The humpback whales were back in Alaska's Prince William Sound this summer, but whale researcher Jan Straley was not there to meet them. The funding to finance her research into how many herring are eaten each year by the 30- to 50-ton behemoths had run dry.

Herring are the last major touchstone of the Exxon Valdez oil spill. As the Sound has steadily recovered in the 21 years since Exxon's tanker hit Bligh Reef and spilled 11 million gallons of crude, the herring have been the species around which the oil giant's critics have always been able to lament serious, ongoing environmental damage.

"The spill stopped after just a few days," The New York Times' William Yardley wrote in May of this year. "Recovery may not have an end date ... The mountain views are still stunning but the herring fishery is gone."

Yardley was among the many reporters who gathered up their fleece and foul-weather gear to troop north to Alaska to report on the legacy of Exxon's oil as the crude of BP spewed a geyser beneath a sunken drilling rig in the Gulf of Mexico earlier this year. The stories all had a similar theme: Old oil can still be found beneath the beaches of the Sound, and the herring have never come back.

"Two decades after the Exxon Valdez spilled almost 11 million gallons of crude oil into Alaska's Prince William Sound, the herring still have not come back," wrote Cindy Chang for the New Orleans Times-Picayune. "Without that cornerstone species, the commercial fishing season now starts two months later, in May instead of March."

Those claims are partially true. Though the herring did come back after the spill, and though there were a couple of Marches after the spill when commercial herring fisheries took place, the herring population eventually shrank and remains at a size that has blocked commercial fishing for a more than a decade.

There are still plenty of herring in the Sound. It's just that there isn't the volume of surplus herring fisheries biologists say is needed to support a commercial fishery. Straley thought she could be on to the reason why. Humpback whales, the University of Alaska Southeast professor of marine biology discovered, were not only feasting on the herring as they had in summers past, but a significant number of the whales had stopped migrating away from the Sound in the winter, choosing instead to hang around and keep chomping herring year round.

Preliminary research, she said back in 2009, showed whales "were exerting predation pressure on Prince William Sound herring, which is potentially impeding the recovery."

Straley wasn't the only one taking note of this. National Oceanic and Atmospheric Administration scientist Stanley "Jeep" Rice in a 2009 report to the Exxon Valdez Oil Spill Trustees stressed that in order to determine what was going on with Sound herring "a necessary piece of information is the whale predation on juvenile herring. Targeted predation on herring is much greater that presumed prior to the start of these studies, and has a large impact on the standing biomass of herring."

Predation on juvenile herring is exactly what Straley would have liked to have been studying in the Sound this summer, but in an e-mail in July she could only observe that "(I) wish I was there. We never got to finish our study looking at what age class is targeted by humpbacks."

Straley couldn't quite understand why the money ran out. How is it, she wondered, that "when science says X, the responsible agency does Y ... makes no sense to anyone, but someone knows why this happens."

Publicly, the answer to this question is that research into whale predation on herring is not directly linked to what damage oil did to the small forage fish. Privately, some say the real answer is that Straley might have been closing in on an uncomfortable answer to the question of why Sound herring stocks these days are too small to support a commercial fishery.