Find an unknown salmon creek and earn $100

Up until last year, Southeast Alaska’s Mitkof Island was home to a creek with some unique salmon: They only turned left. Officially, anyway.

There is a fork in Ohmer Creek, on Mitkof Island. On the west side, the state’s Anadromous Waters Catalog, or AWC, reported the presence of all five species of wild Alaska salmon, as well as Dolly Varden and cutthroat trout. On the east side of the fork, according to the AWC, there were only steelhead.

One afternoon last summer, U.S. Forest Service fish biologist Eric Castro, of the Petersburg Ranger District, pointed out juvenile coho salmon were holding...