The wide-mouthed shark (Megachasma pelagios) remains one of the planet’s most elusive creatures. Since 1976, scientists have recorded this species only 273 times, making each sighting a rare window into its life. A recent study has compiled all the available details following two individuals were captured on video together by amateur fishermen using their cell phones.
Despite its status as one of the ocean’s largest fish, the biology and life history of this species are still not well understood. On September 11, 2022, off the coast of San Diego, California, two wide-mouthed sharks were photographed together from a small fishing boat. Prior to this moment, only five individuals had been documented swimming in the wild in their natural habitat, separate from any hunting events or strandings.
The footage was posted on social networks by the people who recorded it. Scientists who analyzed the videos also interviewed the boat’s occupants to gather more context and verify observations.
In the encounter, the two sharks were about 45 to 60 meters from the boat. The larger shark measured roughly 4.6 meters, while the other was around 3.7 meters long. The larger individual appeared to circle the smaller one as the boat remained nearby, and the smaller shark, a male, moved to greater depths but eventually trailed the larger shark toward the vessel at a different depth.
The biggest shark made several passes near the boat, while the smaller one mostly stayed deeper and only briefly surfaced near the boat’s side.
Two possible explanations
The research team outlines two leading hypotheses for why the two wide-mouthed sharks were together at that moment. The first suggests they were foraging in proximity, possibly attracted by a common food source. Although the diet of Megachasma pelagios is not fully defined, it is believed they are filter feeders that consume krill, squid, and other gelatinous prey.
Observers did not see any feeding behavior during the encounter. It is possible the boat’s presence altered their activity, and the area at that time did contain abundant gelatinous prey.
The second hypothesis proposes a social or mating context. The investigators note that the male’s approach toward the larger shark resembles patterns seen in the mating behavior of other shark species. While paired or courtship behaviors are documented in some members of the family, mating observations among filter-feeders are uncommon and rarely witnessed in natural settings.
Based on the video evidence and initial observations, researchers contend that premating behavior was likely occurring. They also point out that increasing social media sharing and maritime traffic may lead to more such sightings, offering additional glimpses into the lives of these rare giants.
The study underscores the importance of continued monitoring and documentation to better understand Megachasma pelagios, a species whose presence in the world’s oceans raises intriguing questions about deep-sea ecosystems, feeding strategies, and reproductive biology. The findings are discussed in a peer-reviewed article, which provides a detailed account of the sighting and its possible implications for the species’ biology.
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This observation contributes to a growing body of evidence that wide-mouthed sharks, though rarely seen, can reveal unexpected behaviors when humans document them with modern devices and share findings with the scientific community.