Which climate mode leaves a footprint in national marine catches? Field significance for eleven climate modes and 146 countries, the flavour of El Niño and the fallacy of naive screening, 1952–2024
Hangi iklim kipi ulusal deniz avında iz bırakır? On bir iklim kipi ve 146 ülke için alan anlamlılığı, El Niño'nun çeşidi ve naif taramanın yanılgısı, 1952–2024
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Abstract
It is widely accepted that climate modes broadly affect fisheries, and the literature is full of significant relationships found between individual stocks and climate indices. This study asks the question in reverse: what remains when the same method is applied to all countries and all major climate modes? The detrended marine catch of 146 countries from the FAO capture database is related to eleven climate indices (three measures of ENSO, PDO, NP, PNA, NAO, AMO, two tropical Atlantic indices and the Indian Ocean Dipole); significance is tested against a null distribution obtained by shifting the indices in time, which preserves autocorrelation. Three results stand out. First, the footprint of no climate mode in national catches is significant at the field level: for the strongest candidate, the eastern Pacific El Niño index, a significant relationship is found in 17 countries, whereas 12 are expected under the null distribution (p = 0.09). Second, a naive screening shows 47% of countries to be sensitive to at least one climate mode; this share does not differ from that expected by chance (45% expected, p = 0.31), and only 4 of 1,606 tests survive control for multiple testing. For autocorrelated indices, conventional tests raise the false-positive rate from five to eleven per cent. Third, the footprint of ENSO in the world total catch belongs to the eastern Pacific type only: a one-standard-deviation increase in the eastern Pacific index reduces the world catch by 1.9% (t = −3.2), whereas the effect of the central Pacific index cannot be distinguished from zero (t = 0.7). This footprint comes entirely from the Peruvian anchoveta. Together the eleven modes explain only 1.7 percentage points more of catch variability in the median country than expected by chance. The results limit the assumption that climate modes can be used in national catch forecasts and show that stock-level climate–catch relationships are a selected sample.
Keywords
Climate modes; El Niño–Southern Oscillation; Marine catch; Field significance; Multiple testing; Eastern and central Pacific El Niño; Statistical power
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