Rare tropical fish, unusual shark sightings and the first documented sea turtle nests on the U.S. West Coast are drawing scientific attention to California as a strengthening El Niño coincides with exceptionally warm ocean conditions.
Two olive ridley sea turtles laid eggs on Southern California beaches in September 2026, while a longfinned bigeye fish became the first recorded specimen of its species in the state. Whale sharks, hammerheads and other warm-water animals have also been reported along the coast.
The unusual activity, described in Reuters reporting published October 17, illustrates how rapidly marine life can respond to changing ocean conditions. But scientists face a more complicated question: how much of the shift is attributable to El Niño, and how much reflects a separate marine heatwave that was already affecting California?
Rare Species Turn Up Along California's Coast
The most significant confirmed development involves olive ridley sea turtles, a highly migratory species that normally nests much farther south.
According to NOAA Fisheries, a female olive ridley nested near Seal Beach on September 16, 2026, marking the first recorded sea turtle nesting event on the U.S. West Coast. A second female nested approximately eight miles away, near Huntington Beach Pier, on September 19.
Scientists used photographic comparisons of shell patterns and other physical characteristics to establish that two different turtles were involved. On September 25, an interagency team transferred the eggs to the Aquarium of the Pacific in Long Beach for protected incubation. Whether the eggs were fertilized or viable remained uncertain in NOAA's latest published assessment.
Another unusual discovery came from Venice Fishing Pier in Los Angeles, where an angler caught a longfinned bigeye (Cookeolus japonicus), a reddish fish distinguished by its exceptionally large eyes and elongated fins.
The Natural History Museum of Los Angeles County confirmed the specimen's addition to its ichthyology collection. Although the species was already known from warmer waters farther south, the catch represented its first documented California record—not the discovery of a new species.
Museum researchers have also documented reports of hammerhead sharks near Southern California and a whale shark off Malibu. Separately, a suspected yellow-bellied sea snake appeared in Orange County in September. Its identification was supported by expert assessment of cellphone footage rather than examination of a recovered specimen.
Such records establish that unusual animals have appeared in the region. They do not, by themselves, demonstrate permanent population changes or prove that every arrival has the same cause.
How El Niño Changes Marine Habitats
El Niño develops when the tropical Pacific's normal ocean-atmosphere circulation changes. Trade winds weaken, allowing unusually warm surface waters to expand eastward across the equatorial Pacific. The resulting changes in ocean circulation can affect temperatures, currents and marine food webs far beyond the tropics.
In its October 8, 2026, advisory, NOAA's Climate Prediction Center reported that sea-surface temperatures in the Niño-3.4 monitoring region were 2.1 degrees Celsius above average. NOAA assessed the probability of strong-to-very-strong El Niño conditions persisting through January–March 2027 at greater than 83%.
That measurement describes a defined region of the tropical Pacific, not the temperature increase directly observed off California. The ultimate strength and regional impacts of the event remain subject to uncertainty.
California's situation is especially complex because unusually warm coastal waters preceded the current El Niño.
NOAA's California Current ecosystem assessment identifies a marine heatwave affecting parts of the coast since May 2025. NOAA explicitly distinguishes that event from warming driven by El Niño, while warning that additional El Niño-related warming could prolong the period of elevated temperatures.
Under typical conditions, winds help bring cold, nutrient-rich water toward the surface along California's coast through a process called upwelling. This supports phytoplankton, which form the foundation of food webs sustaining fish, seabirds and marine mammals.
El Niño can weaken or disrupt that nutrient supply and change where suitable habitats occur. However, NOAA's September assessment found that nutrient supply, as indicated by its upwelling measurements, was approximately average at that time. A future ecological risk should not be mistaken for an already measured ecosystem-wide decline.
New Opportunities for Fish, New Pressures on Ecosystems
For recreational fishing businesses, the arrival of warm-water species has created opportunities that are unusual for Southern California.
Donna Kalez, co-owner of Dana Wharf Sportfishing & Whale Watching, told Reuters that anglers with the business had caught approximately 5,000 yellowfin tuna in 2026, compared with just two in 2025. Other catches included wahoo and mahi-mahi, also known as dorado.
Those figures describe reported catches associated with one fishing operation. They are not estimates of statewide tuna abundance, and the comparison does not establish how much changing fishing effort, vessel activity or other factors contributed to the difference.
The ecological consequences are less straightforward. Mobile fish may follow suitable temperatures and prey into new areas, while species tied to particular habitats cannot necessarily relocate as easily.
California's giant kelp forests are especially important. These underwater habitats flourish in cool, nutrient-rich conditions and provide shelter and feeding opportunities for numerous marine organisms. Prolonged warming can threaten kelp growth and survival, potentially affecting the wider ecosystem that depends on it.
There is historical evidence for concern. The northeastern Pacific marine heatwave commonly called the Blob, followed by the strong 2015–2016 El Niño, produced more than 700 consecutive days of elevated temperatures in the California Current ecosystem, according to NOAA.
That sequence was associated with shifts in marine species, food-web disruption, harmful algal blooms and losses affecting some marine populations. It provides an important comparison, but does not establish that the same impacts have already occurred on the same scale in 2026.
NOAA scientists identify the duration of elevated temperatures as a particular concern this time. Even if temperatures do not rise dramatically further, a prolonged warm period could extend ecological stress and reduce the availability of suitable habitat for some species.
Will These Unusual Marine Visitors Stay?
The appearance of tropical animals off California does not necessarily mean they are establishing permanent populations.
Marine species can move temporarily into unfamiliar waters when ocean temperatures and currents change. Some may disappear from local observations as conditions cool, while others could return during future warming events. Determining whether a lasting range shift has occurred requires observations across multiple seasons and, in some cases, evidence of successful reproduction.
The olive ridley nests illustrate that uncertainty. Nesting confirms that the turtles reached California's beaches and laid eggs. It does not yet establish successful hatching, survival of offspring or the emergence of a self-sustaining nesting population.
Scientists will continue examining museum specimens, tracking unusual sightings and monitoring ocean temperatures, nutrient conditions and marine habitats. Those observations may help distinguish temporary visitors from more persistent ecological changes.
For now, California's extraordinary marine encounters offer evidence of how responsive ocean ecosystems can be to changing conditions. Whether the current arrivals become a short-lived episode or an early indication of more enduring shifts remains an open scientific question.
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