Rewritten on 2026-09-30 under the current data integrity rules: verified pressure covers only 32 days and there is no effort or blank-trip record, so whether pressure affects catches is inconclusive; the earlier conclusion is withdrawn. Other studies remain under review.
Do Fish Bite Before a Front? Pressure and Catches Are Inconclusive on Current Data
The earlier finding from a 390-day daily series, with opposite freshwater and marine differences on sharp pressure-drop days, is withdrawn. In the 2026-09-26 snapshot only 2,155 catches have integrity-verified weather with pressure between 980 and 1035 hPa, all within 32 days from 2026-08-25 to 2026-09-25; only 31 days have a day-to-day pressure change, and there is no record of effort or blank trips. Whether pressure affects catches is currently inconclusive.
Inconclusive: verified pressure covers only 32 days with 2 sharp-drop days, and there is no effort or blank-trip record.
Reviewed 2026-09-30 | Data 2026-08-25 to 2026-09-25
Verdict: inconclusive
The earlier version tested pressure change on a daily catch series of 390 days from 2025-01-01 to 2026-09-04 (27 sharp-drop days) and reported opposite differences in freshwater and marine waters. That conclusion is withdrawn.
There are three reasons. The earlier pressure values were not checked by the current weather integrity rules, and verified pressure exists only for 32 days from 2026-08-25 to 2026-09-25. Only 31 days have a day-to-day change in mean pressure, of which 2 are sharp drops (3 hPa or more). The data hold successful catches only, with no effort, fishing time or blank trips.
So whether pressure affects catches is currently inconclusive. This is neither a finding of no effect nor a finding of an effect.
What was measured
Of 14,424 eligible catches from 2025-01-01 to 2026-09-25, 2,285 have integrity-verified weather; 2,244 of those have a pressure value and 2,155 fall between 980 and 1035 hPa, from 703 anglers.
They span 32 days from 2026-08-25 to 2026-09-25; 32 days have at least 3 records.
Days with a day-to-day change in mean pressure: all waters 31 (2 sharp drops, 3 sharp rises); marine 31 (2 drops, 2 rises); freshwater 31 (4 drops, 4 rises). Water class is used only for grouping; no record was excluded because of it.
What would be needed
Integrity-verified pressure covering several seasons, so that drop and rise days are numerous enough.
The time and outcome of every trip, including trips with no catch, so each day has an effort denominator.
Hypotheses written down before looking at the data, then a rerun of the daily-series tests and power analysis.
Data and method
Source: a read-only point-in-time snapshot taken 2026-09-26 (38,040 catch records), recomputed offline with no production reads or writes.
Records count when the current record, species identity and context rules all pass and both upload and verified capture time are on or before 2026-09-25; shrimp-fishing, managed-pond and non-fish records are excluded. Pressure counts only when the app's weather integrity check verifies it.
Daily mean pressure uses Taipei dates and needs at least 3 records a day; a sharp drop or rise is a day-to-day change of 3 hPa or more.
Keep a record of your own trips
What this study lacks is longer verified weather data and a record of every trip. Use the App to log your catches, places and times for your own future comparisons.
Citation and data
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