Weather & fly fishing
by Terry Lawton
In what way does the rain effect fish and why are they more easily caught? This two-part question was received recently by the Fish & Fly panel. When I saw it I thought that there was an article in the reply. It goes without saying that fish are effected by the weather, but are they easier to catch when it is raining? I would never rush out to fish if it was raining, in expectation of catching more fish, as I don't enjoy fishing in the rain that much. But if it starts raining and the fishing continues to be reasonable, then I would carry on.
When I started to think about this article and do some research, the only fisherman that came to mind as enjoying fishing in the rain was Jeremy Fisher, one of Beatrix Potter's characters. In The Tale of Mr Jeremy Fisher, Jeremy Fisher '.. was quite pleased when he looked out and saw large drops of rain, splashing in the pond - 'I will get some worms and go fishing and catch a dish of minnows for my dinner.'' His expedition did not go smoothly, as those who have read the tale will know, and he was swallowed by 'a great big enormous trout'. Fortunately for Jeremy Fisher he disliked the taste of his macintosh and spat him out, swallowing only his galoshes.
I then started looking through the indices of books to find references to rain and weather and was surprised by how few there were. In The Art and Science of Fly Fishing, by Lenox Dick and published in 1966, there are two Fishing Adages: Good Fishing and Poor Fishing. Good Fishing - 1. Rising barometer, 2. Falling water and 3, Dark of the moon. For Poor fishing, 1. East wind, 2. Falling barometer, 3. Rising water, 4. First bright day after several dark or rainy days (or vice versa), 5. Full moon, and 6. Thunder.
Changes in atmospheric pressure
I know from personal experience that a change in barometric pressure can bring fish on the feed. Some years ago I was fishing for pike one winter Sunday morning when there was a physically noticeable change in pressure. The pike suddenly started feeding and over the next three-quarters of an hour I caught six pike in eight consecutive casts. It would have been six fish in seven casts but one pike missed my plug the first time. I have never had such an experience since and I doubt that I ever will. I wonder sometimes if I had made it up but it did happen.
Although dull conditions are good for encouraging upwing flies to hatch, sun will dry their wings quicker. Flies will continue to hatch when it is drizzling but as it gets wets wetter, it is obviously going to be more difficult for them to dry their wings and get airborne. Martin Cairncross and John Dawson in their book Trout Fly Fishing, An Expert Approach, quote Irish lough fishermen looking forward to rain 'to bring the olives up'. Later in the same section on weather, they state how frustrated they have been to see fish feeding avidly during thunderstorms.
In his book Reservoir Trout Fishing with Tom Saville, Tom Saville records one of his best days ever on Chew 'in a gale combined with an unrelenting downpour'. He maintains that although it is unpleasant fishing in the rain, it rarely puts the fish off. For him, something that is important is steady barometric pressure. Sudden changes in pressure - in spite of my experience with pike - usually cause problems. If the pressure rises, or falls, and then settles, fishing should be okay.
To find perhaps the definitive answer to the question how does rain effect fish and make them easier to catch, we need to turn to the late Frank Sawyer. Sawyer writes in Keeper of the Stream how you will find a good hatch, and rise of fish, on wet days that follow a period of hot (summer) weather. This would seem to be in contradiction of Lenox Dick's fourth adage for poor fishing: First bright day after several dark or rainy days (or vice versa). Sawyer suggests as a reason that wind and rain break the surface film of river or lake and oxygenate the water: '.... at these times flies may hatch in thousands, or it would seem that the aerating effect of the wind and rain drops provides conditions that are very favourable for nymphs of the ephemeroptera to change into duns.'. At such times the river seems to come alive. If, as Sawyer suggests, the river is benefiting from extra oxygen, the river may, almost literally, be 'more alive'. If flies start hatching, then fish start feeding and we anglers have a chance of catching them.
In damp or wet weather flies will take longer to dry their wings so that they can take-off and will, therefore, spend longer on the water surface which means that trout have more chance of feeding on them. Also the fisherman has longer to see, identify or at least tie on a reasonable match of artificial. And matching the hatch can be crucial on days when more than one variety of fly is hatching, or the fish are being very selective.
I then turned to FM Halford and the Dry-Fly Revolution by Dr Tony Hayter. And there in the index are 13 references to weather! Many are to cold and windy weather in particular as well as rain. For example, we read that in 1892 the early part of the season was spoilt by 'gales and strong winds'. There is a reference to a trout of 6lb 8oz being caught in the rain in 1916 but unfortunately there is nothing to support the argument that fish are easier to catch in the rain. Fishing in the rain in Victorian times must have been very difficult as flies and lines would have got so much wetter than in dry weather.
As I was completing this article, a copy of Lesley Crawford's new book, The Trout Fisher's Handbook, arrived for review. I turned to the index and there was a chapter titled The Weather and Trout Fishing. Although she does discuss weather in some detail, she does not throw that much light on our problem.
Lesley Crawford does stress the importance of barometric pressure on fish and how it is better to fish during settled weather rather than when the pressure has dropped rapidly. Although fishing in thunderstorms should be avoided as carbon rods are excellent lightning conductors, she does say that trout often rise 'quite furiously'. She also writes that 'The odd swift shower of rain also helps stir things up by activating a goodly hatch of insects to make trout rise with gusto.'.
Is it a 'vision thing'?
Another possible explanation why trout can be easier to catch when it is raining could be to do with their vision. It is a known fact that on stillwaters and reservoirs trout tend to feed and swim into the wind which is bringing them their food, be it terrestrials blown from the banks or nymphs and buzzers and so on drifting with the general movement of water down wind. If the wind direction and that of the sun are the same, then the trout swimming straight into the sun are not going to be able to see flies so well. This cannot happen on dull or wet days when the sun is not shining.
I haven't come up with enough evidence to convince myself that fishing is better in the rain. One thing that I do know is the importance of confidence. If you think and are confident that fishing is better in the rain, then you will catch more fish because you expect to and, as a result, probably fish better too - which is, perhaps, the real reason that you are catching fish!
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