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Why are many species of fish growing much bigger?


Guest Steve Burke

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Guest Steve Burke

There's no doubt that some species of coarse fish, notably barbel, carp, bream and tench are growing much bigger than in years gone by. Why do you think this is? is it the same reason for all these species?

 

This is just the sort of topic where many heads are better than one. Before I put my own points of view forward I'd be interested to hear what others think.

 

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Wingham Fisheries

http://www.anglersnet.co.uk/fisheries/wingham.htm

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Guest Alan Pearce

Well it certainly isn't bait Steve, least not on a pit I'm tench fishing. Hardly ever been fished and only two of us fishing there at present. Average size of the fish we are catching over 8lbs, mind blowing. With the exception of heavilly fished/baited carp waters where other species also grow big, it has to be something environmental, Steve Hacketts the man to ask/reply.

 

Alan. smile.gif

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steve,

purely speculation, but could it be climate change? not neccisarily global warming, but a natural flucuation in temprature that changes from century to century or decade to decade? confused.gif

eek.gif

 

 

with our more advanced tackle these day's hooking and landing larger fish is surely getting easier. more bait is going in(in most waters/fisheries), and unhealthy trout pellets are being replaced with healthier specialised carp pellets. confused.gif

eek.gif

 

 

could a combination of these factors be an influence on fish size? confused.gif

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Guest Zaphod

I have read articles suggesting that it is to do with HNV baits. I do not think that this can be so. Carp anglers have been using these baits since the early 70's, and I know that more freebies go in now, but the ammount needed to feed, say 50 20's over a year would be phenomenal.

 

I dont know why they are getting bigger, but I'm not complaning..!!

Long may it continue, a 20lb Tench, Oh suits you sir..!

 

 

 

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Zaphods just 'zis guy, you know..!

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Guest Bruno Broughton

If I had a £ for every time...

 

Notwithstanding bait, temperature changes, better angling techniques and the many other theories, the underlying reason is quite simple: eutrophication. (Stay with me - it will become clear).

 

 

In the late 50s and early 60s, the pattern of agriculture in Britain underwent a major and crucial change. Away went crop rotation and the custom of leaving fields fallow between crops; in came intensification of agriculture, the increased use of all types of fertilisers and - importantly - land drainage schemes on many river catchments.

 

Fertilisers applied to the land make land plants grow; when they enter bodies of water, they work in just the same way... but water plants benefit.

 

This process of enrichment (or 'eutrophication') may occur quite quickly, but often it taken many years before the concentrations of the key nutrients - phosphates and nitrates - build up sufficiently to 'fuel' additional plant growth. Once they do, the consequences are inevitable and irreversible.

 

The growth of water plants can be at either end of the spectrum, giving rise to either (i) lots of rooted plants (Candian Pondweed, Water-milfoil and the like), with clear-water conditions, or (ii) algal growths, causing vast beds of filamentous algae 'blanket weed' or 'silkweed') or suspended algae, which case the water to turn green or greeny-brown during the summer months.

 

More plants provide food for more invertebrate animals and - thus - more food for fish. Where fish numbers are restricted (naturally or by design), each one get more food and (to use the jargon) "achieves its biological potential". That is, they grow like stink!

 

Where fish spawn successfully or stocking enhances the biomass, more fish can be sustained than was the case in yesteryear, albeit that each one may not necessarily be larger.

 

The role of land drainage? Enriched water now runs off the land very quickly, entering watercourses and bringing with it the nitrates and phosphates that the plants need.

 

Depending on your viewpoint (in the conservation movement eutrophication is generally regarded as a "bad thang"), it is predictable that weed problems will keep increasing in many fisheries... and maximum fish sizes will continue rise.

 

This is written after yet another day applying weedkiller to a lake, one of seven such jobs I have undertaken in various parts of Britain in the last two weeks.

 

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Bruno

 

[This message has been edited by Bruno Broughton (edited 17 June 2001).]

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Guest glyn llewellyn

hi steve

 

is it possible that because winters are milder thus being shorter, fish do not use up the energy they have stored for the winter.

 

so when they start to feed the next season they retain some body weight.

 

if this happens over a few years they would increase in size above the average.

 

catch ya later glyn

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Guest Elton
Originally posted by Alan Pearce:

Well it certainly isn't bait Steve, least not on a pit I'm tench fishing. Hardly ever been fished and only two of us fishing there at present. Average size of the fish we are catching over 8lbs, mind blowing. With the exception of heavilly fished/baited carp waters where other species also grow big, it has to be something environmental, Steve Hacketts the man to ask/reply.

 

Alan.   smile.gif

 

Alan,

 

Is this place local to us both? wink.gif

 

All the best,

 

Elton

 

 

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Guest trent.barbeler

Chris,

Eutrophication as Bruno Broughton states is wholly responsible for the rapid rises of weed growth in some stillwaters but that does not necessarily come hand in glove with rapid rises in fish growth.

 

I know of many instances where rapid rises in weed growth in some stillwaters that have not resulted in fish stocks growing above their usual weights.

 

On the other hand, I know of waters that have not hardly any weed growth at all but are experiencing rapid weight rises in their fish stocks. More noticable are known carp for instance that have suddenly grown far above expectatons. These waters are also not heavily fished so anglers bait does not form part of the equation.

 

Conservationists, English Nature being a prime example, embrace all this new found aquatic plant life but that aside such growth is no good from an angling point of view. I once undertook a Draft Management Scheme with English Nature on a SSSI site and had the devils own task of getting them to allow me to cut back copious amounts of common reed that was slowly choking the fishery.

 

Eutrophication may be part of the reason but from what I have witnessed, this may only be part of a larger picture.

 

On the subject of rapid or unusual fish growth, I have read no papers based on any lengthy scientific research myself. I would be very interested if any had been done though.

Perhaps Bruno or Steve know of such research?

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Guest Steve Burke

I was hoping this would get Bruno to answer and Bingo! Any thoughts on the gravel pit feeding times topic, Bruno?

 

I agree with Trent Barbeller that it's unlikely to be a single factor that's the cause. All of those reasons mentioned so far (thanks everyone) could be factors.

 

However, having discussed this many times in the past, I'd go along with Bruno's answer of eutrophication from farming being the main cause. BTW, doesn't sewage also have the same effect?

 

Trent Barbeller mentioned waters that haven't had extra weedgrowth that are growing bigger fish. Lee, have these waters changed in any other way? For instance decreased water clarity caused by increased algae (eutrophication again!), a change of dominant species, or even pollution?

 

I also agree that bait isn't the main factor, even if it's a contributory one. I know of several waters that have hardly been fished for years but are now throwing up much bigger specimens.

 

Tony Miles has in the past put forward the interesting idea that perch disease is responsible, at least for the increased weight of tench. His idea is that tench have been best suited to fill the vacuum left by the perch. This is one of the few times I'd disagree with Tony, as he may not be aware that perch disease is not a modern problem but has been with us since at least Victorian times.

 

Please keep those ideas coming as I find this subject fascinating. Quite apart from anything else it may help us to find waters with incredible big fish potential! smile.gif

 

Assuming euthrophication is a major factor how long will the effect last? Nitrates and phosphates from fertilisers and sewage leach through the soil and eventually get almost everywhere. However, I gather that it can take years to do so.

 

Therefore might the effect be coming to a maximum? In which case will growth rates have peaked? Has anyone got any data on the subject?

 

 

 

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Wingham Fisheries

http://www.anglersnet.co.uk/fisheries/wingham.htm

 

[This message has been edited by Steve Burke (edited 18 June 2001).]

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Guest trent.barbeler

Steve,

 

In answer to your question,

Most of the waters that I mentioned containing little or no weed growth where some of their fish have grown above the norm have seen very little change.

 

Like yourself, I am facsinated but mostly puzzled by some of these occurences.

 

From an angling point of view, I can remember some years back when I sat on the committee of a local club, I drew the committies attention to a forthcoming problem that could have arose from Canadian Pond Weed starting to show up.

 

Bruno knows this water well. He once photographed a big pike for me there. He will testify that apart from a large bed of Bistort, this particular water had no weed problem at all in the years when he fished there.

 

This particular water is typical of a number of mysteries.

 

The committee of that time refused to hear my concerns even after I presented them with various papers written on the subject of nitrates being responsible for rapid aquatic weed growth. Indeed, Bruno was one of the authors of those papers.

 

The committee's arguement was that because the water in question was surrounded by intensely farmed land and that they had never had a promblem from weed before, I was basically talking bunkem!!

 

Imagine that when I had gone to the trouble to gather evidence during my short time as a IFM member in the hope that my revelation would benefit the club before things got out of control.

 

At the time, very little expence and effort was required to keep on top of what was a fairly small problem.

 

Now, the once weed free margins are clogged with Bistort to about 10 yards out and the whole 28 acre lake is clogged with Canadian Pond Weed and Water Milfoil.

 

Interestingly, when their was no weed problem, the carp grew fat and gained weight year on year. Anglers bait was probably part of this scenario because this was a very popular venue for carp anglers. But; when one considers the amount of double and twenty plus pound carp in the lake (over 500 carp) then anglers baits seem to be irrelevant to the fishes diet one would assume.

 

In this lake, there were massive bloodworm beds. It was normal when fishing in certain locations to drag back many bloodworms after reeling in on the bare hook if one was hair rigging baits.

 

Strangely, when the weed growth started to get worse, a lot of known carp began to loose weight. These fish were still healthy but previous weight gains were lost as the weed got worse.

 

It could be of course that the food chain changed when the weed became so prolific. To be honest, I dont have the answers.

 

One thing is certain though, if that blinkered committee had taken serious notice of the evidence that I presented, they would not have the massive problem that they have today.

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