The dynamics in harvested populations
We are interested in the effect of harvesting on population fluctuations and for that purpose we develop and analyze an age-structured model where recruitment is a stochastic process and the adult segment of the population is harvested. When a constant annual harvest is taken the coefficient of vari...
Main Author: | |
---|---|
Format: | Doctoral or Postdoctoral Thesis |
Language: | English |
Published: |
Department of Biology, Lund University
2013
|
Subjects: | |
Online Access: | https://lup.lub.lu.se/record/3516488 |
id |
ftulundlup:oai:lup.lub.lu.se:a177211a-e2c4-4970-9b76-813991c3d1e6 |
---|---|
record_format |
openpolar |
spelling |
ftulundlup:oai:lup.lub.lu.se:a177211a-e2c4-4970-9b76-813991c3d1e6 2023-05-15T16:19:23+02:00 The dynamics in harvested populations Wikström, Anders 2013 application/pdf https://lup.lub.lu.se/record/3516488 eng eng Department of Biology, Lund University https://lup.lub.lu.se/record/3516488 urn:isbn:978-91-7473-474-4 info:eu-repo/semantics/restrictedAccess Doctoral Dissertation; (2013) Ecology fluctuations temporal state-space Harvest cod vendace elasticity stage-structured stochastic growth-rate Baltic Sea Bothnian Bay thesis/doccomp info:eu-repo/semantics/doctoralThesis text 2013 ftulundlup 2023-02-01T23:32:07Z We are interested in the effect of harvesting on population fluctuations and for that purpose we develop and analyze an age-structured model where recruitment is a stochastic process and the adult segment of the population is harvested. When a constant annual harvest is taken the coefficient of variation of the adult population increases for most parameter values due to the age truncation effect, i.e. an increased variability in a juvenescent population due to the removal of older individuals. However, if a constant proportion of the adults is harvested the age truncation effect is sometimes counteracted by a stabilizing dynamic effect of harvesting. To study the effect of a variable harvest we also modelled harvesting as a stochastic processes. We find that harvest noise always has a magnifying effect on the fluctuations of the exploited population. We use cod survey data between 1988 and 2010 and auxiliary environmental data to estimate the parameters in a single species state space model, which is used to predict future development of the eastern Baltic cod (Gadus morhua) under different fishing mortality and assumptions about future abiotic conditions. We have demonstrated that exploitation is far more important than abiotic conditions in driving the temporal fluctuations of the Eastern Baltic cod. We analyzed a stage-structured stochastic environment model of the vendace (Coregonus albula) population in the Bothnian Bay with winter water temperature and winter salinity as environmental variables. We calculated the elasticity of the vendace stochastic growth rate (λs) with respect to the mean and standard deviation in vital rates, salinity and water temperature. We found that the mean value of salinity had the largest influence on λs. The high elasticity of λs with respect to the mean juvenile survival for a fished population indicates that one should avoid harvest the youngest individuals. Doctoral or Postdoctoral Thesis Gadus morhua Lund University Publications (LUP) |
institution |
Open Polar |
collection |
Lund University Publications (LUP) |
op_collection_id |
ftulundlup |
language |
English |
topic |
Ecology fluctuations temporal state-space Harvest cod vendace elasticity stage-structured stochastic growth-rate Baltic Sea Bothnian Bay |
spellingShingle |
Ecology fluctuations temporal state-space Harvest cod vendace elasticity stage-structured stochastic growth-rate Baltic Sea Bothnian Bay Wikström, Anders The dynamics in harvested populations |
topic_facet |
Ecology fluctuations temporal state-space Harvest cod vendace elasticity stage-structured stochastic growth-rate Baltic Sea Bothnian Bay |
description |
We are interested in the effect of harvesting on population fluctuations and for that purpose we develop and analyze an age-structured model where recruitment is a stochastic process and the adult segment of the population is harvested. When a constant annual harvest is taken the coefficient of variation of the adult population increases for most parameter values due to the age truncation effect, i.e. an increased variability in a juvenescent population due to the removal of older individuals. However, if a constant proportion of the adults is harvested the age truncation effect is sometimes counteracted by a stabilizing dynamic effect of harvesting. To study the effect of a variable harvest we also modelled harvesting as a stochastic processes. We find that harvest noise always has a magnifying effect on the fluctuations of the exploited population. We use cod survey data between 1988 and 2010 and auxiliary environmental data to estimate the parameters in a single species state space model, which is used to predict future development of the eastern Baltic cod (Gadus morhua) under different fishing mortality and assumptions about future abiotic conditions. We have demonstrated that exploitation is far more important than abiotic conditions in driving the temporal fluctuations of the Eastern Baltic cod. We analyzed a stage-structured stochastic environment model of the vendace (Coregonus albula) population in the Bothnian Bay with winter water temperature and winter salinity as environmental variables. We calculated the elasticity of the vendace stochastic growth rate (λs) with respect to the mean and standard deviation in vital rates, salinity and water temperature. We found that the mean value of salinity had the largest influence on λs. The high elasticity of λs with respect to the mean juvenile survival for a fished population indicates that one should avoid harvest the youngest individuals. |
format |
Doctoral or Postdoctoral Thesis |
author |
Wikström, Anders |
author_facet |
Wikström, Anders |
author_sort |
Wikström, Anders |
title |
The dynamics in harvested populations |
title_short |
The dynamics in harvested populations |
title_full |
The dynamics in harvested populations |
title_fullStr |
The dynamics in harvested populations |
title_full_unstemmed |
The dynamics in harvested populations |
title_sort |
dynamics in harvested populations |
publisher |
Department of Biology, Lund University |
publishDate |
2013 |
url |
https://lup.lub.lu.se/record/3516488 |
genre |
Gadus morhua |
genre_facet |
Gadus morhua |
op_source |
Doctoral Dissertation; (2013) |
op_relation |
https://lup.lub.lu.se/record/3516488 urn:isbn:978-91-7473-474-4 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
_version_ |
1766005768838971392 |