Fishing within 400 feet of Horn Rapids Dam is prohibited; however, First Nations have a treaty right to fish at the rapids as they have for millennia. Another fishing group are American white pelicans and cormorants.
Both these species have been making a comeback in eastern Washington. Dennis Paulson provides a nice summary on the American white pelican HERE.
Horn Rapids Dam is a irrigation diversion structure on the lower Yakima River. Water is diverted into canals on both sides of the river at the top of the rapids. The spill area makes for good fishing and the rocks downstream provide good perch areas out in the water.