Yield per
Recruit (YPR) is a major revision of earlier
implementations of the basic Thompson-Bell model for estimating the
expected lifetime yield and biomass from a cohort subjected to varying
levels of fishing mortality.
The present version incorporates estimates of life-history
parameters such as mean age, mean generation time, reproductive value,
expected number of spawnings, reproductive output from first-, second-
and multiple time spawners. In addition the user can
investigate the resulting age composition of catch and abundance under
different levels of fishing mortality. Sensitivity analyses allow the
user to investigate the influence of age at entry on the predicted
yield and other population attributes.
The user can enter the known coefficients of either a
Beverton-Holt or Ricker stock recruitment relationship and perform a
Sissenwine-Shepherd analysis for equilibrium estimates of MSY and
biomass at MSY.
The user can also conduct sensitivity analyses for any model
parameter. Data visualization methods are emphasized to allow
exploration of the population consequences of increasing fishing
mortality.
FACT
input files will be automatically converted to the new input file
format.
Gabriel, W.L., M. P. Sissenwine, and W.
J. Overholtz. 1989. Analysis of spawning stock biomass per recruit: An
example of Georges Bank haddock. North American Journal of Fisheries
Management 9:383-391, 1989.
Thompson, W.F. and F.H Bell. 1934.
Biological statistics of the Pacific halibut fishery. (2) Effects of
changes in intensity upon total yield and yield per unit of gear.
International Fisheries Commission Report, No. 8, 1934.
Includes
a new grid editing tool with easier data entry and copy/paste
abilities.
Ability to
save files with spaces in the file name, and use spaces in folder names.
Upgraded
version of the plotting package.
YPR Version 2.6.2 (May 2006)
Fixed minor
graphics bug which constrained the values that could be entered for
recruitment equation coefficients. All constraints have been
dropped
May 2003
The
age based YPR graphical interface was
completely rewritten for this version. In addition to the new
style features the plot displays have been improved.
User
may specify three weight vectors:
Catch Weight, Stock Weight, and Spawning Stock Weight. This may be of
value for fast growing species.
The
model now allows a user to input
parameters for Stock Recruitment equations and perform a
Sissenwine-Shepherd analysis.
