"Lost at Sea"

MCXFisher

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One other issue that might be pertinent to Ireland and possibly south west engerland is the supertrawlers that fish off west Ireland for the blue whitting.
Im not sure when they do it, but if during smolt migration time, it may well be a factor.

Cheers

Mows

Mows,

how close to the shore do they work?

M
 

acercon3

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Mows,

how close to the shore do they work?

M
MCX

The fishery takes place during the Spring , vessels can be operating well offshore quite often at depth.
These vessels are not generally in these areas during the Summer or early Autumn.

I have never seen any salmonid , juvenile or otherwise in a pelagic catch that has been no size graded in a pelagic processing plant. If juveniles were present they would be noticed in the out grades.
It is possible that some may be caught in the Summer mackerel fishery in Area II ( international zone). These smolts would be like a needle in a field of haystacks and would be very unlucky to be caught. I would venture to suggest that their proximity to voracious mackerel shoals would pose a far greater danger than the risk of becoming a commercial fishing by-catch.

To my knowledge there has been a Summer mackerel fishery prosecuted in Area II by mid water trawlers for at least the last 40 years.
 
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Loxie

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Sorry Kerry salmon, but I don't understand how, if smolt numbers are still as good, that salmon are in trouble?
If there are enough salmon returning, to maintain the status quo of smolt numbers, how are they in trouble?

Regards

Mows
That’s a very interesting point. If marine mortality is our problem and smolt production has remained constant the obvious inference is that the 10, 30 or whatever random guessed number % of adults that return compared to the good old days, 5, 30 50 or whatever number you fancy years ago are perfectly capable of producing the same number of smolts, despite all the new abstractions, obstructions pollutions and open cage salmon farms. Remarkable really.
 

Loxie

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Righto, got it.

This is the film that has featured on no fewer than four SFF threads going back five or more years, especially with a seeming AST focus, and basically underlines the POV as to why Salsea was undertaken.

As I understand it, only Donors (as I recall there was a fair bit of enthusiastic fundraising done on here before :cool:) can view it.

I'm looking forward to seeing it. When the original whip round was being corralled on here, and it got a bit ugly as I recall, it looked for all the world as if it was going to be "they're all lost at sea and marine mortality has doubled in the last decades (believe in the Bush), but Salsea will solve everything".

But now, judging from the comments "machine gunning, FOI etc." I can only hope it's broader in it's remit and lays the blame at anthropogenic degradation and fish farming (again, given some of the participants listed on the film's website, I suspected the latter would not even begin to be addressed, so will be happy to be proven wrong!)



PS - Kerry Salmon - I'm only posting the published ICES data in response to your original statement. If you do not like that data, perhaps wishing to change the goal posts, and have other data to support that POV, then by all means feel free to post it. Ta. (BTW - any netting data should have the effort indicators posted too, in order that others may again judge for themselves what any decline means)
From what I’ve seen, and what I know of some of the people involved in making it issues like the huge increase in stripped bass in the Miramichi estuary areas and the huge number of open cage farms in the bay of Fundy are discussed at length. The AST are/were very aware of the numerous issues in fresh water, estuary and near coastal zones. There is some quite interesting stuff on warming and the zooplankton/phytoplankton relative abundance. The headline news is that Salsea wasn’t a huge waste of money that could have been spent better. That said I enjoyed it and it’s a reasonable attempt at getting support from the vast majority of the population who know nothing and care less about Salmon.
 

KerrySalmon

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That’s a very interesting point. If marine mortality is our problem and smolt production has remained constant the obvious inference is that the 10, 30 or whatever random guessed number % of adults that return compared to the good old days, 5, 30 50 or whatever number you fancy years ago are perfectly capable of producing the same number of smolts, despite all the new abstractions, obstructions pollutions and open cage salmon farms. Remarkable really.
Now I understand that you do not understand what I am saying. A smaller number of salmon are capable of producing the optimum number of smolts in a given catchment once all other factors are equal. If the river is polluted and habitat degraded then unfortunately your production of smolts is compromised and cannot be reversed unless these factors are addressed. Once a river has enough adults to seed the system then you will get the amount of smolts as before if all factors are similar. The survival rate of smolts is a very different matter and refers to the adult return from a given number of smolts. Certain systems have the capability to count all exiting smolts and returning adults and thus allows for survival rates to be determined. Burishoole has this capability and has over 50 years of excellent data relating to salmon and sea trout survival indices. The Bush also has this facility along with The Erriff (Limited) in Ireland. Other rivers in the North East Atlantic and indeed Canada have similar facilities and can estimate survival. If a river does not have enough spawners then it cannot produce the optimum number of smolts. In regard to salmon farms in Ireland when we had much better survival figures there was up to 30/35k tonnes being produced while now we have only 12k tonnes (Hopefully never to increase and to be closed permanently) at present with sea lice under much better control unlike Scotland. Hatchery smolts which have been reared in a ranching strain used to have up to 15/20% survival in 80s and early 90s now are at 3.5% on average in Burishoole (Same tanks and same facilities used so problems are at sea for these fish). One interesting point which no one in this forum has spoken about is climate related changes in freshwater with smolts leaving systems earlier than before and over a prolonged period which could account for a mismatch with ocean conditions. It is worthy to note that one year (1989) a drought in Burishoole postponed the normal smolt run by up to a month and this resulted in a massive downturn in adult returns the following year. Certainly some rivers are not capable of producing their optimum number of smolts but some rivers here are still in great condition and can produce large numbers of smolts provided the adults get back.
 

mows

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Kerrysalmon, the issues with smolt condition and timing may well be a factor. There was an interesting piece on here earlier that was explaining that par are currently nearly smolting in year 1. Where as previously it was mainly year 2 and 3. The loss may be at sea, but root cause may well be in river.

Cheers

Mows
 

Loxie

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Now I understand that you do not understand what I am saying. A smaller number of salmon are capable of producing the optimum number of smolts in a given catchment once all other factors are equal. If the river is polluted and habitat degraded then unfortunately your production of smolts is compromised and cannot be reversed unless these factors are addressed. Once a river has enough adults to seed the system then you will get the amount of smolts as before if all factors are similar. The survival rate of smolts is a very different matter and refers to the adult return from a given number of smolts. Certain systems have the capability to count all exiting smolts and returning adults and thus allows for survival rates to be determined. Burishoole has this capability and has over 50 years of excellent data relating to salmon and sea trout survival indices. The Bush also has this facility along with The Erriff (Limited) in Ireland. Other rivers in the North East Atlantic and indeed Canada have similar facilities and can estimate survival. If a river does not have enough spawners then it cannot produce the optimum number of smolts. In regard to salmon farms in Ireland when we had much better survival figures there was up to 30/35k tonnes being produced while now we have only 12k tonnes (Hopefully never to increase and to be closed permanently) at present with sea lice under much better control unlike Scotland. Hatchery smolts which have been reared in a ranching strain used to have up to 15/20% survival in 80s and early 90s now are at 3.5% on average in Burishoole (Same tanks and same facilities used so problems are at sea for these fish). One interesting point which no one in this forum has spoken about is climate related changes in freshwater with smolts leaving systems earlier than before and over a prolonged period which could account for a mismatch with ocean conditions. It is worthy to note that one year (1989) a drought in Burishoole postponed the normal smolt run by up to a month and this resulted in a massive downturn in adult returns the following year. Certainly some rivers are not capable of producing their optimum number of smolts but some rivers here are still in great condition and can produce large numbers of smolts provided the adults get back.
I fully understood your point. My point was that smolt production is nothing close to stable in the vast majority of rivers I have experience of and has declined severely for the reasons I alluded to.

I believe I did mention the effect of climate change on emigrant timing of smolts and the subsequent impact on survival in a different thread. I also made the point that climate change can, and probably has, had a huge negative impact on fry survival at swim up.

I do not really know anything about Irish salmon fisheries so cannot comment on them but in Scotland the return rates of hatchery smolts have been tiny, where measured. The evidence from less anthropogenically impacted catchments in the Far North indicates increasing marine survival from the 1980’s to the present, taking catches as a proxy for stocks. This seems to wholly negate the theory that deep ocean survival is the most important limiting factor on adult salmon numbers returning to freshwater. This makes me somewhat sceptical of the “all at sea” theory.

Another example of why I’m not convinced might be the Tweed. In the 1970’s, when we are told smolt to adult survival was 30%, the rod catch was around 5,000 and the nets took about 65,000 per year. According to The Tweed foundation netting tagging and recapture studies, with no netting around 5% of the net catch would have been caught in the rod fishery so say an adjusted catch of around 9,000. In the last decade, when we are told smolt to adult survival was around 5%, the rod catch was around 12,000. For the survival rates to be correct about 8 times as many smolts must run in the last decade than must have run in the 1970’s. Now even allowing for much greater effort and much previously netted water being now rod fished, the effect of the NE drift nets and a slightly higher percentage of spring fish in the net catch the maths are not even close to believable.
 
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SOS

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In my post i did not mention any names but for some reason a few people got very defensive.
I have never said all the problems are all at sea, was it not me who suggested the adopt a stream scheme.
In the past i have being accused of cherry picking data which seems to be a hobby with a select few on the forum.
Mows you want to down any suggestion that we can do about the problems at sea but unless we know what the problems are we will never fix them so spending money to find out can be money well spent,you know the North Esk well i assume do you think the water quality is worse now than before.
I have a document which was used in court by the in river netting stations to try and get the fixed engine netting stopped on the coast around Aberdeen because it was affecting the in river catches of the Dee and Don and the numbers were far beyond our dreams and this was in a time when the rivers were used as open sewers and were dammed and channeled for industrial purposes, but there were still plenty of Salmon to repopulate the rivers. So my point is it is not all at sea but the smolt to adult returner problem is mostly at sea. If you want to catch salmon parr or smolts you may well do ok. but if you want to catch returning adults you will not do so well.
 

mows

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In my post i did not mention any names but for some reason a few people got very defensive.
I have never said all the problems are all at sea, was it not me who suggested the adopt a stream scheme.
In the past i have being accused of cherry picking data which seems to be a hobby with a select few on the forum.
Mows you want to down any suggestion that we can do about the problems at sea but unless we know what the problems are we will never fix them so spending money to find out can be money well spent,you know the North Esk well i assume do you think the water quality is worse now than before.
I have a document which was used in court by the in river netting stations to try and get the fixed engine netting stopped on the coast around Aberdeen because it was affecting the in river catches of the Dee and Don and the numbers were far beyond our dreams and this was in a time when the rivers were used as open sewers and were dammed and channeled for industrial purposes, but there were still plenty of Salmon to repopulate the rivers. So my point is it is not all at sea but the smolt to adult returner problem is mostly at sea. If you want to catch salmon parr or smolts you may well do ok. but if you want to catch returning adults you will not do so well.
Hi SOS,

I don't want to down any suggestion of sea fixes.
Changing aquaculture practices would make a difference straight away, but I cant see this, or any other government allowing it.
Chickens are slowly coming home to roost with this dirty industry though, so may change over the next decade.

As I said on another post.
The symptoms may be losses at sea, but I think a lot of the root causes are in river.

Quality of smolt going to sea seems to make a big difference.

Recently, when the Spey had less than usual smolt numbers due to the huge spates, the size of smolt increased and as such, there seemed to be little if no reduction in returning fish.

The change to predominately s1 smolting may well also be an issue

WRT to the Northie, I think the river is probably cleaner than it has been in years, from my house up stream. Below that it is probably more contaminated than ever with pesticides and household chemicals. i.e, the majority of the river is clean.
WRT the Southie, I think agricultural contamination goes much further up river and it wouldn't be as clean as before.

I think we all tend to confuse colour of water with contamination. Even if it is bad at the mouth of the river, as long as the rest of the river is suitable habitat and the mouth isn't as bad as to stop fish coming upstream or being damaged by the pollution, then the river should still be fine.

It took only trace DDT to change the world, and I think it is similar with modern pesticides and household chemicals.

From, what ive seen, it is amazing how little effect, removing the costal nets have on any individual rivers population. It seems to me that the costal nets may well be catch fish destined for all rivers rather than just local ones. I also think a lot of these fish may never have reached their final destination whatever.

In my opinion opposing arguments like this are a good thing as long as they remain civil, as it does help filter out noise and hopefully identify root causes.

Cheers

Mows
 

KerrySalmon

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Yes let's please do so.

Whilst never wanting to dismiss an argument as "nonsense" I note that there is no decrease in marine survival evident in the data whereas you claim there is. Others may judge for themselves:

View attachment 24626
Source as quoted, marine survival rate in %.



Again, I would not want to dismiss an argument as "nonsense" but would instead refer anyone interested to ICES where the details of their methodologies confirm exactly that it is based on numbers of dead fish, mainly commercially netted.
This is the data to which you have made reference, the ICES data takes in much more than catches and includes reference rivers, counters, home water exploitation rates etc.
Salmon 1.jpg
salmon.jpg
 

Kype King

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Great to see this - I knew it was comming but didnt see it on RTE (Irish TV) who seem to have the copyright. Does anyone know was it shown yet?
It says copyright 2017 but some of the credits go back a long way and the Salsea program was a few years ago now.
I think this is the director's cut, which is available to those who subscribed to help it get made. The final version will be released in due course. Excellent film!
 

Loxie

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Thanks for that KS.

Clearly shows how briefly the 'mitigation factor' of netting cessation actually lasts. I'll allude to that in another reply.
To me it just looks like the return to home waters estimate was grotesquely innaccurate.
 

westie4566

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Hi SOS,

I don't want to down any suggestion of sea fixes.
Changing aquaculture practices would make a difference straight away, but I cant see this, or any other government allowing it.
Chickens are slowly coming home to roost with this dirty industry though, so may change over the next decade.

As I said on another post.
The symptoms may be losses at sea, but I think a lot of the root causes are in river.

Quality of smolt going to sea seems to make a big difference.

Recently, when the Spey had less than usual smolt numbers due to the huge spates, the size of smolt increased and as such, there seemed to be little if no reduction in returning fish.

The change to predominately s1 smolting may well also be an issue

WRT to the Northie, I think the river is probably cleaner than it has been in years, from my house up stream. Below that it is probably more contaminated than ever with pesticides and household chemicals. i.e, the majority of the river is clean.
WRT the Southie, I think agricultural contamination goes much further up river and it wouldn't be as clean as before.

I think we all tend to confuse colour of water with contamination. Even if it is bad at the mouth of the river, as long as the rest of the river is suitable habitat and the mouth isn't as bad as to stop fish coming upstream or being damaged by the pollution, then the river should still be fine.

It took only trace DDT to change the world, and I think it is similar with modern pesticides and household chemicals.

From, what ive seen, it is amazing how little effect, removing the costal nets have on any individual rivers population. It seems to me that the costal nets may well be catch fish destined for all rivers rather than just local ones. I also think a lot of these fish may never have reached their final destination whatever.

In my opinion opposing arguments like this are a good thing as long as they remain civil, as it does help filter out noise and hopefully identify root causes.

Cheers

Mows
Evening Alan

Excellent post there.

I agree fully with your comments re DDT.

Ok maybe not quite as extreme in our rivers these days, chemical wise. However, the step change from using pesticides to solve a problem when it arose, to their wide spread use as a prophylactic will not have helped rivers that flow through predominantly agricultural land.

As for netting. As said above, no-one here has ever taken into account the mitigation factor accorded by the cessation of netting activities.

A few years ago I supplied info on this subject which clearly showed the huge decline in numbers caught by netting stations. So much so that the decline in salmon numbers put the majority of stations out of business.This was long before the advent of aquaculture too. Naturally this was absolutely slated and buried quickly by some of your chums on here who have their own agenda.

As for the Southie and cessation of netting and any positive effect. With no disrespect at all, I have fished it for many, many more years than you have.(Remember who seconded you...lol) The general consensus of riparian owners and anglers alike is that it will take at least a decade for the river to start to recover from the 7 day a week (illegal) netting that went on for many years. It took a great toll on a wee river that was starting to struggle anyway.

It does start to seem like a whole load of insurmountable problems. Thankfully our Board are pro-active. Much good work done over the past decade.It's never going to be an 'instant' fix, however hopefully the tide will turn.

Like many other anglers I'm dumping a load of fishing as it's simply not worth it anymore. That said the last thing to go will be my Southie/Westie fishing. OK. been another s'hite year...however its been more productive this year than it has for about 5.
 

KerrySalmon

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To me it just looks like the return to home waters estimate was grotesquely innaccurate.
Well that is probably not correct. Between 25 and 50% of the commercial catch was examined for the presence of micro tags which were recovered in large numbers from commercial premises and fishermen. One aspect of the driftnet fishery was its sheer size and thus its great potential for data collection. Also the adult run is trapped in Burishoole and all salmon were examined and checked for presence of tags. Broodstock collection also are checked to recover tags. Up to 250 k hatchery and wild fish are tagged annually but now the emphasis is on instream checking with a number of trapping facilities and checking of salmon catches in certain rivers. It is now difficult to get numbers of fish due to the closure of the mixed stock element. Also the hatchery smolts are not subject to in river problems and their return is poor now whereas it was very good in the 90s up to 15%.
 

Grassy_Knollington

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So much so that the decline in salmon numbers put the majority of stations out of business.This was long before the advent of aquaculture too.

As for the Southie and cessation of netting and any positive effect. With no disrespect at all, I have fished it for many, many more years than you have.(Remember who seconded you...lol) The general consensus of riparian owners and anglers alike is that it will take at least a decade for the river to start to recover from the 7 day a week (illegal) netting that went on for many years. It took a great toll on a wee river that was starting to struggle anyway.

It does start to seem like a whole load of insurmountable problems. Thankfully our Board are pro-active. Much good work done over the past decade.It's never going to be an 'instant' fix, however hopefully the tide will turn.
Westie

The thread you refer to (‘where are the missing salmon’ or something like that), absolutely did not prove that netting declined because of a lack of fish before aquaculture took off. That was your thesis but not one that held water IMO. The data shows Netting catches declining as effort declined, you think it was because the fish ran out. Others because the money ran out.

Your view on the S Esk is definitely NOT what was reflected by Tony Andrews and his co-writer in their T&S article last year. An immediate improvement in spring runs (may/june) was trailed as the payback for the end of netting. A shame that the writers hadn’t done some wider consultation with experienced rods and owners before they wrote that.

Of course the whole point of the ban from ‘our’ POV was to increase numbers of adults and therefore; if it was going to make a difference then it surely would have been noted immediately, at very least in the form of a better than average season? The only reason this wouldn’t have happened is if numbers in the S Esk were so low that the river probably should have been closed to fishing.

Of course it hasn’t been and it won’t be, the ‘saved’ fish will be lost in the noise of the annual catches and nobody will ever be able to say it’s made a difference or not. in 7 or 10 or 15 or 20 years when there is an upturn for some reason I’m sure someone will point to the netting and say ‘that’s what did it, the end of the nets in 2016!’
 

Bann Special

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We also have the vexed 30+% smolt to adult return number, which was a statistical outlier recorded in one river system in one short period. There is no research evidence to support anything like that figure as a North Atlantic regional norm, yet people (including HRH The Prince of Wales) have used it widely in support of campaigning. Indeed the long term scientific evidence for UK rivers indicates a figures in the range 5-8%. Moreover, recent research reported at the AST conference earlier this year showed in-river smolt mortality of 50-60% in some rivers. As an aside, if you run a river population model with smolt to adult survival at 30%, after 3 breeding cycles the fixed nursery food sources are so overburdened that egg to smolt survival falls to 0.5% or less, and you're worse off than before.
This is the plot of all the available marine survival data for UK and Eire rivers. The Eire data is the average for that country taken from their annual report. UK rivers are plotted individually.

Please note that there is considerable range on each years estimation for a single result, but when combined this expermental variation is reduced. The overall trend is clear and 30% or better marine survival was been recorded from North Esk in the 70's and Bush and Eire in the 1980's and early 90's.

salmon smolt survival.jpg
 

Loxie

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Well that is probably not correct. Between 25 and 50% of the commercial catch was examined for the presence of micro tags which were recovered in large numbers from commercial premises and fishermen. One aspect of the driftnet fishery was its sheer size and thus its great potential for data collection. Also the adult run is trapped in Burishoole and all salmon were examined and checked for presence of tags. Broodstock collection also are checked to recover tags. Up to 250 k hatchery and wild fish are tagged annually but now the emphasis is on instream checking with a number of trapping facilities and checking of salmon catches in certain rivers. It is now difficult to get numbers of fish due to the closure of the mixed stock element. Also the hatchery smolts are not subject to in river problems and their return is poor now whereas it was very good in the 90s up to 15%.
As I said I dont know anything about Irish salmon fisheries, but the graph you posted indicates that half to three quarters of the entire years run of salmon back to the river was taken by the drift net fishery right up to its closure in 2007, at which point they immediately disappeared and marine survival dropped back to normal range. This cliff edge has not, to my knowledge been recorded anywhere else for 2007. Some coincidence! To me it seems far more likely that the numbers of fish estimated to be of Bush origin caught in the drift net fishery were massively inflated. When the fishery was closed there was a slight increase in adults running the Bush which more accurately reflected the true exploitation rate in the net fishery. I’m afraid I can’t comment on the coded wire tagging, ranched smolts etc as I have no real data. If you have a link to the real raw data I would love to look at it to lead more!
 

seeking

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This is the plot of all the available marine survival data for UK and Eire rivers. The Eire data is the average for that country taken from their annual report. UK rivers are plotted individually.

Please note that there is considerable range on each years estimation for a single result, but when combined this expermental variation is reduced. The overall trend is clear and 30% or better marine survival was been recorded from North Esk in the 70's and Bush and Eire in the 1980's and early 90's.

View attachment 24656
I don't want to get into a debate about how to engineer a "reverse hockey stick", but it is clear that this graph is a prime example of "apples, oranges and kumquats" and muddies the water somewhat. It's also selective in that it doesn't add in the Burrishoole data I previously posted. The two North Esk datasets are not comparable, because the Logie counter data used to more accurately estimate the returns only exists from 1981. The earlier data used a totally different method and is about as applicable as the Bush estimate.

IMHO it is statistically far more preferable to look at individual river datasets, which use the same methodology which methodology cannot be affected by changes in external influences, on a standalone basis and see what happens to that river.

Especially since the "marine mortality" estimate is very strongly influenced by any factors affecting the smolts as they leave the rivers and estuaries, which of course have recently come to more prominence.

The use of a standard methodology appears why the so-called "marine mortality" estimates for the N Esk are now provided by MSS from the early 1980s only, and the earlier data consigned to well, take your pick, dustbin if interested in data integrity and primetime if wanting to "prove" an SCS point.

Likewise the Bush estimate variance is return to "homewaters" (basically a net anywhere around Ireland) is not using the same methodology as the other datasets and hence should be discarded from a direct comparison. The river returns are within range. It's of course highly subject to the direct influence of the decline in netting.

Must admit I'm not sure of the methodology or integrity of the Tamar data but I understand it also lumps of apples, oranges and kumquats.

What that basically leaves us is a load of flatlines fluctuating around 5-10% give or take a standard deviation or so over the last few decades. So maybe we're just looking at standardisation of method or error :confused:

If you look at the EA 5-point approach graphs here you will see that they use, in Fig 3 p7. data post 1980 and include the two Irish examples with the "return to the coast" hockey stick. The shorter timeframe in Fig 4 is not continued back as far as the data - suspect if it were it would confirm the last 2 or 3 decades have been typified by low marine survival rates, with no collapse evident.

Most of the newer datasets are within range, but comparing them to ones that needed netting to operate (and don't correct for netting decline) is, how can I say this diplomatically, wrong.

More importantly perhaps the past is the past and it is what it is (or what it is alleged to be).

Nowadays we have better controls and better datasets, and the statement that predicates the EA 5-point approach, about the decline in marine mortality of 50% in the last 20 years (see: here), is wrong even on the basis of your reverse hockey stick when applied to EA data...

Still, all interesting information for discussion.
 
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charlieH

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Must admit I'm not sure of the methodology or integrity of the Tamar data. Perhaps you can provide the links ...
Didn't a request much like this from another member to you recently elicit (IMO) the rather rude response "I'm not a skivvy", and a suggestion that they go and look for it themselves? ;)
 

seeking

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T' Edale Trip

Didn't a request much like this from another member to you recently elicit (IMO) the rather rude response "I'm not a skivvy", and a suggestion that they go and look for it themselves? ;)
LOL, I can see why some may wish to cherry pick and selectively quote to prove a point, charleH. In my defence, straight after that bit I did provide the link and the references so that said forum member could benefit from doing the research himself.

But you're right and I'll go and edit my post accordingly now.:cool:
 
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KerrySalmon

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As I said I dont know anything about Irish salmon fisheries, but the graph you posted indicates that half to three quarters of the entire years run of salmon back to the river was taken by the drift net fishery right up to its closure in 2007, at which point they immediately disappeared and marine survival dropped back to normal range. This cliff edge has not, to my knowledge been recorded anywhere else for 2007. Some coincidence! To me it seems far more likely that the numbers of fish estimated to be of Bush origin caught in the drift net fishery were massively inflated. When the fishery was closed there was a slight increase in adults running the Bush which more accurately reflected the true exploitation rate in the net fishery. I’m afraid I can’t comment on the coded wire tagging, ranched smolts etc as I have no real data. If you have a link to the real raw data I would love to look at it to lead more!
There was an immediate increase from under 600 wild fish to over a thousand fish into the traps in 2007. Since then the runs have remained poor. Yes the fish disappeared in 2008 and certainly in 2009 in the fishery that I managed which is much further south. And I mean disappeared with exceptionally low spawning in these two winters. 2010 was a better year along with 2011 but certainly since grilse and autumn/ late summer fish are declining year on year with the late summer and autumn run non existent. Your hypothesis is flawed as what you are suggesting no fish from Burishoole were exploited by the drift net fishery and that returns to the river would stay the same even when nets were removed. Returns to the river have declined with 2014 showing a very poor survival rate. The certainty of survival rates of up to 30% might be questioned but stable smolt numbers in Burishoole demonstrate that survival has declined. It is absolute nonsense to say that we were only getting back 5 - 10 % of smolts to freshwater and discount what was taken by the drift nets. Yes micro tags were taken from around the coast but mostly in close proximity to natal rivers. The drift net fishery was closed here to try and reverse the decline which in the vast majority of rivers has accelerated with a few exceptional years since 2008. Certainly the collapse in recent years cannot be explained by lack of smolts although certain rivers are below the required level of spawning adults. One river which I had the pleasure of fishing in 2007 was like Russia with huge numbers of fish namely the Nore which now has serious problems which again started in 2008 with their now famous Aug Sept run all but extinct. Where smolts can be counted there appears to be a fairly smooth line of production although I note large deviation in Bush figures in regard to smolt numbers. I suggest that since 2000 there has been an accelerated decline overall and I was directly involved in Drift Net closure discussions with fishermen and without doubt they observed the fishery had drastically declined since the mid 70s. One remarked that his boat could catch up to 800 salmon of a larger size in one week but by early 2000s this had reduced to about 500 for the season with a drastically reduced condition and size to the extent that net mesh size had to be reduced.

Atlantic Salmon Condition and survival. I thought this might suggest why survival has declined and may be a result of a vastly changing ecosystem.
A study of Atlantic salmon returning to the Scottish coast was carried out by Bacon et al. in 2009. The study involved a period from 1963 to 2006 and reported on condition and including an analysis of weight and length.
The report stated that condition factor in 2006 was at a low point in the time series from 1963. Accelerated decrease of condition was noted post 2000.
An analysis of decreasing condition relating to SST or NAO only demonstrated a weak correlation.
Todd et al .(2008) demonstrated that growth condition had decreased and related this to SST with the January SST prior to return migration being correlated to condition.
This study related that stored lipids in underweight individuals were up to 80% depleted on return migration. This situation was comparable to somatic condition of Tuna in North American studies.
Todd also points out that condition will have a detrimental impact on fecundity. As the salmon is an opportunistic feeder, the obvious reason for decreased condition is that a recent and marked decline in ocean conditions and ecosystem has taken place.
 

Grassy_Knollington

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There was an immediate increase from under 600 wild fish to over a thousand fish into the traps in 2007. Since then the runs have remained poor. Yes the fish disappeared in 2008 and certainly in 2009 in the fishery that I managed which is much further south. And I mean disappeared with exceptionally low spawning in these two winters. 2010 was a better year along with 2011 but certainly since grilse and autumn/ late summer fish are declining year on year with the late summer and autumn run non existent. Your hypothesis is flawed as what you are suggesting no fish from Burishoole were exploited by the drift net fishery and that returns to the river would stay the same even when nets were removed. Returns to the river have declined with 2014 showing a very poor survival rate. The certainty of survival rates of up to 30% might be questioned but stable smolt numbers in Burishoole demonstrate that survival has declined. It is absolute nonsense to say that we were only getting back 5 - 10 % of smolts to freshwater and discount what was taken by the drift nets. Yes micro tags were taken from around the coast but mostly in close proximity to natal rivers. The drift net fishery was closed here to try and reverse the decline which in the vast majority of rivers has accelerated with a few exceptional years since 2008. Certainly the collapse in recent years cannot be explained by lack of smolts although certain rivers are below the required level of spawning adults. One river which I had the pleasure of fishing in 2007 was like Russia with huge numbers of fish namely the Nore which now has serious problems which again started in 2008 with their now famous Aug Sept run all but extinct. Where smolts can be counted there appears to be a fairly smooth line of production although I note large deviation in Bush figures in regard to smolt numbers. I suggest that since 2000 there has been an accelerated decline overall and I was directly involved in Drift Net closure discussions with fishermen and without doubt they observed the fishery had drastically declined since the mid 70s. One remarked that his boat could catch up to 800 salmon of a larger size in one week but by early 2000s this had reduced to about 500 for the season with a drastically reduced condition and size to the extent that net mesh size had to be reduced.

Atlantic Salmon Condition and survival. I thought this might suggest why survival has declined and may be a result of a vastly changing ecosystem.
A study of Atlantic salmon returning to the Scottish coast was carried out by Bacon et al. in 2009. The study involved a period from 1963 to 2006 and reported on condition and including an analysis of weight and length.
The report stated that condition factor in 2006 was at a low point in the time series from 1963. Accelerated decrease of condition was noted post 2000.
An analysis of decreasing condition relating to SST or NAO only demonstrated a weak correlation.
Todd et al .(2008) demonstrated that growth condition had decreased and related this to SST with the January SST prior to return migration being correlated to condition.
This study related that stored lipids in underweight individuals were up to 80% depleted on return migration. This situation was comparable to somatic condition of Tuna in North American studies.
Todd also points out that condition will have a detrimental impact on fecundity. As the salmon is an opportunistic feeder, the obvious reason for decreased condition is that a recent and marked decline in ocean conditions and ecosystem has taken place.

What Loxie is saying is that your graph shows that of the 30% proposed return to the coast (e.g. 100 fish), 75% were taken by the drift net fishery (e.g. 75 fish) leaving the remaining 25% (25 fish) to run the river. If you remove the nets you would expect that around and about 75 more fish would be running the river the year after.

However, that didn't happen, did it? An increase of 600 to 1000 trapped fish suggests the nets were exploiting about 40% of the catch and that the numbers returning to the coast were over estimated. Clearly the sample size is too small to draw firm conclusions.

The fact that these 'extra fish' then 'disappeared' the following year does confirm what we already know, that net catches and individual river runs are not closely linked and that adult abundance in year 1 doesn't predict abundance in year 2. It doesn't mean that there was a sudden and drastic decline in oceanic survival that caused a precipitous decline from 2008 onwards.

Given that 2008 was a generally good season for returns on counted and other rivers in England & Wales and Scotland I'd be surprised if there was an ocean-wide problem that affected fish in the 2007 marine feeding season and caused the drop in numbers in 2008. Unless of course the fish on the river you discuss go to other parts of the ocean, or more likely, that there is some difference in or along their migration route which are specific to that river / area / country.

The N Esk data, from 1981 until they stopped counting showed a decline in survival until around 2000 and then stable or increased figures. This is at odds with your view that there has been further declines since 2000, certainly as it applied to that river in that country.

Even if it is 'all at sea', what is anyone actually going to do about it? The R Tweed biologist makes a compelling case for the NAO as a key moderator of adult salmon returns, this happens at such a huge scale it is pretty much irrelevant for conservation purposes, what are we going to do about it? Nothing is the answer.
 

Grassy_Knollington

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This is the plot of all the available marine survival data for UK and Eire rivers. The Eire data is the average for that country taken from their annual report. UK rivers are plotted individually.

Please note that there is considerable range on each years estimation for a single result, but when combined this expermental variation is reduced. The overall trend is clear and 30% or better marine survival was been recorded from North Esk in the 70's and Bush and Eire in the 1980's and early 90's.

View attachment 24656
Bann

For me the basic assumptions underlying the arguments behind so much of Salmon conservation just don't add up. We have a triangle of:

Rod exploitation, which we are told is high, 20-30% on many rivers
Smolt production, which, again we are told is stable - based mainly on extrapolating the Girnock data
Ocean mortality, which we are told is at historic relative lows - based mainly on the R Bush data.

If we assume that smolt production is broadly stable 'within range' what would the 2005 returning adult numbers have been if we used the highest or lowest survival rates from the 1970s?

Returns in 2005 were 14801 fish through the counter, survival looks like about 7% - I picked it because it is easy to see.

Survival in the earlier series was between 24% and 50%, or 3.4 - 7 times greater than in 2005. This would have produced all things being equal somewhere around 50 - 103thousand returning adults to the N Esk. We would expect to see something around 20% caught, so following the logic of the figures I see presented, then catches would have been in the order of 10 - 20 Thousand in the 70s. Of course they weren't, I can look them up but they were not even close to those numbers, because the fish were not present in anywhere near those numbers either.

To me that looks like pretty simple finger-tip maths but have I considered that . . . . . .

Maybe the 'extra' fish were caught in the nets in the 70s? I'm not sure the N Esk figures are an estimate of returns to the coast but lets assume they are. I can look up the coastal netting catches and do the comparison; but for now I'll just guess that the difference between the 14801 fish that made it back in 2005 and the 50-103k that would have returned in the 70s will be a significant proportion of the total Scottish Coastal Net Catch for any year in the 1970s and that would be from one river. I know the N Esk is productive but I'll bet if you added in all the other rivers and their 'missing' fish I think you would have a number far in excess of the total net catch i.e. The numbers don't add up because the 'extra' fish weren't there.

Maybe smolt production has significantly increased in recent years? Possibly, maybe warmer summers and colder winters (Girnock data) have bred more smolts with proportionally lower returns. . . . . .but I'm not sure that has been suggested anywhere so probably safe to dismiss that one.

Rod exploitation
Smolt production
Ocean mortality

It doesn't add up for me.
 

Loxie

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What Loxie is saying is that your graph shows that of the 30% proposed return to the coast (e.g. 100 fish), 75% were taken by the drift net fishery (e.g. 75 fish) leaving the remaining 25% (25 fish) to run the river. If you remove the nets you would expect that around and about 75 more fish would be running the river the year after.

However, that didn't happen, did it? An increase of 600 to 1000 trapped fish suggests the nets were exploiting about 40% of the catch and that the numbers returning to the coast were over estimated. Clearly the sample size is too small to draw firm conclusions.

The fact that these 'extra fish' then 'disappeared' the following year does confirm what we already know, that net catches and individual river runs are not closely linked and that adult abundance in year 1 doesn't predict abundance in year 2. It doesn't mean that there was a sudden and drastic decline in oceanic survival that caused a precipitous decline from 2008 onwards.

Given that 2008 was a generally good season for returns on counted and other rivers in England & Wales and Scotland I'd be surprised if there was an ocean-wide problem that affected fish in the 2007 marine feeding season and caused the drop in numbers in 2008. Unless of course the fish on the river you discuss go to other parts of the ocean, or more likely, that there is some difference in or along their migration route which are specific to that river / area / country.

The N Esk data, from 1981 until they stopped counting showed a decline in survival until around 2000 and then stable or increased figures. This is at odds with your view that there has been further declines since 2000, certainly as it applied to that river in that country.

Even if it is 'all at sea', what is anyone actually going to do about it? The R Tweed biologist makes a compelling case for the NAO as a key moderator of adult salmon returns, this happens at such a huge scale it is pretty much irrelevant for conservation purposes, what are we going to do about it? Nothing is the answer.
I would only add that taking 2007 in isolation is unlikely to give much accuracy in terms of likely net exploitation, a 5 year average would be better.

As to KS’s theory that 2008 saw the start of a catastrophic decline in marine survival purely coincidental to the end of netting and supported by thin Tuna and poor conditioned salmon in 2006, well the period 2008 to 2012 saw probably the highest recorded 5 year average catch for salmon in the UK. These 2 things seem mutually exclusive to me. My own experience of fishing in that period, mainly in SW England and the Far North of Scotland, but also Tweed and the Dee, backs this up. From this I think the theory is completely dead in the water. This leaves either some local factor entirely coincidental to the end of netting, or the original estimates were grossly exaggerated. I don’t know enough about Irish salmon fisheries to know which but I rather favour the simplist answer.
 
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