NOAA Fisheries says the 2026-2027 El Niño is already changing marine conditions along the US West Coast, with Southern California fishermen catching large numbers of yellowfin tuna, wahoo and striped marlin normally associated with waters off Mexico. Warmer water, higher sea level and weaker nutrient-rich upwelling can move species north, creating short-term opportunities for recreational and some commercial fishing. Kelp forests, cold-water fish, seabirds and less mobile bottom species may instead lose habitat and food. NOAA is tracking temperature, sea level, plankton and catches. El Niño is a natural cycle, while actual outcomes combine with a preceding marine heatwave, human-driven warming, regional currents and winter storms; the appearance of a single species cannot be treated as a lasting ecosystem gain.