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Forecast F scenarios by fleet

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FI
Francisco Izquierdo, modified 1 Year ago.

Forecast F scenarios by fleet

Youngling Posts: 9 Join Date: 10/30/20 Recent Posts

Dear SS experts, 

I am trying to do forecast scenarios in order to test the contribution to the SSB when reducing to F0 the trawl (medium-size individuals) and longline (big-size individuals) fleets.

I am using F report = 3 (sum apical F's by fleet) as it is the same F that I incude into the forecast file to generate the scenarios. One scenario is the base case, where apical F's from the average 2018-2020 period are projected in equilibrium for all fleets. The second scenario is the trawl fleet F0 case, where apical F is 0 only for trawl fleet and the third scenario would be the same with longline fleet. 

I have tried by setting the same sum of apical F's by year in the different scenarios (by summing to the other fleets the F value rested to trawl, for instance) but the resulting scenarios display different annual F's, so I can not properly compare their SSB contribution (see attached plot). I guess that this input apical F is different from the resulting annual F as it must be influenced by selex, M and morphs. 

I am probably missing something, but I wonder if there is any option or trick that allows to have the same annual F for these scenarios but having different fleet F contribution in each one. 

Thanks a lot,

Fran

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Ian Taylor, modified 1 Year ago.

RE: Forecast F scenarios by fleet

Youngling Posts: 117 Join Date: 12/8/14 Recent Posts

Hi Fran,

Rick can correct me if I'm wrong, but I would think that you could use this option near the top of the forecast file

5 # Forecast: -1=none; 0=simple_1yr; 1=F(SPR); 2=F(MSY) 3=F(Btgt) or F0.1; 4=Ave F (uses first-last relF yrs); 5=input annual F scalar

(followed by input of the annual F scalar).

Then use these option further down in the file to turn on allocation among fleets:

2 # fleet relative F:  1=use first-last alloc year; 2=read seas, fleet, alloc list below

(followed by a table with the relative F for each fleet in each season, ending with a -9999 row).

I'm sorry I don't have time to try to work up an example right now to try it out, but you can keep checking the echoinput.sso file to see if the model is interpreting your inputs correctly.

It may take some iteration to get the annual F scalar correct, but iterating one value is better than iterating over the three F values for the fleet-specific F in each year.

-Ian

FI
Francisco Izquierdo, modified 1 Year ago.

RE: Forecast F scenarios by fleet

Youngling Posts: 9 Join Date: 10/30/20 Recent Posts

Hi Ian, 

Thanks a lot for the suggestion.

As you said, this option may be faster than finding the value iterating over 3 fleet F's.

After some trials I didn't manage to do it yet but I will keep exploring it and I also want to try something similar with the catches instead of F's (I think It can be a bit more intuitive).

Thanks,

Fran