Skip to Main Content
banner NOAA logo            NOAA's National Marine Fisheries Service
            NOAA Fisheries Toolbox

row of waves


 Model List

Length Based Yield Per Recruit

Line Art Drawing of a FishLength Based Yield Per Recruit


|  About  |  Downloads  |  Version History  |



Version 2.1 (April 2012)

Research Model


Length Based Yield per Recruit (YPRLEN) is an implementation of the basic Thompson-Bell model for estimating the expected lifetime yield and biomass from a cohort subjected to varying levels of fishing mortality. 


In the length-based model the user provides parameters of a von Bertalanffy growth equation. Age is taken as relative with the model starting at age zero. The user also provides parameters for equations relating weight, selectivity and maturity to length.


The user provides a small age step as an integration factor. This is converted to length by the von Bertalanffy equation and the other required data is derived from length.


This approach may in many cases provide a more accurate lifetime yield and biomass curve than the traditional age-based YPR model.


In the September 2004 update of YPRLEN, several alternative selectivity models were introduced.


Users can export an age-based file that can be used as input to the age-based YPR model.


Back to Top 


Version History


YPRLEN Version 1.4 (May 2009)

  • Shepherd Recruitment Model is now a Stock Recruitment Model option.

  • Program upgraded to the Visual Studio .Net platform.


YPRLEN Version 1.3 (April 2007)

  • Ability to save files with spaces in the file name, and spaces in folder names.

  • Upgraded version of the plotting package.


Back to Top 


Older Version Changes 


For older changes please contact User Support.


Back to Top 


NOAA Fisheries Toolbox Version 3.1

website last modified May 16, 2016


Printer friendly view

Link disclaimer | Email webmaster | Privacy policy |     File Modified Mar 28, 2008