Evidence for Size-Selective Mortality of Juvenile Sockeye Salmon (Oncorhynchus nerka) in Babine Lake, British Columbia

1987 ◽  
Vol 44 (4) ◽  
pp. 712-721 ◽  
Author(s):  
Cameron J. West ◽  
P. A. Larkin
Keyword(s):  
British Columbia ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Length Distribution ◽  
Fork Length ◽  
Late Summer ◽  
Selective Mortality ◽  
Daily Growth ◽  
Back Calculation ◽  
Spawning Tributaries

Otolith – body length relations and back-calculation procedures were used to test the hypothesis that mortality of juvenile sockeye salmon (Oncorhynchus nerka) in Babine Lake, British Columbia, is size selective. Samples of the 1978 brood of sockeye were collected as fry from spawning tributaries as juveniles in the main basin, and as smolts at the outlet. Total otolith length was chosen as the most useful otolith dimension for back-calculation of fork length at emergence. Sockeye from the various tributaries show different fork length – otolith length relationships necessitating a weighting procedure for comparisons involving samples of mixed stocks from the lake. Instantaneous daily growth rate and In fork length during the early lake-rearing period were significantly correlated. Smaller juveniles grew more slowly than larger individuals in mid-july, and a hierarchy of sizes was maintained. The distributions of total otolith length at emergence for fry, surviving juveniles, and smolts indicate selective mortality of fish with smaller otoliths, hence of small size at emergence. Survivals from the lower and upper halves of the initial total otolith length distribution were 8.9 and 63.6%, respectively. Comparable estimates for back-calculated fork lengths at emergence were 27.2 and 43.4%. Size-selective mortality is most intense in the late summer and early autumn, and may be associated with predation and parasitism.

Daily Growth Rings in the Otoliths of Juvenile Sockeye Salmon (Oncorhynchus nerka)

1980 ◽  
Vol 37 (10) ◽  
pp. 1495-1498 ◽  
Author(s):  
K. H. Wilson ◽  
P. A. Larkin
Keyword(s):  
British Columbia ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Growth Rings ◽  
Daily Growth ◽  
Salmon Fry

Sockeye salmon fry were collected from the Fulton River spawning channel at Babine Lake, British Columbia, in May 1978. The fish were reared for 26 d in enclosures in the spawning channel and were sampled every 7 to 10 d. The sagittae were removed from 25 fish from each sample, and the growth rings in one otolith from each fish were counted. A regression of the number of rings on the number of days since capture showed that these rings are, on average, formed daily, beginning at the time of emergence. A number of possible technical and biological causes of variation in ring counts within and between samples are considered.Key words: otolith, sagittae, daily growth rings, sockeye salmon fry

Relationship Between Thickness of Daily Growth Increments in Sagittae and Change in Body Weight of Sockeye Salmon (Oncorhynchus nerka) Fry

1982 ◽  
Vol 39 (10) ◽  
pp. 1335-1339 ◽  
Author(s):  
Kenneth H. Wilson ◽  
P. A. Larkin
Keyword(s):  
Body Weight ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Regression Line ◽  
Daily Growth ◽  
Daily Increments ◽  
Growth Increments ◽  
Fish Weight ◽  
Daily Change ◽  
Back Calculation

Sixty-four laboratory-reared sockeye salmon (Oncorhynchus nerka) fry were marked to enable identification as individuals. Each was weighed initially on June 6 or 8, 1979; and again on July 6; and surviving fish were weighed a third time on July 20. After the final weighing, sagittae were removed and a standard otolith radius, corresponding to each weight, was determined by counting back from the otolith edge the appropriate number of daily increments. The regression of ln otolith radius on ln fish weight was linear, with r2 = 0.92, demonstrating a relationship between mean thickness of a daily increment in sagittae, and mean daily change in weight of the fry. Using this regression line, previous weights were back calculated from corresponding otolith radii with errors in the order of 15%.Key words: otoliths, daily growth increments, back calculation, sockeye salmon

Does mortality select size or growth potential in young sockeye salmon (Oncorhynchus nerka)? A simulation based on otolith - fish size relationships

1998 ◽  
Vol 55 (7) ◽  
pp. 1674-1681 ◽  
Author(s):  
M G Meekan ◽  
DAJ Ryan ◽  
J J Dodson ◽  
S P Good
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Fork Length ◽  
Field Studies ◽  
Growth Potential ◽  
Selective Mortality ◽  
Fish Size ◽  
Conflicting Evidence ◽  
Selection For ◽  
Otolith Size

There is conflicting evidence on the role of size-selective mortality in the demography of populations of young sockeye salmon (Oncorhynchus nerka). A previous field study suggested that increases in mean fork length and otolith size at emergence observed in a cohort of salmon between fry and smolt stages were due to size-selective mortality, such that fry with small fork lengths underwent higher mortality than larger individuals. However, a subsequent study used a simulation to show that such increases could not have been achieved by size-selective mortality without levels of survivorship of the cohort far lower than those that had been observed in the field. To account for field observations, the simulation study proposed that individuals with high metabolic rates had better survivorship, a process that was termed "selection for growth potential." Here, we use a simulation approach to show that size-selective mortality may result in shifts in mean fork length and otolith size at emergence comparable with those observed in the field at total mortalities within the range of estimates of natural values. The contrasting outcomes of earlier simulation work and the present study are probably due to the assumption by the former that otolith and fish size in young salmon were weakly correlated and the use of an inappropriate model of size-selective mortality. We conclude that size-selective mortality can explain the results of previous field studies and that little empirical evidence exists to support the hypothesis of selection for growth potential in cohorts of young salmon.

Effect of Smolt Size on Smolt-to-Adult Survival for Chilko Lake Sockeye Salmon (Oncorhynchus nerka)

1991 ◽  
Vol 48 (6) ◽  
pp. 988-994 ◽  
Author(s):  
M. A. Henderson ◽  
A. J. Cass
Keyword(s):  
Sockeye Salmon ◽  
Interannual Variation ◽  
Oncorhynchus Nerka ◽  
Fork Length ◽  
Adult Survival ◽  
Threefold Increase ◽  
Limited Variation ◽  
Back Calculation ◽  
The Mean ◽  
Calculation Procedures

Three approaches were used to test the hypothesis that smolt-to-adult survival is independent of smolt size for Chilko Lake sockeye salmon (Oncorhynchus nerka). The mean distance between the focus of the scale and the first annulus, a reliable indicator of smolt size, was greater for adult scales than for smolt scales from the same brood year in two of the three years we examined. This indicated a higher smolt-to-adult survival for larger smolts in these brood years. The abundance of smolts of different fork lengths, based on back-calculation procedures from adult scales, was compared with the abundance of smolts of different fork lengths at the time of outmigration within brood years. In all three years studied, there was a two- to threefold increase in smolt-to-adult survival as smolt length increased. However, there was no significant relationship between smolt-to-adult survival and mean annual smolt fork length based on a 34-yr time series; this lack of relationship was probably caused by limited variation in mean annual smolt fork length over the 34-yr period and other variables, independent of smolt size, that affect survival and exhibit considerable interannual variation.

Fecundity and Egg Retention of Some Sockeye Salmon (Oncorhynchus nerka) Stocks in British Columbia

1986 ◽  
Vol 43 (8) ◽  
pp. 1643-1655 ◽  
Author(s):  
J. I. Manzer ◽  
I. Miki
Keyword(s):  
British Columbia ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Absolute Fecundity ◽  
Egg Retention ◽  
Inadequate Sample Size ◽  
Egg Number ◽  
The Mean ◽  
The Relationship ◽  
Individual Fecundity

The fecundity and egg retention of anadromous female sockeye salmon (Oncorhynchus nerka) collected during 1971–82 from several stocks in British Columbia undergoing controlled fertilization to enhance adult sockeye production were examined. The relationship between egg number and postorbital–hypural length based on 863 females representing 14 stocks was not consistent between all age-types, stocks, and years, probably because of inadequate sample size in some instances. Combined samples, however, revealed a significant positive relationship between postorbital–hypural length and egg number for age 1.2, 1.3, and 2.2 females. Mean absolute fecundity for the respective age-types was 3218, 4125, and 3544 eggs. For samples of 10 or more females, significant stock and annual differences were detected when individual mean absolute fecundity was adjusted to a postorbital–hypural length of 447 mm, but not for females of different age. A comparison of mean fecundities for coastal stocks with historical data for interior British Columbia stocks suggests that coastal stocks are 18% more fecund than interior stocks. Possible causal mechanisms for this regional difference are hypothesized. Examination of 796 carcasses (representing five stocks) for egg retention revealed a range from totally spawned to totally unspawned females, with 56% of the carcasses containing 20 eggs or less and 68% containing 50 eggs or less. The mean egg retention based on all samples combined was estimated to be 6.5% of the mean individual fecundity. This value was reduced to 3.9% when stock means were averaged.

scholarly journals Importance of sample size for estimating prevalence: A case example of infectious hematopoietic necrosis viral RNA detection in mixed-stock Fraser River Sockeye salmon (Oncorhynchus nerka), British Columbia, Canada.

2020 ◽  
Author(s):  
Emilie Laurin ◽  
Julia Bradshaw ◽  
Laura Hawley ◽  
Ian A. Gardner ◽  
Kyle A Garver ◽  
...  
Keyword(s):  
British Columbia ◽  
Sample Size ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Small Sample ◽  
Viral Rna ◽  
Sample Sizes ◽  
Apparent Prevalence ◽  
Infectious Hematopoietic Necrosis ◽  
Mixed Stock

Proper sample size must be considered when designing infectious-agent prevalence studies for mixed-stock fisheries, because bias and uncertainty complicate interpretation of apparent (test)-prevalence estimates. Sample size varies between stocks, often smaller than expected during wild-salmonid surveys. Our case example of 2010-2016 survey data of Sockeye salmon (Oncorhynchus nerka) from different stocks of origin in British Columbia, Canada, illustrated the effect of sample size on apparent-prevalence interpretation. Molecular testing (viral RNA RT-qPCR) for infectious hematopoietic necrosis virus (IHNv) revealed large differences in apparent-prevalence across wild salmon stocks (much higher from Chilko Lake) and sampling location (freshwater or marine), indicating differences in both stock and host life-stage effects. Ten of the 13 marine non-Chilko stock-years with IHNv-positive results had small sample sizes (< 30 samples per stock-year) which, with imperfect diagnostic tests (particularly lower diagnostic sensitivity), could lead to inaccurate apparent-prevalence estimation. When calculating sample size for expected apparent prevalence using different approaches, smaller sample sizes often led to decreased confidence in apparent-prevalence results and decreased power to detect a true difference from a reference value.

Infectious agent detections in archived Sockeye salmon (Oncorhynchus nerka ) samples from British Columbia, Canada (1985-94)

2019 ◽  
Vol 42 (4) ◽  
pp. 533-547 ◽  
Author(s):  
Krishna K. Thakur ◽  
Raphaël Vanderstichel ◽  
Karia Kaukinen ◽  
Omid Nekouei ◽  
Emilie Laurin ◽  
...  
Keyword(s):  
British Columbia ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Infectious Agent

Recent Colonization of a Major Salmon-Producing Lake in British Columbia by Pacific Lamprey (Lampetra tridentata)

1984 ◽  
Vol 41 (2) ◽  
pp. 278-285 ◽  
Author(s):  
Susan P. Farlinger ◽  
Richard J. Beamish
Keyword(s):  
British Columbia ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Nursery Area ◽  
Commercial Fishery ◽  
Rock Slide ◽  
Pacific Lamprey ◽  
Natural Lake ◽  
Lampetra Tridentata

Pacific lamprey (Lampetra tridentata) were first observed in Babine Lake, the largest natural lake wholly contained in British Columbia, in 1963 and are currently found along approximately 15% of the length of the lake near the outlet. The number of spawning adults in 1982 was estimated to be 7281. Since Babine Lake is a major nursery area for sockeye salmon (Oncorhynchus nerka), the colonization of this lake by a parasitic lamprey is of concern, particularly if the species can become nonanadromous. The colonization may be beneficial if a commercial fishery can be sustained and if the species does not begin to feed in freshwater. The reason for the recent colonization is unknown but it coincides with increased human manipulation of fishes and habitat, including the removal of a major rock slide, 65 km downstream of the lake.

An Investigation of the Relative Efficiencies of Natural and Artificial Propagation of Sockeye Salmon (Oncorhynchus nerka) at Cultus Lake, British Columbia

1938 ◽  
Vol 4a (3) ◽  
pp. 151-161 ◽  
Author(s):  
R. E. Foerster
Keyword(s):  
British Columbia ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Free Swimming ◽  
Artificial Propagation ◽  
Natural Spawning ◽  
Significant Difference ◽  
Percentage Efficiency

From three tests each of natural propagation and of artificial propagation involving liberation of free-swimming fry and two tests of artificial propagation involving planting of eyed eggs, it was found that no statistically significant difference occurred between the three methods. Computing the percentage efficiency as the number of seaward migrants produced from the total eggs handled, natural propagation varied from 1.05% to 3.23%—an average of 1.80%; fry liberation from 2.42% to 4.54%—an average of 3.24%; and egg planting from 1.45% to 4.71%—an average of 3.08%. Losses occurring during the five years' stripping and hatchery operations were recorded and, based on total eggs, the hatchery product available for distribution represented from 61.0% to 86.0% for egg planting and from 63.4% to 78.5% for fry liberation. There occurred a lake mortality of approximately 96% of the number of fry liberated. The conclusion was reached that in an area such as Cultus lake, where a natural run of sockeye occurred with a reasonable expectancy of successful spawning, artificial propagation, as commonly practised, provided no advantage over natural spawning, as a means of maintaining the run.

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