SNH announces national pearl mussel survey

Scottish Natural Heritage (SNH) has announced its intention to a carry out a survey of freshwater pearl mussels (Margaritifera margaritifera) across Scotland. It is currently seeking tenders from suitably-qualified contractors, to perform the survey in 2013 and 2014.

Freshwater pearl mussels have disappeared from around a third of the Scottish rivers where they were present a century ago, and half of the remaining populations are non-breeding. Britain supports around 50% of the European population of pearl mussels, and the majority of these are in Scotland.

Illegal harvesting has taken its toll on populations, as have river channel engineering and pollution. Pearl mussels are now strictly protected under Schedule 5 of the Wildlife and Countryside Act 1981 (as amended), and require a licence to disturb or affect them.

The SNH website has a useful page of information and resources on freshwater pearl mussels:

SNH says in its tender invitation: "The only previous national survey was in 1997.  The current survey will visit all known extant pearl mussel populations and survey each river to establish the current status of the freshwater pearl mussel population."

"The national survey will not include rivers designated for the conservation of freshwater pearl mussel as considerable survey information has been collected by SNH since 1997.  However this contract WILL include some surveys of designated sites as part of SNH's Site Condition Monitoring programme.  Therefore, this contract will involve survey of all known extant, undesignated freshwater pearl mussel populations and a selection of designated populations."

"The survey area will extend the length and breadth of Scotland including from the Northern Isles to Dumfries & Galloway and from the Outer Hebrides to Angus.  It is also envisaged that the contract will include monitoring habitat conditions in all the rivers using a redox probe, which can be inserted into river substrate to measure the loss in redox potential."

"It is expected that the eventual contractor will have considerable experience of surveying freshwater pearl mussels, the species' ecology and recording their status in a variety of different river types. It is anticipated that planning the fieldwork will take place during early 2013 and fieldwork take place during 2013 and 2014, with the final report submitted to SNH by late 2014."