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IMPORTANT
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Visit the relaunched
Fish & Fly at fishandfly.com
What's
on the menu?
Our August 2001 contribution from Lesley Crawford
Lesley takes a look at the feeding habits of her highland trout - and finds a few surprises...
I had a salutary lesson in trout feeding behaviour the other day. Having sneaked up and captured a beautiful 1lb 8oz wild brown I felt quietly proud - not to say a little self-satisfied - over my apparent skill in matching the hatch. The trout concerned had been busily chomping on newly emerged Caithness mayfly. Mayfly hatches on northern lochs are dense and profuse from early June to early August and though there are local variations, most lochs see plentiful numbers of these luscious insects.
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My
artificial fly needed not too bright a yellow and not too dark a brown.
Instead soft shades of cream and tan with olive greenish grey wings needed
to be included and after several attempts at the vice my carefully constructed
artificial was a modest but fair replica of the real thing. My lesson
came on gutting the butterball trout for far from it being stuffed with
winged mayflies and nymphs, the trout’s gut actually contained a
tight wedge of uniformly sized blades of grass! Pondering over why this
trout had been so intent on consuming these I could only come up with
the idea that the fish had been taking the ‘caviar’ of the mayfly
i.e. the tiny eggs which the female insects had been depositing back into
the grassy margins of loch. In taking these eggs the trout may have inadvertently
swallowed the bottom hugging grass they were attached to, at least that’s
my explanation as the grass seemed to be too insubstantial for caddis
cases and there did not appear to be any tell tale binding grit present
in the gut.
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brown trout |
This
type of unpredictable feeding, when trout appear to be taking one item
but are in fact consuming something quite different, is not uncommon in
wild trout. I have oft told the story of catching trout of 1lb during
late April and early May which were actually found to be consuming small
frogs while appearing to be feeding on little more than a reed smut. (Early
Spring is frog mating time and the trout were having a ball picking off
small preoccupied amphibians whole as the little frogs sloshed about in
the shallows intent on reproduction).
Equally on cleaning trout I would sworn to have been stuffed full of sedges
I’ve discovered either an empty stomach or one packed with orange
bloodworm. Or how about a sleek fat trout I took from the River Thurso
on a size 18 dry Wickhams only to find the fish had a rock hard stomach
having fed exclusively on snails. Then again there’s that mighty
trout from Loch Calder caught on a Blue Zulu but actually stuffed with
sticklebacks. And friends tell of trout they have caught on artificial
flies which went on to reveal a diet of cigarette butts or water voles
or rice pudding, so much so it makes you wonder why we bother to tie up
our delicate imitative patterns!
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Some
explanations of trout diet are called for even if it’s a bit of a
guessing game. Personally I have a lot of time for the ‘Abundance
Theory’ i.e. the concept that trout will latch on and feed avidly
on the most prevalent hatch (invertebrate or otherwise) of the day, however
this does not explain all the trouts feeding cycles in loch or river.
I am now more given to tempering the Abundance Theory with the idea that
individual trout develop `tastes’ for particular food items which
are easily accessible in their environment. Trout always want a stress
free life with the least amount of energy expenditure during the feeding
process. Thus it is quite possible that while fish do respond to the appearance
of high density hatches of sedge or mayfly, they will have already set
their primary sights on what is easily accessible in their own particular
territory, convenience food in fact. If prolific bottom feeding like shrimp
or snail is on their patch then it would seem the trout develop a taste
for that first and can be a little suspicious of anything else unless
it comes in great profusion. Logically it could be argued that your supposed
well matched artificial has actually been taken by the trout out of curiosity
or aggression and not because its an exact representation of a nearby
hatch.
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All
this asks a lot of questions about why anglers attempt to tie the exact
fly. Those arguments of old about choosing dry (usually a fairly exact
imitation) over wet (usually a more vague representation) seem to count
for little when you look at trout feeding in this capricious way. If the
trout’s menu is diverse yet apparently concentrated according to
its immediate environment would it not be better to sample the surroundings
- particularly the bottom - and then put on a fly according to need. While
for practical reasons this is not always possible, a little effort to
at least examine the general menu by turning over a few stones in the
margins before fishing will pay dividends. And spooning trout after they
are caught may not be as effective a tool as you might think for ascertaining
what the trout are taking. Effectively it will only tell you what the
captured trout munched on in his particular patch but it may not help
much for other trout sitting in a different parts of the lake or river.
Common sense helps a bit here though as if for example the trout has been
caught next to weed beds its likely that trout in the vicinity will be
feeding on similar food items for example nymph or shrimp or winged insects
trapped in the weed edges. However if you then take up a new and environmentally
different fishing position say next to sand and boulders remember the
local diet may not be the same even though it’s all the same water!
When it gets right down to it no one really knows why the trout take one
particular fly over another except the trout themselves. We are intruders
in their watery world trying to put fish logic into human terms. It’s
great fun to try but don`t be too surprised if your analysis turns out
to be way off beam and in the meantime anyone got a pattern resembling
blades of grass?
About
Lesley Crawford
Lesley has fished for brown trout and sea trout from a very early age
and her enthusiasm for these beautiful Scottish fish shows no signs of
diminishing. She is well known as a leading angling writer and photographer
with prodigious articles in a wide range of publications including Salmon
Trout & Sea Trout and the Scotsman.
Lesley is a REFFIS qualified fishing guide and arranges bespoke wild trout angling holidays in the Northern Highlands. Her first major book 'Fishing for Wild Trout in Scottish Lochs' (Swan Hill 1996) was a runaway success and the long awaited follow up 'Scotlands Classic Wild Trout Waters' (Swan Hill) was published in 2000. Order your copy now. Read more about Lesley at www.wildtroutfisher.co.uk