Here is how I understand it now: When there is a full moon the earth is between the sun and the moon and in a gravitational tug of war between the sun and moon. The fish feel this affect go crazy and bite.
When there is a new moon the moon is between the earth and the sun and moon's gravitational pull is added to the sun's onto the earth. The fish feel this affect go crazy and bite.
This gravitational affect on the earth by the moon is not only felt by fish but also by animals and people. Therefore during a full or new moons lookout for lunatics, good fishing!