How Peskio works

Last updated 2026-10-23

Peskio brings the tide, the sun and moon, the weather, the sea and the shape of the coast together on one page for each place, and turns them into a plan for the day. This page explains what each number means and what goes into it.

What the numbers mean

• Tides: the tide times for each day — when high and low water come and how high they reach — and the tide chart showing the height of the water hour by hour.
• Fish activity, from 0 to 100: how favourable each hour looks for fish to be feeding, with the best activity window marked.
• Conditions for each way you fish: how workable the wind, sea and weather look for shore, boat, rock, kayak and spearfishing.

Fish activity is shown in four bands: poor below 35, fair from 35 to 54, good from 55 to 74, and excellent from 75 up. Fish activity and conditions then combine into one call for the day: Go, Marginal or Not today (the map shows today’s fish activity and conditions). Both have to look right for a Go; lively fish activity doesn’t make up for a sea you can’t fish. Each call carries a confidence grade (high, medium or low) that reflects how complete and how recent the data behind it is, and how far ahead the day lies.

Tides

Tides are predicted by harmonic synthesis: the tide at each place is built from up to ten tidal constituents, the regular astronomical rhythms that add up to the rise and fall of the water, with nodal corrections for the slow cycle of the moon’s orbit applied on every calculation. In the United States the constants come from NOAA reference stations; everywhere else they come from the FES global ocean tide model. High and low waters are located and then refined numerically.

Heights are given above a low-water reference: MLLW (mean lower low water) at US stations, and an approximation of the lowest astronomical tide elsewhere. The tide coefficient is our own computation, in the French style: the bigger the number, the bigger the tide.

Sun, moon and solunar periods

Sunrise, sunset, moonrise, moonset, the moon’s phase and the light of dawn and dusk are computed for each place and day. From the moon’s position we derive the solunar periods: major periods around the moon passing overhead and underfoot, and minor periods around moonrise and moonset — what fishing almanacs publish as solunar tables. Solunar timing is a long fishing tradition rather than settled science, so we treat it as one input among many.

Fish activity

Fish activity is a model that weighs many signals, hour by hour: how strongly the tide is running and how big it is, the timing of the moon, the low light of dawn and dusk, the pressure trend, wind, waves and swell, sea temperature, cloud and light, current, and how today’s wind and swell meet this particular stretch of coast. It is built to take further signals too, such as the season and water clarity.

The weighting isn’t the same everywhere. It changes from place to place with the tidal regime and with how exposed the coast is, so a sheltered cove in a tideless sea and an open beach with a big tidal range are read differently. The strongest stretches of a day become its best activity windows — the best fishing times of the day, or what anglers call bite times.

Conditions for each way you fish

Conditions are worked out separately for shore, boat, rock, kayak and spearfishing, because a sea that is comfortable from a boat can keep a kayak on the beach. For each one we blend the factors that matter to it: wind and gusts, sea state and swell, storms and rain, current, comfort, and for spearfishing, water clarity. Combined with fish activity, that gives the day’s Go, Marginal or Not today, and the confidence grade drops when the data is thin.

Your coast, not just your town

For each coastal place we work out which way the shore faces and how far open water runs in 36 directions around it. That is how we know whether today’s wind is blowing onshore or offshore here, whether the swell can reach the shore, and how sheltered a cove is. On an open shore such as Brighton, on the English Channel, a southerly wind blows straight onshore. Two beaches on either side of a headland can face very different seas, and their numbers show it.

Water clarity and plankton

Water clarity starts from satellite observations of the water itself. We take the most recent clear view and combine it with the conditions around the day you are looking at: recent swell, rain and river run-off, onshore wind, current, sudden cooling of the sea, and the light. Where there is no recent clear view of the water, a fallback estimate takes over. Clarity is shown as a class (clear, good, moderate, murky or poor) with an estimated range in metres.

Plankton is the satellite chlorophyll reading, shown with its age: low below 1 mg/m³, moderate from 1 to 4, and high from 4 up.

Seafloor maps

Where we have survey coverage, seafloor maps merge global and regional survey sources (GEBCO, EMODnet and higher-resolution regional surveys) into one map, as on the Costa Brava at Cadaqués. Tap the map to read the depth, with the data source credited on the map.

Freshness and confidence

Weather and ocean data are brought in by import jobs, and every forecast on the page shows how old it is. The forecast’s age, how far ahead the day lies and how complete the data is all feed the confidence grade. Beyond the forecast range a day has no weather and no Go, Marginal or Not today call, and says so; fish activity there runs on the tide, sun and moon alone.

Corrections and questions

Peskio is made by Jordi in Catalonia, Spain (who we are). If a number looks wrong for a place you know, write to [email protected] with the place and the date, and we will look into it.