A Comparison of Sockeye Salmon Catches at Rivers Inlet and Skeena River, B.C., with Particular Reference to Age at Maturity

1958 ◽  
Vol 15 (3) ◽  
pp. 331-354 ◽  
Author(s):  
Harold Godfrey
Keyword(s):  
Sockeye Salmon ◽  
Environmental Influence ◽  
Size Variation ◽  
Age At Maturity ◽  
River Systems ◽  
Age Composition ◽  
Age Class ◽  
Skeena River ◽  
Two Populations

Age composition, size and sex data for sockeye salmon catches (1912–1954) at Rivers Inlet and Skeena River, B.C. were compared. For both river systems there were indications of 4- and 5-year cycles of abundance among the 4- and 5-year-old fish, respectively; but the two populations were not necessarily in phase. Tests for correlation between the numbers of parental and offspring fish strongly suggested the dominance of hereditary over environmental influence in determining age at maturity. The two stocks showed much similarity in annual size variation, among each sex and age-class.

Long-term trends in age-specific recruitment of sockeye salmon (Oncorhynchus nerka) in a changing environment

2004 ◽  
Vol 61 (12) ◽  
pp. 2455-2470 ◽  
Author(s):  
Carrie A Holt ◽  
Randall M Peterman
Keyword(s):  
Kalman Filter ◽  
Sockeye Salmon ◽  
Large Scale ◽  
Oncorhynchus Nerka ◽  
Age At Maturity ◽  
Age Class ◽  
Sibling Models ◽  
Long Term Trends ◽  
Forecasting Errors

Sibling – age-class (sibling) models, which relate abundance of one age-class of adult sockeye salmon (Oncorhynchus nerka) to abundance of the previous age-class in the previous year, are commonly used to forecast abundance 1 year ahead. Standard sibling models assume constant parameters over time. However, many sockeye salmon populations have shown temporal changes in age-at-maturity. We therefore developed a new Kalman filter sibling model that allowed for time-varying parameters. We found considerable evidence for long-term trends in parameters of sibling models for 24 sockeye salmon stocks in British Columbia and Alaska; most trends reflected increasing age-at-maturity. In a retrospective analysis, the Kalman filter forecasting models reduced mean-squared forecasting errors compared with standard sibling models in 29%–39% of the stocks depending on the age-class. The Kalman filter models also had mean percent biases closer to zero than the standard models for 54%–94% of the stocks. Parameters of these sibling models are positively correlated among stocks from different regions, suggesting that large-scale factors (e.g., competition among stocks for limited marine prey) may be important drivers of long-term changes in age-at-maturity schedules in sockeye salmon.

Gillnet Selectivity on Sockeye (Oncorhynchus nerka) and Pink Salmon (O. gorbuscha) of the Skeena River System, British Columbia

1971 ◽  
Vol 28 (6) ◽  
pp. 821-842 ◽  
Author(s):  
Ian St. P. Todd ◽  
P. A. Larkin
Keyword(s):  
Sockeye Salmon ◽  
Pink Salmon ◽  
Mesh Size ◽  
Retention Rates ◽  
Age Class ◽  
Short Period ◽  
Length Range ◽  
Mesh Ratio ◽  
Mean Size ◽  
Skeena River

Exploitation of Skeena River sockeye salmon has been conducted almost solely by drift gillnets since 1875. This study was designed to determine the selective properties of nylon gillnets presently in use; to compare these with properties of linen nets used prior to 1955; and, using statistics of catch and escapement, to estimate the selective action of the fishery as a whole on sockeye and pink salmon in 1968.Unique selectivity curves for nylon nets of [Formula: see text] mesh size could not be determined from sockeye catches. Mean size of age class 1.2 sockeye increased with mesh size but mean size of the predominant age class 1.3 sockeye demonstrated no trend. Age class 1.3 sockeye were among the largest on record and were too large to gill properly in all mesh sizes used.Comparison of [Formula: see text] mesh nylon gillnet with linen nets of [Formula: see text] mesh used in the historic fishery was also influenced by the large size of age class 1.3 sockeye. Nylon nets were 2.5 and 2.7 times as efficient as linen for sockeye, and 8.0 and 9.0 times for pink salmon. Nylon gillnets caught larger sockeye and pink salmon than did linen. Variances of mean size were also greater for catches in nylon.The statistics of catch and escapement for 1968 indicated that selection increased over the length range of age 1.2 sockeye but decreased over the length range of age class 1.3 sockeye. For pink salmon, which were extremely small in 1968, selection was increasingly large for larger size males and females. The length–girth relations of the species and sexes accounted for most of the difference between the selectivity curves. Retention by gillnets declined once the girth/mesh ratio exceeded 1.2 for sockeye. For pink salmon, no females were of a size to equal this ratio; the descending limb of the selectivity curve was due solely to males as the retention rates declined once girth/mesh ratio exceeded 1.0.These findings suggest that in most years the gillnet fishery on the Skeena River would tend to select relatively larger sockeye salmon. In years such as 1968, however, selection would be against smaller fish. This frequent reversal combined with the intense modern fishery, which tends to remove virtually all fish during a short period and allows almost complete escapement in periods between fishing, suggests that selective fishing has probably not been a significant factor in decreased production.

A Hypothesis of Alternation of Age of Return in Successive Generations of Skeena River Sockeye Salmon (Oncorhynchus nerka)

1971 ◽  
Vol 28 (4) ◽  
pp. 513-516 ◽  
Author(s):  
H. T. Bilton
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Female Parent ◽  
Juvenile Growth ◽  
Age At Maturity ◽  
Subsequent Growth ◽  
Initial Size ◽  
Egg Weight ◽  
Skeena River ◽  
Successive Generations

Egg weight of Scully Creek and Lower Babine River sockeye salmon (Oncorhynchus nerka) was positively correlated with length and, usually, age of the female parent. Egg weight was positively correlated with initial size and subsequent growth of juveniles, at least up to 3 months of age. Examination of scales indicated juvenile growth in the lake and ocean was inversely related to age at maturity. Hence it was hypothesized that the larger age 1.3 sockeye spawners tend to produce progeny that mature as smaller age 1.2 fish, which in turn give rise to progeny that mature as larger age 1.3 fish, and so on; an alternation in age of return of successive generations occurs.

scholarly journals Different environmental variables predict body and brain size evolution in Homo

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Manuel Will ◽  
Mario Krapp ◽  
Jay T. Stock ◽  
Andrea Manica
Keyword(s):  
Environmental Factors ◽  
Cognitive Abilities ◽  
Net Primary Productivity ◽  
Brain Size ◽  
Environmental Influence ◽  
Size Variation ◽  
Evolutionary Pattern ◽  
Statistical Framework ◽  
Size Evolution ◽  
Major Predictor

AbstractIncreasing body and brain size constitutes a key macro-evolutionary pattern in the hominin lineage, yet the mechanisms behind these changes remain debated. Hypothesized drivers include environmental, demographic, social, dietary, and technological factors. Here we test the influence of environmental factors on the evolution of body and brain size in the genus Homo over the last one million years using a large fossil dataset combined with global paleoclimatic reconstructions and formalized hypotheses tested in a quantitative statistical framework. We identify temperature as a major predictor of body size variation within Homo, in accordance with Bergmann’s rule. In contrast, net primary productivity of environments and long-term variability in precipitation correlate with brain size but explain low amounts of the observed variation. These associations are likely due to an indirect environmental influence on cognitive abilities and extinction probabilities. Most environmental factors that we test do not correspond with body and brain size evolution, pointing towards complex scenarios which underlie the evolution of key biological characteristics in later Homo.

The role of thermal environment in determining the life history of a terrestrial salamander

2000 ◽  
Vol 78 (10) ◽  
pp. 1702-1711 ◽  
Author(s):  
Carlos D Camp ◽  
Jeremy L Marshall
Keyword(s):  
Body Size ◽  
Thermal Environment ◽  
Negative Relationship ◽  
Size Variation ◽  
Published Data ◽  
Size At Maturity ◽  
Adult Males ◽  
Age At Maturity ◽  
Adult Body Size ◽  
Adult Body

Largely using previously published data, we analyzed geographic variation in adult body size of terrestrial salamanders of the Plethodon glutinosus complex. Maximum body size of adult males is determined by size at maturity. In turn, size at maturity is determined by a negative relationship with environmental temperature. Moreover, both age at maturity and growth rate are correlated with size at maturity, but apparently only as coincidental correlates through the influence of temperature. The number of degree-days, estimated using temperature data from respective geographic locations, accurately predicts age at maturity for salamanders living in these areas. Development under cooler thermal regimes is more depressed than growth and, consequentially, adult body sizes are greater in cooler climates. This pattern of size variation fits thermal predictive models proposed for larval development in amphibians that breed in ponds. Phenotypic variation in adult body size appears to be accounted for largely by plastic responses to variation in thermal environments and may reflect a single reaction norm for the complex.

The Use of Graphical Methods to Estimate Demographic Parameters

1989 ◽  
Vol 69 (2) ◽  
pp. 367-371 ◽  
Author(s):  
Alastair Grant
Keyword(s):  
Undergraduate Students ◽  
Size Structure ◽  
Size Variation ◽  
Demographic Parameters ◽  
Graphical Methods ◽  
Age Classes ◽  
Size Frequency Distribution ◽  
Age Class ◽  
Frequency Histogram ◽  
Size Frequency

The demographic parameters of a population (the number of age-classes present; growth rates; mortality as a function of age and recruitment levels) are of considerable interest to marine biologists. If individuals can be aged from growth rings in their hard parts, then the estimation of demographic parameters is relatively straightforward. If this is not possible, the next best alternative is to tag or mark individuals and use data on the recapture of these to give the information required. For many marine invertebrates, neither of these options is practical and we must resort to estimating the demographic parameters by making assumptions about recruitment and the size variation between individuals of the same age and then infer the age structure of the population from its size structure. This was first done by Petersen (1891) who interpreted each mode on a size/ frequency histogram as representing a single age-class. More recently, extensive use has been made of methods which assume that the sizes of individuals of the same age will be normally distributed. The size/frequency histogram can then be decomposed into a number of normal distributions, each of which represents a single age-class. This can be done graphically (Harding, 1949; Cassie, 1954; Bhattacharya, 1967) or with computerbased numerical methods (Macdonald & Pitcher, 1979). The graphical methods seem to be the most popular and are frequently taught to undergraduate students. The same methods can be used to dissect a size/frequency distribution into components other than age-classes (Harding, 1949), but the principles are the same.

Comment: Population Structure and Run Timing of Sockeye Salmon in the Skeena River, British Columbia

2014 ◽  
Vol 34 (6) ◽  
pp. 1167-1170 ◽  
Author(s):  
Michael H. H. Price ◽  
Andrew G. J. Rosenberger ◽  
Greg G. Taylor ◽  
Jack A. Stanford
Keyword(s):  
British Columbia ◽  
Population Structure ◽  
Sockeye Salmon ◽  
Skeena River ◽  
Run Timing

Movements of Sockeye Salmon (Oncorhynchus nerka) in the Skeena River Estuary as Revealed by Ultrasonic Tracking

1975 ◽  
Vol 32 (2) ◽  
pp. 233-242 ◽  
Author(s):  
C. Groot ◽  
K. Simpson ◽  
I. Todd ◽  
P. D. Murray ◽  
G. A. Buxton
Keyword(s):  
Tidal Cycle ◽  
Sockeye Salmon ◽  
Salt Water ◽  
Oncorhynchus Nerka ◽  
River Estuary ◽  
River Mouth ◽  
Tidal Flows ◽  
Skeena River ◽  
Ultrasonic Tracking ◽  
Passive Movements

Movements of adult sockeye salmon (Oncorhynchus nerka) entering the Skeena River were examined in 1969 and 1970 by ultrasonic tracking methods. Fifteen of 18 sockeye released in the lower river seemed to move passively in and out with flood and ebb streams. Two fish moved upstream independent of tides and one salmon swam against ebb and flood currents. Ground speeds in both years of operation were 1.6 km/h during rising and 2.1 km/h during falling tides, causing the fish to be transported downstream by about 3 km per tidal cycle. Three salmon released outside the river mouth in salt water also seemed to ride the tidal flows passively. Ground speeds during ebb (3.6 km/h) were again greater than during flood (2.0 km/h), indicating a net offshore movement. We conclude that these passive movements are not an artifact but that sockeye salmon normally slow down or pause upon reaching the "home river" and drift for a period in tidal currents in the estuary and river mouth before migrating upstream.

The Skeena River Salmon Fishery, with Special Reference to Sockeye Salmon

1955 ◽  
Vol 12 (3) ◽  
pp. 451-485 ◽  
Author(s):  
D. J. Milne
Keyword(s):  
Special Reference ◽  
Sockeye Salmon ◽  
Coho Salmon ◽  
Pink Salmon ◽  
Relative Size ◽  
Accurate Data ◽  
Gill Net ◽  
History Of ◽  
Skeena River ◽  
Salmon Fishery

The general history of the Skeena River commercial salmon fishery is presented from 1877 to 1948. The changes in fishing areas, seasons and fishing methods are described, together with the trends in the catches obtained. The most accurate data pertain to the important sockeye salmon gill-net fishery. The sockeye catch attained a maximum of 187,000 cases in 1910 and since then has declined to a minimum of 28,000 cases in 1933 and 1943. In recent years the catches have tended to level off. The pink salmon catches declined markedly after 1930. The chum catches also appear to have declined in recent years. Whether or not the spring and coho salmon catches have declined is not known. The size of the sockeye catch appears to be the best available measure of the relative size of the population. An analysis of the age cycles in the catch of sockeye and pink salmon did not reveal a practical basis for prediction. Some possible changes in the fishing regulations are discussed and the need for more data on the fluctuations in the size of the stocks during the fresh water phase is stressed.

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