Barbel in Nets

[Bob Roberts]

Graham,

I'm not asking that in so many words, indeed I'm not asking any deliberately contentious questions, simply trying to put some of the oft quoted lore into perspective.

We are, after all, only having this debate because the one clear fact we have at the moment is that barbel are poorly treated by more anglers than we care to admit.

Indeed it may be out of ignorance but surely that is why we need explore commonly stated scenarios.

Any policy should include clear and concise guidelines while remaining flexible enough to change if a sound enough arguement is put forward.

It's called progress.

Would you sooner have it discussed openly on here or behind closed doors?

So far, whatever anyone has suggested, there has always been a counter argument but let's take high banks as an example. two ropes will position a net securely and it will remain horizontal as sure as it will in 18 inches of water over gravel.

Anyone can be negative and shout about the problems but it takes ingenuity to come up with solutions.

 

[GrahamM]

That wasn't my point Bob, I was saying that maybe we're taking things too far, to the point where, if we take things to the nth degree, we're going to have swims that will be unacceptable.

 

[stuart clough]

There are a number of issues with regard to fish & dissolved oxygen (DO).

I agree wholeheartedly with the earlier post re. temperature being a double whammy, as temperatures rise oxygen becomes less soluble, but the fish need more. It is clear to see why the majority of problems occur in the summer.

In terms of whether oxygen levels vary across a given section of river they do, but not to any great extent within the main channel. Fast broken water will contain higher saturation levels than slow laminar flow, but not such that slow flow can't support fish. Offline areas such as bays and cattle drinks without much water exchange with the main channel do get significantly warmer, and can have much lower oxygen levels. A keepnet in such an area could be a deathtrap to all species. this is exacerbated if the sediment is disturbed, so wading around in the edge, say to land a fish, could kill the fish in a net that were OK up until then.

On top of this, the oxygen requirements of fish also vary by species, and by size. Larger fish need/use more O2, and some species are better adapted to survive at low DO. Although I have no data, observations suggest barbel would be at the high end, demand wise (congregate around weirs in hot weather etc.)

Then there is acclimation and conditioning. fish which regularly experience borderline DO levels can adapt, such that roach in the tidal Thames may have a lower tolerance threshold than those in the Hampshire Avon for example. this comes about via changes in the surface area of the gills, and the oxygen carrying capacity of the haemoglobin - the altitude training mentioned by a previous post.

Then there is the exchange of water through a keepnet. In flowing water the exchange through the net is high, but in stillwater this only occurs by diffusion, and any swimming movements of the fish. In general stillwater fish are better adapted to low DO, but put a high oxygen demand river fish in a stillwater situation, and it is easy to see how this could cause problems.

In terms of testing, it would be relatively straightforward to measure O2 thresholds for barbel, how quickly oxygen became depleted within a keepnet in stillwater etc etc, but there are so many variables it is difficult to see how these data could be used to inform the setting of guidelines.

In summary, a well positioned keepnet, containing appropriate numbers of fish, in well oxygenated, cool water is unlikely to result in any DO related impacts. (there may be other impacts - fin abrasion etc.)

Conversely, a poorly positioned keepnet with too many fish in mid-summer with stirred up sediment is likely to result in DO related problems for all species, not just barbel.

 

[stuart clough]

Apologies for the length of that last post!

 

[STEVE POPE]

Hi Stuart,

Keep your posts coming, by and large they confirm everything anglers who have spent the best part of their life's in pursuit of barbel know only too well.

 

[Matt Brown]

Fascinating post Stuart.

 

[Tony Rocca]

Was indeed a very well put post Stuart, I was thinking about it but you put it far better than I could.

 

[Simon Kelshaw]

Stuart a cracking read, facts are always good, much better than the tosh others have posted.

Peter, Fred, Steve, its nice of you to drag the postings back to who is right and who is wrong!

 

[Bob Roberts]

Thanks Stuart. A clear and informative reply.

At last, a man of substance. Your brains will be picked over the comming days, if you don't mind of course, but it's hard to concentrate after a night like last night.

Oh you poor Aston Villa fans. The gloating things you said on your message board yesterday about this 'suburb of Rotherham' have come home to haunt you big style!

Apologies to you suffering dee-dahs and Crewe fans. I know, off topic, well out of order, but at least give us Donny fans one break every thirty years.

Please.

Now don't go turning this into a footie thread, I've said sorry.

More on barbel care if you will.

I'll get me coat.

 

[stuart clough]

There is a slight conundrum which will arise when attempts are made to design a more fish friendly keepnet design. Intuitively, a soft, close weave mesh is better from the fin abraison standpoint, whereas for maximum throughflow, and therefore maximum oxygen exchange a coarse mesh would be preferable. Not a simple one to resolve, I would suggest.

 

[Big Swordsy :O)]

It al comes down to the pattern of the mesh, the soft abrasion resistant carp type nets are good but because of the tightness of the weave they restrict the flow of water passing through the mesh. The open mesh so beloved of barbel fins is great for water passage but simply will not let go of fins and scales.

How about a hybrid net where the top 3 sections are open weave the next 3 meters are close weave and the bottom is open weave?

I will draw a picture of what I mean and ask Grahan to put a link to it.

Keepnet suitable for barbel, designed by Lee Swords

 

[GrahamM]

I'd also like to add my thanks to Stuart for posting some very eloquent and intelligent messages to this debate.

But I ask, will the best designed, most barbel-friendly keepnet it is possible to manufacture make some barbel anglers change their minds from the inflexible: "NO KEEPNETS FOR BARBEL AT ANY PRICE!"

I think not.

But the rest of us should keep trying and ignore those who can't see past the blinkers.

 

[GrahamM]

Keepnet suitable for barbel, designed by Lee Swords

 

[Bob Roberts]

But Graham, the 'no keepnets, ever' brigade are in such a tiny majority if you think about it.

The Barbel Society represents about point one of one per cent of those who purchase a license and even then not all the membership is quite so dogmatic about that stance.

Now if we renamed them recovery tubes...

I've been musing over what the ideal recovery tube might look like and can't help wondering why tubes are circular and nets rectangular when the logical system for retaining one fish would have a triangular frame.

Now if the base of the frame were heavier than the hollow sides it would always sit upright for a start.

Let's imagine it is, I don't know, 6 feet (does that meet the EA regulations?). The middle four feet might be in a close weave sacking, or this new fangled rubber stuff that's apparently going to make me rich, offering a darkened shelter. The ends could be in an open weave that maximises water and oxygen throughput.

The really clever dodge would be to peg it facing upstream and have a quick-release end, using some kind of a string pull, that forced the end forwards and downwards, hinging at the base so a fish might swim off of it's own accord without further handling by an angler.

When barbel get stuck in nets - and that includes landing nets (a much bigger issue than some would care to admit) - when they are pushed backwards. The serated dorsal spine does not to my knowledge snag on anything when it swims forwards.

And please do excuse me getting a bit giddy over the football earlier. It probably won't happen again for a very long time. Half of Donny is suffering from vertigo this morning!

 

[Dave Lumb]

EA byelaws state that: Tubes must have dimensions of at least 150cm by 30cm by 40cm.

 

[Bob Roberts]

Thanks Dave.

Do current pike and barbel tubes meet this criteria? I presume circular ones would have to be 40cm in diameter.

Lee,

I appreciate that the drawing is a sketch rather than something prepared to scale but on first glance is there not a danger that a barbel might push its head through the slats and become gill netted for want of a better description?

Would it not be better pegged upstream so that a fish in dificulties would be seenat the mouth of the net rather than hidden at the opposite end?

It can then be attended to without having to remove the whole net and slidding the fish back to the entrance.

Not criticising, you are among those with an open mind and who are taking this seriously. I'm just offering possible refinements and further discussion points.

 

[stuart clough]

Interesting design Lee, certainly an improvement on current designs that I have seen. The slats idea might work, but they would need to be carefully sized to prevent fish pushing their heads through. I would also add a ring and a rope to the downstream end of the net, such that when it is being retrieved the fish are cradeled in the soft mesh, not "tipped" down to the coarser mesh in the bottom section (which would then have fins sticking out everywhere!).

Incidentally - I don't think I have used a keepnet whilst fishing for 10 years, and don't plan to anytime soon! But then that isn't really the point, is it.

 

[Big Swordsy :O)]

The slats are part of the weave.Have you seen the dark sacking mesh where there are larger holes amongst a tight mesh? well this idea of mine is similar. The weave incorporats similar holes but they are aranged in such a way as to form interwoven slats where water can pass through easily but they are impassable to fish.

 

[stuart clough]

If you think about it, if the net is going to be already in position when the fish is "inserted" it would make more sense if the opening was in the middle, or even at the downstream end, rather than at the upstream end, as the fish must inevitably drop backwards (risking fin danmage), or turn round (so it is facing the wrong way) to reach the "safe" part of the net.

In this way the fish would have its nose towards the more open mesh, and the flow, and a quick release/hinged front would allow the remote release mentioned by Bob.

My art is crap, but if anyone understands what I am getting at and wants to draw it feel free!

 

[Bob Roberts]

Lee,

Fancy having a stab at drawing the system I've described?

Bob

Stuart,

I rarely use a net either, but my concerns for barbel welfare have grown to such an extent - thanks to various incidents I've witnessed this season - that sensible use of nets would actually be to their advantage, especially if a new design/type of net can be developed.

I cannot remember the last time I had a barbel caught up in a keepnet, probably back in the early eighties when the average barbel we caught on the Trent weighed a matter of ounces.

I've had loads get snagged up in landing nets though.