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Environmental Bottlenecks

Agricultural streams are often assumed to be of little ecological value and as such are generally under-studied. Furthermore, because many of these streams are small (less than 2m in width) they are frequently ignored under the Water Framework Directive (WFD). However, such streams can support important salmonid populations and in some circumstances can constitute a valuable resource. Fisheries management and Legislation such as the WFD and Habitats Directive require an improved understanding of the hydrological and ecological functioning on these streams to inform development of environmental standards and restoration options, if required.

This project developed new methods and approaches to identify the physical and chemical processes influencing embryo survival and juvenile production in a small agricultural stream on Donside – the Newmills Burn (Aberdeenshire). Embryo survival was influenced by canalisation and fine sediment infiltration which affected the exchange of water between the stream and streambed and consequently streambed dissolved oxygen (DO) and embryo survival. Sediment oxygen demand was also greater in the Newmills Burn than a less impacted reference site (Girnock Burn), perhaps reflecting the influence of elevated nutrient concentrations. Juvenile habitat quality was also influenced by canalisation, which limited suitable habitat for salmon and trout parr. The methods developed in this study will have value to the wider scientific community in future studies of embryo survival and juvenile habitat use.