Fish size increase could this be the reason?

[Steve Burke]

It could be that hormones are a contributory factor in the growth rate of fish. However, I suspect that it's a combination of many factors.

 

I don't though agree that the main reason is HNV baits as is commonly suggested, although they almost certainly play a part. I know many waters that are rarely fished (and thus see very little bait) where several species are growing very much bigger. The bream at Wingham are a case in point.

 

We've therefore got to look at factors that affect many different waters, both fished and unfished. We've also got to find factors that changed when the recent growth surges began. A further clue is the species that are benefitting most, such as carp, tench and bream that until recently were largely considered as summer fish.

 

Far more likely therefore as the main causes are global warming and nitrates/phosphates.

 

It's not so much the warmer summers that are important, as in fact it can get too hot for the fish to feed. Rather I believe it's the milder winters that extend the growing season.

 

Nitrates and phosphates from modern intensive farming greatly enrich most of our waters, and the time scale certainly corresponds. As an example gravel pits when I was a lad were relatively barren, crystal clear and largely free of weed. As a result they seldom produced big fish as they do today, when most gravel pits are rich and full of fish food.

 

These I believe are the 2 main reasons for the current high growth rates, although they're are undoubtedly a multitude of other factors. I'm sure members could add a host of others.

[Ken L]

As far as the bait hypothesis goes, I just don't buy it.

When I was growing up in the seventies, it was a real struggle to get a peg on the rivers and everyone seemed to be chucking in gallons of bait - maggots or meat and both are pretty high in protien.

Today, I fish the rivers with lures and even at weekends, most pegs are empty unles there's a match on. There's just no way that there is as much artificial food entering the system as there was 20 or 30 years ago.

[John Ellison]

When I used to have an allotment 20 years ago, You could almost garuantee that the first frost would be October 8th. and the last on May 8th. In deepest Yorkshire.

In recent years this yardstick has gone out of the window bigstyle. The winters that I remember 30 years ago were more severe and longer than they are today and I'm sure this must have a bearing on matters. It suits me, I enjoy fishing in the winter.

[Guest Bish]

Interesting topic.

 

Firstly, hello to all

 

To quote ajp from the link he posted -

quote:

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I've just got this sort of feeling that it's more likely to be something in the water; something like the steroids and other similar stuff that bodybuilders consume on a regular basis.

 

We already know that sewage plants are unable to deal with Oestrogen from the birth control pill so would steroids be any different?

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Oestrogen is a major problem in our river systems today. Research has shown that it is causing fish to change sex & this is a huge worry.

As for steroids causing abnormal growth. It's a possibility, but steroid use isn't on the same scale of birth control & how could steroids account for abnormal growth to fish in still waters? So i have to discount steriods. Phosphates & Nitrates (afaik) woudn't contribute to growth in fish.

 

Steve -

quote:

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I don't though agree that the main reason is HNV baits as is commonly suggested, although they almost certainly play a part

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In my opinion still water fish are affected largely by high protein baits. Twenty five years ago i didn't see obese carp, with their bellies hanging like a swollen balloon like we all see today. I've never seen in twenty five years fish suffering from obesity from a river.

 

Is there any research into abnormal growth primarily in river fish?

 

quote:

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When I was growing up in the seventies, it was a real struggle to get a peg on the rivers and everyone seemed to be chucking in gallons of bait - maggots or meat and both are pretty high in protien.

Today, I fish the rivers with lures and even at weekends, most pegs are empty unles there's a match on. There's just no way that there is as much artificial food entering the system as there was 20 or 30 years ago.

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This is true on a stretch of the Severn i've been fishing for years. Our match weights have plummeted over the years, whereas down stream the same old hot spots are producing 50-70lb bags. If the water ain't fished, fish will move to find the bait.

 

It's clear to see though, that our water eco system is a fragile one & is on the brink of being lost forever if tighter restrictions are not applied. And to put the boot in, mother nature is also a contributing factor. Autumn & spring flooding is doing as much damage on the Severn than anything else at the moment.

 

Hope i haven't rambled too much in my first post

 

[ 10. October 2004, 01:34 PM: Message edited by: Bish ]

[Ken L]

Ramble away and welcome to AN. It's nice to se another midlander posting

[Eddie]

A probably meaningless thought.....

 

I was under the impression that the livestock that is reared by farmers across the land is nowadays pumped full of drugs, steroids being one, to increase the yield among other reasons.

 

Could this not be entering the water system, there's a damn site more livestock vacating their bowels and bladders near to water sources than there are body builders and athletes!

[Guest Bish]

Interesting point Eddie.

 

Maybe a few years ago this was very much a reality, but (afaik) there are now strict Government guidelines & controls on the use of weight promoting hormones & steroids in animals for meat production.

 

Cheers for the welcome Ken

[RollingPinBoy]

Hi Eddie..I think hormones, growth promoters etc were/are administerd via feed pellets. There are natural occuring plant hormones/synthetic hormones used to 'fatten' up fish and grow quicker on fish farms which can cause sex change and behavioural changes as well cause internal organ damage.

As Bish say's it may well be controlled today, but what about fish pellets?

With milk poteins, eggs, etc, they may also contain residues of hormones/synthetic hormones and growth promoters amongst other things!..Food for thought?...Ray

[Steve Burke]

Bish:

Phosphates & Nitrates (afaik) woudn't contribute to growth in fish.

First of all, Bish, welcome to the Forum!

 

As I understand it, nitrates and phosphates affect the growth of fish indirectly by enriching the water. This leads to greater productivity of plankton, which increases the biomass of invertebrates that feed on the plankton. In turn this affects the growth of the fish that feed on the invertebrates.

 

It's interesting that on my pits at Wingham the weed treatment that we undertake every few years has been especially effective this time. The result has been an algal bloom as the nutrients that were in the weed get recycled. The knock-on effect has been an explosion of fry, especially carp and perch, plus an excellent year for fish growth. In fact, such have been the numbers of carp fry this year I may be storing up future problems!

[Guest Bish]

quote:

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As I understand it, nitrates and phosphates affect the growth of fish indirectly by enriching the water. This leads to greater productivity of plankton, which increases the biomass of invertebrates that feed on the plankton. In turn this affects the growth of the fish that feed on the invertebrates.

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Yeah you're spot on, cheers for that

 

On the Severn during the 70's it was full of many different types of weed - huge banks of Streamer weed & Silk weed which we just don't see anymore. It's all gone.

At a guess i'd say there were far more Phosphates & Nitrates getting into the river system now due to intensive farming, which should account for healthy banks of weed during the summer months. Now all we see are carpets of thick brown slimy algae, which takes over & stops the growth of weed.

 

I suppose the stillwater eco system is so very different from the river eco system, & i have have yet to hear about any research to indicate that river fish are increasing in size due to some of the points raised.

 

The debate continues...

 

Thanks for the welcome