Are there seasonal selectivity options In Stock Synthesis?

[jemer...@gmail.com]

Hi,

 

I’m working on a South Western Pacific Ocean swordfish assessment for SPC this year, transitioning an existing Multifan-CL assessment to stock synthesis. I have been reading the manual and searching this forum for information on including seasonality in selectivity in Synthesis, and can’t find any way to do this easily. We have a model for swordfish with a quarterly time step, ranging spatially from the equator to 50 degrees south, so we expect seasonal changes in selectivity may be quite important – with probable spawning in the northern regions in the January-March quarter, with larger fish then thought to be returning to higher latitudes outside of spawning season.

 

One possible method to incorporate seasonal selectivity is to separate each fleet into 4 separate fleets, with one “sub-fleet” for each season, and to estimate selectivity (separately) for each sub-fleet.

 

I was wondering if there was a more elegant solution either using Synthesis features that I am unfamiliar with, or solutions developed by anyone else for other species with similar issues for highly migratory species.

 

Does anyone have any experience or advice on this? 

 

ciao

 

Jemery

 

[Rick Methot]

Hi Jemery,

Alas, this is somewhere down on the wishlist.  Most people in this situation create a separate fleet for each season.  Then if some have similar selectivity and q you can use mirroring.  When you mirror, go ahead and keep the data from both fleet-seasons because all the data will contribute to the estimation of the shared selectivity.

Rick

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[Joel Rice]

Hi Jemery, 

Splitting out  a separate fleet for each season (quarter) and area if you want is what I've done for the Indian Ocean Albacore assessment, can share the files if you want. Though due to North South seasonal movement I did not share /mirror the selectivities. Hope it goes well, good to see that SS3 is still being used at SPC, it was almost taboo when I was there. 

Cheers

Joel

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