Saturday 30 June 2018

Brown Trout colours and spots

A constant fascination for me is the variation of colours that the Brown trout in the local streams exhibit, even within a single stream the colours can vary from pool to pool.  The range of colours fascinate me as do the reasons for it. Not sure that I am really very interested in a scientific explanation  but my experience tells me that the more alkaline and richer in invertebrate the river then the fish are lighter with less vivid and smaller are the red spots. But I stand to be told otherwise.  The first two pictures show a trout caught from my local river last Sunday

The adipose fins of many show the most vivid colours .  This dark fish was caught from a small pool that is quite heavily shaded .  Perhaps partly the reason why the fish was generally dark?.  All the fish on the post whilst being from three separate rivers are all from within a circle of twenty miles diameter. The issue of age of the fish is a difficult one as in this stream the fish don't grow large  12 inches is a good fish 14 inches a potential seasons best .  I do get the impression that the darker fish are more mature . 

This fish below was caught from the same stream no more than 100 yds away.  It was an an area however of sand and gravel rather than the rocky pool the first fish was .

This fish was caught in the same river about a couple of miles upstream 

The fish was from a very small stream a few miles inland ,  better water quality and certainly less acidic , the stream rises as a spring out of limestone but does carry a lot of surface run of as well. The fish there tend to be a bit heavier and lighter coloured with smaller red spots although you do come across the odd darker fish, also the water  does have good invertebrate hatches .

The last is from a local chalk stream .  Whilst been a very rich stream it is not a large river with few deep pools and the fish whilst been fairly prolific do often reach substantial sizes .  Fish generally have smaller and fewer red spots.  

One interesting fact from the Wild trout trust website."Brown trout are one of the most genetically diverse vertebrates known. There is far more genetic variation present across British populations of wild brown trout than between any populations in the entire human race".  So it seems to me that you have possible genetic variations as well as local responses to habitat and water quality.  Also on a lighter note. " All fishermen know that trout get progressively larger after they have been caught!"


Bill Trussell said...

Hard to explain the color variation on some of the browns or even rainbows and brook trout. Every time I land a trout I marvel at their beauty. Thanks for sharing

Mark Kautz said...

Certainly gives one something to think about between trips to the stream.

The Two Terriers said...

When I was a lot younger I lived on a farm in Bilsdale with an Uncle and Aunt, the River Seph ran through the land and there was a paved watersplash about a foot and a half deep. There were always trout and a few grayling ranked across the large stones, the colour of the slabs was uniform but the fish ranged from perfect camouflage in terms of colour to really dark almost black. It must be in the genes. Regards, John

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