to come up with a number, it's series of complex trigonometry and algebraic equations, but lets just say that if you do not carry the 1, then you will come up with an incorrect number, you must also consider fish/per casts category as well, but the important thing is to maintain all the necessary parameters of the situation.
it can also be calculated, down to 3 decimals points that the lower river, below the crossing, seems to statistically produce more fish, while, oddly, the mid-river from crossing to tahamhi seems to have come away with the lowest rating in the 3 "sections" of the river. However over the course of a 20 year cycle, the upper river constantly seems to produce fish per day per 100 anglers, that is a fact.
food...for thought