Contributions of adult mortality to declines of Puget Sound Pacific herring

2017 ◽  
Vol 75 (1) ◽  
pp. 319-329 ◽  
Author(s):  
Margaret C Siple ◽  
Andrew O Shelton ◽  
Tessa B Francis ◽  
Dayv Lowry ◽  
Adam P Lindquist ◽  
...  
Keyword(s):  
Age Structure ◽  
Puget Sound ◽  
Adult Mortality ◽  
Forage Fish ◽  
Pacific Herring ◽  
Natural Mortality ◽  
Structured Population Model ◽  
Adult Age ◽  
Age Structured

Abstract Forage fish undergo dramatic changes in abundance through time. Long-term fluctuations, which have historically been attributed to changes in recruitment, may also be due to changes in adult mortality. Pacific herring, a lightly exploited forage fish in Puget Sound, WA, have exhibited shifts in age structure and decreases in spawning biomass during the past 30 years. Here, we investigate changes in adult mortality as a potential explanation for these shifts. Using a hierarchical, age-structured population model, we indicate that adult natural mortality for Puget Sound Pacific herring has increased since 1973. We find that natural mortality has increased for every age class of adult (age 3+), especially age 4 fish, whose estimated mortality has doubled over the survey time period (from M = 0.84–1.76). We demonstrate that long-term shifts in mortality explain changes in age structure, and may explain biomass declines and failure to reach management thresholds for two spawning sites in Puget Sound (Cherry Point and Squaxin Pass). Temporal shifts in natural adult mortality could have negative implications for herring and herring predators. We demonstrate that adult mortality, in addition to recruitment variation, is an important driver for forage fish, which face exceptionally high natural mortality compared with other fishes.

scholarly journals Towards a replicator dynamics model of age structured populations

2021 ◽  
Vol 82 (5) ◽  
Author(s):  
K. Argasinski ◽  
M. Broom
Keyword(s):  
Sex Ratio ◽  
Age Structure ◽  
Replicator Dynamics ◽  
Structured Populations ◽  
Reproductive Value ◽  
Leslie Matrix ◽  
Age Classes ◽  
Structured Population Model ◽  
Age Class ◽  
Age Structured

AbstractWe present a new modelling framework combining replicator dynamics, the standard model of frequency dependent selection, with an age-structured population model. The new framework allows for the modelling of populations consisting of competing strategies carried by individuals who change across their life cycle. Firstly the discretization of the McKendrick von Foerster model is derived. We show that the Euler–Lotka equation is satisfied when the new model reaches a steady state (i.e. stable frequencies between the age classes). This discretization consists of unit age classes where the timescale is chosen so that only a fraction of individuals play a single game round. This implies a linear dynamics and individuals not killed during the round are moved to the next age class; linearity means that the system is equivalent to a large Bernadelli–Lewis–Leslie matrix. Then we use the methodology of multipopulation games to derive two, mutually equivalent systems of equations. The first contains equations describing the evolution of the strategy frequencies in the whole population, completed by subsystems of equations describing the evolution of the age structure for each strategy. The second contains equations describing the changes of the general population’s age structure, completed with subsystems of equations describing the selection of the strategies within each age class. We then present the obtained system of replicator dynamics in the form of the mixed ODE-PDE system which is independent of the chosen timescale, and much simpler. The obtained results are illustrated by the example of the sex ratio model which shows that when different mortalities of the sexes are assumed, the sex ratio of 0.5 is obtained but that Fisher’s mechanism, driven by the reproductive value of the different sexes, is not in equilibrium.

Effects of an erroneous natural mortality rate on a simple age-structured stock assessment

1999 ◽  
Vol 56 (10) ◽  
pp. 1721-1731 ◽  
Author(s):  
William G Clark
Keyword(s):  
Mortality Rate ◽  
Stock Assessment ◽  
Natural Mortality ◽  
Structured Model ◽  
Harvest Rate ◽  
Specific Selectivity ◽  
Age Structured ◽  
Age Structured Model ◽  
Size Estimates

The abundance of many stocks is estimated by fitting an age-structured model to catch-at-age and relative abundance data from the commercial fishery and scientific surveys. The natural mortality rate used in the model is usually estimated externally and its value is uncertain. An erroneous natural mortality rate will bias the stock size estimates obtained by fitting the model and will also bias the yield calculations that are done to choose a harvest rate and recommend quotas. This paper describes the general features of both effects by analyzing a simple age-structured model fitted to artificial data. It is shown that an erroneous natural mortality rate mainly affects the estimates of fishing mortality and hence abundance but not the estimates of age-specific selectivity. Errors in estimated abundance and target harvest rate are always in the same direction, with the result that, in the short term, extremely high exploitation rates can be recommended (unintentionally) in cases where the natural mortality rate is overestimated and historical exploitation rates in the catch-at-age data are low. A conservative (low) estimate of natural mortality can avoid that danger. Long-term yield under either an FMSY or F35% strategy is not very sensitive to error in natural mortality rate unless it is grossly underestimated.

scholarly journals An empirical Bayesian approach to incorporate directional movement information from a forage fish into the Arnason-Schwarz mark-recapture model

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Mary A. Bishop ◽  
Jordan W. Bernard
Keyword(s):  
Bayesian Approach ◽  
Gulf Of Alaska ◽  
Forage Fish ◽  
Pacific Herring ◽  
Prince William Sound ◽  
Modeling Framework ◽  
Empirical Bayesian ◽  
Directional Information ◽  
Directional Movement ◽  
Empirical Bayesian Approach

Abstract Background Over the past two decades, various species of forage fish have been successfully implanted with miniaturized acoustic transmitters and subsequently monitored using stationary acoustic receivers. When acoustic receivers are configured in an array, information related to fish direction can potentially be determined, depending upon the number and relative orientation of the acoustic receivers. However, it can be difficult to incorporate directional information into frequentist mark-recapture methods. Here we show how an empirical Bayesian approach can be used to develop a model that incorporates directional movement information into the Arnason-Schwarz modeling framework to describe survival and migration patterns of a Pacific herring (Clupea pallasii) population in coastal Alaska, USA. Methods We acoustic-tagged 326 adult Pacific herring during April 2017 and 2018 while on their spawning grounds in Prince William Sound Alaska, USA. To monitor their movements, stationary acoustic receivers were deployed at strategic locations throughout the Sound. Receivers located at the major entrances to the Gulf of Alaska were arranged in parallel arrays to determine the directional movements of the fish. Informative priors were used to incorporate the directional information recorded at the entrance arrays into the model. Results A seasonal migratory pattern was found at one of Prince William Sound’s major entrances to the Gulf of Alaska. At this entrance, fish tended to enter the Gulf of Alaska during spring and summer after spawning and return to Prince William Sound during the fall and winter. Fish mortality was higher during spring and summer than fall and winter in both Prince William Sound and the Gulf of Alaska. Conclusions An empirical Bayesian modeling approach can be used to extend the Arnason-Schwarz modeling framework to incorporate directional information from acoustic arrays to estimate survival and characterize the timing and direction of migratory movements of forage fish.

scholarly journals The status of Japanese fisheries relative to fisheries around the world

2017 ◽  
Vol 74 (5) ◽  
pp. 1277-1287 ◽  
Author(s):  
Momoko Ichinokawa ◽  
Hiroshi Okamura ◽  
Hiroyuki Kurota
Keyword(s):  
Maximum Sustainable Yield ◽  
Production Model ◽  
Structured Population Model ◽  
Total Allowable Catch ◽  
Quick Recovery ◽  
Stock Status ◽  
Surplus Production Model ◽  
The Status ◽  
Stock Recruitment ◽  
Age Structured

We present the first quantitative review of the stock status relative to the stock biomass (B) and the exploitation rate (U) that achieved the maximum sustainable yield (MSY) (BMSY and UMSY, respectively) for 37 Japanese stocks contributing 61% of the total marine capture production in Japan. BMSY and UMSY were estimated by assuming three types of stock-recruitment (S-R) relationships and an age-structured population model or by applying a surplus production model. The estimated stock status shows that approximately half of the stocks were overfishing (U/UMSY > 1), and approximately half of the stocks were overfished (B/BMSY < 0.5) during 2011–2013. Over the past 15 years, U decreased and B slightly increased on average. The rate of decrease in the U of the stocks managed by the total allowable catch (TAC) was significantly greater than that of the other stocks, providing evidence of the effectiveness of TAC management in Japan. The above statuses and trends were insensitive to the assumption of the S-R relationship. The characteristics of Japanese stocks composed mainly of resources with relatively high natural mortality, i.e. productivity, suggest that Japanese fisheries have great potential of exhibiting a quick recovery and increasing their yield by adjusting the fishing intensity to an appropriate level.

Differential fertility among immigrants to England and Wales and some implications for population projections

1969 ◽  
Vol 1 (S1) ◽  
pp. 119-127 ◽  
Author(s):  
Jean Thompson
Keyword(s):  
Age Structure ◽  
Age Groups ◽  
Population Projections ◽  
Fertility Rates ◽  
Female Population ◽  
Differential Fertility ◽  
England And Wales ◽  
Adult Age ◽  
Completed Family Size ◽  
Socio Economic Factors

SummaryThe age structure of the immigrant female population as shown by the 1961 Census was heavily biased towards the young adult age groups, where fertility rates are highest. The birth rate for such a population could be expected considerably to exceed the average for this country as a whole, due to differences in age structure alone. The Census also showed marked differences betwen the fertility rates of different groups of immigrants but suggested that for the most important groups —from the Irish Republic, the Indian sub-continent and the Caribbean—they then amounted to a completed family size of roughly ½ child above the England and Wales average. There were also marked differences in 1961 between the socio-economic structure of immigrant groups; such evidence as there is points to socio-economic factors as playing an important part in explaining the fertility of immigrants, and its possible change over time.

Mending Broken Hearts

2012 ◽  
Vol 53 (1) ◽  
pp. 33-49 ◽  
Author(s):  
Ellen L. Idler ◽  
David A. Boulifard ◽  
Richard J. Contrada
Keyword(s):  
Medical Records ◽  
Lower Risk ◽  
Adult Mortality ◽  
Men And Women ◽  
Never Married ◽  
The Social ◽  
Using Data ◽  
Long Term Mortality

Marriage has long been linked to lower risk for adult mortality in population and clinical studies. In a regional sample of patients ( n = 569) undergoing cardiac surgery, we compared 5-year hazards of mortality for married persons with those of widowed, separated or divorced, and never married persons using data from medical records and psychosocial interviews. After adjusting for demographics and pre- and postsurgical health, unmarried persons had 1.90 times the hazard of mortality of married persons; the disaggregated widowed, never married, and divorced or separated groups had similar hazards, as did men and women. The adjusted hazard for immediate postsurgical mortality was 3.33; the adjusted hazard for long-term mortality was 1.71, and this was mediated by married persons’ lower smoking rates. The findings underscore the role of spouses (both male and female) in caregiving during health crises and the social control of health behaviors.

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