Moon phases and fishing: tides, night light and evidence

The phases and the 29.5-day cycle

Half of the moon is always lit by the sun. The phase is how much of that lit half can be seen from Earth as the moon travels round its orbit. One full cycle takes about 29.5 days, so the four main phases come roughly a week apart and their dates drift through the calendar.

New moon: the moon lies roughly between the Earth and the sun, and its lit side faces away. It rises and sets with the sun, so the night is dark.

First quarter: about a week later, half the disc is lit. The moon rises around the middle of the day and sets around the middle of the night.

Full moon: the moon is opposite the sun. It rises around sunset and sets around sunrise, so it is up all night.

Last quarter: half the disc is lit again. The moon rises around the middle of the night and is still in the sky through the morning.

Phase and the size of the tides

This is the firm physical link. The moon and the sun both raise tides, with the moon having the larger effect. Around the new moon and the full moon the two are in line and their pulls combine, producing spring tides: higher high waters, lower low waters and stronger tidal currents. The name has nothing to do with the season. Around the first and last quarters the sun and moon pull at right angles, producing neap tides, with a smaller range and weaker currents.

The largest tides usually arrive a day or two after the new or full moon rather than exactly on it, and the delay differs from place to place. The moon's distance matters as well: when it is at its closest to the Earth near a new or full moon, the spring tides are larger than usual.

For fishing, springs move more water. They flood ground that neap tides never reach, uncover more at low water and run harder through channels and around headlands. That can concentrate feeding, and it can also make some marks awkward or impossible to fish. Neaps are gentler. How much any of this matters depends on the coast, because in some regions the tidal range is small at every phase.

Phase and night-time light

Around the full moon a clear night stays bright from dusk to dawn. Around the new moon it is dark throughout. At the quarters only half the night is lit: the evening at first quarter, the hours before dawn at last quarter. Thick cloud can cancel all of this.

Light matters because many fish hunt by sight and many small prey animals rely on darkness for cover. In open water, large numbers of small animals rise toward the surface after dark and sink again before dawn, and researchers have found that bright moonlight can change how close to the surface some of them come. Fish that feed on them may shift depth to match.

What anglers believe

That fish feed through a bright full-moon night and are therefore harder to catch the following day.

That the dark nights around the new moon are the best for night fishing, or, according to others, the worst.

That the few days either side of the new and full moon are the best of the month, a view shared with solunar theory.

These beliefs do not all agree with each other, and they change with the region and the target species.

What the evidence shows

Studies of commercial and recreational catches have found a lunar pattern for some species and fishing methods and none for others. Where a pattern appears, its direction is not consistent: some catches peak near the new moon, some near the full. It is also well documented that a number of marine species time their spawning to the lunar and tidal cycle, which can make them easier or harder to catch at particular phases.

Several things make a direct effect hard to pin down. On the coast, phase and tidal range change together, so an apparent moon effect may really be a tide effect. Angler behaviour changes too, since more people fish at night under a bright moon. In fresh water there is no meaningful tide, which leaves light as the main plausible route, and results there are no more consistent.

The honest position is that the moon's phase matters to some fish in some places, mostly through tide and light, and that no universal rule has been shown.

What to take from this

On the coast, look at the tidal range for the week rather than at the phase alone. The spring and neap pattern tells you how much water will move, and the tide table tells you when. For a night session, check when the moon rises and sets and how much cloud is forecast.

Phase has a safety side as well. Spring tides come in further and faster and can cut off sandbanks, rocks and causeways that stay dry on neaps. The dark nights around the new moon call for good lighting and a known route back.

CatchWindow location pages show the moon phase next to sunrise and sunset, and tide predictions where a tide station applies, so the three can be read together. After that, a log of your own catches by phase and tide will say more about your water than any general rule.