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Barbel Diet Analysis

Howard Cooke

Senior Member
Dear all,

I thought you might be interested in the attached summary report analysing barbel diet in four rivers: Kennet, Lee, Teme and the Hampshire Avon. The Barbel Society helped fund the scientific analysis (performed by Bournemouth University and Queen Mary University of London). As well as providing funding, the Society also provided scale samples and logistical support. As the summary report explains (although it's still baffling to me!), scale samples were used rather than stomach contents.

The conclusions may not astound folk and if not, it's still perhaps a useful validation of existing thinking and logic especially by those very familiar with these rivers.

https://dub128.mail.live.com/m/mess...b-001e0bcc44e0&attdepth=0&attindex=0&CP=65001

I have also included the link below to another summary of the report (this one is particularly indigestible if, like me, you don't have a science background) and this is also where you can purchase the full report. Copyright issues prevent its full reproduction here or elsewhere.

Angling baits and invasive crayfish as important trophic subsidies for a large cyprinid fish - Online First - Springer

I do think this sort of analysis is important as it adds to our broader understanding of barbel and their environment. If there was more resources available- dosh and the free time of able and willing enthusiasts, then we could of course learn more and do it faster.
 
Cheers for this Howard. I can't access the first link as I need a microsoft account but it was interesting to see that where invasive crayfish aren't present the barbel are reliant on anglers pellet baits, with up to 79% of their food being from this source! If my logic is correct, the fish should be where the bait is going in in copious amounts. The so-called watercraft we are led to believe that is crucial to locating barbel and which we all read about, probably puts us all in the vicinity of overhanging trees, drop-offs and rafts etc where we pile in the bait. Is it the angler that's creating the holding spot for the fish? Nurture v nature ;)

Question: If I were to repeatedly pre-bait a featureless stretch with kgs of pellets over a few weeks or so, would the barbel move in?
 
Hi Anthony- this is the content within the first link:

Are angler baits and invasive crayfish important components of barbel diet in English rivers?

Study completed at Queen Mary University of London and Bournemouth University.

The aim of the study was to assess how angler baits - primarily fishmeal-based pellets - and invasive signal crayfish influence the diet composition of barbel in English rivers. Previous studies have suggested that barbel, whilst being omnivorous, mainly feed on benthic macro-invertebrates, with small fish sometimes taken.

It was completed on four rivers: the Rivers Kennet and Lee, where signal crayfish were present, and the Rivers Teme and Hampshire Avon, where they are largely absent (or at least in very low abundance). Fieldwork was completed in summer 2013, when samples of macro-invertebrates and crayfish were collected from each river (as appropriate), along with scales from angler-caught barbel.

To assess diet composition of barbel, stomach contents analysis was not used. This was because the method tends to be destructive to the fish and can require large sample sizes in order for patterns to emerge. Instead, a method known as stable isotope analysis was used. This uses material, such as fish muscle, fin clips and/ or scales within mass spectrometry to determine their ratios of 12C:13C and 14N:15N. Allied with the same data from their likely food resources (i.e. macro-invertebrates, fish-meal pellets, small fish, crayfish) then statistical models can predict the likely diet composition of the barbel, with associated levels of confidence, on the basis of the differences in the isotopic values between the species. It is an increasingly common method used in ecology.

All of the barbel analysed were 42 to 80 cm in length, i.e. no small barbel were used. In general, fishmeal pellets generally made a large contribution to their diet (up to 59 % in each river). In the Kennet and Lee, crayfish were also an important resource (up to 30 % of population diet). Importantly, the proportion of diet derived from macro-invertebrates (excluding crayfish) was substantially lower. Further modelling revealed considerable variability in barbel diet within each river. In the Avon and Teme, where there were no crayfish, up to 79 % of barbel diet was based on pellets. In the Kennet and Lee, where crayfish were present, they effectively replaced and so reduced the contribution of pellets to individual fish diet.

In summary, the evidence from the stable isotope analyses revealed that from three of the four rivers (Teme, Kennet, Avon), the barbel were heavily reliant (>50%) upon angler-introduced baits, with the River Lee showing that invasive crayfish can also be an important dietary component.
 
What doesn't quite add up is that on rivers where there's a lot of crayfish like the Kennet, you would expect there to have been a population explosion of barbel who get bigger quick by eating them. But, while there are some big lumps about, I don't think anybody claims these days that there are more barbel in the Kennet than there used to be.

Or is it simply a case of the crayfish winning by eating barbel eggs quicker than the barbel can eat the crays?
 
I think your second paragraph is right Steve in terms of recruitment issues. There may well be other factors too of course- otters, floods damaging spawning sites and fry bays etc. Again we simply don't have enough data. We do know that the Kennet is burdened (and quite heavily in places as far as I can tell) and you get a sense of that by just fishing the place and if you ever peek into one of the traps- the evidence is pretty clear.

Otters eat crayfish too of course so weirdly, they might be helping to give eggs a chance! Wouldn't that be a turn up for the books. However, arguably the balance remains in favour of the crayfish despite it providing a food source for the barbel.
 
Astute observation Steve. Perhaps fishery managers could organise serious cray trapping at known spawning sites through May to July end to help address that.

During the analysis did anyone check the breath of the barbel for garlic?
 
Cheers for this Howard. I can't access the first link as I need a microsoft account but it was interesting to see that where invasive crayfish aren't present the barbel are reliant on anglers pellet baits, with up to 79% of their food being from this source! If my logic is correct, the fish should be where the bait is going in in copious amounts. The so-called watercraft we are led to believe that is crucial to locating barbel and which we all read about, probably puts us all in the vicinity of overhanging trees, drop-offs and rafts etc where we pile in the bait. Is it the angler that's creating the holding spot for the fish? Nurture v nature ;)

Question: If I were to repeatedly pre-bait a featureless stretch with kgs of pellets over a few weeks or so, would the barbel move in?

You would have to factor in catchibility of individual fish - its highly likely that some fish are aware of anglers lines etc ( as are carp in korda videos) and either ignore bait that makes them suspicious or possibly eat the pellets when they believe it is safe too e.g. when no lines are in water. Its also highly likely that fish eat more regular at times when they feel safe e.g. pike in margins during dark.

As regards to creating holding spots then yes this does happens but not for all fish and not at specific times. Bream and pike can be very easy to pre bait as can carp sometimes, as for barbel aim not sure.
 
Hi Chaps

While I congratulate Howard on an interesting find, I don't believe these results for a moment!

The percentages just do not add up, I suspect the author found what he was looking for and looked for what he found.

In my opinion Barbel like all omnivores will eat what is available, when it is available, sure some will be dependant on anglers baits when available, but not all will do this.
I fish a section with very heavy stocks of Barbel, it is obvious from captures that many fish are bait dependant (and I assume for the sake of this study "pellets" means anglers bait including boilies), yet many are not, even given very high concentrations of bait going in!
For example I was amazed to find in September that several of the fish I caught had obviously been gorging themselves on Elderberry (the "exhaust" is easy to spot and can stain your hands), these fish had no evidence of "anglers baits" at all, surprising given the amount of bait that goes in on this venue.

Even if we assume these fish are "bait dependant", what happens in the close season, on this particular very heavily populated section that IS heavily fished each and every day, if we assume certain aspects of this study to be correct, on March the 15th (just as the fish NEED to gain weight for spawning), their principal food source dissappears!!!
Yet in June these fish are fat and healthy, despite 3 months of their main food source being absent?

In my opinion Barbel are oppertunisic feeders and that is the main weapon that we can use in our quest, the way that they feed and the the way in which we anglers feed our chosen swims, can, when we can get these two factors to intertwine produce the results that we desire.

This is not always easy, but it IS doable.

Obviously this is NOT the opinion of someone with a PhD in freshwater biology, however I have given this a little thought over the years.

Tight lines gentlemen.
 
Interesting Keith and demonstrates the difficulty of accurate analysis. Ideally, we would want to see more analysis across more rivers and over a greater time span. Many people viewing the analysis simply regarded it as an obvious conclusion, but perhaps not appreciating the extent to which the fish relied on angler's bait.

I don't readily see how the results can be disbelieved, other than by successfully challenging the validity of the science behind the analysis. Certainly the conclusions in terms of what this tells us about barbel behaviour etc. are quite appropriately there for debate.

Keith-I'm not sure that it is scientifically robust to conclude that many barbel in the heavily stocked section you mention do not rely on angler's bait simply because you have caught fish that have clearly fed heavily on elderberry. How do you know that they are not also feeding on angler's bait and do elderberries provide all the protein and other nutrients required by barbel? Are elderberries more nutritious than, say, hemp? I ask because it has always been my understanding that hemp is an effective loose feed because of its ability to attract barbel and encourage them to feed, without actually filling them up in a way that angler's high protein baits might.

In terms of fish caught in June, I would welcome opinions from others on this. When I have caught barbel in June it is generally post spawning and they are typically regarded as "empty".

I would certainly agree that barbel are opportunistic feeders and quite naturally they will gravitate to food sources that provide what they need for minimal effort and danger. Anglers baits-especially free offerings, would generally fulfil this requirement. If angelr's baits are not present then doesn't this simply mean that barbel might need to work harder to obtain the food they need?
 
Hi men ,

Howard , I to am scratching my head a bit . Take as an example the Teme , on stretch where me and sue fished exclusively for 3 seasons ( other than the very odd visit from at most a couple of anglers each season ) see no angling pressure at all , and our little bag traps were nothing compared to the whole seasons feeding activities , the percentage of pellets going in on this stretch compared to the natural food larder possible would not show up at all ?.

A second stretch downstream that had a few anglers turn up on the opposite bank ( not many tbh ) , and the zero amount on our bank other than me , Sue and James with our little bag traps could have seen more anglers pellets , but still as the first stretch, im sure not enough for the barbel to rely on to the percentage quoted . So what im saying is , are the results reprosentive of a section of the river , rather than it from its viable fishing lengths ?.

All very interesting stuff though mate ,worth reading , and I will have to read it all again ;) . The crayfish problem is a real concern for all , I spoke at length with a couple of people doing a study of them in a Oxfordshire river , and their view was that there is almost no way of controling them , other than " arking " , where all life is eradicated from the water in question , and started again , not an option then !. I asked about crays in the Teme , as we was fishing it at the time , and they thought it might not suit them , and they might not thrive in that type of enviroment . They also said the effect on the banks of the Teme if they did could be bad , with burrowing and bankside erosion a real possibility , which on that river could change it for the worst.

Regards the food fish eat , im always guarded with studies , as with the often quoted otter study where they seemed to like eels , where in fact the study was only done on a game river with eels being realy the only large food sorce .

Hatter
 
I am not sure about the Teme Mark in terms of where the scales came from but could find out more from Pete. People can acquire the detailed paper which is published now after being peer reviewed. As I have said before, with more resources then more extensive studies can be carried out and over longer time spans to give us more accuracy and insight.

There have been some good observations made on Facebook too and in particular that overseas, the use of scales for diet and other analysis is fairly commonplace. There is also a debate about whether or not barbel are physically capable of eating (mature) crayfish. However, plenty of folk are saying that in their experience-they absolutely can.
 
What is interesting is the fact that during the back end, when there have been far fewer anglers on the bank for months, the fish (and I'm referring to most species) have all put weight on.

Elderberry boilies...



now there's a thought!
 
Hi Howard, I hope you are well?

With regard to my post, I do not question the science behind the study, merely the way the science was applied, science is oft subject to theories, these can change and the same science can both prove and disprove, one or an alternative, after all science proved the world was flat, that machines could absolutely NOT fly faster than sound and that we are absolutely alone in the universe.

My doubt comes not from a scientific point of view but more from practical experience and the fact that the author considers such high values in Barbel being reliant on anglers baits?????

I am afraid this I take with a huge pinch of salt, yes I believe this may be the case on some waters, some of the time, where pellets Etc probably are a good source of food, but not for all fish and definitely not all of the time.

The water I mentioned has an unbelievably high biomass of Barbel, as I stated it is fished every day and a huge amount of anglers bait goes into this fishery.
In this case I concede many of the fish will, for a large percentage of the time be reliant on anglers bait, yet this very water is also a place where some of the fish show a typical fight or flight reaction to certain baits, it is not the only place I have seen this, I remember fishing on the Kennet many years ago when luncheon meat was the "In" bait.
When cubes of meat were introduced in popular swims the Barbel would instantly "spook", yet the very same Barbel would confidently take a similar bait when residing in un-fished sections of the river!
We considered that it was not only the bait but its location that provoked these different reactions.
Barbel like all wild creatures act by instinct, this instinct has a default setting (which applies often to humans too), they need to feed, so they will take the maximum nutrition, with the minimum of effort, as long as they feel safe in doing so !!
Consider a McDonalds in America, then consider the same McDonalds when a man with an assault rifle walks in!!

In the case of the Elderberries, the Barbel in question may have been afraid to munch on pellets, my presentation of the other baits I used that day may have simply been wrong, they may have been pre-occupied on the berries because of a seasonal glut, or they may just have been sick to death of eating pellets (I would love to eat at The Fat Duck every day, but I suspect I would soon long for a home made cheese and beetroot sarnie).
Barbel can and will, eat many things, the very reason there are sooooooo many Barbel in this particular section of river is NOT because of angers bait, but rather because we, that manage the fishery, have a very good handle on habitat development and management, we put in place exactly the right conditions for habitat development.

We narrowed the river with flow diverters, this increased the flow and produced clean gravel, behind the diverters silt deposited, we utilised this silt by planting Yellow flag on the angling bank and Reeds on the opposite bank and we removed the overhanging trees to ensure maximum use of light.

With more flow came more oxygenation, the planting exploded and crossed the river creating large overhangs of reed and flag, producing large areas of sanctuary, the more light produced water weed growth, which promoted an explosion of invertebrates.

These conditions were taken into account by the fish and their populations increased exponentially, today we have a fishery that has large populations of every river species, in fact, although it is famous for its Barbel and Chub in actuality the other species like Roach and Dace, Gudgeon and Perch grow to sizes that are much bigger as a percentage of the record, than the Barbel and Chub.
This fishery produces many Barbel, despite the enormous pressure put upon them and these Barbel grow to a fair size, yet the bigger fish are extremely difficult to catch AND are extremely difficult to get to take ANY anglers bait.

The venue record is around 12lb, yet my friend Dave and I spent an afternoon (laying on our chests, peering over the edge of a swim), watching some of the larger Barbel taking small amounts of Hemp that we were introducing, slowly, very slowly, several other bigger fish moved out from the other bank cover to move in on the Hemp, these fish were as spooky as hell, but with perseverance we got them to come and feed every now and then, we estimated these fish to be about 12lb.
After an hour or so two other fish of 14 to 15lb, crept out took a sample of the Hemp and moved back into cover, they did this several times and Dave and I were discussing in very hushed tones how we could possibly target such spooky fish.
Even after these fish had established that the feed was potentially safe they would take about 15 mins to come back out to take a little feed, when it had been introduced (by laying on our backs throwing it over our heads from behind cover), eventually an other angler walked across the field behind us and the fish melted away, never to come back.

My suspicion is that these large fish do not rely on anglers baits at all, yet they are obviously eating something!

To conclude, it is for these reasons that I do not give this latest study much credence, I concede my argument for this post only mentions one very un-usual fishery, I could site more, but time is against me and my dog is sitting with his legs crossed, also it is not a fishery I spend much time Barbel fishing on, as, to be honest, the size of the fish is not big enough to interest me much, but that said I honestly believe this water, although remarkable is not a-typical of other less highly populated fisheries.

I do not know just how long this study took, but I suspect, I have studied this subject for longer and I try and do this with an open mind, I have few fixed theories and these I will change in a heartbeat when I see evidential proof!!

Howard, we were going to have a day out on the Kennet, it would be great to do this and have a catch up!

Tight lines mate.
 
This thread has provoked the most fascinating discussion for a long time and I am grateful to all contributors.

What puzzles me is, if barbel are not dependent on anglers' baits, why do so many of the largest barbel have fat 'boillie bellies' ? Like the massive carp they have little resemblance to the natural, wild fish.

Regards,

Hugo

 
Hi Ian

Perhaps with the introduction of high volumes of highly nutritious bait, which in the case of most pellets and some boilies breaks down easily in water, the Barbel feed on those creatures that feed on the broken down baits?
Certainly those creatures (invertebrates and the like) will become extremely plentiful if the bait is a regular feature throughout the season.

Barbel will already be hard wired to feed on these as they have done for thousands of years?

I think this is possibly what Barbel in some fisheries may rely upon, certainly Carp in many fisheries do!

Discuss??


Tight ones,

Keith
 
I wonder if they tested any (dare I mention?) still water barbel to see what they'd been eating? I suspect not, although they would be interesting as a control group especially where boilies are banned and 'fishery only pellets' are the order of the day.

P.S. Keith, you need to make some space available in your mailbox.
 
Hi Keith and thank you for the further perspectives, it's interesting analysis this. The scientific work has some natural limitations in its ability to reveal a broader story and that is simply because it is based on results taken at a certain point in time and on a small handful of rivers. However, these are rivers that are, I would say, fished regularly for barbel so do see the a fairly consistent level of attention from anglers and their baits. I think we should respect the results of the study as being accurate based on the scale samples acquired and scientific methods used. However, this does not mean to say that the conclusions reached will play out in exactly the same way on all rivers- as your own experience demonstrates. The diversity of our river systems might well offer up a diverse range of results.

I do think that many people would contend that angler's baits have had a profound effect on barbel growth rates- some have argued detrimentally so. I think I am right in saying that the British record barbel stood at around the 14lb mark for well over a century- originally a fish from the Thames (?) and then the Hampshire Avon. Baits, I suspect would have been naturals-maggots, worms etc. We then move to a period of great change in both the methods used and the introduction of HNV baits such as pellets etc. Of course these pellets were used in fish farming to accelerate and increase the growth rates of game fish so we shouldn't be surprised by their impact on barbel when used extensively across many rivers. And then there are boilies- a bait used with increasing regularity as barbel fishing popularity has exploded over the last two decades or more.

It must be difficult to argue against the notion that the steady rise in barbel weights over the last 20 or so years correlates to this material increase in barbel fishing popularity and the extensive use of pellets- often in extraordinary quantities. Unless of course it is possible to point to another event or events whereby natural food sources have become abundant and nutrition rich when compared to previous levels. I'm not sure if a study has been performed that analyses the average amounts of free baits (loose feed, ground baits and so on) deposited in a river during an average fishing session, but just based on what I have witnessed I can only imagine it's significant. Certain bait companies have themselves grown fat on the profits from the sale of pellets.

I think it was Fred Crouch who wrote about the effect of angler baits on the Hampshire Avon, I believe back in the 70's. Barbel weights had been on average fairly constant with fish in the 4lb-7lb range being caught with the odd larger specimen. The main bait used was maggots where gallons could be used but their relatively low nutritional value meant that barbel could happily work through all that anglers offered. Then maggots were banned and more and more anglers turned to using meat, often rolled through the swim. Many pieces of meat could have been used before a fish was hooked thereby leaving many free offerings for the barbel to enjoy. Over the subsequent seasons it was noted that the average size of barbel being caught was increasing markedly on the river.

Personally, I am not sure that anyone has performed detailed scientific research explaining the increase in barbel weights over the last 20 years or so. However, I think many people would place a firm bet on the link to angler's HNV baits. But that isn't to say that this would be the precise answer on every river in the country but logically, it has to play a significant role on many.

This latest study arguably provides some scientific validation of that theory. On my own river, the Kennet, I felt no jolt of error in the results presented because of how I and countless others fish this river. Other factors could well be at work to distort matters further on different rivers such as the changing biomass of barbel stocks within a river system, caused by predation, recruitment or water quality.

Generally speaking I do think it is important that we all get behind research work such as this as well as other initiatives that seek to gather data and insight. That doesn't mean that the outcomes shouldn't be debated in a healthy and measured manner. I think we can forget the great gift we anglers have as a collective to advance our knowledge and understanding of our beloved fish and their environment and do so for the greater good and to protect fishing as best we can for future generations. Sadly, we do seem to spend disproportionately unhealthy amounts of time arguing amongst ourselves and often over the most trivial of things.

I would dearly love another days fishing with you on the float but after reading the description you have given of the stretch you help to manage, I would prefer to come to you!

All the best.
 
I wonder if they tested any (dare I mention?) still water barbel to see what they'd been eating? I suspect not, although they would be interesting as a control group especially where boilies are banned and 'fishery only pellets' are the order of the day.

P.S. Keith, you need to make some space available in your mailbox.

Barbel in commercial lakes where matches take place gorge on everything that goes in and the majority of bait going in is made up of pellet.

I've fished a fair few matches and seen a fair few Barbel get caught and its mainly pellet, meat and maggot they get caught on and its normally down the edges they patrol and move into once the bait goes in.

The fish I've seen always seem to be in good shape, long and lean and fighting fit.

I know of a stretch of river (stream really like all the upper sections, Keith will more than likely know of) stuffed with small Barbel up to about 6lb and its rarely gets fished and no one manages it and its in a natural state as its been for years.
 
Its a good thread this one isnt it, my view on this one is that it would need a greater degree of detail on the study side,

for me its like walking into a pub full of smoke, not nowadays but back when, you came out smelling of smoke, not because you'd been smoking but by being in the environment you were a passive smoker,

translate this to the smoke being the pellets and the pub being the river / water and the barbel have not choice once dissolved what ends up in the bellies, whether thats from pellets boillies etc but if a bait is water soluble then its bound too happen, eg when bait is going in they are constantly exposed / feeding on it whether in its solid form or not

Or am I way off the mark????
 
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