The Easter Island ecoregion, which includes the islands of Salas y Gomez and Rapa Nui (also called Easter Island), is one of the most isolated islands inhabited by humans. Despite limited scientific documentation, anecdotal evidence suggests that the area is home to a variety of marine species, including sharks. Only six species of shark have been scientifically recorded in the region, including the Galapagos shark (Carcharhinus galapagensis) is the predominant presence year-round. However, in June 2021, a local fisherman off the southeast coast of Rapa Nui made an interesting catch – a female tiger shark with a total length of 3.5 meters.

Tiger sharks (Galeocerdo cuvier) are impressive apex predators in warm temperate and tropical marine waters, known for their imposing size and worldwide distribution. Although they prefer coastal areas, these animals are not restricted to specific habitats, as evidenced by their presence in a wide variety of marine environments from continental shelves to the open ocean. Despite isolated evidence of several shark species inhabiting the waters around Rapa Nui, scientific documentation is sparse. A new paper presents the first photographic evidence of a tiger shark in the waters around Rapa Nui, giving scientists concrete evidence of the species’ presence in these remote waters.

However, the predator, caught along with juvenile Galapagos sharks, unfortunately bore marks from a previous encounter with fishing gear. Whether it sustained these scars in the Easter Island ecoregion or elsewhere is uncertain. After all, they are widely distributed in the Pacific, from Japan to New Zealand in the west and from southern California to Peru in the east, including numerous tropical Pacific islands. Recent genetic analyses across the Pacific have revealed remarkable population connectivity among tiger sharks, suggesting extensive migratory ability across vast ocean regions. Surprisingly, there are no scientific records to date documenting their presence in the southeast Pacific.

Subsequent anecdotal reports of tiger shark sightings, including one by recreational divers in February 2023, confirmed the species’ occasional presence near Rapa Nui. Their presence in these waters raises questions about their migratory routes and preferred habitats: do we really know the full picture of the Pacific? Since sea surface temperature plays a critical role in their distribution, warmer-than-usual conditions may have facilitated the transport of these large predators from west to east. Indeed, previous work has linked tiger shark movements to sea surface temperature anomalies, with warmer waters facilitating poleward dispersal beyond their typical range. Such dynamics likely played a role in the tiger shark’s emergence near Rapa Nui, where sea surface temperatures exceeded seasonal averages.

Similar patterns have been observed in other transient marine species, such as the whale shark near Rapa Nui, suggesting broader changes in marine biodiversity. Increased sea surface temperatures associated with climate phenomena such as El Niño and La Niña are altering marine ecosystems worldwide, prompting scientists to reassess species distributions and migration patterns.

Or maybe there’s more to this story. Perhaps the sharks have always been there and the region’s low population density, coupled with limited fishing practices and minimal scientific research, contributed to the rarity of documented sightings of the species. This, say graduate students and co-authors Amy Rose Coghlan and Naiti Morales, underscores the importance of integrating traditional ecological knowledge with scientific observations. Such collaborations, they say, provide invaluable insight into species distribution and behavior, especially in regions where scientific efforts are limited. “However, we suspect that the increased number of new and recent sightings of the shark and fish species discussed here are genuine consequences of increased sea surface temperature anomalies,” the authors conclude.