Brown trout
Wild trout naturally reproduce in Hammersley Fork from its headwaters downstream to its mouth. Great blue herons have been observed at the headwaters of Hammersley Fork, despite the fact that they are more commonly found in large river valleys. Little yellow stoneflies also inhabit it. Brown trout first appeared in the stream in the 1920s after being stocked in Cross Fork and in the 1940s the brown trout populations significantly increased.