of the cargo barged on the lower Snake River. In 1998, over of grain were barged on the Snake. Before the completion of the lower Snake dams, grain from the region was transported by truck or rail to Columbia River ports around the Tri-Cities. Other products barged on the lower Snake River include peas, lentils, forest products, and petroleum. Biology The World Wide Fund for Nature (WWF) divides the Snake River's watershed into two freshwater ecoregions: the "Columbia Unglaciated" ecoregion and the "Upper Snake" ecoregion. Shoshone Falls marks the boundary between the two. The WWF placed the ecoregion boundary about downriver from Shoshone Falls in order to include the Big Wood River (the main tributary of the Malad River) in the Upper Snake ecoregion, because the Wood River is biologically distinct from the rest of the downriver Snake. Shoshone Falls has presented a total barrier to the upstream movement of fish for 30,000 to 60,000 years. As a result, only 35% of the fish fauna above the falls, and 40% of the Wood River's fish fauna, are shared with the lower Snake River. The Upper Snake freshwater ecoregion includes most of southeastern Idaho and extends into small portions of Wyoming, Utah, and Nevada, including major freshwater habitats such as Jackson Lake. Compared to the lower Snake River and the rest of the Columbia River's watershed, the Upper Snake ecoregion has a high level of endemism, especially among freshwater molluscs such as snails and clams. There are at least 21 snail and clam species of special concern, including 15 that appear to exist only in single clusters. There are 14 fish species found in the Upper Snake region that do not occur elsewhere in the Columbia's watershed, but which do occur in Bonneville freshwater ecoregion of western Utah, part of the Great Basin and related to the prehistoric Lake Bonneville. The Wood River sculpin (Cottus leiopomus) is endemic to the Wood River. The Shoshone sculpin (Cottus greenei) is endemic to the small portion of the Snake River between Shoshone Falls and the Wood River. The Snake River below Shoshone Falls is home to thirty-five native fish species, of which twelve are also found in the Columbia River and four of which are endemic to the Snake: the relict sand roller (Percopsis transmontana) of the family Percopsidae, the shorthead sculpin (Cottus confusus), the margined sculpin (Cottus marginatus), and the Oregon chub (Oregonichthys