Important SS3 Set-up Decisions

Model dimensions to figure out before adding data

Areas

Number of areas

Yes

Yes

Yes

No

No

No

How many areas should I have?

Do I have lots of data

Is there limited movement

Is there evidence of significant spatial
differences in growth or relative stock size?

Use more than one area

Use one area

Seasons

Yes

Yes

No

No

Yes

No

How many seasons should I have?

Is it a short-lived,
fast growing species?

Am I using length data?

Use multiple seasons

Use one season

Is fishing during a short season that
precedes the survey or spawning?

Empirical weight-at-age (EWWA) vs. parametric growth

Yes

Yes

No

No

Should I use EWAA or parametric growth?

Do I have lots of age data

Is there evidence of variability
in weight-at-age

Use EWWA

Use parametric growth

Fleets

Yes

No

Yes

No

How many fleets should I have?

Are there significant differences in size
composition of the catch of different subsets
of the fishery?

Multiple fleets

Is there some management reason to
model the catch separately?

Group all catch as one fleet

One sex or two

Yes

Yes

Yes

No

No

No

Should I have one sex or two

Am I modeling growth?

Is the species sexually dimorphic?

Use two sexes

Do I have sex-specific composition data?

Combine females and males into one sex

Number of population age bins

Data age bins should cover the majority of the observed ages (i.e. not too large that a fraction is in the maximum age/plus group).

The first age is always 0, but recruitment can occur at age 1.

No

Yes

Yes

No

Can population age bins go
higher than data age bins?

Is growth asymptotic within
observed ages?

Is unfished equilibrium estimated to
have older fish than has been observed?

Population age bins can go
higher than data age bins

Population age bins can't go
higher than data age bins

In models with growth, the plus group should be old enough so that fish nearly achieve Linf by the time they are in the plus group.