Tench - Growth Rates Body Shape & Potential Max Size

[Andy_1984]

AVG Free. Screw norton.

[Vagabond]

In the days when I was very interested in such things, I used to do a lot of measuring, length and girth, Weighing, and counting rings on scales. Seeking an answer to the question you ask.

One was long but the other was very stocky and very deep from top to bottom

Is there something in the body shape at an early size that points to its likely ability to reach a big size?

Quick answer Maybe


There are three levels at which an angler (as opposed to someone doing a thesis on fish growth) can observe.


Level one is in the first sentence of the quote above

Level two is to measure the length, weigh the fish and work out the ratio of the cube of the length to the weight. Not too troublesome - and puts a figure on the observations of level one.

Length in inches³ /Weight in pounds = about 1600 for an "average" tench. The lower the figure, the fatter the tench. The fattest tench I have measured was 979 which gives an idea of how much the figures vary. It is OK for comparing tench from different waters, and seeing if you have more than one population of tench in a particular water.

You can of course re-arrange the formula to work out a probable weight from the length, bearing in mind what I have just said above about the range of length/weight ratios.


You can also plot a regression line for a given population if you are so inclined. From that, any anomalies (like a picture of someone holding an eighteen-inch tench and claiming it weighs seven pounds) stand out like a sore thumb.

Level three is to measure length, measure maximum girth, weigh the fish and work out the ratio of girth squared times length divided by weight. ;A bit more troublesome.
Girth in inches² X length in inches/Weight in pounds = around 700 for the "average" tench. This formula doesn't help much on identifying differences in fatness, but might be of more use if you have lost your scales but have a tape measure with you - and have measured and weighed enough tench beforehand to know that 700 is the ratio figure to work with.


NB the ratio figures I have given will be different for different species, and of course different if you measure in metric or any other units - but the principle is the same.

Beyond level three, you need the age of the fish, which involves messing with the fish and a level of knowledge I don't have time to go into. No doubt someone will show us how erudite he is

Edited July 21, 2015 by Vagabond

[Vagabond]

I don't know what triggered the machine code (is that the right term?) mess above, can someone put it right please ? I have tried modifying it but no joy.

 

Later, managed to clean it up myself

Edited July 21, 2015 by Vagabond

[chesters1]

AVG Free. Screw norton.

If free was as good as bought there would be no avg to buy

[Dales]

Thanks Vagabond, very interesting stuff.

[Andy_1984]

If free was as good as bought there would be no avg to buy

now you are just being silly. Free one is free cause it doesnt have quite so much added extras to slow down your computer as the paid version. Free is more than adequate.

[OTIB]

If free was as good as bought there would be no avg to buy

Do people still pay for that ?

 

AVG is fine, no traumas, and no cost..simples .

 

You should try it.

[chesters1]

Do people still pay for that ?

 

AVG is fine, no traumas, and no cost..simples .

 

You should try it.

i have more than once but it usualy ends up in tears but norton 360 is far better and at a fiver a year almost free,used it since 1996? woth only one hiccup no company onnearth makes money giving stuff for free

perhaps a mod could put the virus rlated bits on the non fishing to save the nice thread we are disagreeing on LOL

Edited July 22, 2015 by chesters1

[wyeknot]

Hi Dales,

 

Well done on your PB. Great stuff!

 

There is quite a lot on growth rates of tench in the literature but, in a nutshell and ironing out the variations that occur from water to water, it seems that tench will grow in length and girth for about 15 years reaching anything up to about 25" or more in length. After that they continue to bulk up (similar to human middle age spread ) for, maybe another 5 years. A reasonable average growth rate is probably about 8ozs per year but could easily be double that in ideal waters (e.g. Wingham) so an average 10 year old fish would weigh in the order of 4 to 5 lbs and up to 8 to 9lbs in good waters.

 

Having said all this, you also have to take into consideration genetics as the strain of tench can play a big part in how big they grow. Why do some lakes continually produce large numbers of really big fish year in, year out when others struggle to reach the dizzy heights of a double when, to all intents and purposes, they are almost identical waters? For instance, the gravel pits in the Medway Valley have produced really big doubles for well over twenty years and still do - Dai Gribble had an amazing 8, yes eight, doubles including an 11 and a 13lb in one three day session on Larky 2 this spring. Wingham, despite it's very fast growth rate and ideal conditions, hasn't managed to do an 11lb yet even though the first double came out quite a few yeas ago. It is a very prolific tench water though with an extremely large head of 8 to 9lb fish so maybe the really big old girls haven't been caught yet.

 

Sorry there's no hard and fast rule on the subject, Dales, but then if there were it would take all the mystery and excitement out of going fishing, wouldn't it?

 

Regards,

 

Steve C.

[Dales]

Thanks, Steve.

 

It's certainly an interesting topic, I have always been curious if there were any clues as to which young fish may have that something special that allows them to push on to a big size. But as you pointed out, the mystery keeps it interesting and exciting.