tides and moon in fishing
Spring and neap tides, high and low tide, slack water, rising and falling tide, tide tables and solunar theory: what really matters and how to use it without fanaticism.
why the tide rises and falls
Tides are caused mainly by the Moon's pull and, to a lesser degree, the Sun's. Along most of the Brazilian coast they are semidiurnal: two high and two low tides a day, in a cycle of about 12 hours and 25 minutes. That's why the tide is about 50 minutes later each day.
tips
- High tide: the peak of high water.
- Low tide: the lowest point.
- Rising tide: the water is coming up, with current flowing into estuaries.
- Falling tide: the water is going down, with current flowing out.
- Slack water: the pause at the turn of the tide, near high and low tide, when the current nearly disappears.
- Tidal range: the difference between high and low tide. In Maranhão it exceeds 6 m; in the South it stays under 1 m, and there wind and pressure often move the level more than the moon does.
spring and neap tides
At new and full moon, the Sun, Earth and Moon line up and their forces add together. That's a spring tide: bigger tides, with higher high tides, lower low tides and stronger currents. At the first and last quarter, the forces cross. That's a neap tide: smaller tides and weak currents. The effect usually comes one or two days after the phase.
tips
- Spring tide: strong current stirs up food and gets fish active, but muddies estuary water and calls for heavier sinkers.
- Neap tide: clearer water and weak current. Makes bottom fishing with light sinkers and artificial lures in clear water easier.
- Spring low tide exposes sandbars, channels and rocks. Use it to study the spot.
tide table
The tide table gives, for each day, the times and heights of high and low tide at a reference port. The official tables come from the Brazilian Navy (Marinha do Brasil). The app shows sea level from a global ocean model, with zero at mean sea level: it helps you see the tide's rhythm (rising, falling, spring and neap tides), not compare heights with the Navy's table.
- Find the reference port closest to your spot.
- Note the times and heights of high and low tide for the day.
- Remember that inside estuaries and rivers the tide arrives later than at the bar, sometimes by more than an hour.
- In the Navy's table, a negative height means water below the chart datum: a very low low tide. In the app zero is mean sea level, so every low tide shows as negative.
- Use the twelfths rule: over about 6 hours, the water rises or falls 1/12 in the first hour, 2/12 in the second, 3/12 in the third and fourth, 2/12 in the fifth and 1/12 in the sixth. The current is strongest in the middle hours.
- Factor in the weather: strong onshore wind and cold fronts can push the water above the forecast (meteorological tide).
how to use the tide in fishing
Every spot has its own good tide. Find yours by noting your catches.
tips
- Moving water usually bites better than still water.
- Estuary: on the falling tide, water flows out of the mangroves and gamboa creeks carrying shrimp and baitfish, and snook wait at the mouths. On the rising tide, fish move in to hunt the shallows.
- Beach: a rising tide covering the sandbars is usually good.
- Where the current is very strong, slack water is the window for bottom fishing with a light sinker.
- Log in the app what the tide was like for each catch. After a few trips, your spot's pattern shows up.
common mistakes
- Using a distant port's table without correcting for the delay.
moon and solunar theory
Solunar theory, popularized by John Alden Knight in the 1920s and 1930s, holds that fish feed more during periods tied to the Moon's position. The major periods, about 2 hours long, occur when the Moon passes overhead and at the opposite point, under your feet. The minor periods, about 1 hour long, occur at moonrise and moonset. The best days would be near new and full moon, and the best periods those that coincide with sunrise and sunset.
tips
- Use it without fanaticism. The scientific evidence is weak and inconsistent; weather, water level, tide and location matter far more.
- Use it as a tiebreaker: between two similar times, pick the one that falls in a solunar period.
- A full moon lights up the night. Many anglers say some fish hunt more at night and slow down in the morning. Treat it as a hypothesis and test it at your spot.
- In the sea and estuaries, the Moon's most concrete effect is the tide.
checklist
Check off what's ready. Saved on this device.
sources and references
- official Marinha do Brasil/Centro de Hidrografia da Marinha (CHM) — Tábuas das MarésOfficial tide tables for Brazilian ports.
- official NOAA National Ocean Service — Tides and Water Levels (tutorial)
- technical Knight, J. A. (1942). Moon Up, Moon Down: the story of the Solunar Theory. Nova York: Charles Scribner's Sons.Book presenting solunar theory. The theory is empirical, with no general scientific proof. The URL is the bibliographic record on Open Library.
keep reading
how to read the beach and rocky shore
Find troughs, sandbars and rip currents, choose tide and time, and fish the rocky shore without risking your life.
weather and moonhow weather affects fish
Pressure, cold fronts, friagem (cold spells), wind, rain and water temperature: what changes in fish behavior, and how to read the app's index, confidence and forecast horizon.
technicalsurf and rocky shore rigs
Paternoster, 2-to-3-hook rig, pyramid sinker, feeder float for mullet and a rig for pompano, with practical measurements and the shock leader that prevents accidents.