Working together, state and tribal shellfish managers have calculated not only the rate of allowable harvest but also the stopping point. The rate of harvest is slow enough to allow for healthy reproduction. The tracts are closed once 35 percent of the original amount of geoducks remain. Once that mark is reached, a tract won't reopen for at least another four decades. In other words, divers may only harvest a few tracts over the span of their lifetimes. The Tulalips and other tribes across Washington had their treaty rights to harvest fish reaffirmed by the landmark 1974 Boldt decision. The case forced big changes as it recognized the tribes' demands to co-manage fisheries alongside the state. It wasn't until 1994 that another federal judge ruled that the same treaty rights applied to shellfish. Today, geoduck tracts are split up 50-50, with the state sharing annual harvest quotas with tribes who self-govern and regulate their own operations.