An embarrassment of riches

Just because there are some Mayflies on the water and the trout are rising freely, we should not suppose they are necessarily taking Mayflies, says Peter Lapsley. The key to success is observation and experimentation … don't be fooled.

It has been said that the hatch charts found in instructional books on fly-fishing should come with a health warning, because Mother Nature is nothing like as tidy minded as we would like her to be. Influenced by a number of environmental factors, chiefly the weather, and by their own idiosyncrasies, insects do not observe the hatch charts quite as assiduously as we might wish.

River keepers will tell you they see almost every fly of interest to trout in almost every month of the year. The truth is, though, that occasional Mayflies hatching in October, or the odd blue-winged olive fluttering up from the surface in December, are curiosities – interesting but of little real consequence. It is very rare indeed that they appear in numbers sufficient to provoke a response from the fish.

Assuming that they happen at all, the species in question not having been wiped out by diffuse pollution and the like, most significant hatches of most insects are, in fact, reasonably predictable – some, of course, more so than others. I do not recall ever having seen a grannom after the end of April, a hawthorn fly much before or after the last week in April and the first in May, or a caperer much before the end of August.

Mayflies, in particular, are very largely creatures of habit. While the beginning and end of the hatch varies from river to river and even from fishery to fishery on the same river, the start of the local hatch can usually be forecast quite accurately to within a day or two. End dates can be more difficult to predict because hatches tend to peter out over a week or so, the trout losing interest gradually. (Incidentally, I have long since ceased to be excited by the sighting of occasional Mayflies a fortnight or more before the hatch proper is due. It happens every year and rarely, if ever, excites the trout, which almost always seem either oblivious to the giant flies or even a little nervous of them.)

All of this is a somewhat roundabout way of saying that the unreliability of hatch charts, such as it is, has more to do with the weather and, in May at least, the choice of flies available to trout than with inherent inaccuracy. The majority of hatches large enough to interest the fish do, in fact, occur in accordance with established hatch charts. But that does not mean that fishing hatch-matching flies will necessarily guarantee us heavy baskets.

Last year, I visited the little Hampshire chalkstream upon which I do most of my fishing three times between April 24 and May 2. On each occasion, so confident was I that an artificial Hawthorn would be the panacea of the day that I knotted one on when tackling up at the car before strolling down to the river. Sure enough, on each of those days, there were huge numbers of hawthorn flies, black as your hat and seemingly bigger, fatter and juicier than any I had seen before, bumbling about in vast swarms in the lee of almost every waterside bush and hedge.

Did I take fish on my Hawthorn pattern? Er, no. On not one of those visits did I see a single hawthorn fly on the water, nor did the fish show the slightest interest either in my own tying or in any of the two or three other Hawthorn patterns I dug out of my fly box. Instead, I took two fish on a Pheasant Tail & Hare’s Ear (PTHE) Nymph on April 24; three on a Parachute Adams and two on a PTHE Nymph on April 30; and two each on a Parachute Adams and a PTHE Nymph on May 2.
The reason for the Hawthorn’s failure, of course, was that the natural is a terrestrial which only ever arrives on the water by accident, born there on a sufficiently strong wind coming from the right direction – from our and the trout’s point of view, if not from the hawthorn’s. As it happened, breezes in late April and early May last year were remarkably light and the naturals, although notoriously inept fliers, were well able to hold their own against them and avoid being blown onto the river.

The choice of the Parachute Adams and the PTHE Nymph as alternatives to the Hawthorn at that time of year was easy. There is no grannom hatch on this particular river and the only aquatic flies that do appear fairly consistently throughout April are large dark olives (LDO), usually around the middle of the day. The Parachute Adams does a good impersonation of a variety of hatching up-winged flies, including the LDO, and the PTHE Nymph (or almost any similarly Pheasant Tail Nymph-like offering) will often take fish before and during hatches of LDO. In some areas, choice may be complicated slightly by the availability of the march brown or, perhaps, one or more species of stonefly. Generally, though, neither fish nor fisherman is confronted with complex choices in April.

Two or three weeks later, fly selection can become very much more difficult due entirely to an embarrassment of riches. Although up-winged fly populations are in serious decline on many rivers, more species can still be expected to appear at this time of year, and in greater numbers, than in any other month. Almost every fly species upon which trout feed hatches, or begins to hatch, during the last three weeks of May. Depending upon where you live or fish, medium olives, small spurwings, small dark olives, olive uprights, iron blues, pale wateries, caënis, black gnats, sand flies and stoneflies can all put in appearances alongside the mayflies, and identifying what the fish are feeding on can become quite a challenge.

The complexity can be compounded from mid-May to mid-June by our understandable preoccupation with the mayfly. So iconic has it become and so easily convinced are we by the term ‘duffer’s fortnight’ that we tend to suppose, albeit perhaps subconsciously, that it is the only thing trout feed on at this time of year. It is not. But I must confess to having been duped by this supposition myself on a number of occasions.