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  1. #71
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    Quote Originally Posted by MCXFisher View Post
    On the other hand, if there were plenty of facts available relating to C&R mortality, this thread would have died after a couple of pages at most. Opinion makes for more lively discussion.

    As far as I can tell we don't have any sort of handle on what proportion of salmon die before they even get to spawn. At the moment I'm trying to build a population model for a typical river in order to analyze the sensitivity of each step in the process, and this factor is one of the black holes. However, iterations with pre-spawning mortality assumptions in the range 20-40% don't seem to have much impact on population outcomes.

    It's an interesting question because a steady population state only requires each hen fish, on average, to breed 2 surviving progeny during her entire reproductive lifetime. But with 5,000 eggs in play, there isn't a normal distribution of success and failure. The vast majority of fish will fail altogether for a variety of reasons, but a few may be massively successful. In one research case (yes, I've mislaid the reference) it was claimed that a single hen was responsible for 72% of the smolts emerging from a spawning stream. The only way you can have an average of 2 successful outcomes per 5,000 inputs is in a skewed distribution, massively weighted towards zero, but with a very long and thin tail. Chance plays a huge role in the process: get lucky and you generate 100 progeny; or have another hen churn your beautifully dug redd, then it's zero.

    You can come at the figures from the opposite direction. If every hen fish dug a perfect redd in the right place, based on documented average egg to smolt survival rates, each would send 100-150 smolts to sea, and thereby create 3-9 returning adults (at 3-6% smolt-adult survival). The redundancy margin in those figures underlines the very high spawning failure rate, including an unknown factor of adult pre-spawning mortality.

    The trouble is, when you kill a fish you've got no means of knowing whether it was destined to succeed or fail in its life's mission.
    Good points. Seemingly ones underlying the science.

    No trouble. I just look at it from a "statistical chance" perspective.

    Remove it from the gene pool and fortunately for the species (but not that individual) there are another 9 chancers I will never catch that can have a go at getting lucky... And good luck to them.

    Still, as we know, it's the smolts getting out quickly and safely and being fit to survive that really matters, and that appears slightly decoupled from the luck of the adult. Lucky smolts, now that's a whole other equation.


    PS - I also can't seem to find that paper but recall it was on a tributary with a fish pass where they genetically fingerprinted all the adults in and all the smolts out. Any kindly person remember the link and would care to post it? It will be burried in the archives on here. Thanks in advance.
    "...hooking mortality is higher than you'd expect: further evidence that as a numbers game, catch-and-release fishing isn't always as straightforward as it seems"
    John Gierach


    Fed up of debating C&R - see Hidden Content

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  2. #72
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    Quote Originally Posted by MCXFisher View Post
    On the other hand, if there were plenty of facts available relating to C&R mortality, this thread would have died after a couple of pages at most. Opinion makes for more lively discussion.

    As far as I can tell we don't have any sort of handle on what proportion of salmon die before they even get to spawn. At the moment I'm trying to build a population model for a typical river in order to analyze the sensitivity of each step in the process, and this factor is one of the black holes. However, iterations with pre-spawning mortality assumptions in the range 20-40% don't seem to have much impact on population outcomes.

    It's an interesting question because a steady population state only requires each hen fish, on average, to breed 2 surviving progeny during her entire reproductive lifetime. But with 5,000 eggs in play, there isn't a normal distribution of success and failure. The vast majority of fish will fail altogether for a variety of reasons, but a few may be massively successful. In one research case (yes, I've mislaid the reference) it was claimed that a single hen was responsible for 72% of the smolts emerging from a spawning stream. The only way you can have an average of 2 successful outcomes per 5,000 inputs is in a skewed distribution, massively weighted towards zero, but with a very long and thin tail. Chance plays a huge role in the process: get lucky and you generate 100 progeny; or have another hen churn your beautifully dug redd, then it's zero.

    You can come at the figures from the opposite direction. If every hen fish dug a perfect redd in the right place, based on documented average egg to smolt survival rates, each would send 100-150 smolts to sea, and thereby create 3-9 returning adults (at 3-6% smolt-adult survival). The redundancy margin in those figures underlines the very high spawning failure rate, including an unknown factor of adult pre-spawning mortality.

    The trouble is, when you kill a fish you've got no means of knowing whether it was destined to succeed or fail in its life's mission.
    That's a very interesting post MCX and a part of the statistical story that I had never heard of or thought about. With the massive weighting toward nil success I suppose there would be an increased tendency toward hereditary trends being more rapid than otherwise (which may have all sorts of pertinent implications)

  3. #73

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    Quote Originally Posted by Handel View Post
    Sorry, being lazy. Where did you get it from?
    Glasgow angling centre had them.
    peter

  4. #74
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    Quote Originally Posted by ozzyian View Post
    That's a very interesting post MCX and a part of the statistical story that I had never heard of or thought about. With the massive weighting toward nil success I suppose there would be an increased tendency toward hereditary trends being more rapid than otherwise (which may have all sorts of pertinent implications)
    I reckon the hereditary trends are on a hiding in the face of random chances, because it's the third-raters that can really mess up the prime salmon's efforts.

  5. #75
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    Quote Originally Posted by MCXFisher View Post
    I reckon the hereditary trends are on a hiding in the face of random chances, because it's the third-raters that can really mess up the prime salmon's efforts.
    Yes I suppose. It wouldn't take too many of those 72% situations to cause a massive hereditary bias if they were compounded. But statistically unlikely though?

  6. #76
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    Quote Originally Posted by ozzyian View Post
    Yes I suppose. It wouldn't take too many of those 72% situations to cause a massive hereditary bias if they were compounded. But statistically unlikely though?
    Skewed distributions and rare events are full of surprises. Believe or not that's an accepted statistical phenomenon.

  7. #77

    Default Thanks y'all

    Very interesting thread.
    I don't know for sure if my fish handling is acceptable or if fish die or not after I release them.
    After this thread I do know I can improve the way I do things so I've taken away a few things from this and other similar threads. I'm more than a little embarrassed about my own fishing after reading many of the posts on here.

    One member pointed out that catch and release always takes place after the fish is tired after a long fight. This is rather like starving Mo Farah of oxygen for 2 minutes after he crossed the line when winning a gold medal. Even he would struggle. Most ordinary people would perish. I hadn't thought of it like that before reading that post. I won't be removing fish from the water from now on.

    I'm carrying a fine mesh net now at all times when night fishing. No more beaching of sea trout from me at night, even if there is some wet grass at the river bank. They will also stay in the water at all times. BTW, beaching is widely practised on the Wear, mostly because it's a pain untangling a net in the dark. Surely it's more of a pain to the fish to be dragged onto a gravel bank. I've ordered a fine mesh gye net for salmon during the day.

    I don't mess about getting my fish in to the net. Rarely more than 5 minutes. For two reasons - my old dad taught me how to so it's habit, and I reckon if they don't come in quick, there's a good chance the line will chafe and I'll lose it anyway. Besides, in most cases the connection to the fish, the hook hold, is the weakest point and if that is bad, the fish will be lost however gently it's played. I'll be making more effort than usual to get them in quick. 70 minutes for that fish on the other thread was imho just an example of very poor fishing technique, probably as bad as my Spey casting which is really saying something.
    I'm replacing my flying C and mepps trebles with single circle hooks. I lost 4 from 4 on trebles last time out so I figure it can't be any worse. Hopefully, I'll also lose fewer on the bottom and be able to fish deeper with more confidence. I hope I'll get more takes this way which might make up for fewer hookups.

    Finally, I always say that no fish grows faster than a freshly released salmon. I've seen many 8 pounders "grow" into double figure fish just seconds after disappearing into the depths. After being on here for just a few months, it's also obvious that no fish loses weight faster than a freshly posted salmon :-)

    Thank you to all those who put their knowledge and experience on here. It does help and don't assume if it was said a few years ago that it is common knowledge to everyone. I don't know if my actions will help at all but I will feel like I've improved as a fisherman which is important to me.

  8. #78
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    Quote Originally Posted by Walleye View Post
    Very interesting thread.
    I don't know for sure if my fish handling is acceptable or if fish die or not after I release them.
    After this thread I do know I can improve the way I do things so I've taken away a few things from this and other similar threads. I'm more than a little embarrassed about my own fishing after reading many of the posts on here.

    One member pointed out that catch and release always takes place after the fish is tired after a long fight. This is rather like starving Mo Farah of oxygen for 2 minutes after he crossed the line when winning a gold medal. Even he would struggle. Most ordinary people would perish. I hadn't thought of it like that before reading that post. I won't be removing fish from the water from now on.

    I'm carrying a fine mesh net now at all times when night fishing. No more beaching of sea trout from me at night, even if there is some wet grass at the river bank. They will also stay in the water at all times. BTW, beaching is widely practised on the Wear, mostly because it's a pain untangling a net in the dark. Surely it's more of a pain to the fish to be dragged onto a gravel bank. I've ordered a fine mesh gye net for salmon during the day.

    I don't mess about getting my fish in to the net. Rarely more than 5 minutes. For two reasons - my old dad taught me how to so it's habit, and I reckon if they don't come in quick, there's a good chance the line will chafe and I'll lose it anyway. Besides, in most cases the connection to the fish, the hook hold, is the weakest point and if that is bad, the fish will be lost however gently it's played. I'll be making more effort than usual to get them in quick. 70 minutes for that fish on the other thread was imho just an example of very poor fishing technique, probably as bad as my Spey casting which is really saying something.
    I'm replacing my flying C and mepps trebles with single circle hooks. I lost 4 from 4 on trebles last time out so I figure it can't be any worse. Hopefully, I'll also lose fewer on the bottom and be able to fish deeper with more confidence. I hope I'll get more takes this way which might make up for fewer hookups.

    Finally, I always say that no fish grows faster than a freshly released salmon. I've seen many 8 pounders "grow" into double figure fish just seconds after disappearing into the depths. After being on here for just a few months, it's also obvious that no fish loses weight faster than a freshly posted salmon :-)

    Thank you to all those who put their knowledge and experience on here. It does help and don't assume if it was said a few years ago that it is common knowledge to everyone. I don't know if my actions will help at all but I will feel like I've improved as a fisherman which is important to me.
    Excellent post their Walleye!

    Must say I do like the 'cut of your jib!'
    ..........so many flies, so little time!

  9. #79

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    Quote Originally Posted by westie4566 View Post
    Excellent post their Walleye!

    Must say I do like the 'cut of your jib!'
    Welcome back Westie. From someone who is obviously well liked and respected by many on this forum that's quite a compliment.

  10. #80
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    Quote Originally Posted by Walleye View Post
    Welcome back Westie. From someone who is obviously well liked and respected by many on this forum that's quite a compliment.
    Not at all, Walleye. Just good old common sense, which you appear to have in spades!

    We need more like you on both the river bank and in this forum!

    Never the less, many thanks.
    ..........so many flies, so little time!

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