“The case of the missing killer whales will be examined when the Orca Conservancy meets Thursday on Whidbey Island.Greenbank resident Susan Berta said whale watchers in the San Juan islands have failed to account for seven orcas that should have returned this summer, including two young calves. Six are part of the L-pod; in addition, another calf from K-pod is missing.One oddity of killer whale research is that it is uncertain where the San Juan killer whales spend their winters. It’s always been a mystery, said Howard Garrett, who with Berta founded the Orca Conservancy. We really don’t know.Researchers were surprised two years ago when members of the K and L pods showed up off the Monterey, Calif. coast, but they haven’t been sighted there since. They’re generally not seen from the end of September until June, Garrett said.Whidbey Island residents see orca whales that belong to J-pod, which sticks closer to home.Berta said the missing whales will be discussed June 27 at 7 p.m. at the Central Whidbey Fire District meeting room. The agenda also includes a presentation on orca behaviors.The Center for Whale Research in the San Juans issued a report June 16 detailing the disappearance of seven killer whales missing from what is called the southern community orca population. The center has been documenting killer whale movements for 26 years.L-pod, the largest of the three resident pods, first arrived in the San Juan Island May 20 and center staffers began a detailed inventory of the returning animals. Missing are three adult males, one adult female and three calves. The center’s Kelley Balcomb-Bartok said that with the loss of the two L-pod calves, no calf born in that pod has survived since 1996.Taking into account the missing seven, the total population of the southern community is now 78 killer whales, with L-pod at 41, K-pod at 17, and J-pod at 20. When research began on these pods in 1976 there were 71 whales; the population peaked in 1995 with 99 whales.Balcomb-Bartok listed several possible reasons for the decline in the number of killer whales:* Salmon stocks have decreased dramatically, reducing the whales’ food supply.* High levels of two types of toxins, PCBs and PBTs, have been found in samples taken from recovered bodies of several members of L-pod and J-pod.* In the past 10 years there has been a dramatic increase in the number of whale watching vessels that follow the whales, which may add stress on already weakened individuals in times of duress. “