First it was yellowfin tuna, arriving two months early. Hammerhead sharks formed the second wave, swarming in by the hundreds. A manta ray soared past a kelp forest and a whale shark vacationed at Catalina Island. Bluestriped chub, pufferfish, tripletail, and baqueta stopped by to check out our local reefs. Blue marlin and wahoo, virtually unheard of in southern California, delighted offshore anglers.
This manta ray (Manta birostris
) was filmed at San Clemente Island by Carter Jessop in mid-August. Mantas are found worldwide in tropical and subtropical waters but only very rarely visit southern California.
As a fish ecologist who also enjoys recreational saltwater fishing, I often receive pictures from fishing friends asking to help identify unusual species. As all of these tropical fish species flooded into southern California waters. Their pictures also flooded into my email inbox.
Surely this tropical fish invasion is a sign that we must be having a tremendous El Niño, right?
Not so fast.
In fact, all summer we were stuck in neutral. ENSO-neutral, that is. ENSO stands for El Niño-Southern Oscillation, and it’s the technical term for the interaction between atmospheric and oceanographic conditions in the Pacific Ocean near the equator. ENSO-neutral means that conditions are roughly average, that is, neither El Niño (positive ENSO index) nor La Niña (negative ENSO index).
Slender sunfish (Ranzania laevis
) are related to the more familiar ocean sunfish (Mola mola
) but only rarely make it north of southern Baja California. This one washed up at Catalina Island and large schools of them have been seen by divers in local waters. Photo credit: Juan Aguilar
Throughout the summer months, climate scientists saw signs of a growing, potent El Niño. Notably, ocean waters in the central and eastern Pacific warmed dramatically, similar to the summer of 1997. That summer marked the development of El Niño in the winter of ’97-’98, which was one of the strongest ever recorded.
This summer, however, the atmosphere just never got on the same page as the ocean, keeping conditions stuck in an ENSO-neutral state.
The latest forecast still predicts a weak El Niño to develop in the coming months,
but it may not be nearly as strong as previously thought.
This sea surface temperature (SST) anomaly figure shows whether ocean surface waters are warmer or colder than normal. Notice that the waters off southern CA are 1-3°C warmer than usual for September.
So, why did all of these tropical fishes invade southern California?
Despite the lack of true El Niño conditions at the equator, water temperatures in southern California and northern Baja were up to 3°C (~6°F) warmer than usual. These warm conditions allowed tropical species to swim farther north than they normally do, invading southern California in surprisingly large numbers and giving local anglers and fish biologists a rare treat.
This blue striped chub, a.k.a. rainbow chub (Sectator ocyurus) was caught aboard the sport fishing boat Sum Fun near Dana Point, CA in early July. This species is typically found in the eastern Pacific from southern Baja CA to Peru. (Photo credit: Brian Wooley)
In southern California, the biggest effect of El Niño on local fish occurs after
it peaks in the winter. Given that we saw this big tropical species invasion even before El Niño really gets underway, who knows what next summer will bring!
Find out more about El Nino at the ENSO Blog.
Author: Jeff Barr, Ph.D. Candidate, contact at email@example.com