LOS ANGELES (Reuters) - El Nino's warm currents have brought fish in an unexpected spectrum of shapes and colors from Mexican waters to the ocean off California's coast, thrilling scientists with the sight of bright tropical species and giving anglers the chance of a once-in-a-lifetime big catch.
Creatures that have made a splash by venturing north in the past several weeks range from a whale shark, a gentle plankton-eating giant that ranks as the world's largest fish and was seen off Southern California, to two palm-sized pufferfish, a species with large and endearing eyes, that washed ashore on the state's central coast.
Scientists say El Nino, a periodic warming of ocean surface temperatures in the eastern and central Pacific, has sent warm waves to California's coastal waters that make them more hospitable to fish from the tropics.
El Nino is also expected to bring some relief to the state's devastating four-year drought by triggering heavy rains onshore.
But so far precipitation has been modest, and researchers say the northern migration of fish in the Pacific Ocean has been one of the most dynamic, albeit temporary, effects of the climate phenomenon.
Even as marine biologists up and down the coast gleefully alert one another to each new, rare sighting, the arrival of large numbers of big fish such as wahoo and yellowtail has also invigorated California's saltwater sport fishing industry, which generates an estimated $1.8 billion a year.
"Every tropical fish seems to have punched their ticket for Southern California," said Milton Love, a marine science researcher at the University of California, Santa Barbara.
Some fish made the journey north as larva, drifting on ocean currents, before they grew up, researchers said.
The first ever sighting off California's coast of a largemouth blenny fish was made over the summer near San Diego, said Phil Hastings, a curator of marine vertebrates at the Scripps Institution of Oceanography.
That species had previously only been seen further south, he said, off Mexico's Baja California.
Small, colorful cardinalfish were also spotted this year off San Diego, while spotfin burrfish, a rounded and spiny species, were sighted off the coast of Los Angeles, said Rick Feeney, a fish expert at the Natural History Museum of Los Angeles County.
Those tropical species are hardly ever found in Californian waters, he said.
Some small tropical fish could remain in the state's waters over the coming months, researchers said, as El Nino is expected to last until early next year.
"As soon as the water gets cold, or as soon as they get eaten by something else, we'll never see them again," Love said.
For sports fishers, it was so-called pelagic zone fish like wahoo, that live neither close to the bottom nor near the shore, which made this year special.
Before the El Nino, California anglers only saw wahoo, a fish with a beak-like snout and a slim body that often measures more than 5 feet (1.5 meters) in length, when they made boat trips south to Mexican waters.
This year, there were 256 recorded catches of wahoo by sport fishing party boats from Southern California, with almost all of those being taken on the U.S. side of the border, said Chad Woods, founder of the tracking company Sportfishingreport.com.
Last year, he said, the same boats made 42 wahoo catches.
Michael Franklin, 56, a dock master for Marina Del Rey Sportfishing near Los Angeles in the Santa Monica Bay, said this was the best year he can remember, with plentiful catches of yellowtail and marlin.
"I've been fishing this bay all my life since I was old enough to fish, and I've never seen it like this," he said.
Many hammerhead sharks also cruised into Californian waters because of El Nino, experts say.
Sport fisherman Rick DeVoe, 46, said he took a group of children out in his boat off the Southern California coast this September. A hammerhead followed them, chomping in half any tuna they tried to reel in.
"The kids were freaking out because the shark's going around our boat like 'Jaws'," DeVoe said.
Reporting by Alex Dobuzinskis; Editing by Daniel Wallis and Andrew Hay