What strange sea life shows up in San Diego during El Niño — and should I worry?
Warm El Niño water brings tropical visitors like hammerhead sharks, devil rays and swarms of bright-red tuna crabs; they're mostly harmless to people, but don't eat the crabs, don't handle a sea snake, and report anything unusual to Scripps.
- Seen off La Jolla, Sept 2026
- Hammerheads, devil rays
- Red crab rule
- Look, don't eat
- Report fish
- Scripps El Niño Fish Records Form
- Stranded mammals
- NOAA (866) 767-6114
The short version
- Scripps researchers were already reporting hammerhead sharks and devil rays off La Jolla in September 2026 — species "we don't typically see here."
- Tuna crabs (pelagic red crabs) strand on San Diego beaches by the thousands when warm water pushes them north from Baja; Scripps advises against eating them.
- Scripps' Marine Vertebrate Collection runs an El Niño Fish Records Form so anglers, divers and beachgoers can report unusual fish with photos.
- The same warm water that brings visitors starves kelp forests and sea lion pups — in past El Niños, stranded pups spiked.
- Report a stranded or injured marine mammal to NOAA's West Coast hotline: (866) 767-6114.
Every strong El Niño turns Southern California's coastline into a bit of a field guide to Mexico. Warm water pushes north, and animals that normally stay off Baja — or much farther south — follow it. This year it started early: a marine heat wave has persisted since 2025, and by September Scripps scientists were already logging visitors.
“We're at the edge of a very strong El Niño that's bringing pretty warm water to the Southern California area, and with that we're seeing species that are popping up that we don't typically see in this area.”
Jack Elstner, Scripps Institution of Oceanography (Sept 2026)
Who's visiting, and what to do about it
El Niño visitors on San Diego's coast
| Tuna crabs (pelagic red crabs) | Hammerheads, devil rays, whale sharks | Yellow-bellied sea snake | |
|---|---|---|---|
| What you'll see | Beaches carpeted in small, bright-red lobster-like crabs | Fins offshore, sightings from boats and kayaks | Rare — a yellow-and-black snake on the sand |
| Why | Warm water intrusions carry them north from Baja on currents | Tropical species following warm water north | Tropical open-ocean species that washes up in warm years |
| Risk to you | None to touch — but Scripps advises against eating them | Very low; lifeguards may post advisories after sightings | Venomous; harmless unless handled. Do not pick it up |
| Verdict | — | — | The one to keep kids and dogs away from |
The red crab days
The most photogenic El Niño sign is the tuna crab, Pleuroncodes planipes (recently reclassified as Grimothea planipes). These crabs spend their whole lives drifting in open water off Baja and in the Gulf of California. When warm water and winds push them north, they strand on beaches in their thousands and turn the tideline red. "Typically such strandings of these species in large numbers are due to warm water intrusions," Scripps' Linsey Sala has said. They're fine to look at and photograph. They are not dinner — Scripps says human consumption isn't recommended because of unknown toxins they may carry.
1949
Year CalCOFI ocean sampling began — the baseline scientists compare against
2025
Current marine heat wave has persisted since
4
Recent strong El Niños Scripps tracks for comparison: 1957–58, 1997–98, 2015–16, 2023–24
The part that isn't fun
Warm El Niño water is nutrient-poor. Upwelling weakens, plankton shifts, and the whole food web feels it. Scripps researchers list the effects: giant kelp forests shrink and are battered by bigger winter swells, cool-water seabirds decline, and sea lion pups starve when their mothers have to swim farther to find food. If you see a thin, lethargic sea lion pup on the beach, it's not resting — but it's also not yours to rescue.
- 01
Stay back
Federal law protects marine mammals; keep people and dogs well away and don't pour water on or feed the animal.
- 02
Call it in
NOAA's West Coast stranding hotline is (866) 767-6114. Note the exact location, the animal's size and whether it's moving.
- 03
Photograph unusual fish
Caught or spotted something tropical? Submit photos with time and place through Scripps' El Niño Fish Records Form.
KEEP READING
SOURCES
Everything above traces back to one of these. Follow them — if one has changed and we haven't, that's our mistake, not yours.
Scripps Institution of Oceanography (republished by Maven's Notebook) · 2026-09-11
Kelp, sea lions, seabirds, tuna range, red crabs, Fish Records Form
Scripps Institution of Oceanography
Species, cause of strandings, not recommended to eat
San Diego Union-Tribune (syndicated) · 2026-09-28
Elstner quote; hammerheads and devil rays
Long Beach Post · 2026-09-23
Sea snake guidance; NOAA stranding hotline