The River Bjerkreim in SW Norway - Successful chemical and biological recovery after liming

On a large scale, the acidified River Bjerkreim, southwestern Norway, has b een treated with lime since the autumn 1996. During the Atlantic salmon (Sa lmon salar) smolting period pH has been above 6.2 and LAl concentrations be low 10 mug L-1. Before 1996, only the western part of the watercourse harbo ured acid-sensitive species, such as the Atlantic salmon, snails, mayflies, daphnids and Gammarus lacustris. Prior to liming in 1996, Atlantic salmon fry (0+) and parr (greater than or equal to1+) were found in 4 of 20 sampli ng sites, contrary to 17 (fry) and 12 (parr) in 1999. Atlantic salmon catch es have increased from about 0.8 tons in 1994 to about 10 tons in 1998 and 1999. Acid-sensitive invertebrates have invaded the limed parts of the rive r.