Solunar Theory Explained: Do Moon Phases Really Move Fish?

The idea in brief

Solunar tables were popularized by John Alden Knight, whose book Modern Angler, published in 1936, set out the theory and whose tables are still published. They predict days and hours when fish and game should be more active, based on the positions of the sun and moon. On our pages, the longer "major" periods are centered on the moon passing overhead and underfoot, and the shorter "minor" periods stand in for moonrise and moonset. Knight attributed the effect to "inland tides" in barometric pressure and to gravity, but, as the authors of a 2014 study of muskellunge catches note, he never described a biological mechanism.

What the studies say

Studies of catch records disagree, and where they find a lunar signal it is small. An analysis of 341,959 muskellunge catches from North American fisheries, published in PLOS ONE in 2014, found more fish caught around the full and new moon, with a predicted peak effect of about 5% more fish than on a random day; the effect was stronger at night, for fish over 40 inches, in midsummer and at northern latitudes, and was not explained by moonlight. A study of 13 years of creel records at Escanaba Lake, Wisconsin, found walleye anglers were roughly 10 to 12% more likely to catch a fish when the moon passed overhead or underfoot during their trip. In the same study, who was fishing, the bait used and how much of the population had already been caught mattered more than any lunar variable. A 2023 study of a North American recreational trout fishery, published in SN Applied Sciences, compared anglers' catch per unit of effort with the values of several popular solunar services and found no significant relationship with any of them, nor with the moon's phase or illumination; air temperature predicted fishing success better than any of the tables.

How this site calculates its windows

Our water pages print two majors and two minors each day, calculated for the water's own coordinates and local time. The majors run an hour either side of the moon's upper and lower transit (overhead and underfoot on that meridian), and the minors half an hour either side of moonrise and moonset. The moon's position comes from a standard low-precision astronomical formula, the same kind used by common open-source sun and moon libraries; checked against the US Naval Observatory's tables for three places on October 6, 2026, the transit, rise and set times agreed to within five minutes. Because a lunar day lasts about 24 hours 50 minutes, as NOAA describes, some days have no moonrise, moonset or one of the transits; the page then places that window 12 hours from the opposite transit, or six hours from the transit, so treat it as approximate on those days.

See today's windows on any water →

Using the windows sensibly

The windows do not change our daily score; they are printed beside it. Given effects of the size the studies found, use them to choose between two otherwise similar hours, not to decide whether to go. On the coast, the moon's larger effect works through the tides: NOAA notes that tidal ranges run slightly larger around new and full moon, so a tide table for your spot will tell you more than a solunar rating.

Saltwater reports → · Tides explained →

Common questions