More Salmon Statistics

In my last post, using Jim McLaughlin’s data taken from the Wye over the last three years, we showed, conclusively in my opinion, that there is a correlation between the height of water and the chance of catching a salmon.
Using the same data we can plot the number of fish caught on rising and falling water levels.

Rising Falling River CatchesThe graphs show the river level (blue) taken from the EA gauge at Redbrook on the Wye, every 15 minutes. The green bars indicate the number of salmon caught on falling water and the red bars indicate those caught on rising water. It is apparent that more fish were caught when there was a falling water level.
What we can also observe is that most of the fish were caught when the gauge was between 0.4 and 1.0 metres.
You will see in the same chart that the moon phases are marked in light blue and shown as vertical lines, representing the beginning of each moon phase.
The results for the moon phases are summarised in the following diagram…

Catches by moonThis appears to indicate that more fish were caught between when the moon was waxing and the full phase (days 18 to full moon +3).
Taking this one step further, we can make a comparison between the number of fish caught on “Good Days” and “Bad Days”. We define good days as those which fall in the in the waxing to full moon period and when the river height is between 0.4 and 1.0 metres.

Good Days vs Bad DaysWhat we can derive from the data is that there really are good days and bad days and if we take 2013 as an example a few more good days made a significant difference to the salmon catch numbers, even though there were obviously more fish in the river in this year.
So in conclusion, for our stretch of the Wye:-

  • The range of the water height is critical
  • There is a better chance of catching a salmon on a falling river height
  • The moon phase appears to affect the taking behaviour of salmon and the “Goldilocks Period” (Jim’s phrase) is between when the moon is waxing and three days after it is full.

We can’t say if these are universal laws for all rivers because we don’t have any data but at least you can use them as a guide.

About John Symonds

I mainly fish the rivers Wye,Usk and Ithon for salmon, trout and grayling. Also fish in Ireland on the rivers Moy, Suir and Blackwater. Specialist skills photography and graphic design relating to fishing, casting and fly-tying. Qualifications include Advanced Professional Game Angling Instructor (APGAI) single and two-handed fly rods, International Federation of Fly Fishers (FFF) two handed casting instructor and Level 2 Angling Trust Coach.
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