The basis of the Solunar Theory were put by John Alden Knight, in 1926 ("SOL" from sun, "LUNAR" from moon ) and outlines the effect of the sun, tides and moon phases over fish feeding including over fishing activities.
At the beginning , only moon influences were taken into account, being obvious the fact that, in extreme moments such as the maximum/minimum point of Moon attraction over Terra, alive being feeding activitiy was much more active. These periods were called Major Periods or Major Solunars, being centered on the moment in which the moon is located in the maximum point over the geographical point taken into consideration or in the minimum point when the Moon is located exactly in the opposite side.
The research revealed that the biological "clock" of fish as well as of a lot of other animal species coincides with Selenic Time, which is the period in which the Moon, after a complete rotation of Terra, appears in the same position.