Riverfly Results

Volunteers do a three-minute kick sample and count eight groups of river invertebrates that are sensitive to pollution. Each group gets an abundance rank: A (1 to 9 found, score 1), B (10 to 99, score 2), C (100 to 999, score 3) or D (1,000 or more, score 4). The quality score adds the eight group scores together, so it can range from 0 to 32. A sudden drop compared with a site's usual scores is the thing to watch for.