Before the tanker Exxon Valdez hit Bligh Reef in 1989 and smeared Prince William Sound with 11 million gallons of crude oil, salmon catches in the sheltered waters in the curve of Alaska's underbelly had been averaging less than 10 million fish per year all the way back to statehood.

Since the tanker accident, in the wake of what was North America's biggest oil spill up until the still unfolding Deepwater Horizon disaster in the Gulf of Mexico, the annual salmon catch in the Sound is averaging more than four times that number.

The average annual harvest for the most recent decade-long period stands near 45 million salmon per year.

How salmon harvests in the Sound doubled, and then doubled again, has everything to do with human alterations to the environment. But not in the form of spilled oil.

"It's the hatchery fish,'' said John Hilsinger, commercial fisheries supervisor for the Alaska Department of Fish and Game. "There's a real large number of hatchery fish.''

When it comes to the Sound, the oil doesn't appear to have changed much in regards to salmon, but the hand of man certainly has been messing with nature big time in other ways. The Sound has changed radically due to human-spilled fish. The ecology, in fact, has been so radically altered that state scientists have started to raise questions about when enough hatchery salmon are enough.

"Our obligation to manage wild (salmon) stocks in Prince William Sound is very challenged at current levels of population,'' an April memorandum from the Alaska Department of Fish and Game warns. "Department straying studies suggest that at current production levels, hatchery salmon straying may pose an unacceptable risk to wild salmon stocks.''

In that memo responding to a new request to expand Sound hatchery operations even further, state fisheries biologists hint at fears that the wild salmon that survived the mess of an accidental oil spill could be decimated by well-intentioned annual salmon spills. Others think those concerns are overblown.

"I don't think we've done any damage to the ecosystem in Prince William Sound,'' said William Smoker, a respected federal scientist and university professor. "It's pretty hard to detect any ecological effect. I found some aspects of that Fish and Game memo troubling.''

What has been done in the Sound that is of greatest importance, Smoker said, is the creation of an economy. Before the hatcheries came on the scene, one out of every five summers there weren't enough salmon to even prosecute a Sound salmon fishery. Every fifth summer was -- for lack of a better comparison -- an Exxon Valdez summer with fishermen ordered to stay in port.

"You can't have an economy based on salmon fishing if every fifth summer you have to shut down,'' Smoker said.

Hatcheries changed this. To truly get an idea of how much they changed this, you actually need to go back more than a decade before the Exxon oil spill to what historically existed in the inland waterway south of Anchorage, the state's urban center, and west of Valdez, the shipping port at the end of the trans-Alaska oil pipeline.

Back when the Sound was truly wild -- back when the population of all of Alaska was about the same as that of Anchorage today and the oil terminal in Valdez had yet to be built -- the average annual salmon harvest for the Sound hovered around 3.3 million fish per year.

Not until man started messing with nature did that begin to change. A hatchery program backed by the state but later turned wholly over to a private business -- the Prince William Sound Aquaculture Corp., a commercial fisherman-funded cooperative -- started boosting salmon runs in the mid-1970s.

This was before the oil business took over the economy and bumped billions into state coffers. Prior to that, salmon fishing in large part fueled the Alaska economy. And with salmon fisheries floundering in the 1970s, there was huge political pressure to do something. "They were going to build hatcheries come hell or high water,'' said Doug Eggers, the state's former chief fisheries scientist. The state started that process, then brought private, non-profit corporations funded by commercial fishermen into the act all over the state.