Prince William Lake, Prince William River
We're taught that salmon return to the shores and streams (or--nowadays--some also to the hatcheries) of their birth because that is where they are programmed to spawn. People who study salmon suspect that the fish actually do this to embarrass fisheries managers.
Salmon are edible, catchable, and, because of their programming to return home, easily extirpated or even exterminated: it's a combination that demands management. So, for decades, agencies responsible for the survival and success of the salmon fishery have been amassing data and predicting how many salmon will return to their hatching sites. Sometimes the managers call it right, and fishing fleets and fish apparently follow their directives, but not always. A predicted record-breaking return turns out to be a mere trickle of fish, or a few-day fishing season suddenly must be extended to weeks as hordes of salmon come pouring home.
Fish in Prince William Sound often upset the predictors. A few years ago, a huge and unexpected surplus of pink salmon came charging into their home waters; the fishing fleet and the processors couldn't keep up with the salmon stampede. The next year, everyone was ready for them--and only a comparatively few salmon showed up.
The interaction of human-caused disturbances (from the catastrophe at Bligh Reef to the chronic trickles of outboard fuel at the Whittier wharf) with the natural perturbations to be found in a complicated subarctic sound shaken by earthquakes and drenched by heavy runoff from glaciers and rainfall, from a fish-predictor's viewpoint, is a mess. And that doesn't include the possible effects from different salmon-eating predators, diseases, and foodstuffs, all of which can surge or subside depending on imperfectly understood factors.
Scientists bent on helping the predictors, and thus the people who fish for a living in the sound, are involved in a massive effort to identify the important factors controlling Prince William Sound's marine ecosystem. The Sound Ecosystem Assessment project--with its apt acronym of SEA--involves about 16 separate research studies, several institutions, and five fishing vessels. The SEA study plan was devised by academic and agency scientists working with members of fishing organizations, and is funded by the joint federal/state Exxon Valdez Oil Spill Trustee Council.
Some of this season's data-gathering efforts test a hypothesis devised by Ted Cooney, a professor at UAF's Institute of Marine Science. Cooney's work has centered around zooplankton, the tiny animal flotsam that includes fish eggs and larvae of all sorts as well as creatures that can be the size of dust motes when full grown. Young salmon (and many other fish, for that matter) eat great quantities of zooplankton. The number of young salmon that survive their early days in the sound has a profound effect on the number of adult salmon that return again from the sea, so the quantity of zooplankton available to feed the young fish could indicate the size of the eventual run of adults home from the ocean.
Cooney hypothesized that the currents of Prince William Sound make a crucial difference in zooplankton availability. Major currents sweep into the sound through Hinchinbrook Entrance, and strong outgoing currents leave through Montague Strait. In years with little current flow, he suspected, the sound assumes many lakelike characteristics. The zooplankton float slowly in these lazy currents, staying within reach of the hungry little salmon. But in years with strong currents, the zooplankton can be swept along like twigs in a flooding river. Under these conditions, the food for baby salmon could be whisked through the strait and into the open ocean before the fry emerge to begin eating. Worse, in such riverlike years, the infant salmon might well be eaten by other hungry predators that normally prefer zooplankton.
So, while researchers gather all manner of information about the sound's oceanography this summer, they're trying to answer one peculiar question: is Prince William Sound a river this year, or is it a lake?