Kennet Chub Weight 'Progression' since 1982

[Anderoo]

Interesting stuff Chris, thanks for putting these up. I only seriously started perch and chub fishing since moving to Oxfordshire in 2005 so I missed the start of the increase in weights.

 

As I've said many times before, I too think that crays have had a really big influence in this. However that can't be the only factor. Other species have also really increased in weight over the last couple of decades, and in some cases it does seem like a new type or increased amounts of available food is not responsible. Take bream and tench as examples. Carp too - if you ignore all the waters where bait is piled in, carp have still got much heavier overall.

 

Oddly some species like roach, rudd and pike have stayed pretty much the same.

 

I expect warmer weather and longer growing seasons are an influence, but I don't know why that would benefit some species and not others?

Edited March 23, 2015 by Anderoo

[Anderoo]

PS not all the chub and perch down here are huge great fat things. They do often pile on weight at the back end of the season but that must be spawn. Not always though, this one was on the final day of the season from a stretch with a lot of crays:

 

 

They are generally pretty short fish but with deep flanks and thick across the shoulders, which is where the weight is. But they are very healthy and very fit. The really big ones are the same kind of proportions, but caught at a time when they are also full of food and/or spawn.

 

In contrast, this one from a few years ago was about the same length but weighed over half a pound more:

 

 

And this one also from a few years ago was about the same lenght and weighed over a pound more:

 

 

It has been a few seasons since I've seen them this shape, now I think about it...

Edited March 23, 2015 by Anderoo

[Steve Burke]

As I've said many times before, I too think that crays have had a really big influence in this. However that can't be the only factor. Other species have also really increased in weight over the last couple of decades, and in some cases it does seem like a new type or increased amounts of available food is not responsible. Take bream and tench as examples. Carp too - if you ignore all the waters where bait is piled in, carp have still got much heavier overall.

 

Oddly some species like roach, rudd and pike have stayed pretty much the same.

 

I expect warmer weather and longer growing seasons are an influence, but I don't know why that would benefit some species and not others?

I'd bet on it being a number of factors in combination including, but not limited, to signal crayfish, excess fertilisers and warmer winters.

 

The species that have benefitted most from warmer winters, and therefore a longer growing season, are largely what the Mr Crabtree books of my youth called the summer species e.g. carp, bream, tench and barbel. The records for those species that feed throughout the winter such as chub and pike haven't increased in percentage terms so much.

 

It's interesting that when I did a lot of chub fishing in the late 70s and early 80s, the Chub Study Group rated a 4lb chub as a specimen. In fact in, I think 1981/2, my 5lb 1 1/2oz chub was the biggest caught by a member until the last few days of that season!

Edited March 24, 2015 by Steve Burke

[Steve Walker]

Crays, eutrophication, climate change, changing patterns of predation, changes in river management practices, changes in angling pressure, Chris Plumb getting ever better at sniffing out big chub (the bounder!)?

 

A change in a river so that more of the population is made up of large, old fish is not necessarily a good sign!

[Latimeria]

Would be a start for the Chub Study Group to follow the Barbel Soc.'s lead and part-fund some studies into some isotope analysis for chub tissues in rivers where a problem is perceived, see whether they're also becoming essentially marine consumers in areas because of the quantity of bait going into these systems. That would take the debate from "I think this" or "I think that" to "There's some evidence that". If crayfish were available enough as a food source to result in the sort of rugby ball fish seen, would the oft-mentioned Lutra even bother eating everyone's precious PB?

[Anderoo]

Crays, eutrophication, climate change, changing patterns of predation, changes in river management practices, changes in angling pressure, Chris Plumb getting ever better at sniffing out big chub (the bounder!)?

 

A change in a river so that more of the population is made up of large, old fish is not necessarily a good sign!

 

Agreed Steve, that's not what's happening at the Thames however - there are lots of small chub and perch constantly coming through.

 

L's point on bait is an interesting one and I would also like to see some hard evidence to back up my assumptions. All I can say from an anecdotal point of view is that the rivers I fish are so rarely fished by anyone that I assume bait simply cannot be a factor. This is also the case for big gravel pit fish like bream, tench and carp, which have all grown huge in many very lightly fished waters where bait can't be having any effect.

[Steve Walker]

The questions for me would be - what is the distribution of biomass by age/size? What is the total biomass of chub? Has it changed?

[Anderoo]

That's a good question Steve, wouldn't it be great to have an answer...!

 

The trouble we always have is that this is always based on captures, and one person's 'fact' about fish populations in a certain river/stretch never seems to match someone else's.

[Steve Walker]

Would be interesting to see EA survey data, though any survey method is itself only ever an estimation.

 

One thing that springs to mind - cormorants. What would the effect be of taking out significant numbers of fish at the lower to middle end of the size range? Less competition for those that make it through?

[Anderoo]

Again that wouldn't apply to the Thames, where in the summer you can't get a bait to the bottom because of all the fish! That may have an impact on other waters though.