When ocean temperatures rise during an El Niño event, the first industry to feel the impact is commercial fishing. The eastern Pacific anchoveta fishery — the largest single-species fishery on Earth, producing up to 6 million metric tons annually — can collapse by 60-80% during a strong El Niño. This guide explains how warming waters cascade through marine food webs and reshape global seafood production.

The Anchoveta Collapse: Peru's Economic Barometer

Peru's anchoveta fishery accounts for roughly 10% of all global fish landings by weight. During normal conditions, nutrient-rich cold water wells up from the deep ocean, fueling massive phytoplankton blooms that anchoveta feed on. When El Niño arrives, the thermocline deepens and warm surface water cuts off this nutrient supply. Plankton populations crash, anchoveta starve or migrate south toward Chile, and the fishery collapses. The 1997-98 El Niño reduced Peru's fishmeal exports by $2.2 billion. During the 2023-24 El Niño, Peru's first anchovy season was canceled entirely — a decision that rippled through global aquaculture feed prices.

Tuna Migration Shifts

Tuna follow temperature gradients. During El Niño, skipjack and yellowfin tuna shift their range eastward by 1,500-3,000 kilometers. This creates winners and losers: Pacific Island nations like Kiribati and Tuvalu see increased tuna catches in their EEZs during El Niño years, while the Philippines and Indonesia experience declines. A 2023 study in Nature Climate Change found that El Niño-driven tuna redistribution has already sparked international disputes over fishing rights as stocks move across jurisdictional boundaries.

Salmon: Temperature Thresholds and Disease

Pacific salmon are cold-water fish with specific temperature tolerances. When El Niño warms coastal waters above 15-16°C, salmon metabolism accelerates, growth slows, and disease susceptibility increases. The 2015-16 El Niño contributed to a 50% decline in California Chinook salmon returns the following year. Alaska's Bristol Bay sockeye fishery — the world's largest — saw catches drop from 56 million fish in 2015 to 37 million in 2016. Aquaculture operations face different pressures: warmer water holds less dissolved oxygen, increasing aeration costs and mortality rates in salmon pens.

Coral Reef Fisheries: The Long-Term Damage

Coral bleaching during El Niño destroys reef habitat that supports 25% of all marine species. The 2015-16 global bleaching event — the worst on record, driven by a strong El Niño superimposed on background warming — affected 70% of the world's coral reefs. Reef fisheries in Southeast Asia, the Caribbean, and the western Indian Ocean lost an estimated 30-40% of their fish biomass within two years of severe bleaching. Unlike pelagic fisheries that recover within 1-2 years, reef fisheries take decades to rebuild.

Regional Winners

Not all fisheries suffer. Warm-water species like squid, sardines, and mackerel sometimes thrive during El Niño. California market squid landings surged during the 1997-98 event. Humboldt squid expanded their range from Mexico to Alaska during the 2009-10 El Niño, creating a temporary but lucrative fishery. The key pattern: small, fast-growing species with short generation times can exploit the ecological disruption, while large, slow-growing predators lose out.