Fishing and the Moon Phases

Written by erica dreisbach
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Fishing and the Moon Phases
Many fishermen believe that the phase of the moon impacts the behaviour of fish. (fisherman image by Igor Murtazin from

Just as the moon is known to control the tides on earth, some believe that the phase of the moon similarly affects the behaviour of fish. Solunar theory proposes that each day has four periods (two major and two minor) when the gravitational forces created by the alignment of the sun and moon are strong enough to increase fish activity and yield a greater catch. These forces are thought to be strongest when the moon's phase is full or new. However, there is very little concrete scientific evidence that the phase of the moon directly impacts fish and wildlife activity.

Solunar Periods

Daily solunar periods occur when the sun and moon are roughly perpendicular to each other and will last anywhere from one to two hours. The major solunar periods are when the sun is perpendicular to the moon at zenith (overhead) or nadir (underfoot), and minor periods are when the sun is perpendicular to the moon at the horizon. The times in between major and minor periods are sometimes referred to as "dead zones" of the day, with supposedly limited fishing activity. Solunar effects are thought to be strongest each month during the full and new phases of the moon. Absolute peak fishing and feeding times occur when a major solunar period coincides with the moon's position at exactly zenith or nadir, or, in other words, at sunrise and sunset.

Research by Knight

John Alden Knight first conducted scientific study on the link between the moon and peak fishing in 1926. His research in Florida examined 33 separate factors across approximately 200 catches that might influence the behaviour of fresh- and saltwater fish. He discovered that over 90 per cent of the catches were made during the new moon. Knight later applied his research to game birds and other animals and concluded that these animals show activity levels that are also dependent on the phase of the moon.

Solunar Tables

Knight's research was later formulated into solunar tables that calculate the date and time of peak fishing and hunting based on the phase of the moon and position of the celestial bodies. The first solunar tables were published in 1936 and are still available in most fishing and hunting guides, adjusted for local longitude and Daylight Savings Time.

Research by Brown

Further research on fishing and the phases of the moon was conducted by Dr. Frank A. Brown, a biologist at Northwestern University. At the time, it was well established that oysters opened their shells at high tide, but Brown isolated whether this was due to tidal changes in water levels or from forces from the moon itself. Brown kept oysters from the Atlantic in water without sunlight. He found that for the first week, the oysters continued to open their shells according to the tide schedule on the East Coast, but by the second week they opened their shells when the moon was at zenith or nadir relative to the lab in Chicago.

Debunking the Theory

While solunar tables are still used to calculate optimal fishing times and are available in most hunting and fishing guides, there is no conclusive theory that explains the mechanism by which the moon's gravity affects fish and game. A simpler explanation is that insects and baitfish are more active during the light of a full moon, leading to greater activity by fish and a larger catch for those out fishing. Similarly, the "absolute peak" times in solunar theory correlate with sunrise and sunset, when baitfish move between shallow and deep water.

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