Can GIS be used to identify streams with successful recruitment of freshwater pearlmussels (Margaritifera margaritifera)?

Abstract: The freshwater pearl mussel (Margaritifera margaritifera) has declined dramatically throughout its range and is faced with recruitment problems in most of the streams where populations still persist. Human activities, such as forestry and agriculture, are thought to be the main reason for these problems. In this study, spatial information on landscape features along 38 streams with known recruitment status were analyzed in an effort to determine if GIS-tools could be used to identify streams with successful recruitment. Differences in the distribution of various landscape features, measured in stream corridors of 50 and 150 m, and differences in several water chemical factors between streams with and without recruitment were investigated. The distribution of landscape features was also compared with host fish (brown trout) density and any statistically significant water chemical factor.  Both mussel recruitment and trout density were found to be negatively related to clear-cuts, and mussel recruitment was also negatively related to high water color, which has been shown to be correlated with high nutrient content, one of several adverse effects of clear-cutting close to streams. Recruitment was expected to be negatively affected by roads, but no such relationship could be found. Instead, mussel recruitment was found to be positively related to the number of road crossings per kilometer, but the strength of this relationship was questionable. In addition, even though it was somewhat unclear, high proportions of lakes and ponds were found to be positive for both recruitment and high trout density. The results of the study indicate that GIS-tools can be used to find landscape features that affect recruitment of freshwater pearl mussel and they support the belief that forestry activities are an important cause for the decline of the species in Sweden. In addition, the results indicate that leaving protective zones of forest between streams and clear-cuts can be a possible conservation method for the freshwater pearl mussel.