Relationships between habitat characteristics and breeding population densities in sockeye salmon (Oncorhynchus nerka)

2011 ◽  
Vol 68 (5) ◽  
pp. 758-767 ◽  
Author(s):  
Douglas C. Braun ◽  
John D. Reynolds
Keyword(s):  
Sockeye Salmon ◽  
Woody Debris ◽  
Oncorhynchus Nerka ◽  
Information Criterion ◽  
Breeding Population ◽  
Habitat Characteristics ◽  
Population Densities ◽  
Ecological Processes ◽  
Risk Of Predation ◽  
Stream Characteristics

We examine the importance of stream habitat characteristics in governing variation in spawning densities of sockeye salmon ( Oncorhynchus nerka ) across 32 streams in the Fraser River Basin, British Columbia, Canada. We used mixed-effects models to examine four competing hypotheses for the influence of abiotic stream characteristics acting on either adult salmon or embryo mortality. All models that received support using Akaike’s information criterion included stream characteristics that are associated with cover. These included the percent area of pools, percentage of the banks that were undercut, and large woody debris (in that order). These results suggest the importance of stream characteristics, which reduce risk of predation on adults, in determining spawning sockeye salmon densities. Thus, identification of a small number of physical characteristics of streams provides insight into ecological processes that determine population densities. This information can be used to quantify habitat quality, which can guide habitat prioritization for conservation.

Effects of a Transmission Line on Bird Populations in the Red Lake Peatland, Northern Minnesota

The Auk ◽  
1984 ◽  
Vol 101 (3) ◽  
pp. 487-498 ◽  
Author(s):  
Gerald J. Niemi ◽  
JoAnn M. Hanowski
Keyword(s):  
Transmission Line ◽  
Habitat Structure ◽  
Breeding Population ◽  
Habitat Characteristics ◽  
Population Densities ◽  
Yearly Variation ◽  
Bird Populations ◽  
Census Methods ◽  
Habitat Differences ◽  
Transect Counts

Abstract The effects of a 500-kV transmission line on bird populations were assessed by comparing paired treatment areas [which included a transmission line and right-of-way (ROW)] with similar control areas in six different habitat types during the breeding and migration seasons. Habitat structure was measured to examine the inherent differences between control and treatment areas. Using two census methods, territorial mapping and transect counts, we determined that Sedge Wrens and LeConte's Sparrows had lower breeding-population densities in treatment areas than in control areas. LeConte's Sparrows and Connecticut Warblers occurred at greater mean distances from the transmission line in treatment areas than from a similarly positioned line in control areas. Fifteen paired t-tests (five habitats in 3 yr), in which territorial mapping data were used, revealed that community densities were lower in one treatment habitat (high shrub) in 1 of 3 yr (P < 0.05). A two-way analysis of variance with transect counts, however, was not confirmatory when yearly variation was included. Transect counts revealed lower population densities in one treatment habitat (low shrub) in 2 of 3 yr (P < 0.05). In contrast, we observed greater species richness (P < 0.05) in two treatment habitats (closed spruce and sedge fen) than in controls. Treatment habitats were most similar in habitat structure to their paired control habitats, but each habitat of the pair was significantly different (P < 0.05) from the other in at least 2 of 10 habitat characteristics analyzed. We suggest that the avian differences observed between paired areas were primarily attributable to (1) the inherent habitat differences between control and treatment areas, and (2) the new habitat created under the transmission line. Our data indicated negligible effects of this transmission line on bird populations, but interpretations are difficult, because the effects varied with (1) habitat, (2) season, and (3) method considered. Postimpact studies, which compare control and treatment areas, are less effective than before-and-after studies, because differences in habitat structure exist between any two areas.

Selective predation by brown bears (Ursus arctos) foraging on spawning sockeye salmon (Oncorhynchus nerka)

2000 ◽  
Vol 78 (6) ◽  
pp. 974-981 ◽  
Author(s):  
Gregory T Ruggerone ◽  
Renn Hanson ◽  
Donald E Rogers
Keyword(s):  
Sockeye Salmon ◽  
Ursus Arctos ◽  
Oncorhynchus Nerka ◽  
The Body ◽  
Upstream Migration ◽  
Selective Predation ◽  
Bristol Bay ◽  
Brown Bears ◽  
Risk Of Predation ◽  
Salmon Population

Selective predation by and predation rates of brown bears (Ursus arctos) foraging on spawning sockeye salmon (Oncorhynchus nerka) in a small shallow creek in the Wood River lake system near Bristol Bay, Alaska, were quantified during 1986 and 1990–1992. Bears killed a high proportion of spawning salmon when few salmon entered the creek (92% of 505 fish) and a much smaller proportion when the spawning population reached a historical high (16% of 15 631 fish). Selective predation on salmon that differed in length, sex, and spawning condition was measured by tagging salmon at the mouth of the creek immediately prior to upstream migration and then recovering dead tagged fish during daily surveys of the entire creek. The relative frequencies of large, medium-sized, and small salmon killed by bears indicated that the risk of predation was more than 150% greater for large than for small salmon. A higher proportion of the male salmon population was killed and a greater proportion of male bodies were consumed than female salmon. Selectivity for male salmon increased as the spawning season progressed, possibly because male salmon weakened earlier and lived longer in a weakened state than female salmon. Male salmon were attacked mostly along the dorsal hump area, whereas female salmon tended to be attacked along the abdomen, where eggs could be exposed. Bears selectively killed female salmon prior to spawning during 1 of the 3 years, but only 6.1–7.8% of the female spawning populations were killed prior to spawning. These data support the hypothesis that selective predation by bears may influence the body morphology of spawning salmon.

Genetic Variation in Sockeye Salmon (Oncorhynchus nerka) Populations of Asia and North America

1994 ◽  
Vol 51 (S1) ◽  
pp. 132-146 ◽  
Author(s):  
Nataly V. Varnavskaya ◽  
Chris C. Wood ◽  
Rebecca J. Everett
Keyword(s):  
Population Structure ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
High Variability ◽  
Allele Frequencies ◽  
Habitat Characteristics ◽  
Ice Age ◽  
Variant Allele ◽  
Composition Analysis ◽  
Protein Coding

We investigated population structure in sockeye salmon, Oncorhynchus nerka, in relation to ecological characteristics and geographical distribution using allozyme allelic frequencies compiled from new and previously published analyses for 71 populations (300 collections) throughout the species' range. Up to 87 protein-coding loci were screened in some samples, but of these, 55% were monomorphic, and another 31% were only slightly polymorphic with variant allele frequencies <0.01. Only 8 loci were moderately or highly polymorphic with variant allele frequencies exceeding 0.10 in at least some collections. The highest variation ever reported in salmon was discovered at LDH-B2* where the *100 allele was fixed in some populations but rare in others. Genetic differentiation was typically greater among populations within regions than among regions. However, stock composition analysis based on patterns of variation at the nine most useful loci appears to be feasible for most major stocks examined in this study. The low level of polymorphism in sockeye despite high variability at a few polymorphic loci is attributed to precise homing to natal rivers and interactions among several colonizing races that survived the Pleistocene ice age in isolated refugia with different habitat characteristics.

Effects of the abundance of spawning sockeye salmon (Oncorhynchus nerka) on nutrients and algal biomass in forested streams

2004 ◽  
Vol 61 (3) ◽  
pp. 384-403 ◽  
Author(s):  
N T Johnston ◽  
E A MacIsaac ◽  
P J Tschaplinski ◽  
K J Hall
Keyword(s):  
Chlorophyll A ◽  
Sockeye Salmon ◽  
Stream Water ◽  
Woody Debris ◽  
Oncorhynchus Nerka ◽  
Terrestrial Ecosystem ◽  
Late Summer ◽  
Nutrient Budget ◽  
Nutrient Concentrations ◽  
Epilithic Algae

We used natural variation in sockeye salmon (Oncorhynchus nerka) spawner biomass among sites and years in three undisturbed, forested watersheds in interior British Columbia to test the hypotheses that salmon were a major source of particulate organic matter inputs to the streams and that carcass biomass determined stream-water nutrient concentrations and epilithic algal production. Sockeye carcasses were retained at the spawning sites, primarily (75–80%) by large woody debris (LWD) or pools formed by LWD. The abundance and distribution of sockeye salmon determined stream-water nutrient concentrations and epilithic chlorophyll a concentrations during late summer and early fall when most primary production occurred in the oligotrophic streams. Periphyton accrual rates were elevated at sites with high salmon biomass. Peak chlorophyll a concentration increased with increasing carcass biomass per unit discharge above a threshold value to reach maxima 10-fold greater than ambient levels. Epilithic algae were dominated by a few common, large diatom taxa. Salmon carcasses were the dominant source of particulate organic carbon in low gradient stream reaches. Nutrient budget modeling indicated that most of the salmon-origin nutrients were exported from the spawning streams or removed to the terrestrial ecosystem; diffuse impacts may extend over a much larger area than simply the sites used for spawning.

Resumption of anadromy or straying? Origins of Sockeye Salmon Oncorhynchus nerka in the Elwha River

2021 ◽  
Author(s):  
Thomas P. Quinn ◽  
George R. Pess ◽  
Ben J.G. Sutherland ◽  
Samuel J. Brenkman ◽  
Ruth E. Withler ◽  
...  
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Elwha River

Alternative Recruitment Models of Adams River Sockeye Salmon, Oncorhynchus nerka

1987 ◽  
Vol 44 (9) ◽  
pp. 1551-1561 ◽  
Author(s):  
Jeremy S. Collie ◽  
Carl J. Walters
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Status Quo ◽  
Management Policy ◽  
Best Management ◽  
Interaction Terms ◽  
Ricker Model ◽  
The Status ◽  
Stock Recruitment ◽  
High Yields

Despite evidence of depensatory interactions among year-classes of Adams River sockeye salmon (Oncorhynchus nerka), the best management policy is one of equal escapement for all year-classes. We fit alternative models (Ricker model and Larkin model) to 32 yr of stock–recruitment data and checked, using simulation tests, that the significant interaction terms in the Larkin model are not caused by biases in estimating the parameters. We identified a parameter set (Rationalizer model) for which the status quo cyclic escapement policy is optimal, but this set fits the observed data very poorly. Thus it is quite unlikely that the Rationalizer model is correct or that the status quo escapement policy is optimal. Using the fitted stock–recruitment parameters, we simulated the sockeye population under several management policies. The escapement policy optimal under the Ricker model is best overall because of the high yields if it should be correct. If the three stock–recruitment models are equally likely to be correct, the simulations predict that adopting a constant-escapement policy would increase long-term yield 30% over the current policy and that an additional 15% increase in yield could be obtained if the policy were actively adaptive.

Reduced growth in wild juvenile sockeye salmon Oncorhynchus nerka infected with sea lice

2017 ◽  
Vol 91 (1) ◽  
pp. 41-57 ◽  
Author(s):  
S. C. Godwin ◽  
L. M. Dill ◽  
M. Krkošek ◽  
M. H. H. Price ◽  
J. D. Reynolds
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Sea Lice

Validation of daily increments and a marine-entry check in the otoliths of sockeye salmon Oncorhynchus nerka post-smolts

2015 ◽  
Vol 87 (1) ◽  
pp. 169-178 ◽  
Author(s):  
C. Freshwater ◽  
M. Trudel ◽  
T. D. Beacham ◽  
C.-E. Neville ◽  
S. Tucker ◽  
...  
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Daily Increments
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