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Thread: Pew @ work!

  1. #11
    Senior Member Tarponator's Avatar
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    Very interesting. Thanks for doing the legwork...

    Question: Are those # of fish catch data or stock data?

    Because if it is catch data, it sure looks like MPAs (or something else) is making the fishery better. I've taken your data and added the rightmost column:

    Year Anglers Fish Fish/Angler
    2004 708000 352000 0.50
    2005 902000 462000 0.51
    2006 896000 601000 0.67
    2007 768000 492000 0.64
    2008 640000 453000 0.71
    2009 676000 582000 0.86
    2010 655000 481000 0.73
    2011 621000 584000 0.94

    If it is catch data, it sure appears as if those MPAs (or other regulations) might actually be working (i.e. fish per angler goes from 0.51 in 2004 to 0.94 in 2011). If it is stock data, then it suggests we should consider doing even more to rebuild the stocks (i.e. a relatively flat population from 2004 to 2011 despite a drop in anglers/pressure).

    Was that what you hoped to show?
    Last edited by Tarponator; 11-30-2012 at 07:49 PM.

  2. #12
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    California rockfish are a complex system. They include relatively short lived "pelagic" species, which are the bulk of the catch, and other species that take 50-60 years to reach sexual maturity. The purpose of the MPAs is to protect the long lived species.

    I used to fish out there and I can tell you that most of the data collected in California are not really relevant to our fisheries.

    To add to the confusion, many of the designated MPAs had little to do with biologically important spawning or rearing areas. Some people just didn't want to see sport fishermen interfering with the view from their homes.

    One reality of MPAs is that many of the best fishing areas need to be included if the preserves are going to work.

  3. #13
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    Quote Originally Posted by Tarponator View Post
    Very interesting. Thanks for doing the legwork...

    Question: Are those # of fish catch data or stock data?

    Because if it is catch data, it sure looks like MPAs (or something else) is making the fishery better. I've taken your data and added the rightmost column:

    Year Anglers Fish Fish/Angler
    2004 708000 352000 0.50
    2005 902000 462000 0.51
    2006 896000 601000 0.67
    2007 768000 492000 0.64
    2008 640000 453000 0.71
    2009 676000 582000 0.86
    2010 655000 481000 0.73
    2011 621000 584000 0.94

    If it is catch data, it sure appears as if those MPAs (or other regulations) might actually be working (i.e. fish per angler goes from 0.51 in 2004 to 0.94 in 2011). If it is stock data, then it suggests we should consider doing even more to rebuild the stocks (i.e. a relatively flat population from 2004 to 2011 despite a drop in anglers/pressure).

    Was that what you hoped to show?


    Hey Tarponator, yes, this is the catch data for the entire state. Thanks for adjusting, I was in a hurry and didn't do a decent job. In CA, they break the state into districts. In the districts, there was some increased landing fluctuation, a general down turn in effort, between the year prior to an MPA going on line then stabilized afterward. (apparently they broke the state into 4 or 5 sections for the MPA). The Southern CA, where most of the fishermen are, didn't go online until 2012. That will be interesting to look at when the data is available to see if it is comparable to the other years

    And Doc, I realize there isn't much in common with the fishery as it is CA. I grew up there (then got the hell out at 18!). What I am trying to show is to provide a quantitative data set showing what happens when MPAs occur. Many are saying how they will kill the fishery, so I investigated to see what happens when they are implemented. In the Gulf, MPAs at least for offshore species, would be nearly impossible to enforce. The CA MPAs are all attached to shore, no pelagic. The nearshore areas in the Gulf are all state waters, and doubtful they would implement MPAs.

  4. #14
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    It is very interesting how two people can look at the same set of numbers and come up with two completely different conclusions. BTW - I am not arguing the validity of the data or the complexity of the fishery, just the interpretation of the numbers. This is how I read them:

    From 2004-2007, pre MPA, fishing pressure increased to an average of 20.8% above the 2004 level and fish/angler increased by 28% at the end of the period.

    From 2007-2011, post MPA, fishing pressure decreased to an average of 15.6% below the 2007 level and fish/angler increased by 47% at the end of the period which is 33% longer.

    Just using this number set I see two things. First, in a period of significantly increased pressure we had improvement of fish/angler without MPAs. Why would closing large areas to fishing be needed when the fishery is in recovery despite increased pressure? Aren't the current regs in effect having a positive affect on the fishery? Second, when you factor in the decreased effort and longer time period I don't see a significant increase in the velocity of the recovery.

  5. #15
    Senior Member Tarponator's Avatar
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    I think your first sentence is very insightful -- I think to a certain extent we see what we want to see. Beyond that, you ask very good questions, and I appreciate your response...

    Two questions, if I may:

    First, how do you define "fishing pressure"? I'm not sure I follow.

    Second, your interpretation seems to draw a hard line in 2007, yet it is my understanding that only a few (one?) MPA started then and they have been phased in over time -- so is it fair to draw "pre-" and "post-MPA" conclusions? More broadly, and understanding the slow effect on fish stocks, is it safe to attribute anything to MPAs yet?

    FWIW, the last line of questioning centers on why I used the words "or other regulations" and looked at the trends across the entire timeline in the response above -- I'm not sure it's as cut and dried as is suggested by your analysis.

    Respectfully...Mike
    Last edited by Tarponator; 12-04-2012 at 12:45 AM.

  6. #16
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    In full disclosure, I used a wrong variable in the data query for these data. It seemed as if the rockfish catch was way too low to me. Sorry. I actually selected against rockfish. So, I went back (based on Fish'ns question) and queried the data correctly, I asked the RecFIN people for help, very quick response!

    This data shows 1) the entire state and 2) the section where the MPAs were enacted first. Using the whole state may mask the MPA effects.

    Again I apologize. Computers....
    Click image for larger version. 

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    Last edited by TrippleTailIV; 12-04-2012 at 11:45 AM.

  7. #17
    Senior Member Cyclist's Avatar
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    You can't hunt ALL public land and there is no earthly reason why you should be able to fish ALL public waters.

  8. #18
    Senior Member Tarponator's Avatar
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    Thanks for the update TT. I think the first set of revised numbers show strongly the overall trend and make the argument that something is wrong with the rockfish fisheries -- the trend is not good (with the possible exception of an uptick in 2011). The second sent of numbers also suggests either the jury is out or the MPAs (or the underlying regulations) aren't having a significant effect in recovering the fishery.

    But perhaps I'm just seeing what I want to see...

    What do the rest of you think?
    Last edited by Tarponator; 12-04-2012 at 12:54 PM.

  9. #19
    Moderator Gary S. Colecchio's Avatar
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    I think there is enough doubt concerning the "health" of a fishery though sampling that makes recreational fishing excluding MPAs a questionable practice.

    The ultimate goal of establishing the MPA is to ensure "recovery", what ever that means since a backwards projection needs to be made which literally cannot about the original population, and what a sustainable population should therefore be.

    What those tables indicates to me is an increase of effort and decrease in catch; a declining CPUE. What this shows in terms of a CPUE as an indicator of relative abundance is that the MPAs failing to accomplish that goal.

    Which is great if you don't want people to fish, because you now have data to support total closures.
    "If I can't win, I won't play." - Doris Colecchio.

    "Well Gary, the easiest way to look tall is to stand in a room full of short people." - Curtis Bostick

  10. #20
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    The thing that gets to me are the questions of how do we judge the efficacy of an MPA? As I understand it, based on the CDFG website, MPAs in California are up for review every 5 years. But, those areas and adjacent areas were not surveyed prior to creation. So, how does one judge if an MPA is working or not if there isn't a comparable data stream?

    Figuring out where people fished when pre/post MPAs would be interesting too, meaning, did MPAs spread effort out or concentrate it. IF it concentrated it, then I could see how this could have negative effects on the fishery. Which could 'substantiate' claims of overfishing or the like.

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