The terminal F value is the expected asymptotic value of the F ratio between the model and residual variances in the Von Bertalanffy growth model used for VPA analysis. It is used to estimate the final size of the fish population.

To calculate the terminal F value, you can use the following formula:

Ft = ((Linf/K)^3)/(1+(t0/K))

where:

• Ft = terminal F value
• Linf = maximum length of fish (in cm)
• K = growth coefficient (per year)
• t0 = theoretical age at zero length (in years)

You can estimate these parameters from the length-at-age data for the fish population using a non-linear regression analysis. Once you have estimated these parameters, you can plug them into the formula to calculate the terminal F value.

Alternatively, you can use an empirical value for the terminal F ratio based on the expected growth and mortality rates for the fish population. This value can be obtained from previous studies or expert opinions. However, using an empirical value may not be as accurate as calculating the terminal F value from the length-at-age data.

I hope this helps

Sachin Kumar thanks a lot brother for your information.

do you have a reference for this formula?

Sorry for not be able tot help you. N ow, I am a retired reseracher, and my field was related with abalone and lobster fisheries.

I use other models, but never VPA.