Status and Distribution of Fish in an Acid-impacted Watershed of the Northeastern United States (Hubbard Brook, NH)

Stream acidifi cation across the northeastern US impacts fi sh abundance and fi sh communities. In this study, we document a fi sh community shift in the upper mainstem of Hubbard Brook (NH) from the presence of at least three species in the 1960s to the presence of only one species today. Cottus cognatus (Slimy Sculpin) and Rhinichthys atratulus (Blacknose Dace) are no longer present in this system, and we suggest that extirpation occurred during a period of chronic acidifi cation during the early 1970s. Today, Salvelinus fontinalis (Brook Trout) is the only fi sh species present in the upper reaches of the Hubbard Brook Valley. The current upstream extent of Brook Trout is limited primarily by physical obstructions such as waterfalls or cascades. Acidifi cation may lead to chemical barriers that limit upstream movement during high fl ow in a few streams. As recovery from acid deposition begins, and as regional climate changes, our observations demonstrate the value of periodic evaluations documenting shifts in the distribution and composition of fi sh communities in headwaters of the northeastern US.