“That’s because in the spring is when we have upwelling. Upwelling brings lots of nutrients and lots of nutrients bring phytoplankton and zooplankton.” Kudela said.
The upwelling concentrates the animals offshore, and then a change in wind patterns or ocean currents can push them ashore.
Recent rain storms and winds coming from the south and moving north have blown them ashore. “They don’t wanna be on the beach particularly, but they end up there because they can’t control where they go,“ Kudela said.
His forecast for continuing to see them in the coming weeks is rosy.
“I would say if we get a nice high pressure system, which is generally associated with nice clear skies, but also upwelling, it’s going to really concentrate them just offshore,” Kudela added. “And then all we need is a break in that — a low [pressure system] coming through or the high weakening — and then we would probably see a nice big raft of them come washing into the beaches. It’s kind of cool to see, they’re really beautiful.”
If it feels that they’re being seen more often along the coast, there’s a good reason.
Thousands of Velella velella are scattered along the beach at Aquatic Park in San Francisco on April 3, 2025. (Beth LaBerge/KQED)
They’ve always been around and they’re not particularly unusual, Kudela said. However, some research indicates that the frequency of seeing them is increasing over time. Scientists think climate change may be influencing these strandings.
Julia K. Parrish, marine biologist and professor at the University of Washington, studied Velella velella in 2021. Through community science data, she found a possible link between rising sea surface temperatures and increased strandings. “When we see them a lot, it’s sort of like they’re putting up a huge billboard that says, ‘Hey, pay attention, things are changing,’” she told KQED in 2023.
While there is still a lack of concrete evidence, the rising sea temperatures linked to human-caused climate change may lead to more sightings of these disc-like creatures.
“When we see signals coming from the ocean to the coast, we should pay attention,” she said. “The Velella velella is an early-warning bell that we may be seeing some shifts.”
