Fertile fish

When Joseph Merz acted on a hunch in 2004 and ran lab tests on grape leaves from vineyards along the Mokelumne and Calaveras rivers, he found that 20 percent of the nitrogen in the plants’ tissue bore a so-called “marine signature,” evidenced by the higher number of electrons clinging to the atoms. To Merz, at the time a graduate student at UC Davis, the explanation was obvious: Generation after generation of chinook, or king, salmon—which live at sea, spawn in rivers and die immediately after—had donated their bodies to the land and its soil. The Central Valley, Merz concluded, owes much of its fertility to salmon.

Today, factory-made fertilizers serve the function that the fish once did, and life on the farm goes on without salmon. In the San Joaquin River, for instance, the huge annual salmon runs went extinct in 1949 after construction of the Friant Dam, which blocked access to spawning habitat while diverting 95 percent of the river’s water to farmlands and municipalities. The Sacramento runs are now facing increasing danger of disappearing for similar reasons.

But Merz believes in the greater moral of his research: that profitable agriculture should and can coexist with functioning river ecosystems. Farmers and fish might even have more in common than at odds: Each depends on fresh water.

A rebound in the salmon population has spurred authorities to open the first full-fledged commercial salmon season since 2007, and the fruit of this fishery can be found at select seafood markets, including the Davis Farmers Market. The high oil content of king salmon makes it incomparable to related species, and for crying out loud, don’t discard the delicious fat-rich belly meat.

Fishing, like farming, can also coexist with salmon. The salmon fishery, in fact, is among the most closely guarded and managed there is. Regulations are reset every year based on estimated abundance, and, always, strident efforts are taken to assure that enough adult fish make it home, upriver, to seed the world with the next generation and fertilize the Earth.