Global warming and fish size.

markg

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I seem to remember a long time ago reading that tench had increased in size due to a longer feeding period and more food availability down to longer hotter summers. My vague minds eye impression is that coarse species have got bigger in my lifetime although, possibly not more numerous. I seem to read about more 10lb, 12lb even 16lb + more barbel than I ever did. Roach seem to be fairly common over a 1lb than I ever remember. Big dace and perch, not as uncommon as they once were. I think the record bream is topped by 20lb+ fish, I would never had thought that possible once upon a time.
I don't have any facts just my general impression, if I am right and this is down to global warming, what happens when it all stops and goes into reverse, will it get colder and this trend will be reversed, will we be wondering one day where all the big fish have gone.
 

Keith M

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will it get colder and this trend will be reversed, will we be wondering one day where all the big fish have gone.
We will probably be blaming (rightly or wrongly) the lack of big fish on the Otters :wh:)

Keith
 

peterjg

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Markg, re your post. I suppose if with global warming there is a longer feeding period then lots of species should grow bigger. However, I now catch fewer 1lb plus roach than 30 years ago but perch are much bigger.
 

Keith M

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Markg, re your post. I suppose if with global warming there is a longer feeding period then lots of species should grow bigger. However, I now catch fewer 1lb plus roach than 30 years ago but perch are much bigger.
I know it may be taking our climate change a little too far but have you thought that as the water temperatures start to get higher and higher the less oxygen it will hold (fact) and the less oxygen there is in the water the less the fish would probably feel like feeding and therefore not putting on as much weight?

Plus the low levels in our rivers and stillwaters could become more of a permanent feature in a warmer climate and that can’t be a plus factor either.

How many times have you fished during a heatwave where the only thing that seems to move in the constant heat are fish basking and gasping for air?

And the reason that the Perch seem to be getting larger could possibly be because it’s prey is becoming a little more lethargic during the hotter days and becoming a little easier to catch in the sweltering heat?

Climate change may not all be plusses.

Just a thought.
 
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john step

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Lots of variables in this. Fish bigger by eating crays? Some species getting bigger as stated having longer feeding seasons? We may be catching up to what the more southern European countries were 30 years ago with regard to carp. More 1lb roach that in reality are mainly from commercials with plenty of grub going in?
I just wish I had another 70 years to see it through!
 

sam vimes

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The biggest factor I see, at least in the less managed fisheries, is the lower heads of fish being a contributing factor. A distinct lack of smaller fish, or gaps in year classes, allows existing fish to get bigger than they might otherwise. The snag with this is that once the big fish die off, you aren't left with a great deal. The monster Great Ouse barbel would be a fine example.
 

markg

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Thanks for the replies, I like to just ask what others think sometimes. All these climate change announcements lately just got me thinking about what happens after if the desired effect is achieved. No one ever seems to talk about that. I quite understand why we don't want it to get any hotter but do we want it to get colder. I take into account there are many reasons why fish may have got bigger but, at least part of that may have had something to do with since warming began especially in the last 50 years or so. If green house gas levels are reduced to the same levels as circa 50 years ago are we going to get the same weather of 50 years ago IE winters of 63 and 47. And how is the flora and fauna going to cope with that after it has adjusted itself to present climate conditions. In the case of fish it must have some affect if bigger sizes has at least in part been due to longer hotter summers. If zero emissions is achieved is the world going to become extremely cold?
There doesn't seem to be any plan, talk, or any thought into how much green house gas should be reduced by and what it will lead to; the affect it will have on our lives, economies and flora and fauna.
 
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Keith M

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Thanks for the replies, I like to just ask what others think sometimes. All these climate change announcements lately just got me thinking about what happens after if the desired effect is achieved. No one ever seems to talk about that. I quite understand why we don't want it to get any hotter but do we want it to get colder. I take into account there are many reasons why fish may have got bigger but, at least part of that may have had something to do with since warming began especially in the last 50 years or so. If green house gas levels are reduced to the same levels as circa 50 years ago are we going to get the same weather of 50 years ago IE winters of 63 and 47. And how is the flora and fauna going to cope with that after it has adjusted itself to present climate conditions. In the case of fish it must have some affect if bigger sizes has at least in part been due to longer hotter summers. If zero emissions is achieved is the world going to become extremely cold?
There doesn't seem to be any plan, talk, or any thought into how much green house gas should be reduced by and what it will lead to; the affect it will have on our lives, economies and flora and fauna
.
There have always been natural fires and volcanoes since the year dot which until now haven’t been a real problem; and there are still going to be natural fires and a few people living in remote places burning natural fuels like wood & coal etc. so I can’t see zero emissions ever happening realistically; although getting as far down in emissions that we can; without any unnecessary adding to it; can’t be a bad thing surely our Ice Caps might start to return, and climate changes might slow down, and the hole in our ozone layer may reduce or close up again.

Whether our coarse fish would get smaller or not wouldn’t be a real issue as most of our larger fish would be lying on the bank with their eyes and throats eaten out by predators that us humans had decided to re-introduce well before then :wh:bolt:

Keith
 

Philip

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As a few have suggested I dont equate warmer tempreture automatically to increased fish size. In some cases I would expect the opposite to happen. Also with warmer tempreatures we would see other species begin to populate and perhaps impact some of the species we have now. Two examples I would expect to see more of if tempreatures went up would be Black bass and Catfish as well as explosions of fry leading to stunted stock on some waters.

Obviously its a complex thing with allot of variables but higher temps dont always mean bigger fish imo.
 

daniel121

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OK Tench got bigger with the large gravel pits and the high protein bait carp fishermen was spodding in and Roach for my money have shrunk, certainly in my local rivers anyway.

I'm just going to chuck a question out because why not eh? Have fish got bigger or are we just better at catching larger fish due to technology advancements?
 

Philip

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I'm just going to chuck a question out because why not eh? Have fish got bigger or are we just better at catching larger fish due to technology advancements?
I would say the growth of specialist angling has certainly played a part and tackle advancements are part of that. Plus we are now catching the same big fish over and over again giving an unrealistic image of how many big fish are actually out there.
 

Hogweed

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Thanks for the replies, I like to just ask what others think sometimes. All these climate change announcements lately just got me thinking about what happens after if the desired effect is achieved. No one ever seems to talk about that. I quite understand why we don't want it to get any hotter but do we want it to get colder. I take into account there are many reasons why fish may have got bigger but, at least part of that may have had something to do with since warming began especially in the last 50 years or so. If green house gas levels are reduced to the same levels as circa 50 years ago are we going to get the same weather of 50 years ago IE winters of 63 and 47. And how is the flora and fauna going to cope with that after it has adjusted itself to present climate conditions. In the case of fish it must have some affect if bigger sizes has at least in part been due to longer hotter summers. If zero emissions is achieved is the world going to become extremely cold?
There doesn't seem to be any plan, talk, or any thought into how much green house gas should be reduced by and what it will lead to; the affect it will have on our lives, economies and flora and fauna.
We can only reduce output. Limiting Green house gas emissions will not reverse warming. After several centuries maybe. But unless someone invents a way of capturing the gases already in the atmosphere we will have to wait for nature to absorb them naturally, which will take centuries. The target of reducing emissions to 20% of 1990 levels by 2020 and the other targets for 2030 etc (1990 because this is when it was first considered a problem) will only limit the amount of warming. It is still going to happen but hopefully the effects will be manageable if this target is met.
 

keora

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Thanks for the replies, I like to just ask what others think sometimes. All these climate change announcements lately just got me thinking about what happens after if the desired effect is achieved. No one ever seems to talk about that. I quite understand why we don't want it to get any hotter but do we want it to get colder. I take into account there are many reasons why fish may have got bigger but, at least part of that may have had something to do with since warming began especially in the last 50 years or so. If green house gas levels are reduced to the same levels as circa 50 years ago are we going to get the same weather of 50 years ago IE winters of 63 and 47. And how is the flora and fauna going to cope with that after it has adjusted itself to present climate conditions. In the case of fish it must have some affect if bigger sizes has at least in part been due to longer hotter summers. If zero emissions is achieved is the world going to become extremely cold?
There doesn't seem to be any plan, talk, or any thought into how much green house gas should be reduced by and what it will lead to; the affect it will have on our lives, economies and flora and fauna.
The world's churning out increasing amounts of carbon dioxide and we will never be able to reduce atmospheric temperatures to those experienced fifty years ago. The most we can do is try and reduce outputs of carbon dioxide so that the earth warms up at a slower rate. This isn't easy to do - wind power and solar power are only used because they receive subsidies, which are paid for by the tax payer. Developing countries such as India and China will continue to burn huge quantities of coal to generate electricity. Their view is that the west used coal for energy after the industrial revolution and they are only doing what the west did in the past.

There is in fact lots of talk about the level by which greenhouse gases should be reduced. There was a meeting of many nations in Poland last week to discuss greenhouse gases and climate change.

Britain itself is committed to the Climate Change Act 2008 - see the summary from Wikipedia below.

"The Climate Change Act 2008 is an Act of the Parliament of the United Kingdom. The Act makes it the duty of the Secretary of State to ensure that the net UK carbon account for all six Kyoto greenhouse gases for the year 2050 is at least 80% lower than the 1990 baseline, toward avoiding dangerous climate change."

The idea of the act was that Britain would lead the world in reducing carbon emissions. But it's not happened. No other country has adopted such extreme targets -its too expensive. And Britain itself will have great difficulty in reaching the targets.

The effect of a warmer climate on UK fishing is that warm summers will enable more coarse fish fry to survive, and fish may grow larger because the summer lasts longer. The downside will be that rivers will be affected, as they were this summer, by droughts, low flow rates and excessive temperatures.

Trout fishing may be harmed by long hot summers as generally they prefer habitats with lower temperatures
 
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Mark Wintle

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Anything done by the UK to reduce greenhouse gases has so little overall effect as to be pointless and so far has actually increased pollution and raised the cost of living. Our total is something like 2% of the overall total and if we reduced our output to nil the effect overall would not be measurable ie it would be so small to be well within the margin of error. The main greenhouse gas is actually water vapour not methane or CO2.

I don't think temperature is the main factor in explaining the huge difference in size of a number of species compared to the past; there are other factors. Roach and dace seem to be of similar size but bream, carp, barbel, chub and tench reach sizes unimaginable 50 or 60 years ago.
 

keora

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There's a number of factors which have caused the maximum size of many of our coarse fish species to increase. Warmer weather is one. Another one is predation by cormorants, which have reduced fish stocks in many waters. For the few fortunate fish that survive, there will be less competition for food so they'll grow bigger.

And modern angling techniques are highly effective. We now have more time to spend fishing, we don't need to rely on public transport. Elaborate methods have been developed to catch more and bigger fish. Developments in high nutrition baits have had an effect on fish size, especially when large amounts of boilies are introduced into waters. Hasn't the Record Fish Committee rejected a few carp because they were considered to have been artificially grown to near record weights before being released?
 
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markg

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Personally I think David At-em/scientists are barking up the wrong tree. There are over 1 billion cars today, there were less than a million 100 years ago. That's half a billion on the road at any one time with an average surface temperature 200f. A surface area of 2 sq-yds multiplied by 200f multiplied by 1/2 billion going at it 24/7. The rise of the motor car corresponds nicely with the rise of global temperatures, and greenhouse gases or not, all that heat would still be trapped by the earths atmosphere. Then there's a billion fridge motors going at it and loads of other stuff. Investing money in technology to cool all this stuff down might be better spent than on gas.
What really bothers me is I never see this quantified in their scientific calculations, I mean I don't really know myself but you would think it must be important when calculating the rise of the earths temperatures. I have read many articles by the worlds best and most respected scientists and climatologist in the Geographic magazine which I get every month and never a mention.
 
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Hogweed

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Personally I think David At-em/scientists are barking up the wrong tree. There are over 1 billion cars today, there were less than a million 100 years ago. That's half a billion on the road at any one time with an average surface temperature 200f. A surface area of 2 sq-yds multiplied by 200f multiplied by 1/2 billion going at it 24/7. The rise of the motor car corresponds nicely with the rise of global temperatures, and greenhouse gases or not, all that heat would still be trapped by the earths atmosphere. Then there's a billion fridge motors going at it and loads of other stuff. Investing money in technology to cool all this stuff down might be better spent than on gas.
What really bothers me is I never see this quantified in their scientific calculations, I mean I don't really know myself but you would think it must be important when calculating the rise of the earths temperatures. I have read many articles by the worlds best and most respected scientists and climatologist in the Geographic magazine which I get every month and never a mention.
I think the heat from a car pales into insignificant when compared to the heat from the sun. I've seen reports that say the sun delivers more energy in 1 hour than the total energy consumed in a year by the entire world.
 

markg

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I think the heat from a car pales into insignificant when compared to the heat from the sun. I've seen reports that say the sun delivers more energy in 1 hour than the total energy consumed in a year by the entire world.
Is that the heat from the suns surface or once its reached the earth's surface? What is it, an average temperature of 59f over half the earths surface in comparison to a billion sq/yds at 200f, is it that insignificant not to be included in calculations for the earths overall surface temperature?
 
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Hogweed

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Is that the heat from the suns surface or once its reached the earth's surface? What is it, an average temperature of 59f over half the earths surface in comparison to a billion sq/yds at 200f, is it that insignificant not to be included in calculations for the earths overall surface temperature?
That's energy at the earths surface. It is significantly higher in the upper atmosphere and at source the energy is beyond imagination. Only a billionth of the sun's energy gets as far as the Earth. If you are going to include heat from cars in the equation why not add the heat from houses?

The heat created within our atmosphere is small in comparison to that from the sun. If we all stopped using cars and heating our homes tomorrow the planet will carry on warming up because of the greenhouse gases already in the atmosphere. It is the gases that are the problem.

I'm sure that of the 1000's of climate scientists looking at this issue they would have thought of heat from cars etc if it was at all relevant.
 

keora

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Personally I think David At-em/scientists are barking up the wrong tree. There are over 1 billion cars today, there were less than a million 100 years ago. That's half a billion on the road at any one time with an average surface temperature 200f. A surface area of 2 sq-yds multiplied by 200f multiplied by 1/2 billion going at it 24/7. The rise of the motor car corresponds nicely with the rise of global temperatures, and greenhouse gases or not, all that heat would still be trapped by the earths atmosphere. Then there's a billion fridge motors going at it and loads of other stuff. Investing money in technology to cool all this stuff down might be better spent than on gas.
What really bothers me is I never see this quantified in their scientific calculations, I mean I don't really know myself but you would think it must be important when calculating the rise of the earths temperatures. I have read many articles by the worlds best and most respected scientists and climatologist in the Geographic magazine which I get every month and never a mention.

Mark, the energy used and carbon dioxide produced by vehicles are included in forecasts of climate change.

A petrol engine pumps about 3kgs of carbon dioxide into the atmosphere when it burns one litre of petrol. Carbon dioxide in the atmosphere reduces the amount of heat energy which is radiated into space. Carbon dioxide in the atmosphere has risen by about 40% since the start of the industrial revolution.
 
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