eslie Kretschmar was amazed to see a pod of pilot whales, rare in Orange County waters, swim up to the Ocean Institute’s boat.

She was leading a group of 30 elementary-school students from San Clemente on a Friday morning educational trip when the dark black-gray cetaceans, about 18 feet long, came right up to the Institute’s R/V Sea Explorer vessel.

“It was just astonishment,” said Kretschmar, a marine biologist and director of at-sea programs for Dana Point’s Ocean Institute. “None of our staff or myself had ever seen them before. It was a pretty incredible experience for all of us.”

It is fairly rare to see pilot whales around here, Kretschmar said. While there were common sightings in the 1970s and 1980s, sightings have been rare since then, she added. It’s been about 20 to 30 years since pilot whales have been seen in local coastal waters, said biologist Diane Alps, vice president of the American Cetacean Society and president of the Los Angeles chapter.

After a strong El Niño in 1982-1983, pilot whales disappeared from the area, said Lisa Ballance, director of marine mammal and turtle research division at the National Oceanic and Atmospheric Administration’s Southwest Fisheries Science Center. They have been slowly coming back, she said, with more and more common sightings. The Register reported a similar sighting in Dana Point of a pod of 50 pilot whales in June.

Kids on board were, naturally, excited. Typically in a school trip, the Ocean Institute will see perhaps common and bottlenose dolphins. The pod of about 30 whales spotted on Oct. 17, about 3 miles off the Dana Point Harbor, included both short-fin and long-fin pilot whales, Kretschmar said.

“I don’t think they really understood the gravity of what they were seeing,” Kretschmar said of the children. “We explained to them this is a once-in-a-lifetime opportunity, they may never see these animals ever again.”

These mammals aren’t the only ones arriving unexpectedly. About 50 sperm whales were spotted off the coast in early October, an unprecedented event. Whale sharks, Bryde’s whales, yellowfin tuna, pufferfish and hammerhead sharks have been seen in Southern California waters, and a Fullerton resident caught a wahoo in Newport Beach in late August, according to Register archives.

Just a few days after spying pilot whales, Kretschmar and her captain spotted a humpback whale and Risso’s dolphins on another field trip with students a few miles off the Dana Point Headlands on Oct. 22. Although humpbacks are considered less rare than pilot whales, Kretschmar said there have been multiple sightings of humpback whales all summer and fall, and suspects this particular cetacean has stuck around for a week. The “extremely friendly” young humpback was about 35 feet long and played with kelp and criss-crossed under the ship.

Recent hurricanes off of Mexico have contributed to warmer waters, said Alps, who is also the programs coordinator at the Cabrillo Marine Aquarium in San Pedro. Those storms pushed warm water north to the Southern California area, and animals are following those currents, she said.

While warmer temperatures are one factor, the precise reasons why these mammals have been visiting the local coast is something of a mystery.

“All of a sudden, we started to see (pilot whales) here again. We’re wondering what’s going on,” Alps said.

What’s interesting, Alps said, is that pilot and sperm whales are typically deep-water animals and tend to be squid-eaters, and it is unclear if these mammals will be seen more often or if this is a random occurrence. The waters here are not usually this warm, so they would not be seen in this area, she said. Having them so close to shore is rare.

“There’s a lot of difficult-to-answer questions,” she said.

At least for humpback whales, a lack of commercial exploitation coupled with protection under the Endangered Species Conservation and Marine Mammal Protection acts have helped increase their population, Ballance said. With a recovering population and a productive California current ecosystem filled with food, more humpback whales are being seen.

Presently, NOAA is conducting a research survey in the California current, which stretches from the U.S.-Mexico border to the U.S.-Canada border. Ballance, who recently returned from the trip, said loggerhead turtles and a school of pygmy killer whales were some unusual surprise sightings. The latter, as far as NOAA knows, have never been recorded in California waters. The sightings are “almost certainly associated with warm-water events,” she said.

With many factors at play, it’s hard to nail down a concrete answer for the unusual activity, Alps said. In addition to whale sightings, there have been sport fish spotted that Southern Californians usually don’t see, such as mahi-mahi, marlin and so on, Alps said.

“The ocean is ever-evolving,” Alps said.

Contact the writer: 949-492-4316 or kzhou@ocregister.com