Spinning for Brown Trout on Lough Corrib

Kaysen Rapping Beige wrote: »

I wouldnt worry about it to be honest. take laugh ree as an example, lots of bream, and they never effected the may fly

The Shannon lakes never had the density of small trout that Corrib had, and likewise Corrib never had the Mayfly hatch Derg has for example.
Someone introduced those Bream, as well as the Roach and they are having an effect on the lake, the Roach look like they pushed the Char into extinction and the Bream will be eating large amounts of food that otherwise would have supported the native species. All the non native flora and fauna should have regular culls made on them, though we can forget about that affecting the Zebras and weed.

Speaking about the Zebra's are people noticing the lake's rocky shallows are harder to spot as they are now black with the Zebra's ? The lake is a lot more dangerous now.

Zzippy wrote: »

A thread about fish stocks and spinning, and you have to jump in with a misleading and sensationalist post slagging off fisheries. Maybe you should educate yourself on basic chemistry, as well as getting your facts straight, before posting in future.

http://www.fisheriesireland.ie/FAQ/lagarosiphon-control-in-lough-corrib.html

Casoron-G herbicide was used in a tiny number of infested areas, where mechanical cutting was not possible At the time, Casoron-G was licensed for use and was approved by the Department of Agriculture. It is no longer licensed or approved, and has not been used since January 2011. Casoron-G is a granular herbicide that is extremely localised in its effect, and the granular nature means it does not dissolve into the water column. It was used in 0.01% of Lough Corrib.

Benzene is toxic and carcinogenic, that is true. Many thousands of benzene-derived products, however, are not. Common everyday materials that are derived from benzene include nylon, resins, plastics, synthetic fibers, dyes, rubbers, pesticides, detergents, drugs and lubricants. You are probably wearing and using benzene-derived products right now.

Saying something that is derived from benzene is dangerous is patently untrue - benzene in its pure form is dangerous, but many denzene-derived compounds are not. But that wouldn't suit your argument would it? A little bit of pseudo-science and misinformation goes a long way to muddy the waters, doesn't it.... same happened in the local press all of 3 months ago, but no one took much notice once they read the facts.

You clearly have a chip on your shoulder about IFI, but at least get your facts straight before you make your next drive-by post. :rolleyes:

Wouldn't call it a "chip" more an out and out dislike of a lot of there policies. I also support a lot of there policies as well by the way. You can dress it up all you want with facts, figures and chemical whatever, I just don't like the idea of chemicals being dumped into a lake I live very close to to kill weeds. Don't come on here and say all they (IFI) do turns to gold because it doesn't, granted they are doing what they feel is best for the lake, doesn't nessesarily make it so or mean everybody has to agree with them. You might like to point out which facts I didn't get straight, the fisheries did use it, it does contain benzene and benzene is nasty stuff.........? I don't think for a second you or anybody else have the slightest idea of what implications such actions might have on the lake. You can wheel out experts to tell you this that and other but it's mother nature that has to deal with things like this not some "expert" sitting in an office somewhere.

Having had a look through the report I think that the most important information, from a pike anglers view, given in the report actually has nothing to do with the 2012 survey at all !!. This important comment is at the top of page 6 and actually refers to the 1996 survey. Dr O`Grady wrote re trout stocks
" The size and stock structure of the trout population, as measured in the 1996 survey, represents the ideal in fishery management terms - substantial numbers of young adult fish (< 40cm) many of whom will be large enough to be cropped by anglers in 1996 and 1997 angling seasons. The numbers of older larger fish (>40cms) will ensure a good spawning population in the following year. The angling catches in both 1996 and 1997 were considered to be good."
The 1996 survey also showed that there were good numbers of pike of all year classes. I dont believe that there had been mich if any pike removal for around a decade before 1996.
In 1996 there appeared to be ideal trout and pike populations. This is far from what we were told at the time. At the time we were told the large pike numbers were a huge threat to the fragile trout population and that the pike stocks must be reduced hugely and quickly. This led to a major pike removal programme funded by the Tourism Angling Measure which goes on to this day. It was never admitted at the time that trout stocks were very healthy. Now the pike stocks have been reduced by over 46% and instead of increasing the trout stocks have fallen by over 20% in this survey and 33% in waterframework directive surveys 2008 - 2011 and this in spite of extensive in stream development work carried out under the Tourism Angling Measure.
It was good to note that one of the conclusions in the current report is that "predation by pike on trout cannot be held responsible for the reduced trout stocks".
While I am a pike angler I do want to see healthy stocks of wild brown trout in the Western Lakes. The drop in trout numbers, especially juveniles, is hard to understand. OK perch numbers have gone up but in 1996 the numbers were crazy low. They would have been much better before that. Maybe perch have been feeding on juvenile trout but to what extent ?
I did spend a day out on Corrib during the survey closely observing four 220 metre nets being raised in Cornamona. In around a mile of nets there was one trout and one pike each around 5 lbs. There were around 40 roach bream hybrids and these were large fish of 2 to 4 lbs. There were also maybe 40 roach and 30 perch. The perch were small with nothing over 4 or 5 ozs.
Ferox trout are officially blamed for the demise of char in Corrib. When char were present stomach contents of ferox trout indicated that they fed exclusively on char.
Something strange has now happened on Sheelin. Zebras have been all over Sheelin for a number of years. The big roach population collapsed two years ago and this was shown in the annual March stock assessment programme. The arrival of the zebras was blamed for this. Pike stocks also collapsed and this was put down to the wipe out of roach. The zebras are still there and lo and behold this years survey has shown that the roach are back bigtime. People are still scratching their heads on this one as it had been thought the huge zebra population would have prevented an increase in roach numbers.
Constant research and monitoring needs to be done to try to understand whats going on under the waves. Unfortunately to do that you need money and staff two things which IFI are now being starved of. Dont be surprised if the word permit/controbution/licence raises its head in the near future.

jkchambers wrote: »

Having had a look through the report I think that the most important information, from a pike anglers view, given in the report actually has nothing to do with the 2012 survey at all !!. This important comment is at the top of page 6 and actually refers to the 1996 survey. Dr O`Grady wrote re trout stocks
" The size and stock structure of the trout population, as measured in the 1996 survey, represents the ideal in fishery management terms - substantial numbers of young adult fish (< 40cm) many of whom will be large enough to be cropped by anglers in 1996 and 1997 angling seasons. The numbers of older larger fish (>40cms) will ensure a good spawning population in the following year. The angling catches in both 1996 and 1997 were considered to be good."
The 1996 survey also showed that there were good numbers of pike of all year classes. I dont believe that there had been mich if any pike removal for around a decade before 1996.
In 1996 there appeared to be ideal trout and pike populations. This is far from what we were told at the time. At the time we were told the large pike numbers were a huge threat to the fragile trout population and that the pike stocks must be reduced hugely and quickly. This led to a major pike removal programme funded by the Tourism Angling Measure which goes on to this day. It was never admitted at the time that trout stocks were very healthy. Now the pike stocks have been reduced by over 46% and instead of increasing the trout stocks have fallen by over 20% in this survey and 33% in waterframework directive surveys 2008 - 2011 and this in spite of extensive in stream development work carried out under the Tourism Angling Measure.
It was good to note that one of the conclusions in the current report is that "predation by pike on trout cannot be held responsible for the reduced trout stocks".
While I am a pike angler I do want to see healthy stocks of wild brown trout in the Western Lakes. The drop in trout numbers, especially juveniles, is hard to understand. OK perch numbers have gone up but in 1996 the numbers were crazy low. They would have been much better before that. Maybe perch have been feeding on juvenile trout but to what extent ?
I did spend a day out on Corrib during the survey closely observing four 220 metre nets being raised in Cornamona. In around a mile of nets there was one trout and one pike each around 5 lbs. There were around 40 roach bream hybrids and these were large fish of 2 to 4 lbs. There were also maybe 40 roach and 30 perch. The perch were small with nothing over 4 or 5 ozs.
Ferox trout are officially blamed for the demise of char in Corrib. When char were present stomach contents of ferox trout indicated that they fed exclusively on char.
Something strange has now happened on Sheelin. Zebras have been all over Sheelin for a number of years. The big roach population collapsed two years ago and this was shown in the annual March stock assessment programme. The arrival of the zebras was blamed for this. Pike stocks also collapsed and this was put down to the wipe out of roach. The zebras are still there and lo and behold this years survey has shown that the roach are back bigtime. People are still scratching their heads on this one as it had been thought the huge zebra population would have prevented an increase in roach numbers.
Constant research and monitoring needs to be done to try to understand whats going on under the waves. Unfortunately to do that you need money and staff two things which IFI are now being starved of. Dont be surprised if the word permit/controbution/licence raises its head in the near future.

I wonder are there other factors at play here such as the netting procedures themselves or weather conditions at the time. If there was a few days of settle weather verses a few very windy days. I think I read somewhere that fish move around a lot more in stormy conditions. Either way I doubt the fact that pike numbers have reduced so much will stop the gillnets.

@Zzippy - do you know how specific the Castron G was in targetting the Langarosiphon as opposed to other naturally occuring plants. Understand that the invasive species was choking the water and witnessed enough of it but was it a case of more or less killing off everything in specific patches to clear the weed and then hopefully allow the native species to return?

:rolleyes::rolleyes:What is Lagarosiphon and what damage can it cause?
Lagarosiphon major (Curly leaved waterweed) is a high priority invasive species in freshwater systems. It was introduced to Ireland by the horticulture industry as an oxygenating weed for use in artificial lakes and ponds. It originated in Southern Africa. It was probably introduced into the lake from an artificial pond in the upper catchment.
It was first identified in 2005 in a few sheltered bays along the western shore of the upper lake. It is estimated that the weed was first introduced into the lake in the early 1990s. Since that time the weed has expanded its range and, by 2011, it was present in more than 160 bays in the upper and middle lake. Results from studies conducted by IFI has demonstrated that, if Lagarosiphon was to colonise all suitable habitat in the lake, it would overgrow some 11,000 ha or 61% of the area of this national aquatic resource.
No Lagarosiphon has yet been recorded in lower Lough Corrib and it is important that IFI and all stakeholder groups work together to ensure that it is not introduced here. The lower lake is shallow (mean depth circa 3m) and presents an ideal habitat for Lagarosiphon. If it becomes established in this basin it could totally overgrow this large expanse of water. The consequences for the ecology and amenity use of this area would be enormous but could possibly be overshadowed by the risks posed by water retention and consequent flooding.
At sites in Lough Corrib where Lagarosiphon has successfully established it has adversely impacted native plant, insect and fish communities. It also completely fills the water column and restricts water movement, which can result in elevated water levels during times of high rainfall.
What was done by IFI when Lagarosiphon was first identified?
In light of the known environmental and economic impacts that Lagarosiphon could have on Lough Corrib, a special Lagarosiphon Task Force was convened within weeks of the initial discovery of the weed. The objective of this Group was to propose coordinated actions that would help control the weed. Specifically, the Group would identify and source funds that would be used to conduct research into a diversity of methods that might control the spread of this invasive weed, and to raise awareness of the dangers that it poses.
What agencies collaborated with IFI in the fight against Lagarosiphon?
This Lagarosiphon Action Group comprised personnel from agencies including Central and Western Regional Fisheries Boards (now IFI), the National Parks and Wildlife Service, the Office of Public Works and Galway County Council, and the Heritage Council by way of funding.
Who funded research to identify control methods for Lagarosiphon?
Written proposals for funding to conduct research into the ecology of the plant and appropriate control methods were prepared by the Lagarosiphon Action Group in 2006 and 2007. The proposals were forwarded to a number of State bodies and agencies, and sufficient funding to permit the commencement of research activities on the lake was received from NPWS, OPW, Galway Co. Co. and the Western River Basin District. Subsequently, funding to continue research was secured from the EU Life+ fund to cover the period from 2009 to date. Additional funding has been received from the Heritage Council, Galway County Council and Galway City Council.
What weed control methods were initially considered to tackle Lagarosiphon?
The weed control methods that were selected for trial purposes on Lough Corrib were carefully considered and were informed by practical experience in Irish aquatic situations and based on best practice abroad. These included: manual removal using scuba divers, mechanical control and harvesting using traditional and innovative devices, light interception using black plastic and other materials and selected, approved aquatic herbicides.
Considerable focus was placed on research into the life cycle traits of the weed in an attempt to find a weak link that may be exploited.
What weed control methods were ultimately used to control Lagarosiphon?
Following extensive trials work with a variety of methods, the following proved most successful and contributed best to the removal of the weed from infested areas: manual removal using divers in areas where the plant is present with low abundance; mechanical cutting with paired V-blades or cutting knives, followed by meticulous weed harvesting; the approved aquatic herbicide Casoron G; and light exclusion using jute matting.
Why was the decision made to use aquatic herbicides in Lough Corrib?
The decision to trial the aquatic herbicide Casoron G on Lagarosiphon in Lough Corrib was based on more than 20 years’ positive experience using this product for aquatic weed control throughout Ireland and because of the excellent results that had been achieved using it for weed management in watercourses in the UK and in Europe. Scientific research conducted within IFI and abroad has clearly demonstrated that, where Casoron G is used according to manufacturer’s guidelines, it has little or no adverse impact on non-target organisms (be they plants, insects, fish or mammals).
Is Casoron G an approved herbicide for use in water?
Casoron G had full approval for use in aquatic situations by the Pesticide Control Service of the Department of Agriculture at the time it was used in Lough Corrib.
What is Casoron G?
Casoron G is a granular herbicide that contains 6.75% active ingredient (dichlobenil). The chemical name of dichlobenil is 2,6-dichlorobenzonitrile. Dichlobenil is metabolised by bacteria and microfauna in the mud to produce 2,6- dichlorobenzamide (BAM)
How does Casoron G operate?
The Casoron G granules are applied to the water surface directly above the area of lake to be treated. They sink directly to the lake bed from where the active ingredient (dichlobenil) is adsorbed onto the mud particles before being translocated through the target plant. Dichlobenil is poorly soluble in water and, as a consequence, there is a minimum of lateral movement in the mud. Thus, plants (or animals) that are not directly targeted by the granules are not impacted. This property of the herbicide is one of the reasons why IFI scientists favoured this herbicide for weed management purposes over others.

The dichlobenil residue in water almost completely dissipates in 5 to 6 months.
Dichlobenil affects growing points (interferes with cellulose production) in the plant and the herbicidal activity is characterised by a powerful inhibition of plant growth. It is particularly effective on young, growing plants. Rooted, submerged aquatic plants are most susceptible.
Are there any restrictions or exclusions pertaining to the use of Casoron G?
The product label indicates no restriction or exclusion from its use in water systems, once its use is approved by the appropriate regulatory agencies.
Has registration for dichlobenil been withdrawn by Europe?
The registration of all dichlobenil products (including Casoron G) was revoked in Ireland from 18th March 2009, under Commission Decision 2008/754/EC of 18th September 2008. A period of grace for the disposal, storage, placing on the market and use of existing stocks expired on 18th March 2010.
When did IFI last use Casoron G in Lough Corrib?
The controlled, targeted and localised use of Casoron G was continued until March 2010. Subsequent to this, IFI received an emergency derogation, in writing, from the Pesticide Control Service of the Department of Agriculture to treat localised patches of Lagarosiphon. The last application of Casoron G in Lough Corrib was made on 27th January 2011.
Does Casoron G effectively kill Lagarosiphon?
Trial results conducted in Lough Corrib indicated that Casoron G effectively and efficiently killed Lagarosiphon.
Is Casoron G used for wide-scale Lagarosiphon treatment in Lough Corrib?
Based on the positive results achieved during trials with Casoron G, it was decided to use it to treat relatively small and localised Lagarosiphon stands, particularly where no other control method was feasible. This included very shallow weed beds and small areas of lake where rock outcrops prevented access to weed cutting or jute matting boats. The majority of the sites treated in the lake between 2006 and 2011 measured less than 100 m2. Treatment sites were very localised and none were in the vicinity of water supply take-off points.
The area of Lough Corrib treated with Casoron G between 2006 and 2011, the quantity of Casoron G used each year during that period and the percentage of the total lake area treated are presented in the table below:
Area treated (m2) Herbicide used (kg) % lake area treated
Are the after-effects of Casoron G on water quality and native plants, insects and fishes scientifically monitored?
Results from extensive research conducted abroad recorded ‘no detrimental effects to water chemistry’ from the use of Casoron G as recommended by the manufacturers.
Work conducted in US showed that, after 50 days, no dichlobenil could be detected in Chara (this is an aquatic plant species that is the cornerstone of productivity in Lough Corrib).
IFI has an ongoing monitoring programme on Lough Corrib, operated over the 12-month cycle. Water quality is assessed at sites in the upper, middle and lower lakes on a monthly basis and this intensive programme has been in place since late 2009. No adverse effects from the use of Casoron G have been recorded through this sampling programme. Galway County Council also runs a comprehensive sampling programme on Lough Corrib and report that the water used for drinking purposes continues to be in full compliance with standards in the EU drinking water regulations.
In addition, IFI regularly monitors the status of native aquatic plant, insect and fish communities in Lough Corrib. Results from regular surveys of each of these biotic communities have revealed the presence healthy populations throughout the lake, accepting the normal dynamic cycles that occur in nature. It is noteworthy that, in a number of areas where Lagarosiphon has been successfully removed using Casoron G., native plant and insect species have recolonized and virtually pre-Lagarosiphon conditions have been re-established.
Is Casoron G toxic to insects, fish or mammals?
Research conducted in the UK and the US concluded that the addition of dichlobenil to waters at recommended rates had no direct toxic effect on aquatic insects.
Similarly, there are no toxic effects to fish, particularly where the total area of water treated at any one time is less than 20% of the total surface area (as is the case in any treatment applied to Lough Corrib). Analytical results from the dissection of large numbers of fish, representing all species, that were captured during the IFI Water Framework Directive fish stock surveys of 2008 and 2011 revealed no liver tumours or obvious damage to the reproductive organs of these Lough Corrib fishes.

Analytical results suggest that acute mammalian toxicity to dichlobenil is low and, at the levels used in the lake, there is an enormous safety margin. Toxicity data suggests that the acute mammalian toxicity of dichlobenil is low (for rats and mice) and, when used at recommended rates there is an enormous safety margin. A yearling cow would need to drink about 6,250 l of water that contains the recommended herbicidal dose before registering any harmful effect.
As no Casoron G has been used in the lake since 27th January 2011, there is no chemical residue remaining in the lake substrate.
Dichlobenil is virtually immobile in still or slow flowing waters and even that small element of the chemical that may enter into solution following spraying will be diluted to undetectable limits in a very short period, particularly in a lake as vast as Lough Corrib. The product is designed in a manner that ensures practically all of the active ingredient is actively adsorbed onto the mud particles on the lake bed, leaving only minute quantities to enter into solution in the water.
What will happen now that Casoron G has been withdrawn?
IFI is confident that the correct decision was made by the collective of State agencies to use Casoron G to treat inaccessible and localised population of the highly invasive weed Lagarosiphon in Lough Corrib. The herbicide worked in an environmentally safe and effective manner, and yielded excellent results in respect of invasive weed control. In its absence it will be necessary to deploy more time consuming methods, such as manual removal using divers, to effectively treat these less accessible lake areas.

Imho weedkiller had very little effect on over all trout population, we need to recognize that there is no silver bullet here, many factors at work. We need action fast to discover what is happening to the juvenile fish. this will cost money

We need to work together, argument s over pike weedkiller etc. are pointless

I was doing a shakedown on the survey boat today - and thought I'd see if I could find some of the missing fish.

I've been doing sonar surveys on the Lough for many years now, and have never seen concentrations quite like these. There were a couple of guys trolling around in the area unsuccessfully (while I was there) - I've no idea if they knew what was below.

http://www.anglingcharts.com/images/N_corrib_fish1.jpg
http://www.anglingcharts.com/images/N_Corrib_fish_2.jpg

anglingcharts

anglingcharts wrote: »

I was doing a shakedown on the survey boat today - and thought I'd see if I could find some of the missing fish.

I've been doing sonar surveys on the Lough for many years now, and have never seen concentrations quite like these. There were a couple of guys trolling around in the area unsuccessfully (while I was there) - I've no idea if they knew what was below.

http://www.anglingcharts.com/images/N_corrib_fish1.jpg
http://www.anglingcharts.com/images/N_Corrib_fish_2.jpg

anglingcharts

Sorry would you mind explaining these charts?

anglingcharts wrote: »

I was doing a shakedown on the survey boat today - and thought I'd see if I could find some of the missing fish.

I've been doing sonar surveys on the Lough for many years now, and have never seen concentrations quite like these. There were a couple of guys trolling around in the area unsuccessfully (while I was there) - I've no idea if they knew what was below.

http://www.anglingcharts.com/images/N_corrib_fish1.jpg
http://www.anglingcharts.com/images/N_Corrib_fish_2.jpg

anglingcharts

Very interesting but what are the fish on these charts, pike, roach, perch, trout, salmon, ferox, bream, eels etc. Any way of telling accurately what species they are?

More than likely Trout feeding on Daphnia, right time of year, right water column.

I was working near Mollies Rock and Rabbit Island today, yet again - full of fish. Around the back of Devinish was heaving. A few flies on the surface, a couple on the boat, nothing dramatic - no rises seen at all.
http://www.anglingcharts.com/sidescan/devinishisland.html

I'm having a job equating what I'm seeing with the results of the netting !


I found an ancient dugout canoe as well - made my day.

anglingcharts.