Thanks Thanks:  14
Likes Likes:  226
Page 14 of 14 FirstFirst ... 4121314
Results 131 to 134 of 134
  1. #131
    Join Date
    Mar 2013
    Location
    North Yorks
    Posts
    3,087

    Default

    Jockie,

    I don't think you can dismiss Seeking's 'local problem' quite so easily because there's an interesting parallel between Irish rivers and those of south west England, many of which suffered catastrophic falls in catches, long before at sea mortality was ever considered. A major factor there was the many effects of the UK joining the (then) Common Market and the implementation of the Common Agricultural Policy, which coincided with the arrival of cheap bulk nitrogen fertilisers. The CAP incentivised huge increases in stocking levels of cows and beef cattle, while the new fertilisers made it possible. By 1980 the livestock in the Torridge catchment had reached a level at which their daily discharge of untreated excrement exceeded the mass generated by the City of Plymouth. The salmon population of a formerly excellent and productive river completely collapsed. The same happened in other rivers across the south west.

    I'm not saying that the CAP and cows is the answer to your question: in may be in some rivers, in others not. In Yorkshire it was the production of lead additives for petrol. The point I'm making is that these sort of localised collapses have occurred relatively recently, and their impact is felt much more rapidly than would be the case of increased attrition at sea. For that reason we need to investigate all possible local river-specific causes, and only when all possible options there have been ruled out should we look out to sea.

  2. #132

    Default

    I started to write this yesterday but got distracted by actual work.....

    If we aim for complete data on a complex natural system to give us perfect information on performance, then we are bound for disappointment. Instead of requiring perfect data we should be critically analysing the available data from more than one perspective, while pushing for better sources. Mows covers this point above.

    The focus of Seeking's analysis is on how the existing imperfect data that is used to demonstrate the need for C&R, (or to Ban the Nets, or that Ocean mortality has declined in a linear fashion for 40 years), actually shows the opposite when it is critically analysed. Or even when it is used in a non-selective manner. For example, the EA in England are pushing for more C&R using the decline in rod catches as evidence of a decline in stocks. Yet their own rod effort data, based on the same catch return data indicates that catch per angler is pretty much stable. Who is guessing? Both of them?

    If this data is good enough to demonstrate the need for C&R from a policy POV, then it's also good enough to demonstrate that it doesn't work.

    I also disagree that there isn't enough data on C&R success or otherwise on the Dee to prove that this does not improve stocks. For C&R to work as an improvement or conservation tool it must be the case that more adults = relatively more adults returning in any given year. For this to happen, it must be the case that more adults on the redds = relatively more smolts leaving the river 1 or more years before.

    1. Over 20+ years stocks on the Dee have not increased, end of. If we are to believe that C&R works to improve stocks, then we can see that this is clearly not the case. Stocks have not increased.

    2. Can we use catches as a proxy for stocks? Not in any single year we can't because exploitation varies so widely with available fish and fishing conditions. However over 20+ years there will have been high water / low water years, good fish years, bad fish years, lots of Scandis, not a lot of Scandis, high exploitation, low exploitation, good marine survival, bad marine survival i.e. the variations effectively cancel themselves out over time. MCX makes this point repeatedly....

    The only way that variations don't cancel over time is when there is a consistent underlying trend that we are not measuring. For example, maybe exploitation rates have been consistently going up on the Dee, year on year over time, this would indicate that there are less fish year on year but we catch more of them. Perhaps this could be the case with fish (re)caught in the autumn and during the extension period in particular, but over the whole year? With much less spinning and less people in the poor years, I doubt it.

    3. Would stocks have declined further without C&R? For this to be true we must believe that in every year starting 2 years after the imposition of C&R,) more fish are returning as a result of C&R than would otherwise have been the case, that good years are even better because of C&R and bad years would have been even worse without it. This idea rests on the notion that increasing the number of eggs laid down increases the number of smolts produced. This is not supported by the most perfect data set available from the Girnock / Baddoch burns. More eggs will add redundancy, especially where there are lower numbers of spawners, but they don't seem to result in more smolts. It sounds counter-intuitive but it isn't really when you look at how the Salmon population is structured.

    Think about what measurement is required to give complete data on C&R and decide if this is even a remotely realistic prospect:

    Firstly we have to accept that smolt output is the best and only real measure of productivity & stocks at the river level. Next we decide if we are releasing or killing our fish. Then we have to start validated counting of all adult salmon returning to the river, we have to sex, weigh and age them, as well as recording where they came from; our river system or somewhere else? We have to conduct validated and representative counts of all smolts leaving the river and mark them so we know they are 'ours' or not. We have to do this for a decent period of time to allow the breeding cycles to feed in and even out external variations. We really should measure all the other key variables of smolt production, water temperature, acidity, insect life parr numbers, fry numbers over the same time series to make sure there isn't a long term trend that is reducing or increasing productivity. Perhaps hardest of all, we need to record all catches, weight, sex, age class and origin, remember don't keep that fish out of the water too long when weighing.

    We run this for perhaps 10 or 20 years and then reverse the release or kill decision and keep everything else the same. Measure the differences and voila! perfect information on whether C&R has an impact on stock levels in the real world. I'll collect my bursary on the way out.


    WRT the OP, It doesn't make any difference, not biologically anyway. Morally it's a different question but not one that worries me in any way.

  3. #133
    Join Date
    Sep 2015
    Location
    Cheshire
    Posts
    723

    Default

    Quote Originally Posted by MCXFisher View Post

    I'm not saying that the CAP and cows is the answer to your question: in may be in some rivers, in others not.
    Did you miss a letter out of the word in capitals?
    I think I've got this work life balance thingy right.

    That is to say I spend more time in work thinking about fishing than I spend fishing and thinking about work!

  4. #134
    Join Date
    Aug 2008
    Location
    Yorkshire (were there a god it'd be god's own country)
    Posts
    3,247

    Default

    Quote Originally Posted by Jockiescott View Post
    This is where seeking and myself disagree.

    Most rivers on the Foyle System, of which my own river is part of, has had counters in place since the 1960's and 70's. We had nets on the Foyle up until 2009. The counter figures are available on the Loughs Agency website and I have passed the Foyle Status Reports on to Seeking. Rivers that were counting 20,000 salmon in the mid 90's are now counting between 1000 and 2000. Nets that were once taking 80,000 salmon per season off the Foyle caught 1500 in the last year of netting. Perhaps not extinction but a serious, serious, decline. This seems to reflect what is happening in the vast majority of Irish rivers. However, seeking dismisses this as an area specific problem.

    I agree entirely with seeking that farming practices and human factors are part of the problem facing our salmon but I cannot agree that it is this and this alone. I believe that there are problems at every stage of the lifecycle and a huge part of this has to be problems at sea. Now, perhaps not "all at sea" but the problems at sea simply cannot be dismissed in my own, and many others, peoples opinions.

    Where I disagree with seeking 100% entirely with is that salmon are a tasty meal!
    Hi JS

    Again, you have my sympathies about not eating proper fish

    I'm not so sure we actually do disagree. I respect what you think, and your reasons for it. But please note I don't really use island of Ireland examples, nor talk about fisheries restrictions in its waters. I use data from rivers I know in countries I fish, in GB. EA and ScotGov are the methodologies of interest, and their feedback and results to ICES. The hard primary data is easily obtained. And of course, their legislation affects both myself, my acquaintances and the clubs I know.

    The Foyle secondary data is there in a report, sure, (reference below) and it may support one view or other. But as ever with salmon, there are so many variables and the rivers where variables that are best controlled and best understood are perhaps better to use as baselines. I don't know the real challenges the Foyle catchment faces and the changes it has undergone in the last few decades so, understandably I hope, I won't want to make too much of it. The actual primary hard data is also much harder to get IME than dealing with EA/MSS where primary data is easily obtained.

    On the basis of the graphs in the 2016 Foyle report (reference below) all I can really say is reducing the netting never lead to a massive increase in stocks spawning in the rivers, nor rod catches, which is a very common fact in GB too. This of course has significant ramifications for the accuracy or otherwise of the ER rate guesstimate that ICES use to estimate stocks (see the link to the ICES thread in my earlier post responsing to Dryfly).

    The graph on p11 of the report indicates anglers fishing from 2001 to 2015 caught more fish and were probably happier than those whose career covered 1970 to 2000, when less fish were apparently caught. Maybe the catch data is bunk. The counter data presented in the report also indicate that the counts go up and down cyclicly and many, but not all, are currently towards the low average position, but again, no collapse in comparison to historical precedents. Not only that but the CL methodology they apply shows that stocks rebound over it when lots of salmon have been killed in the run-up to the increase, even when the stock being cropped is below CL. Which would seem to shed even more doubt on the rationale of the methodology being applied. Either way, maybe the counter data is bunk, or variable with flow, location of counter compared to most of the fishing etc.

    By contrast to salmon, Foyle sea trout catches appear to really have collapsed. But not much discussion of why in the report Economics perhaps?

    A whopping great chunk of the catchment is classed as ďModerateĒ under WFD, so again, that may be a factor in any perceived stock decline. Thereís no smolt production data presented so who knows whether the catchment is producing as many smolts as it could/should. That may be key. Certainly the Girnock / Baddock burn data from the Dee we keep referencing shows how important monitoring this is.

    So perhaps all we can say on the basis of the report, linked here: https://www.loughs-agency.org/wp-con...eport-2016.pdf is that it seems to further support the view that thereís no extinction vortex; salmon stocks recover over Conservation Limit (CL) levels when the stock is below the CL level and is still being heavily harvested; and stocks act independently of netting. All good food for thought, IMHO.


    I think Grassy Knollington has outlined the problem in a nutshell. But there are other issues that need to be borne in mind.

    The best counter data in GB (i.e. decent counters, less by-passable than most, as low down as possible on a semi-pristine catchment with limited hydrological and anthropogenic modification) indicate there is not a collapse in salmon stocks evident. This happens to be true regardless of whether the estimates of marine mortality (extrapolated/applied from elsewhere in some cases) were very high, or very low. So that should cast doubt on the estimates of MM, perhaps.

    Now that is still not perfect, but it's the best we have.

    In this, these counter data tend to parallel the rod catches, on average, and CPUE data (where available - like it or not) indicating stocks fluctuate over decades but are not "threatened" in a meaningful sense. Finally, two of the best both have significant netting (offshore in one case, in-river in the other), that kills significantly more salmon than the total rod catch of the river, and yet still plentiful salmon return to spawn and there is no collapse in stock abundance evident.

    So with respect the best data in GB indicate no major issues*, and yet the very impact of increasing C&R levels causes a decline in ICES salmon stocks.

    But I am truly sorry about upsetting your breakfast





    *Thatís not to say some rivers donít seem to perform as well as others, stock and catch wise, but there will be a reason for that, and C&R will seemingly not change matters (as it didnít on the Dee or with Spring fish in EA areas). Unfortunately
    Last edited by seeking; 25-10-2017 at 05:32 PM.
    "...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

    Unless otherwise stated, data used in any graph/figure/table are Crown copyright, used with the permission of MSS and/or EA and/or ICES. MSS / EA / ICES are not responsible for interpretation of these data by third parties

Page 14 of 14 FirstFirst ... 4121314

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •