NASA Sees Early Signs El Niño Could Impact US Fish Supply

NASA satellite data suggests El Niño may already be altering marine conditions in the Pacific, potentially impacting fish populations and fisheries on the West Coast and further afield. El Niño is a climate pattern characterized by warmer-than-normal waters in the equatorial Pacific and changes in atmospheric and ocean circulation.

The National Oceanic and Atmospheric Administration (NOAA) predicts a more than 90% chance of a very strong El Niño event by 2027, with a 69% chance of a historic event surpassing previous El Niño strength since 1950.

NASA detected warmer sea surface temperatures, higher sea surface height, and reduced chlorophyll-a levels in the central equatorial Pacific in June 2026 compared to neutral conditions in June 2025. Phytoplankton, microscopic organisms forming the base of the marine food web, are indicated by chlorophyll-a levels. NASA’s PACE satellite observed substantially lower chlorophyll-a concentrations during June 2026 compared to neutral conditions in June 2025, a pattern typically seen during El Niño when weakened trade winds and deeper warm surface waters suppress cool, nutrient-rich upwelling that supports phytoplankton growth.

Experts caution that while satellite images of surface chlorophyll-a levels provide insight, they represent only one aspect of the ecosystem. NOAA research oceanographer Andrew Leising stated that reduced phytoplankton levels "definitely can ripple through the ecosystem." Phytoplankton, forming the base of the food web, supply energy to a wide array of marine life, from zooplankton to fish, seabirds, and marine mammals.

Warm waters, whether near the equator or the U.S. West Coast, generally inhibit upwelling, the process that replenishes surface waters with cold, nutrient-rich water essential for phytoplankton growth and the broader ecosystem.

Michael Jacox, a research oceanographer at NOAA’s Southwest Fisheries Science Center, emphasized that the tropical Pacific, particularly the eastern Pacific beyond the tropics, is a critical area of action. The U.S. West Coast, as well as the eastern Pacific regions, are expected to be strongly affected by El Niño due to teleconnections between the tropics and the ocean and atmosphere.

Along the U.S. West Coast, reduced productivity can result from weakened coastal upwelling, increased ocean stratification, and a deeper nutricline, the depth at which high nutrient concentrations are found.

The impacts on the U.S. West Coast may vary depending on the species. Cold-water species might migrate north or to deeper waters, experiencing lower growth and reproduction rates. However, some warm-water species, such as tunas, may move closer to shore and northward during El Niño conditions, potentially presenting new fishing opportunities.

Nevertheless, experts caution that El Niño does not guarantee specific impacts. Instead, it shifts the odds toward warm, low-productivity conditions, and the severity of these impacts increases with the strength of the El Niño event.

Leising emphasized the limitations of relying solely on surface chlorophyll-a levels, noting that satellites generally capture only the top few meters of the ocean. Phytoplankton can exist deeper in the water column, and surface chlorophyll-a levels often correlate with chlorophyll levels in the upper water column but not always.

Additionally, equatorial chlorophyll-a levels are typically lower than in coastal regions, meaning small changes can appear larger in relative terms. Furthermore, a single chlorophyll-a image reflects the presence of phytoplankton at a particular moment, not necessarily the extent of biological production over time.