[qfish] reference points with bycatch-only fleets
- From: "Lee, Laura" <laura.lee@xxxxxxxxxx>
- To: "qfish@xxxxxxxxxxxxx" <qfish@xxxxxxxxxxxxx>
- Date: Wed, 11 Oct 2017 13:10:51 +0000
Hi all-
I'm using Stock Synthesis to develop a two-season model that incorporates three
fleets and eight surveys (three are YOY surveys). One of the fleets is a
bycatch-only fleet (southeast shrimp trawl). My estimates of the fishing
mortality target, F35%, have been very low (<0.10). I e-mailed back and forth
with Dr. Methot and he suggested it was, in part, due to the bycatch fleet's
selection of fish that are much younger/smaller than the age at which they
mature. This is correct. He also pointed out that the currently available
versions of Stock Synthesis does not differentiate between bycatch-only fleets
and directed fleets when searching for the F multiplier that produces F35%.
There is a workaround one can implement through changes to the forecast file,
but I have been unsuccessful in getting it to work, despite the generous
assistance of others who have dealt with this issue.
So, I'm thinking of using the Thompson-Bell model to estimate F35%. Would there
be any issues with taking this approach? Also, the F I'm estimating from Stock
Synthesis is a real annual F calculated as a numbers-weighted F for ages 1-3.
Can someone provide advice on how to make the F35% derived from the
Thompson-Bell model comparable? I'm planning on setting up the model in a
spreadsheet.
Thank you for your time and I look forward to your advice.
Cheers,
Laura
Laura M. Lee
Senior Stock Assessment Scientist
Division of Marine Fisheries
Department of Environmental Quality
252 808 8094 office
252 726 6062 fax
Laura.Lee@xxxxxxxxxx<mailto:Laura.Lee@xxxxxxxxxx>
3441 Arendell Street
P.O. Box 769
Morehead City, NC 28557-0769
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