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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif";color:#1F497D">Sounds perfect! Any rational, papers that suggest this approach I can read up on?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext;mso-fareast-language:EN-GB">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext;mso-fareast-language:EN-GB">
flr-list-bounces@lists.r-forge.r-project.org [mailto:flr-list-bounces@lists.r-forge.r-project.org]
<b>On Behalf Of </b>Laurie<br>
<b>Sent:</b> vrijdag, augustus 10, 2012 15:42<br>
<b>To:</b> flr-list@flr-project.org<br>
<b>Subject:</b> Re: [FLR-list] Estimating Btrigger suggestions<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">60% of BMSY<br>
<br>
On 10/08/12 15:31, Hintzen, Niels wrote:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif";color:#1F497D">Hi Laurie,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif";color:#1F497D">Thanks for this, and I agree that F = Fmsy if B > Bmsy where Bmsy can be Btrigger. However, based on other criteria than biology alone, you could choose for
different Fmsy values (upper or lower bound for example) which automatically will result in different Btrigger values. The problem is that I do NOT want to derive a Btrigger through MSE as you suggest, we’ve done that before, it works well, but if you are
kind of in the dark where Btrigger should be, you are up for lots of scenarios, the one thing I try to prevent here. Hence, I’m looking for a smart way to get an estimate of Btrigger which is related to Fmsy without doing lots of scenario testing.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif";color:#1F497D">Any other suggestions?</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif";color:#1F497D">Cheers, Niels</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext;mso-fareast-language:EN-GB">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext;mso-fareast-language:EN-GB">
<a href="mailto:flr-list-bounces@lists.r-forge.r-project.org">flr-list-bounces@lists.r-forge.r-project.org</a> [<a href="mailto:flr-list-bounces@lists.r-forge.r-project.org">mailto:flr-list-bounces@lists.r-forge.r-project.org</a>]
<b>On Behalf Of </b>Laurie<br>
<b>Sent:</b> vrijdag, augustus 10, 2012 15:17<br>
<b>To:</b> <a href="mailto:flr-list@flr-project.org">flr-list@flr-project.org</a><br>
<b>Subject:</b> Re: [FLR-list] Estimating Btrigger suggestions</span><o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">Btrigger is a level of biomass that if the stock falls triggers management action to rebuild the stock as part of a HCR.<br>
<br>
Choosing a value that is too small will result in higher risk of stock collapse and loss yield since biomass will fall below BMSY, Choosing a value that is too high will result in loss yield due to fishing effort being reduced unnecessarily. Blim needs to balance
these objectives. The best way to do this would be to conduct an MSE with appropriate uncertainty, i.e. try a variety of values for Btrigger and choose the one that performs best. If you have an MSY harvest control rule there is no need for an Ftrigger as
you would be setting F to FMSY if B>BMSY and F to that given by the line joining (FMSY, Btrigger) to (Flim,blim).<br>
<br>
Laurie<br>
<br>
<br>
<br>
<br>
On 10/08/12 14:32, Hintzen, Niels wrote:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif"">Dear all,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif"">Sometime soon, I’m faced with another Management Plan Evaluation for North Sea herring. Obviously we’ll be using FLR. However, I’d like to gain a bit more insight into good
practices to ‘estimate’ a specific biomass reference point, so it is a bit off-topic but the expertise in this group is so high I could not resist sending this question!</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif"">The current HCR prescribes an Fbar of 0.1 below Blim (determined on a biological basis) and increases linearly with SSB up to a Btrigger biomass point (determined in 2008
based on a performance basis, i.e. scenario testing, which scenario performed best). Above this Btrigger, the HCR prescribes an Fbar of 0.25 (considered Fmsy).</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif"">Within the new evaluation, Blim, Btrigger and Fmsy will be a point of discussion (because the stock assessment changed considerably). I have some ideas on how to estimate
Blim and Fmsy, but with Btrigger I’m a bit in the dark. What I can think of so far is to run stochastic equilibrium simulation assuming constant Fs (over a range) and, as a first guess, taking Btrigger as the median equilibrium SSB. Does this make sense, and
if not, what would you suggest to do. I need some sort of approach to link potential Ftrigger points to Btrigger points because else I will be running far too many scenarios to be able to analyse and discuss later on.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif"">Many thanks in advance for your suggestions.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif"">Kind regards,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif"">Niels</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><br>
<br>
<br>
<br>
</span><o:p></o:p></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>flr-list mailing list<o:p></o:p></pre>
<pre><a href="mailto:flr-list@flr-project.org">flr-list@flr-project.org</a><o:p></o:p></pre>
<pre><a href="https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/flr-list">https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/flr-list</a><o:p></o:p></pre>
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<br>
<br>
<o:p></o:p></span></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>flr-list mailing list<o:p></o:p></pre>
<pre><a href="mailto:flr-list@flr-project.org">flr-list@flr-project.org</a><o:p></o:p></pre>
<pre><a href="https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/flr-list">https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/flr-list</a><o:p></o:p></pre>
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