the math of fishing,
done right
Weight, line, drag, moon and tide: the math everyone does in their head on the riverbank. Everything works on your phone, most of it even without internet.
weight from length
Measure the fish on the ruler and release it. Each species' length-weight relationship (W = a·Lb) estimates the average weight.
estimated weight
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how we calculate
line converter
drag on spinning and baitcasting reels
Field rule: between 25% and 33% of the strength of the weakest part (line, leader or knot). With mono, stay close to 25%.
set the drag between
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With a hand scale: line through the guides, rod bent, pull until the line comes out steadily. Without a scale: pull the line by hand; it should come out with firm effort, without jerking.
spool capacity
The spool states its capacity for one line (e.g., 150 m of 0.30 mm). Find out how much fits of a different thickness.
fits roughly
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Capacity drops with the square of the diameter. Leave 2 to 3 mm of free edge on the spool.
monthly solunar table
Stars: strength of the day based on the moon phase and on solunar periods lining up with sunrise and sunset. Major periods (moon overhead and underfoot) last ~2 h; minor ones (moonrise and moonset), ~1 h.
tide table
Pick a point on the coast: use the location button at the top, or one of the shortcuts.
Model tide, not a harbor tide. Sea level comes from a global ocean model (Open-Meteo Marine, ~8 km grid), with zero at mean sea level: that's why low tide shows as negative and heights can't be compared with the Brazilian Navy's tide table. Times are approximate (hourly data, ±30 min) and, in large-tide bays and estuaries (Maranhão, Pará, Amapá), the real range can be much larger. For navigation, use the Brazilian Navy tide table.