So here you have two definitions of a blue moon but the one for a calendar blue moon does not describe the true meaning of a blue moon. Here's why:
To increase your fishing success you're going to want to concentrate you're fishing efforts at two specific times of the month. These times are the four day period that coincides with either a Full Moon or a New Moon. Using these two time frames will increase you chances of success tremendously. You will find that it is not only going to improve your success, but that the chance of catching larger fish is also greatly improved during these two phases of the Moon. If knowing this simple fact is going to improve your success why would you not at least give it a try?
Sagittarius role, after the introspection of Scorpio is to take the hard won wisdom and create something worthwhile from it and spread it around.