Freshwater environments are threatened worldwide, of which many of the species associatedwith freshwater. In 2014, 243 freshwater mussels were on the international Red List. One ofthem is the freshwater pearl mussel, Margaritifera margaritifera, which because of itscomplex life cycle can be counted as an indicator of whether a stream is worth protecting. It's since the early 1900's in decline throughout their range. Sweden is counted as a core area which is why we have not only a national but an international responsibility to conserve the species. The mussel is covered by the County Administrative Board of Hallands action plans for threatened species. The County Administrative Board has since 2004 made a number of inventories in the county to get an overview of the occurrence of the freshwater pearl mussel. Still, there are some streams that are not fully inventoried. We have inventoried the mainstream Fylleån from outlet to Gyltigesjön to Bygget, as well as tributaries. In the 80's some parts further downstream in Fylleån were inventoried and then no freshwater pearl mussels were found. Per Ingvarsson who is leading the inventories of freshwater pearl mussels in Halland has pointed out the upper part as an interesting area for mussels. This upper part of Fylleån has previously only been inventoried on two locations, therefore, we have now done a complete inventory to examine the presence of mussels.
Some of the results of our survey:
• No fresh water pearl mussels were found in the investigated waters.
• The water in the river was heavily colored which complicated the inventory.
• The majority of the route consisted of flowing water with a bottom of stone and/or blocks which are suitable habitat for mussels, but there were silt on the bottom.
• No fish or fish larvae were found.
• One duck mussel was found in the outlet to Gyltigesjön.
In closing, we discuss what could be causing our results.
2015. , 22 p.