Temporal coherence in Salmo trutta in Swedish streams/rivers : Analyze of long term monitoring data on trout abundance in northern Sweden

• Main Author: Johansson, Petter
• Format: Bachelor Thesis
• Language: English
• Published: UmeÃ¥ universitet, Institutionen för ekologi, miljö och geovetenskap 2015
• Subjects: Ecology; Ekologi; Northern Sweden
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105667

By using long-term monitoring data on trout (Salmo trutta) abundance in streams and rivers in northern Sweden synchronous patterns of trout abundance at both regional and local (i.e., within watershed) scales was investigated. Spearman’s rank correlation tests were conducted on the trout abundance data to quantify the degree of synchrony among and within watersheds. The results showed synchronous patterns at both local and regional scales. There were also signs of asynchronous patterns, which indicate presence of local scale filters and their impact on trout population dynamics. Synchrony for young and older trout individuals showed a different response to increasing distance among watersheds. This result is important because it indicates that synchronous population dynamics for trout is partly determined by its life-history stages and how mortality is affected differently by certain factors throughout life. Regional trends in synchrony of young individuals suggest that broad scale trends in climate properties are important. This study shows how complex and variable synchrony patterns can be when investigating fluctuations in natural populations across different scales.