For the Nez Perce, fishing traditionally took place throughout the summer and fall, first on lower streams and then on higher tributaries. Most of the supplies for winter use came from a second run in the fall when large numbers of fish appeared in the rivers. Even today, the Big Hole River at Big Hole National Battlefield is known for its rich variety of fish. The river is nationally known as one of the premiere blue-ribbon trout waters in Montana. The river is home to high numbers of large trout.
Confirmed fish species at the park include: white sucker (Catostomus commersonii), longnose dace (Rhinichthys cataractae), burbot eelpout (Lota lota), mountain whitefish (Prosopium williamsoni), brook trout/charr/salter (Salvelinus fontinalis), and mottled sculpin (Cottus bairdii). Other species that may be present are: longnose sucker (Catostomus catostomus), mountain sucker (Catostomus platyrhynchus), rainbow trout (Oncorhynchus clarkii), redband trout (Oncorhynchus lewisi), steelhead (Oncorhynchus mykiss), brown trout (Salmo trutta), and arctic grayling (Thymallus arcticus). Brown trout, brook trout, and rainbow trout are all nonnative fish species.
Strict fishing regulations on the river help maintain both the fly fishing quality as well as limit the use of the river to some extent, keeping fishing pressure at tolerable levels most of the year.