TY - JOUR
T1 - A random effects population dynamics model based on proportions-at-age and removal data for estimating total mortality
A1 - TRENKEL,Verena
A1 - BRAVINGTON,Mark V.
A1 - LORANCE,Pascal
AD - IFREMER, F-44311 Nantes 3, France.
AD - CSIRO, Hobart, Tas, Australia.
UR - https://doi.org/10.1139/f2012-103
DO - 10.1139/f2012-103
N2 - Catch curves are widely used to estimate total mortality for exploited marine populations. The usual population dynamics model assumes constant recruitment across years and constant total mortality. We extend this to include annual recruitment and annual total mortality. Recruitment is treated as an uncorrelated random effect, while total mortality is modelled by a random walk. Data requirements are minimal as only proportions-at-age and total catches are needed. We obtain the effective sample size for aggregated proportion-at-age data based on fitting Dirichlet-multinomial distributions to the raw sampling data. Parameter estimation is carried out by approximate likelihood. We use simulations to study parameter estimability and estimation bias of four model versions, including models treating mortality as fixed effects and misspecified models. All model versions were, in general, estimable, though for certain parameter values or replicate runs they were not. Relative estimation bias of final year total mortalities and depletion rates were lower for the proposed random effects model compared with the fixed effects version for total mortality. The model is demonstrated for the case of blue ling (Molva dypterygia) to the west of the British Isles for the period 1988 to 2011.
Y1 - 2012/11
PB - Canadian Science Publishing, Nrc Research Press
JF - Canadian Journal Of Fisheries And Aquatic Sciences
SN - 0706-652X
VL - 69
IS - 11
SP - 1881
EP - 1893
ID - 24168
ER -