scholarly journals On estimating the age composition of the commercial catch of Northeast Arctic cod from a sample of clusters

2003 ◽  
Vol 60 (2) ◽  
pp. 297-303 ◽  
Author(s):  
Aanes Sondre ◽  
Michael Pennington
Keyword(s):  
Age Structure ◽  
Age Distribution ◽  
Significant Loss ◽  
Effective Sample Size ◽  
Commercial Fishing ◽  
Total Catch ◽  
Intracluster Correlation ◽  
Age Composition ◽  
Commercial Catch ◽  
Arctic Cod

Abstract Assessment of Northeast Arctic cod is based on estimates of the commercial catch in numbers at age. The age structure of the catch is estimated by sampling fish from commercial fishing trips. Although it is commonly assumed that a sample of individuals is a random sample from the population, fish sampled from the same trip (i.e. from a “cluster” of fish) tend to be more similar in age than those in the total catch. For Northeast Arctic cod, the intracluster correlation for age is positive, and therefore the effective sample size is much smaller than the number of fish aged. Given the number of fish aged, the precision of the estimated age distribution is rather low, and the number of fish aged from each trip could be reduced from approximately 85 to 20 without a significant loss in precision.

Run reconstruction of mixed-stock salmon fisheries using age-composition data

2007 ◽  
Vol 64 (11) ◽  
pp. 1479-1490 ◽  
Author(s):  
Brandon Chasco ◽  
Ray Hilborn ◽  
André E Punt
Keyword(s):  
Sockeye Salmon ◽  
Commercial Fishing ◽  
Age Composition ◽  
Commercial Catch ◽  
Composition Data ◽  
Migration Timing ◽  
Highly Correlated ◽  
And Migration ◽  
Mixed Stock ◽  
Salmon Fishery

A method for using age-composition data to determine stock-specific migration timing and abundance in a mixed-stock salmon fishery is developed. The Chignik sockeye salmon (Oncorhynchus nerka) fishery has two stocks, but only aggregate catch and escapement data are available. The age composition of the two stocks, however, is known to be consistently different, and age-composition data are collected from one stock at the beginning of the commercial fishing season and from the commercial catch throughout the season. Using the changes in age composition in the commercial catch throughout the season, we estimate the total abundance and migration timing for the two Chignik stocks using maximum likelihood and Bayesian methods. The outcomes of this stock separation model are highly correlated with that of scale pattern analysis for most years from 1978 to 2002 (r = 0.89). The results suggest that age composition may provide salmon managers with a reliable and inexpensive method for determining stock-specific migration timing and abundance in a mixed-stock fishery.

scholarly journals Tracking Pandemic Severity Using Data on the Age Structure of Mortality: Lessons From the 1918 Influenza Pandemic in Michigan

2021 ◽  
Vol 111 (S2) ◽  
pp. S149-S155
Author(s):  
Siddharth Chandra ◽  
Julia Christensen
Keyword(s):  
Public Health ◽  
Age Structure ◽  
Goodness Of Fit ◽  
Influenza Pandemic ◽  
Age Distribution ◽  
Test Statistic ◽  
Goodness Of Fit Test ◽  
1918 Influenza ◽  
Death Data ◽  
Excess Deaths

Objectives. To test whether distortions in the age structure of mortality during the 1918 influenza pandemic in Michigan tracked the severity of the pandemic. Methods. We calculated monthly excess deaths during the period of 1918 to 1920 by using monthly data on all-cause deaths for the period of 1912 to 1920 in Michigan. Next, we measured distortions in the age distribution of deaths by using the Kuiper goodness-of-fit test statistic comparing the monthly distribution of deaths by age in 1918 to 1920 with the baseline distribution for the corresponding month for 1912 to 1917. Results. Monthly distortions in the age distribution of deaths were correlated with excess deaths for the period of 1918 to 1920 in Michigan (r = 0.83; P < .001). Conclusions. Distortions in the age distribution of deaths tracked variations in the severity of the 1918 influenza pandemic. Public Health Implications. It may be possible to track the severity of pandemic activity with age-at-death data by identifying distortions in the age distribution of deaths. Public health authorities should explore the application of this approach to tracking the COVID-19 pandemic in the absence of complete data coverage or accurate cause-of-death data.

The age distribution in the Taimyr population wild northern deer (Rangifer Tarandus) in the first decades of 21 centuries

2021 ◽  
pp. 15-21
Author(s):  
A. Shapkin ◽  
R. Ivanova ◽  
N. Arsentseva ◽  
N. Sukhanova
Keyword(s):  
Age Structure ◽  
Rangifer Tarandus ◽  
Age Distribution ◽  
Age Groups ◽  
Base Material ◽  
Middle Level ◽  
Reproduction Rate ◽  
Male And Female ◽  
Field Samples ◽  
Wild Deer

Objective: mathematical demography means to identify and evaluate the age distribution of male and female of Taimyr tundra reindeer in the first decade of the XXI century and future trends in demographic situation Taimyr population.Materials and methods. The base material for evaluating the current state of the population age structure Taimyr steel fishing representative sample of male and female wild deer (n = 10845 individuals) collected in the West, Central and Taimyr Putorana in 2001-2008., And the deer samples (n = 1569 individuals), the floor of which is unknown. Determination of individual animals from age and older (n = 9773 individuals) performed on histological sections of cutters according to the corresponding procedure. To repay the random deviations of sample data because of a lack of presence of immature animals (calves, yearlings, young 1-2 years) (selectivity of fishing is directed primarily at the production of individuals older than 3 years, why animals in different age groups in the samples is greater than there are in the population) applies a smoothing procedure. Then, positive deviation of the number of individuals in the same age group were leveled due to negative deviations in adjacent groups.Results. By smoothed age ranges of the field samples from 2001-2008 the current age distribution of Taimyr wild reindeer calculated and analyzed. The study showed that the theoretical current age distribution of males with realized breeding is 77.03, females - 80.56, in the combined groups of animals - 82.35%. The real population has 18-19 age generations of males and females. The reproductive core of males from 3 to 10 years old is 48.43%, individuals of age limit 11 years and older occupy 1.96% of this sex and age structure, calves and young animals for 1-2 years - 24.64%. For the reproductive part of females aged 3–15 years, the overall age distribution is 55.34%, and the proportion of juveniles and young animals, according to calculations, is determined in this part of the population at 25.16%. In the combined current age distribution, males, females: calves and young animals accounted for 27.72%, the sexually mature part with animals of older and age-specific ages - 54.63%.Conclusion. Demographic Taimir population modeling operation in the first decade of the XXI century long materials commercial samples collected at commercial points shown at current age distribution of the realized and reproduction conditions for existing commercial load males - 77.03 for females - 80.56 and for unified groups (males, females) - 82.4%. Meanwhile, the steady state and stable age distribution Taimyr tundra wild deer can reach a middle-level only when the fecundity of female reproductive generations with clean reproduction rate (R0) equal in population groupings 1.0

scholarly journals The demographic dividend is more than an education dividend

2020 ◽  
Vol 117 (42) ◽  
pp. 25982-25984
Author(s):  
Rainer Kotschy ◽  
Patricio Suarez Urtaza ◽  
Uwe Sunde
Keyword(s):  
Human Capital ◽  
Age Structure ◽  
Age Distribution ◽  
Age Groups ◽  
Demographic Dividend ◽  
Positive Growth ◽  
Working Age ◽  
Age Structured ◽  
Positive Effect ◽  
Effect Of Age

The demographic dividend has long been viewed as an important factor for economic development and provided a rationale for policies aiming at a more balanced age structure through birth control and family planning. Assessing the relative importance of age structure and increases in human capital, recent work has argued that the demographic dividend is related to education and has suggested a dominance of improving education over age structure. Here we reconsider the empirical relevance of shifts in the age distribution for development for a panel of 159 countries over the period 1950 to 2015. Based on a flexible model of age-structured human capital endowments, the results document important interactions between age structure and human capital endowments, suggesting that arguments of clear dominance of education over age structure are unwarranted and lead to potentially misleading policy conclusions. An increase in the working-age population share has a strong and significant positive effect on growth, even conditional on human capital, in line with the conventional notion of a demographic dividend. An increase in human capital only has positive growth effects if combined with a suitable age structure. An increasing share of the most productive age groups has an additional positive effect on economic performance. Finally, the results show considerable heterogeneity in the effect of age structure and human capital for different levels of development. Successful policies for sustainable development should take this heterogeneity into account to avoid detrimental implications of a unidimensional focus on human capital without accounting for demography.

scholarly journals Demographic science aids in understanding the spread and fatality rates of COVID-19

2020 ◽  
Vol 117 (18) ◽  
pp. 9696-9698 ◽  
Author(s):  
Jennifer Beam Dowd ◽  
Liliana Andriano ◽  
David M. Brazel ◽  
Valentina Rotondi ◽  
Per Block ◽  
...  
Keyword(s):  
Critical Care ◽  
South Korea ◽  
Age Structure ◽  
Care Needs ◽  
Age Composition ◽  
The World ◽  
Specific Mortality ◽  
Population Sizes ◽  
Age And Sex

Governments around the world must rapidly mobilize and make difficult policy decisions to mitigate the coronavirus disease 2019 (COVID-19) pandemic. Because deaths have been concentrated at older ages, we highlight the important role of demography, particularly, how the age structure of a population may help explain differences in fatality rates across countries and how transmission unfolds. We examine the role of age structure in deaths thus far in Italy and South Korea and illustrate how the pandemic could unfold in populations with similar population sizes but different age structures, showing a dramatically higher burden of mortality in countries with older versus younger populations. This powerful interaction of demography and current age-specific mortality for COVID-19 suggests that social distancing and other policies to slow transmission should consider the age composition of local and national contexts as well as intergenerational interactions. We also call for countries to provide case and fatality data disaggregated by age and sex to improve real-time targeted forecasting of hospitalization and critical care needs.

The Tasmanian Trout Fishery. III. The Rivers of the North and East

1958 ◽  
Vol 9 (2) ◽  
pp. 167 ◽  
Author(s):  
AG Nicholls
Keyword(s):  
Growth Rate ◽  
Age Distribution ◽  
Total Catch ◽  
River Systems ◽  
The North ◽  
Full Capacity ◽  
The Mean ◽  
Trout Fishery ◽  
Distribution Of Fish

The study of the daily catch from the Korth and South Esk River systems, as derived from anglers' returns, shows a general fall which appears to be statistically significant in all rivers except the Meander. It appears to become increasingly important from west to east. It is accompanied by a fall in the annual catch per angler which is closely correlated with an increase in the number of licences issued, from which it might appear that these streams are being fished to their full capacity. A study of the mean lengths of fish at capture does not show any decrease compatible with over- fishing, and there has been no increase in growth rate, which might be expected under conditions of overfishing. The age distribution of fish caught bv anglers does not indicate any decrease in the proportions of older fish. A personal canvass of 53 anglers in one district showed a mean total catch per angler of 259 fish, whereas the figure derived from anglers' returns for the same season was 20 fish per angler. It is concluded that the apparent decline in catching rate was due to the returns from anglers being unrepresentative. So correlation was found between the catches by anglers and the fish available to them as a result of stocking these streams.

The Effect of Fry Plantings on Whitefish Production in Eastern Lake Ontario

1956 ◽  
Vol 13 (4) ◽  
pp. 547-558 ◽  
Author(s):  
E. D. Lapworth
Keyword(s):  
Lake Ontario ◽  
The Other ◽  
Entire Period ◽  
Age Composition ◽  
Commercial Catch ◽  
Other Hand

Whitefish fry were planted in the Bay of Quinte and adjacent waters in numbers varying from 208 millions in 1927 to none in 1945. Since 50% of the commercial whitefish catch from these waters consisted of five-year-old fish, whitefish production in each of the years from 1929 to 1951 was compared to the number of fry planted 5 years previously (1924–1946). No correlation could be found between the number of fry planted and the production of whitefish 5 years later. The largest number of fry planted (208 millions in 1927) was followed by the lowest production of the entire period (95 thousand pounds in 1932). On the other hand, following no planting in 1945, production in 1950 was approximately normal (162 thousand pounds).The age composition of the commercial catch in the years 1944–1951 was determined from scale samples. By applying the age composition to the total catches in these years the contributions of the year-classes 1940–1945 have been estimated. The number of fry planted probably did not affect the contribution of these year-classes to the fishery.

An Application of Computers to the Estimation of Exploited Populations

1969 ◽  
Vol 26 (1) ◽  
pp. 179-189
Author(s):  
K. Radway Allen
Keyword(s):  
Mortality Rate ◽  
Age Distribution ◽  
The Other ◽  
Population Estimates ◽  
Distribution Data ◽  
Natural Mortality ◽  
Computer Programme ◽  
Total Catch ◽  
The Third

This paper describes a computer programme for the estimation of the size of exploited populations by methods described in Allen (1966, J. Fish. Res. Bd. Canada 23: 1553–1574). Although these methods were originally developed for use on whale populations, they are applicable to any other populations where suitable data are available. The essential data are the total catch, the catch for a known amount of effort, and the age distribution of the catch, all for a series of years. An estimate of natural mortality rate is also required but population estimates may be obtained for up to 10 values of this parameter in a single computer run.The entire programme incorporates six subroutines, as well as the main controlling programme. One subroutine reads in the catch and effort data, a second reads in the age distribution data for each year and, if necessary, converts it according to a predetermined transformation from age expressed in terms of whale ear-plug laminations to age in years. The third subroutine estimates the rate of recruitment as the proportion of newly recruited animals in the catch for each year, using the method of Allen (1966). The other three subroutines derive population estimates, using the "q," modified DeLury, and actual and expected catch methods (Allen, 1966). As many sets of data as desired may be processed in a single computer run.

An analysis of variations in the age structure of Fasciola hepatica populations in sheep

Parasitology ◽  
1982 ◽  
Vol 84 (1) ◽  
pp. 49-61 ◽  
Author(s):  
Gary Smith
Keyword(s):  
Mathematical Model ◽  
Mortality Rate ◽  
Age Structure ◽  
Distribution Curve ◽  
Fasciola Hepatica ◽  
Age Distribution ◽  
Parasite Population ◽  
Simple Mathematical Model ◽  
Age Classes

SUMMARYThe processes which govern the age structure of Fasciola hepatica populations in sheep were investigated by means of a simple mathematical model. The mortality of the metacercariae on the pasture was shown to be a factor of major importance. The mortality rate depends on the micro-climate that prevails at the pasture surface, and thus the age distribution curve of a population of flukes is also determined in part by the weather. This has important implications for the chemotherapy of fascioliasis: flukicides are not equally effective over the whole range of age-classes of parasite and so the factors which govern the age distribution curve of the parasite population within individual hosts ultimately determine the efficiency of chemotherapy.

Dynamics and Species Interactions in the Commercial Fishery of the Red lakes, Minnesota

1992 ◽  
Vol 49 (2) ◽  
pp. 293-302 ◽  
Author(s):  
Donald L. Pereira ◽  
Yosef Cohen ◽  
George R. Spangler
Keyword(s):  
Species Interactions ◽  
Yellow Perch ◽  
Animal Feed ◽  
Age Distribution ◽  
Power Spectra ◽  
Commercial Fishery ◽  
Catch Per Unit Effort ◽  
Commercial Catch ◽  
Aplodinotus Grunniens ◽  
Freshwater Drum

The Red Lakes, Minnesota, have supported a commercial fishery for walleye (Stizostedion vitreum vitreum) and yellow perch (Perca flavescens) since 1917. Since 1972, harvests indicate increased variance in recruitment of percids and an increase in biomass of freshwater drum (Aplodinotus grunniens). We subjected commercial catch-per-unit-effort (CPUE) records of walleye, yellow perch, and animal feed (composed primarily of drum) to spectral analysis. Estimated power spectra displayed peaks at 8.5, 10, and 17 yr for walleye, yellow perch, and animal feed, respectively. Walleye and yellow perch CPUE time series were significantly coherent at periods ranging from 5to 10 yr, confirming the predator–prey relationship and common recruitment patterns of these two species. Interpretation of coherency between drum and the two percid species required knowledge of the age distribution of freshwater drum. The apparent exponential increase in drum biomass as indicated by commercial CPUE is primarily due to strong year classes in 1955, 1970, and 1983. While drum recruitment and growth are consistent with the periodicity in the autospectrum, we find little evidence from coherencies that drum recruitment is related to the dynamics of wlleye or perch populations.

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