Successful Restoration of an Acidified Native Brook Trout Stream through Mitigation with Limestone Sand

• Published in: North American journal of fisheries management 2000-05, Vol.20 (2), p.453-466
• Main Authors: Hudy, Mark, Downey, Daniel M., Bowman, Darrell W.
• Format: Article
• Language: English
• Subjects: Freshwater; Salvelinus fontinalis; USA, Virginia
• ISSN: 0275-5947; 1548-8675
• DOI: 10.1577/1548-8675(2000)020<0453:SROAAN>2.3.CO;2

Limestone sand was added by helicopter directly to the headwaters of Fridley Run (Mountain Run), a first‐order stream in the George Washington National Forest, Virginia, in August 1993. This was done to mitigate the effects of anthropogenic, atmospherically derived acid deposition and to enable restoration of a reproducing population of brook trout Salvelinus fontinalis. Brook trout, which had been historically present in this stream, had been absent for at least the last 20 years. Water quality improved immediately following liming, and the effects of the direct application have lasted 44 months to date. The mean monthly water chemistry difference between the acidic control and upper sampling sites (1.1 km below the liming site) was an increase in pH (+1.14 units), acid neutralizing capacity (ANC; +49 μeq/L), Ca2+ (+73 μeq/L), and Ca: H ratio (+382) and a decrease in total Al (−279 μgm/L). The mean monthly difference between the acidic control and the lower sampling sites (1.8 km below the liming site) was an increase in pH (+0.62 units), ANC (+30 μeq/L), Ca2+ (+40 μeq/L), and Ca: H ratio (+422) and a decrease in AlT (−155 μg/L). One month after liming, native brook trout were transplanted into Fridley Run from a nearby circumneutral stream. A brook trout year‐class was produced in 1994 and every year since (1995–1997). Offspring from the originally transplanted brook trout have survived and successfully reproduced, thus accomplishing a primary objective of the study. Populations of brook trout in the study sections increased from 0 to 54/100 m2. Transplanted nongame fishes survived in the stream but did not reproduce. Aquatic macroinvertebrate communities improved in treated and untreated sections. The direct application of limestone sand provides inexpensive, short‐term mitigation of acidity in aquatic ecosystems. On case‐specific merits and objectives, such applications can be implemented as a routine management tool to temporarily protect, enhance, or restore important recreational fisheries, biodiversity, and other important riparian features.