Some further thoughts on the use of salt

[carpepecheur]

In a recent thread about bait, I expressed my concern about the safety of using salt when carp fishing. It has been niggling me that I did not make my concern known very clearly. I set up an experiment to try and demonstrate my thoughts more clearly. I would be interested if anyone else shares my concerns.

 

 

[yonny]

The video says you were very surprised but the result of this experiment but I think the result was exactly what you and I expected buddy.

We already know that a salt water solution is denser than water and the volumes you use in the vid are very effective in demonstrating that. To replicate those volumes in a water body of any significance would take many thousands of tonnes of salt at a guess.

What happens if you pop your hand in that tank and waft it across the bottom to replicate the activity of a swimming/feeding carp (or any fish for that matter)? I'm surprised you didn't do that as part of the experiment tbh. Or maybe you did but it was not featured in the vid?

If we imagined that the salt did stay in a concentrated area when introduced to a large body of water it could certainly go some way to explaining why "salting a spot" can be so effective, particularly on rich, weedy waters. It'd clear the spot nicely ready for perfect presentation.

I think the statement that still waters have no natural mechanism by which salt can be removed is misleading. Salt is water soluble and the water in lakes is constantly recycled through natural water cycles (rain vs. dispersal through groundwater). In the concentrations used for carp fishing this has a negligible effect (imo) on a water body.

[bluelabel]

there is also that fact that anglers rarely use a saturated solutions (did I see undissolved salt in the glass before it was added to the pva bag?) also that the premise of carp liking salt is down to the fact that nutrients in the floor of the lake bed can make the pH different in that area,  so even a small amount would trigger a slight pH imbalance and possibly entice a carp to feed...  for me, it's a moot point however, as I for one don't use salt in my carping, the fact that salt is used as a preservative in boilies is enough for me,

 

(addendum....)

I don't think carpers should be adding salt to baits in large volumes, as I too have concerns over it's use, but let's not  confuse the fact that it can work, my concern stems from people seeing it on youtube or some such video and emulating it on a grander scale thinking "Oh well a bit more won't hurt" the media need to emphasise the possible dangers from the outset before advocating the use of a possible poison 

[yonny]

8 minutes ago, bluelabel said:

the premise of carp liking salt

It's more a case of them needing it than liking it. It's a mineral that is very difficult for them to obtain in a freshwater environment and carp need it to function.

10 minutes ago, bluelabel said:

even a small amount would trigger a slight pH imbalance and possibly entice a carp to feed

A pH change cannot entice a carp to feed. It is merely an investigation trigger. It is the food signals from the bait you use on that spot that triggers feeding. But I do not believe that is how salt works either way. Carp need salt, it's as simple as that, and if we introduce an easily accessible source they will come.

19 minutes ago, bluelabel said:

"Oh well a bit more won't hurt"

I agree with you that anglers should be aware of possible dangers but imo that "oh well" decision couldn't possibly result in the hundreds of tonnes of salt it would take to even match the salinity levels preferred of their tanks by koi keepers.

[carpepecheur]

Thanks for comments. Just what I was looking for. In reply :-

“you were very surprised but the result of this experiment but I think the result was exactly what you and I expected”

I was expecting some separation between the denser salt and the water but I was astonished that the salt remained so concentrated in such a very thin layer on the bottom of the tank. 

“To replicate those volumes in a water body of any significance would take many thousands of tonnes of salt at a guess.”

I used about 10 ml of rock salt and it covered about 0.1 square metres. That equates to 100 ml per sqr metre. A 5 acre lake is roughly 4000 square metres so it would need 400 litres of salt to entirely cover it under the same conditions. That is not a huge amount. Roughly 1000 kilo. Ok this is under laboratory conditions and there are many variables in real life. I suspect the salt solution would roll down hill and fill up hollows and low spots. I have no idea how long it would take to diffuse through the water column. I feel another experiment coming on.

“If we imagined that the salt did stay in a concentrated area when introduced to a large body of water it could certainly go some way to explaining why "salting a spot" can be so effective, particularly on rich, weedy waters. It'd clear the spot nicely ready for perfect presentation.”

Yes, that is precisely my point. You create a mini desert in that area. I believe that, when salt is initially introduced, it kills off the microorganisms and the carp move in for a free lunch. However it leaves behind an inert bed. Is that what we really want to do?

“I think the statement that still waters have no natural mechanism by which salt can be removed is misleading. Salt is water soluble and the water in lakes is constantly recycled through natural water cycles (rain vs. dispersal through groundwater). In the concentrations used for carp fishing this has a negligible effect (imo) on a water body.”

This is a relevant point and I have no understanding of how salt may disperse through groundwater. I would suggest that even if it does, it has already done its damage to the lake bed.

“ anglers rarely use a saturated solutions (did I see undissolved salt in the glass before it was added to the pva bag?) “

Yes I just put in a tablespoon of salt into a glass. But surely if people are putting a salt lick into a swim the initial solution in direct contact with the salt is saturated so the demo is not that representative 

“for me, it's a moot point however, as I for one don't use salt in my carping,”

I think that is the attitude everyone should adopt.

“It's more a case of them needing it than liking it. It's a mineral that is very difficult for them to obtain in a freshwater environment and carp need it to function.”

I am not sure I agree. Is there any evidence for this? Carp seem to have evolved for thousands of years without the need of extra salt added artificially. I have never come across a case of carp suffering from a lack of salt. But I could be completely wrong.

“I agree with you that anglers should be aware of possible dangers but imo that "oh well" decision couldn't possibly result in the hundreds of tonnes of salt it would take to even match the salinity levels preferred of their tanks by koi keepers.”

I have been trying to demonstrate that it is NOT the levels of salt that the Koi experts find acceptable that is the danger. It is the much smaller amounts that endanger microorganism growth.

 

 

[yonny]

4 minutes ago, carpepecheur said:

I used about 10 ml of rock salt and it covered about 0.1 square metres. That equates to 100 ml per sqr metre. A 5 acre lake is roughly 4000 square metres so it would need 400 litres of salt to entirely cover it under the same conditions. That is not a huge amount. Roughly 1000 kilo. Ok this is under laboratory conditions and there are many variables in real life. I suspect the salt solution would roll down hill and fill up hollows and low spots. I have no idea how long it would take to diffuse through the water column. I feel another experiment coming on.

 I will admit that is less than I expected you had used. I would say that without our knowing these micro organisms specific resistance to salt that doesn't mean much to us though. The red layer at the bottom of your tank looks savage, but if salt concentration is not high enough to make any difference then it matters not.

15 minutes ago, carpepecheur said:

You create a mini desert in that area. I believe that, when salt is initially introduced, it kills off the microorganisms and the carp move in for a free lunch. However it leaves behind an inert bed. Is that what we really want to do?

Agreed, in the long term that's the last thing we want. But knowing some of the weedy waters I fish in the UK have been subject to salt hits for many, many years, I don't think it happens. They're still weedy and rich as hell!

19 minutes ago, carpepecheur said:

Carp seem to have evolved for thousands of years without the need of extra salt added artificially. I have never come across a case of carp suffering from a lack of salt. But I could be completely wrong.

I didn't say they need extra salt. I just said they need salt. And if we offer it to them though a source that is easier to access than the very scarce natural sources it stands to reason that they will take advantage in the same way that when food is in short supply we tend to have it off over bait.

[yonny]

2 hours ago, yonny said:

What happens if you pop your hand in that tank and waft it across the bottom to replicate the activity of a swimming/feeding carp (or any fish for that matter)? I'm surprised you didn't do that as part of the experiment tbh. Or maybe you did but it was not featured in the vid?

Did you try this buddy?

[carpepecheur]

50 minutes ago, yonny said:

Did you try this buddy?

No I didn't. The reason was I was surprised by how slow the PVA took to melt and did not want to disturb it. We know that adding salt to a mix allows you to put a wet mix in a pva bag without it melting but I expected it to dissolve from the outside very quickly. What seems to happen is a skin forms inside which doesn't fully dissolve. The sequence after the bag was in the tank took about 15 minutes. I speeded it up because it was boring to watch. I will try as you suggest and see if it disperses quicker through the water or if it settles back down again. I am also interested to see how it disperses in the water over time.

[yonny]

15 minutes ago, carpepecheur said:

What seems to happen is a skin forms inside which doesn't fully dissolve.

That's interesting. It be interesting to see how it looks with a rig in there too. Pretty awful I'd guess lol.

[carpepecheur]

That's a good point. When I cleaned the tank the lead weight I used was covered with a gloopy mess. I wonder what would happen to a bag of sweetcorn? Lots of stuff to investigate and so little time.

[bluelabel]

There is also the point that very few lake beds are flat and using the video's coloured layer as the solution in normal circumstances, it would collect in depressions an hollows as it flows down slopes and into gulleys so what you would get are pockets of concentrated spots.... also these pockets would see a change in the surrounding pH of the water

[yonny]

2 hours ago, carpepecheur said:

I suspect the salt solution would roll down hill and fill up hollows and low spots.

 

6 minutes ago, bluelabel said:

it would collect in depressions an hollows as it flows down slopes and into gulleys

We need to bear in mind that a carp lake is not a stagnant hole in the ground. It is a dynamic environment with undertows that change with the direction of the winds. You also have the fish themselves that disrupt the bottom of the water column as they swim around and hopefully feed, kicking up the silty sediment.

[chillfactor]

I was always of the thinking if you are to use salt then early spring is the time ?, as Yonny mentions they seem to need it after losing condition a  bit through winter . Was chatting to someone years ago who watched carp dig out a huge hole after he primed it a few time with sticks of rock salt . So they defiantly search it out if on offer at the right time of year .

 

[yonny]

12 hours ago, chillfactor said:

I was always of the thinking if you are to use salt then early spring is the time ?

Yeah that theory came from Mark Holmes I believe.

12 hours ago, chillfactor said:

Was chatting to someone years ago who watched carp dig out a huge hole after he primed it a few time with sticks of rock salt .

Yeah I've known of this too which may add weight to my theory that salt generally does not sit on the bottom and kill everything.

[carpepecheur]

Mark Holmes apparently watched carp dig a hole around some sticks of rock salt and came to the conclusion that carp were attracted to salt. It is a reasonable conclusion to come to. However my interpretation of that observation is that the salt kills all the small organisms within a small area and the carp move in to eat them. I believe Mark Holmes suggestion is they do not eat the salt but rub against it to absorb salt into their bodies to replace that lost over winter. If that is the case why dig a hole? If, on the other hand, the salt had penetrated a small distance into the silt, the carp would dig to find even more dead organisms to eat ths supporting my suggestion.

I can't find any scientific evidence that carp actively seek out high salt concentrations of salt for their osmoregulatory process. The process takes place naturally from salts already in the system. If, has been suggested, that they are attracted to an area baited with salt, how much do they need and how often? I would guess that one block of salt would serve the entire fish population for many months. It seems self evident that the actual amount of salt they actually need is incredibly small compared to the amounts being spodded in by anglers.

Yonny, I see you have a theory that salt does not sit on the bottom and kill everything. Other than wishful thinking how do  you know? Sure there is disturbance by water currents and fish activity but my simple experiment suggests a fair amount of salt at toxic levels will rest on the bottom causing damage to aquatic life. I have access to an unvisited lake and next spring I am going to make some PVA salt water bombs and see what happens in a real environment. Meanwhile I think the best approach is - if in doubt leave it out.

 

[yonny]

7 minutes ago, carpepecheur said:

Yonny, I see you have a theory that salt does not sit on the bottom and kill everything. Other than wishful thinking how do  you know? Sure there is disturbance by water currents and fish activity but my simple experiment suggests a fair amount of salt at toxic levels will rest on the bottom causing damage to aquatic life.

I don't know it, but I do believe it, for the simple reason that I know of several rich waters that've been subject to salt hits for years and continue to flourish with almost impenetrable weed and associated naturals year on year. The spots do not stay there year after year (I wish they did, it'd make them a hell of a lot easier to fish lol). New spots are created each year and old ones grow over (this can happen in weeks or even days when the conditions are right).

Given that your 0.1 square meter tank contains no undertow, no currents and no fish I can't see how your experiment suggests anything other than what we already know regards density.

19 minutes ago, carpepecheur said:

I have access to an unvisited lake and next spring I am going to make some PVA salt water bombs and see what happens in a real environment.

That would be interesting to see what would happen over the course of a season. Make sure the water contains carp though lol.

[carpepecheur]

Yes totally agree. I have just the spot in mind. It is an enclosed and gated lake with hardly any fishing activity. It holds a huge head of carp at around the 10 lb mark. There is a shallow area dropping off into deep water. I have already tested the use of raw maize there and the carp hoovered it all up. Watch this space.

[greekskii]

Just a few things;

1. Totally agree with Yonny, carp require salt, it's a key part of osmosis so if they can access it much easier they will. My dissertation concluded that a salinity of 2ppt actually provided better feed conversion and growth rates in juvenile carp at least. My conclusion was that there was less energy being utilised processing small levels of sodium for osmosis and other regulatory processes. The chemical balance of the carp was much easier for them to maintain, hence more energy for other processes.

2. 1000kgs of salt is A LOT. A tonne. and it would all have to be put in at the same time, distributed evenly across the waterbody to kill off the entire lake bed. It's unrealistic. What happens is small spots get a bit of salt, they are fed on by whatever fish or bird species and then re-colonised if not having another dose of salty bait regularly. Food for thought - a 5 acre lake with an average depth of 1.5m would require over 12,000kg of salt to take it above a 2ppt salinity level. 6000m3 is roughly 6million litres. That level is based on my findings, which I do not say are gospel but its the best I have to my knowledge. 

3. Again, I dont think anyone puts a 2kg salt lick on a spot. It's crushed up and introduced in smaller quantities over a spaced out time. Water movement and topography will distribute it. Example, I fished an 880m long pit which had a SW or NE wind blow the length of it. In strong winds a 350-400m undertow was common, normal winds 100-150m. Salt granules wont stay in situ for long when you take in to account water movement, fish and bird activity and also topography. I feel like you are investigating extremes, not real angling situations but as you said you will be doing it and it'll be interesting to see what you find, as long as you introduce the salt how anglers do, not in a big block of salt!

Interesting stuff though and good on you for doing some experiments and things. Personally I dont not think that it makes much difference at all to the environment of a lake in the ways that it is used. I don't agree in block input of it like you said as I agree that it will just kill everything off. 

Just to touch on the groundwater thing as you say you dont quite understand it. Basically every piece of land has it's level on the water table, hence why lakes are normally in river valleys as the water table level is low so they naturally fill up. As groundwater level (aquifers) diminish during drier periods the water in the lakes will be drawn down through the ground as the water level drops. Gravity. As groundwater levels rise in wetter periods the lakes recharge. 

 

[yonny]

3 hours ago, greekskii said:

Example, I fished an 880m long pit which had a SW or NE wind blow the length of it. In strong winds a 350-400m undertow was common, normal winds 100-150m.

To totally change the subject (temporarily), can you expand on this bit Vik? I always thought that an undertow basically travelled the full length of a water, in the opposite direction to the winds. Is that not the case?

[greekskii]

18 minutes ago, yonny said:

To totally change the subject (temporarily), can you expand on this bit Vik? I always thought that an undertow basically travelled the full length of a water, in the opposite direction to the winds. Is that not the case?

basically there around midway there was a plateau which pretty much eradicated any significant undertow as it was a few feet raised. Amazing debris trap and prolific fishing on the base of either side after a strong wind in the respective direction. You are right about opposite sides, I just assumed it as common knowledge. A SW wind would blow toward the 'bottom' end of the pit, undertow travelling toward the 'top end' before hitting the plateau and losing steam and vice versa for a NE wind. 

[carpepecheur]

I am learning a lot from this discussion. Greekski, you said carp can osmote (I think I just invented a new verb) better in a salinity of 2PPT. Do you know what the typical salinity of a carp lake normally is? I have no idea myself as I am not a biologist but I am curious.

The point I was (badly) trying to make is that the danger is not to the carp directly but to the aquatic flora and fauna on and in the lake bed. I repeat I am not a biologist but I suspect some at least some of it has a lower tolerance to salt. Surely we are [censored]ing up the aquatic ecosystem by adding salt even by just a small amount just to give an edge to our fishing.

My comment about not understanding the water table was to say I do not understand how salt can be purged from a lake by diffusion or filtration through the water table, especially as the consensus seems to be that the salt is distributed throughout the water column and not as I hypothesise forming a layer on the lake bed. I am fairly convinced by the evidence I have seen that salt accumulates.

The idea seems to be that the amount of salt polluting our lakes by anglers is so small we should not worry about it. Well when we started dumping plastics in the oceans it was thought they were so vast in expanse and depth it that surely it couldn’t do any harm. Now generations later we are somewhat wiser (although still not doing enough about it).

 

[oscsha]

@carpepecheur I admire your thinking but I think your over thinking the situation . You could argue that even putting any bait in or removing any weed or silt is messing the ecosystem up . Why pick on the poor old salt granule.

Edited January 9, 2020 by oscsha

[carpepecheur]

"Why pick on the poor old salt granule"

Because, unlike bait or weed removal, the evidence I have seen suggests salt has an accumulative effect. Bait disintegrates, weed grows back but salt just goes on building up. People thought a few bits of plastic would have no effect on the vast oceans - well we are better educated now ---- aren't we?

However I proudly accept your criticism that I over think things. Yes I do.

Edited January 9, 2020 by carpepecheur

[chillfactor]

10 hours ago, carpepecheur said:

 

Yonny, I see you have a theory that salt does not sit on the bottom and kill everything. Other than wishful thinking how do  you know? Sure there is disturbance by water currents and fish activity but my simple experiment suggests a fair amount of salt at toxic levels will rest on the bottom causing damage to aquatic life. 

 

Nick,  put some photos up years back of a pile of pellet that was dumped in the margin . Killed the lake bed as it rotted down , left in bare . Point being lots of items lobbed in lakes in high quantities have the ability to cause the effects you mention , if they weren't eaten or disturbed .  Not a salt user myself so not trying to defend anything. 

Really good read so far 😎

[greekskii]

2 hours ago, carpepecheur said:

I am learning a lot from this discussion. Greekski, you said carp can osmote (I think I just invented a new verb) better in a salinity of 2PPT. Do you know what the typical salinity of a carp lake normally is? I have no idea myself as I am not a biologist but I am curious.

Freshwater is 0ppt. Sea water is around 32/34ppt. Anything over 2ppt I found had significant negative impact. 

I agree, the danger is not to carp. It’s to the invertebrates and plants and the rest. I don’t think the consensus has been that salt will damage carp, I thinks it’s always been that it’s the smaller organisms which will be affected. 

I look at it this way. If someone is hung up on if a bit of salt kills off a 30cm square bit of the lakebed then don’t try and put a bit of metal in a fish’s face and drag it out of the water so it can’t breathe just for your own enjoyment. There’s a fine line in there somewhere I guess. In my opinion, and my career is river ecology and restoration, anglers look after the environment more than any other user leisure or commercial user of the rivers.