Friday 22 February 2013

Fast Food & Broad Beans

In the last post I looked at how to present the fly at the right depth to prompt a take.  We now turn to the horizontal plane, which comprises first getting the fly to the right place, and making it behave in a way that may stimulate a salmon to take.  However, I am going to take those two elements in reverse order, because the desired behaviour of the fly drives its delivery.

We do not know exactly why a non-eating salmon takes a fly, but let us assume that there is some connection with embedded reflexive responses.  It takes an object into its mouth because something in the nature or movement of the object triggered a feeding reflex.  No one teaches a salmon to eat, but their life is characterised by the unrelenting consumption of protein leading to spectacular growth.

Once the alevin sheds the yolk sac and becomes a fry, it automatically starts to feed on small invertebrates.  A parr eats progressively larger invertebrates, mostly ephemera nymphs and stonefly larvae.  As this blog is about salmon rather than trout, for simplicity I use the abbreviation ‘nymph’ to include all the different species and types of waterborne larvae (and hope that the experts forgive me).  The time spent as a parr and the amount it eats embed high-speed food recognition and instinctive response.  Salmon are short sighted as a consequence of their very wide, indeed near-spherical field of view.  Survival is not cost free.  Parr feeding in flowing water therefore do not have much time to decide: the slow-witted starve.  At this stage of life it needs around 8% of its body weight daily in protein, which is a lot of nymphs - thousands per month.  Consequently the size, shape, tone and movement of nymphs become printed in the forefront of the young salmon’s brain in order to achieve the necessary speed of decision and action.  Those features are:

Size – small, in the range 3-20 mm
Profile – roughly cylindrical with legs sticking out
Tone – dull, but in the final ascent towards hatching, gas bubbles on the body may reflect ambient light brightly.

Movement – very slow, in the range 1-5 cm/sec (< 2”/sec): try timing your finger along a ruler.  Most travel is horizontal and near the bottom, but the ascent to hatch (when their food value is highest) is upward and thus clearly visible in Windows 2 & 3.

Once the smolt reaches the sea it has a cornucopia of high-protein prey species.  Sand eels and sprats congregate in huge numbers.  For their part the smolts form shoals for protection from predators; improved observation and prey detection; and increased hunting efficiency to counter the prey species’ defences.

The sand eel has a tough life at the top of every fish’s menu.  It is bite-sized, easily swallowed and high in protein.  Once the sand eel is deprived of its shallow water defence of burrowing into the sand, its 2 metre dash is no defence against smolts or salmon.  An adult salmon carving at speed through a shoal of sand eels may swallow several in each pass, an exercise conducted at such speed that only reflex can deliver the required coordination of tail and mouth.  Although the sand eel’s range is limited to shallower waters, its importance lies in being the first and most plentiful food that the salmon encounters during its early development in the North Sea and Shetland Banks.

The sprat, which is more widely distributed across the salmon’s range (the Faroese call them brisling), shares top of the menu with the sand eel.  Better still, it’s even easier to catch and has exceptional protein density.  It’s shorter and fatter than the sand eel, lacks its dash speed, and forms very dense shoals.  A mature salmon might be taking over 1lb/0.5Kg of sprats per day to maintain its growth rate.

The key characteristics of the 2 species are:
Size – in the range 3-15 cm.
Profile – oval, with a large length to diameter ratio.
Tone – grey green with silver sheen that increases with ambient light.  In a grey-green ocean in winter light it’s lateral movement that gives them away.
Movement – from slow at cruising speed to fast in survival dash (about 1.5-2m/sec, which is very fast for such a small fish).  Movement tends to be in straight lines and broadly horizontal unless panicked.  They wriggle continuously.

The two listings of characteristics frame the images we probably need to create in the salmon’s brain in order to trigger a response.  From that we can derive how best to fish the 2 generic types of fly:


Blue Charm 14
Note legs & gas bubbles in the dressing
The movement is slow, ideally upwards and interspersed with short pauses.  Therefore:
  • There’s not much logic in casting small flies into fast water where they will tumble and move chaotically like the rest of the debris coming downstream, and be similarly disregarded.
  • Remember that it would take a live nymph 2-3 seconds to traverse the palm of your hand, so slow the fly down to match.
  • The fly can only move upwards if it first went down: use a fluorocarbon tippet and/or an intermediate polyleader, but always keep the fly above the salmon’s sight-line.
  • At all costs stop a belly forming in the line which will otherwise accelerate the fly to sand eel warp velocity.
  • Towards the dangle, slowly retrieve a few inches; pause to allow your fly to sink back; and then repeat.


Sunray Shadow 12 cm
Off-centre dressing increases wiggle
The movement is steady but brisk, horizontal and animated.   Therefore:
  • Obey Newton’s Law: you will only get lateral movement and wiggle by applying tension on the line. 
  • If the leader does not lay out straight at the completion of your cast, take up the slack immediately, otherwise the fly will just hang in the water pointing skywards for much longer than you think.  It’s better to fish a smaller area effectively than waste the first third of the swing.
  • Eliminate line belly: a fly moving downstream achieves nothing; and a fly at warp speed even less.

Of course none of that guarantees success.  But we can help to improve the odds by eliminating things that are handicaps and hindrances to securing the fluke, even if a fish with a brain the size of a broad bean will remain unimpressed for 99.9% of the time.

You may wonder about the Broad Beans in the post's title.  This is a sad little story of a failed experiment and humiliation.  I got myself into position nearly 20 feet above a nice clear pool crammed with plainly visible salmon milling about soaking up the oxygen before launching themselves at a testing ascent of the falls behind me.  They were all awake, alert and active.  I attached an exceptionally realistic imitation plastic sand eel, cast beyond the fish and stripped it back through their midst at the appropriate speed.  There was not even a flicker of interest, despite the eel’s seductive wiggling only inches from their noses.  Ten minutes of repetition achieved nothing: their bean-brains were obviously wholly focused on the task in hand, and any way, the eel was at or below their sight line.  I gave up trying. Twenty feet below me at the water’s edge Patrick rolled a small Stoat into their midst, stripped it back heading downstream and promptly hooked a nice hen fish.  You can generalise about broad beans, but there’s no two that are identical.  So no matter how confident my assertions may be, remember that it only takes the intellect of a broad bean to prove me wrong!

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