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Trout size: Let's keep a sense of proportion

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The majority of wild brown trout caught on Dartmoor and in South Devon are less than eight inches long, but each season anglers catch larger 12 or 13 inch fish.

As guides and instructors we are often asked:
  • Are big fish more difficult to catch than smaller fish?
  • Are big fish 'smarter' than smaller fish?
As guides and instructors we often ask ourselves:
  • Do skilled anglers catch more fish?
  • Do skilled anglers catch bigger fish?

This page discusses the size of trout in the rivers we fish on Dartmoor and in South Devon. I hope it will help you appreciate our fish - of whatever size. It's our job to show you the necessary skills to catch them and explain why we treat them all with great care.

This graph shows the numbers of trout of various sizes caught by anglers on a West Country river:
  • most of the trout were less than 8 inches long
  • relatively few trout of 10 inches or longer were caught
  • hardly any fish of 13 inches or longer were taken
Two questions spring to mind:
  • Why were so few big fish caught?
  • Are bigger fish 'older and wiser' and therefore less likely to be caught by anglers?
size of trout caught

The larger fish are certainly older.
This graph shows the growth rate of wild brown trout in our area.

  • fish of 12 to 14 inches take six years to reach that length
  • our trout are about three years old before they spawn for the first time
  • consequently small fish should be carefully returned to the water so that they have an opportunty to reproduce
  • it also helps to use barbless hooks

But, are older fish 'wiser?
bigger trout are older handle with care
Handle wih care;
a fish this size may be four or five years old

The older fish are certainly 'survivors'.
This graph shows that out of 1000 eggs laid by a female trout only two will survive to their  fourth birthday.

  • mortality is especially high in the period between hatching from the egg to establishing a territory
  • only 20 fish reach their first birthday
  • so, the next time you hear someone complain about the small size of the fish they are catching, remind them that an eight inch fish is probabaly three years old and is one of a group of maybe only six fish that remain from a clutch of 1000 eggs!

But are larger surviving fish necessarily 'smarter' and more difficult to catch than smaller younger fish?

They are better at avoiding predators. They may be more easily 'scared' by unfamiliar shadows, sights and vibrations than non-survivors. But we need to remember that fish have evolved to deal with their natural enemies, not necessarily angler's flies. Provided you can present an appropriate fly at an appropriate time and place and most importantly - do it in such a way that you do not scare the fish - there is no reason why you should not be successful.

But how do you catch the bigger fish? There is a well known saying that "10% of the anglers catch 90% of the fish". The graphs suggest that there are simply fewer bigger fish and therefore the more fish you can actually catch then the greater the chance that one of them will be big.

If you do catch a big one, treat it with the respect it deserves. After all it's one of nature's great survivors.

But don't worry if you don't catch a big fish, it really is just a matter of proportions!
survival curve

Frost and Brown, "The Trout", published by Collins, London 1967
Watson, "The Trout: A Fisherman's Natural History", published by Swan Hill Press, Shrewsbury, 1993

"The great charm of fly-fishing is that we are always learning." - Theodore Gordon
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