recruit survivorship

[Michael Schirripa - NOAA Federal]

Group;

I want to examine the survivorship of age_0 fish (s0) by dividing the number of age_0 fish  by SSB. Since SS defines recruitment in term of age_1 fish I believe I should calculate s0 as 

s0 = nage_1 (t+1) / SSB(t)

But since the nage_1 is at the beginning of the year I am not certain I need to stagger it one year. So maybe it's more correct to use:

s0 = nage_1 (t) / SSB(t)

Appreciate any thoughts on this. Thank you.

[Richard Methot - NOAA Federal]

SS3 defines the age at recruitment according to the user setting here in the control file:

#GPattern month  area  age (for each settlement assignment)
 1 1 1 0

The regular expectation in SS3 is that recruits later in the same year as spawning will be age 0 at settlement, then advance to age 1 on Jan 1.

But if spawning event is in one calendar year and settlement of recruits is the following year, then the settlers are expected to be set to be age 1 at the time of settlement.  

See this vignette on the recently greatly upgraded SS3 website:  https://nmfs-ost.github.io/ss3-website/qmds/settlement_timing.html

[Michael Schirripa - NOAA Federal]

Thanks Rick;

Since my control file is set up like your example (i.e. age = 0), I see that the appropriate way to calculate survivorship is not to stagger it by a year.

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 Michael J. Schirripa, Ph.D.

 Research Fishery Biologist, Sustainable Fisheries, SEFSC
 NMFS | NOAA Fisheries | U.S. Department of Commerce
 Miami, FL 33149