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Thread: Risk Analysis and Stock Recovery option priority.

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    Default Risk Analysis and Stock Recovery option priority.

    I wanted to start a new thread to get this out clean. I just read a paper that is titled " Bayesian Decision Analysis for Evaluting Management Options to Promote Recovery of a Depleted Salmon Population" that was published in Conservation Biology Vol 22 No 2 351-361 2008. Authors are Lynsey R. Pestes, Randall M Peterman, Michael J Bradford, and Chris Wood. These guys are top notch (Simon Fraser University School of Resource and Environmental Management, Pacific Biological Station Nanaimo) and part of the abstract is below for your interest.

    The endangered population of sockeye salmon (O. nerka) in Cultus Lake, B.C Canada migrates through commercial fishing areas along with other, much more abundant sockeye salmon populations, but it is not feasible to selectively harvest only the latter, abundant populations. This situation creates controversial trade-offs between recovery actions and economic revenue. We conducted a Bayesian decision analysis to evaluate options for recovery of Cultus Lake sockeye salmon. ....We also quantified how much reduction in economic value of commercial harvests of the more abundant sockeye salmon populations would be expected for a given increase in the probability of recovery of the Cultus population.


    This type of approach is what I would like to see in the trade-off discussion with UCI allocation and stock management options. For example what is the trade off of a 1000 chinook under an MSY goal vs going over the upper end of the sockeye goal by 500,000. This type of work could be invaluable to decision makers if ADF&G took the lead and got it done.

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    WHAT!?!

    How could you? We're talking about the world-famous Kenai River King! Everyone knows that nobody cares about Sockeye, (or any other stock in the Inlet for that matter). After all, we have enough of Sockeye for everyone, it'll always be that way, and the more we pack up the river, the more we will have coming back later!

    Kidding, of course. Just though I'd give a Penney's thoughts for free;-)

    Nice post. Important topic.

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    Member fishNphysician's Avatar
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    Trade-offs indeed.

    Life's full of uncomfortable compromises.

    Nerka, do you really think that the relative abundance ratio is really 500:1?

    In round numbers (orders of magnitude) I've always thought of it in terms of about 100:1 give or take.
    "Let every angler who loves to fish think what it would mean to him to find the fish were gone." Zane Grey
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    The KeenEye MD

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    Quote Originally Posted by fishNphysician View Post
    Trade-offs indeed.

    Life's full of uncomfortable compromises.

    Nerka, do you really think that the relative abundance ratio is really 500:1?

    In round numbers (orders of magnitude) I've always thought of it in terms of about 100:1 give or take.
    In 2012 and 2013 I believe the ratio was in the order of 500 to 1 as fishing did not take place when fish were heavy on the beach. Your 100:1 is over the whole season. In 2013 the lost of the Weds. fishing period was probably close to the same. I suspect around 500 chinook would have been harvested and 200,000 sockeye on Weds July 17. Remember the chinook run is lower and the sockeye returns have been pretty healthy so the ratio on a period when fish are on the beach will be much higher than a season average.

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    Using grossly rounded numbers, sockeye return is around 4,000,000 and king escapement is around 20,000. Allowing for king harvest, the ratio for the season is in the range of 150 to 1. Alternate views?
    Terry

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    Quote Originally Posted by Tee Jay View Post
    Using grossly rounded numbers, sockeye return is around 4,000,000 and king escapement is around 20,000. Allowing for king harvest, the ratio for the season is in the range of 150 to 1. Alternate views?
    Terry
    Terry, you missed the point. The ratio you used is for a whole season but that ratio is skewed by fishing when sockeye are not on the beach. So if you look at an individual period the ratio is much higher for some. Also your sockeye numbers are for total return (including Kasilof I assume as Kenai is around 3.3 million) and not harvest - half of the harvest is taken by the drift fleet so your overall numbers are not correct. The actual UCI sockeye return averages closer to 6 million fish.

    A trade off comparsion would be harvest sockeye to harvest of chinook. So here are real data. In 2013 the ESSN on July 15th caught 341,180 sockeye and 277 chinook. That ratio is 1/1231. That is the point I am making not the season average. When in a closure or restriction the cost of every chinook goes up significantly when one does not fish when the sockeye are there and is 341,000 sockeye a good trade off.

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    Interesting idea - these risk analysis frameworks are becoming widely incorporated into weak stock salmon management. The cool thing about the risk analysis approach is it could estimate the probabilities of yield tradeoffs for instance given the normal variability around the stock-recruitment curve. The risk analysis approach explicitly incorporates all the scatter around the stock-recruitment curve while Alaska's conventional approach to deriving biological escapement goals does not. Peterman's decision analysis framework also allows incorporation of more subjective uncertainties like the significance of a brood year interaction in large sockeye returns. I suspect you might not like the answer though. Yield risks can be much higher for low escapements on the steep part of the ascending limb of the stock recruitment curve than the flatter parts around the top or descending limb.

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    Member MRFISH's Avatar
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    We (the AYKSSI) have been working with Mike Jones and Matt Catalano to adapt their "management strategy evaluation" to AYK fisheries and it's quite interesting. It sounds similar. Last year, I had the opportunity to sit in during a hands-on workshop we held (with a bunch of ADFG staff attending). Pretty intersting stuff. Here's one of their newsletters that talks about it. http://qfcmsu.wordpress.com/tag/mana...gy-evaluation/

    I'll see if I can dig up one of their papers...
    "Fishing relaxes me. It's like yoga, except I still get to kill something." --Ron Swanson

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    Quote Originally Posted by Bfish View Post
    Interesting idea - these risk analysis frameworks are becoming widely incorporated into weak stock salmon management. The cool thing about the risk analysis approach is it could estimate the probabilities of yield tradeoffs for instance given the normal variability around the stock-recruitment curve. The risk analysis approach explicitly incorporates all the scatter around the stock-recruitment curve while Alaska's conventional approach to deriving biological escapement goals does not. Peterman's decision analysis framework also allows incorporation of more subjective uncertainties like the significance of a brood year interaction in large sockeye returns. I suspect you might not like the answer though. Yield risks can be much higher for low escapements on the steep part of the ascending limb of the stock recruitment curve than the flatter parts around the top or descending limb.
    Come on Bfish - why the comment I might not like the answer. If it is good science, peer reviewed, and appropriately used it is worth doing. That is why I posted the paper-- to get people thinking about these approaches. But in point of fact there is no one answer. The purpose is to define the options and the probable outcomes. The public via the BOF will make the call on what options and risk they are willing to take.

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    Just funning ya, Nerka.

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    Quote Originally Posted by Bfish View Post
    Just funning ya, Nerka.
    I figured that out after I posted as I know you- a got me on this one. We may disagree on some issues but we both want good science.

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