 5 in the spawning stocks and a somewhat larger rate of harvest of the nondominant lines. The only plausible type of explanation that has been suggested so far involves interaction between the dominant line and the others, and the only specific example involves a 4-year cycle of abundance of a predacious fish at Shuswap Lake, described by F.J. Ward and P.A. Larkin. Other types of interaction are possible, but have not been documented. The magnitudes of the instantaneous interaction mortality rates at Shuswap Lake are estimated as about 0.78 per generation for the subdominant line out of a 7.65 total, and 1.11 out of 7.94 for the weak line 3, line 4 being similar.

Seismic-stratigraphy of Shuswap Lake, British Columbia, Canada

Shuswap Lake is a glacially-overdeepened ‘fiord lake’ located in the Shuswap Highlands of southern British Columbia, Canada, and consists of two sub-basins each nearly 60 km long and up to 3 km wide. Single-channel seismic reflection data, collected along 218 km of track line, identifies a tripartite infill stratigraphy up to 800 m thick preserved in bedrock basins eroded as much as 298 m below sea level. A similar tripartite stratigraphy is exposed in nearby outcrops along the valley of the South Thompson River and allows interpretation of age and depositional settings for the infill identified on seismic records. In Shuswap Lake, the lowermost seismic-stratigraphic sequence (SSSI), up to 407 m thick, shows chaotic seismic facies with large-scale diffractions and fills axial parts of V-shaped bedrock basins. Outcrop data suggest that this sequence consists of subaqueously-deposited, ice-contact silts, sands and gravels deposited in a deep (1 km?) ice-frontal lake during late Wisconsin deglaciation (ca. 10 ka). The overlying seismic-stratigraphic sequence (SSSII; up to 403 m thick) shows continuous, high-frequency seismic facies that pass down-basin into transparent (reflection-free) facies. High-frequency facies are interpreted as rhythmically-deposited silts and sands deposited by underflows (varves?); such facies are well exposed along the South Thompson River valley. Transparent ‘distal’ facies likely record uninterrupted settling from suspended sediment transported down-basin by interflow or overflow plumes and similar deposits are reported as currently forming in nearby Kamloops Lake. A relatively thin (<70 m) postglacial sequence of rhythmically-laminated Holocene silts (III) immediately underlies the modern lake floor. Deposition of very thick late-glacial stratigraphic successions and an absence of older pre-Late Wisconsin strata, appears to be a characteristic shared by other narrow, glacially-overdeepened valleys and basins in central British Columbia. This may be the result of scour by subglacial meltwaters and sediment focussing during deglaciation of fiord-like valleys occupied by deep ice-frontal lakes and rapidly retreating ice margins.

Paleozoic plutonism in southeastern British Columbia

U–Pb dates from zircons indicate that plutonic events occurred during the Paleozoic in the Omineca Crystalline Belt in southeastern British Columbia. In the Kootenay Arc, granitoid cobbles in conglomerate of the Carboniferous Milford Group were derived from quartz monzonite and diorite plutons of probable Ordovician age. Near Little Shuswap Lake, gneissic granitoid units have yielded Cambro-Ordovician ages. At least one episode of deformation affected country rocks of unknown age before intrusion. In the Monashee Complex south of Thor–Odin Nappe in South Fosthall Creek, lineated quartz monzonite is of probable Ordovician age. Comparison of fabrics suggests that at least one episode of metamorphism and deformation occurred prior to intrusion. No clear relationship between the cobbles and these plutons can be demonstrated because major faults lie between them, but substantial revision to accepted models of Paleozoic paleogeography of this region will have to be made. In the Clachnaeudainn tectonic slice east of the Monashee Complex, granitic gneiss is of Paleozoic, possibly Siluro-Devonian, age. This pluton appears to be involved in all phases of deformation that affected its country rocks. Near Quesnel Lake, parts of a composite gneissic granitoid pluton appear to be of Devonian or earliest Carboniferous age.

Incidence and importance of Crumenula sororia on Lodgepole pine.

In stands of Lodgepole pine over 6 years old, 68% of stems in Climatic Zones A and B, characterised by a relatively short growing season, and 63 % of stems in Climatic Zone C were infected by Crumenula sororia. On individual trees, the number of stem whorls showing C. sororia infection increased significantly with increasing stand elevation and with decreasing exposure in crops on Alberta and Shuswap Lake provenances over 30 years old, whereas in Shuswap, Long Beach and Vancouver Island stands less than 30 years old, increasing elevation and decreasing exposure had little effect on numbers of infected whorls. The numbers of infected whorls were not related to compartment aspect in crops of Alberta provenance, whereas in stands of Shuswap Lake, Long Beach and Vancouver Island provenances, W, SW and S-facing compartments showed fewer infections. In contrast the numbers of active cankers showed a positive correlation with increasing compartment elevation and exposure. In Zones B and C, cankers were concentrated on Northerly and Westerly aspects of individual stems. The evidence suggests that particular climatic regimes in different zones of the tree and in different ages of crop may be critical in determining the success of failure of infection by C. sororia.

Restocking Depleted Sockeye Salmon Areas by Transfer of Eggs

Eggs from Cultus lake, a lower Fraser river tributary, and from Adams river, in the Shuswap lake region, were transferred to Eagle river, a formerly important sockeye salmon stream at the head of Shuswap lake. The resulting fingerlings were marked, prior to liberation into Eagle river, by removal of certain fins for subsequent identification. Recovery of surviving adults—few in the commercial fishery, few, if any, in the original native spawning areas, none at Eagle river from the Cultus lake egg transfers and very few from the Adams river shipments—indicates that restoration of depleted sockeye areas cannot be achieved merely by introducing eggs from any outside well-populated areas.

The Food of Young Spring Salmon in Shuswap Lake, B.C.

The Food of Young Spring Salmon in Shuswap Lake, B.C.