Guest Blog – Mollusc of the Glen – by Peter Cosgrove

Peter Cosgrove’s passion for pearl mussels began in 1996. He carried out the first national pearl mussel survey and in one of those wonderful moments of happenstance, submitted his final report which recommended full legal protection during a periodic review of the Wildlife and Countryside Act.  It had the desired effect and the law was changed in 1998 and Peter always highlights this to those cynics who think our conservation efforts are pointless and make little or no difference. Since then Peter has spent hundreds of days in more than a thousand Scottish rivers and burns surveying for pearl mussels.

Mark has kindly asked me to write a guest editorial on an issue close to my heart after reading his blog on wildlife crime.  For 17 years I have worked on an obscure, and important species called the freshwater pearl mussel.  It was once very numerous but is now globally threatened and a high proportion of world’s remaining populations are found in the Britain.  It is currently in very serious trouble.

The Roman biographer Suetonius, after speaking of the admiration which Julius Caesar had for pearls, stated that their occurrence in Britain was an important factor for inducing the first Roman invasion of Britain in 55BC.  Given the profound effect this subsequently had on Britain I can’t help but think of misquoting John Cleese and Monty Python with ‘what did the pearl mussels ever do for us’ line.  The species also has a fascinating symbiotic relationship with our native Atlantic salmon and sea/brown trout, which carry the tiny microscopic mussel larvae on their gills as they migrate up and down our rivers.

Freshwater pearl mussels live on the beds of fast-flowing, unpolluted rivers and subsist by inhaling and filtering the minute organic particles on which they feed (each mussel filters ca. 50 litres of water a day).  Where naturally abundant (and many of our rivers used to have millions of them), this filtration acts to clarify the water to the benefit of other species such as salmon and trout, especially around their spawning and nursery areas.  When left alone they can live in excess of 120 years.  They are one of those keystone species, which ecologists get excited about.  I have often wondered which British species have had the greatest impact on us Britons (rather than everyone, like say the earthworm) and I think that Margaritifera margaritifera would ‘medal’ if it came to a contest.  An idea for Spring Watch perhaps?

Pearl mussels are now fully protected and thanks to recent awareness raising efforts, more people now know about this species than previously.  However, not everyone is enlightened and some people actively seek to destroy the last of this species.  In an attempt to highlight this threat, I have written an article with colleagues on wildlife crime and pearl mussels in this month’s British Wildlife magazine.  Most people know of tiger and rhino poachers and those custodians of the countryside who hate raptors, but few know of the illegal pearl fishers who kill thousands of mussels every year in Scotland in an attempt to find an illusive pearl.

Illegal damage to pearl mussels has been recorded every year since the species was fully protected in 1998.  Indeed the National Wildlife Crime Unit has recorded at least 10 incidents of criminal damage, or suspected criminal damage, every year since then.  However, it is believed the real annual number could be as high as 30.  These incidents have been recorded across the Scottish mainland, from Dumfries and Galloway to Sutherland and several in the Hebrides.

So what can be done?  Given the high proportion of the remaining pearl mussel populations found in Britain, we have a moral and legal obligation to protect this species.  Fishermen, estate workers, ecologists, walkers, locals and tourists in Scotland are urged to be vigilant for people acting suspiciously around watercourses and report suspicious activity to the police as soon as possible.  This can include people using glass-bottomed viewing buckets and finding dead pearl mussel shells in and around rivers.  Politicians and the media should raise the profile of wildlife crime with the public and ensure pearl mussel conservation is given the highest priority.  Pictures of shot or poisoned golden eagles should and do make us angry and we should have the same response to those criminals who target less ‘charismatic’ protected species.  Wildlife crime is having a devastating effect on the last of the Scottish pearl mussels and increased efforts are needed to protect this fantastic and important Mollusc of the Glen.

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24 Replies to “Guest Blog – Mollusc of the Glen – by Peter Cosgrove”

  1. Hi Peter, hopefully these acts of wildlife crime can be stopped in the very near future. If the crimes are brought under control, in your opinion, will the water quality be an issue for the populations to grow? I read some estimates saying that one third of the population has disappeared completely and one third is only old mussels with no sign of reproduction. Have there been studies into why these old mussels are not reproducing? Or would this be down to water quality?

    1. Hi Luke,
      Since I began working on the species in the mid 1990s freshwater quality in Scotland has generally improved thanks in many ways to the efforts of SEPA and the like. Some of the (formerly grossly) polluted Central Belt rivers lost their pearl mussels many decades ago (e.g. prior to 1900 during the industrial revolution), so I think it is fair to say that poor water quality has probably had its most adverse effects already. There is no room for complacency though and non-point source pollution (e.g eutrophication) has slowly killed off some of the Scottish east coast and probably southwest river populations. The water quality in these rivers has been poor (for mussels at least), but not nasty enough to kill the mussels outright. Instead recruitment fails and the adult mussels, which are less sensitive than the juveniles, hang on, get old without being replaced and die. On the good news front, most of the extant rivers occur in catchments with little industrial agriculture and general industry. However, as you point out there has been a worrying lack of juvenile recruitment in many of these otherwise apparently 'healthy' populations, particularly on the Scottish west coast. This has coincided with declines and collapses in the wild migratory host fish populations. We have worked with fishery scientists and published work on this threat, but much is still unknown. The reasons for the collapse of migratory fish populations are complex and controversial for some, but it directly impacts on a large proportion of the extant global pearl mussel population. Conservationsists and fishery interests need to work together to tackle this pressing issue.

  2. Great article. I think that this should be promoted widely. Outdoors magazines spring to mind. Local papers in the areas where there are FWPM. Can I copy it to the Aberfeldy Comment?

    1. Thanks Helen,
      I have no problems with spreading the messaging far and wide, but please reference it to Marks' blog. This winter I hope to get round to writing articles for the likes of Trout and Salmon etc. As my blog hinted, I would like to see the species and the crime issue widely discussed in the popular media. If it made it on Spring Watch next year, that would be just before the summer wildlife crime season kicks off in earnest and it might, just might help catch someone.

      1. It's rather depressing to think of a crime 'season' but thanks very much for a fascinating blog on something I knew nothing about

      2. I wonder can the pearls be indentified as from these mussels? presumably there is a trade in them and can anything be done to criminalise buying and selling them? There doesn't seem to be an argument to say it is ok for them to come from outside of the UK as they are even more endangered abroad.

        1. Hi Giles,
          I've tried to cover the issue of buying and selling of pearls in my response to Jonathan below. Trade in pearls (from freshwater pearl mussels and other non-threatened species) is a complicated business. It is difficult to openly discuss the intricacies of it on-line without potentially providing ideas to criminals on how to beat the system and our efforts to protect the species.

  3. Peter, do you have any updates on the River Ehen incident, (in England, I know), and how things are looking there now?

    1. Hi Peter,
      No, only what I've read in the media. I've not worked on any of the English rivers, so have no first hand experience. It is terribly depressing though. The last good pearl mussel population in England devastated by all accounts.

  4. Thank you Peter for your work conserving this fine animal and highlighting its plight.

    We have more than half of the world population of Freshwater pearl mussels in the UK. While the plight of the species in Scotland is bad enough, in England and Wales reproduction rates of the remaining populations are so low that most have had to be taken into captivity by the Environment Agency to ensure their survival.

    Distressingly the last big viable population in England in the River Ehen was hit by a major incident this year with thousands killed and up to 90% of the population severely stressed and weakened following repeated low water flows. We are still waiting to hear from the Environment Agency what action will be taken as a result of this incident and how they will avoid it ever happening again.

    Siltation is also a problem for these animals, 100 years ago, when many were born, the rivers contained much less silt. While the adults sit on the surface of the river beds, young mussels live in watery spaces between gravel, simply not possible now in many rivers.

    Another problem is unauthorised channel engineering. This destroyed a key population on one of the Scottish SACs, but, because SACs are only surveyed by SNH every six years, the two year deadline for taking a prosecution had expired when the damage was discovered and no prosecution was possible.

    The Freshwater pearl mussel is a profound part of the culture of these isles and the current situation is wholly unsatisfactory.


    Buglife - The Invertebrate Conservation Trust

    1. Thanks Matt for your update on the English situation. Wholly unsatisfactory seems an almost polite understatement to what has happened and I'm sure more choice words spring to mind! The relevant statutory authorities (in particular SNH and SEPA) in Scotland have done a pretty good job given their limited powers and budgets and I know that several of their key staff are as passionate about the pearl mussel's plight as I am.

      Recent discoveries in Scandinavia suggest that researchers there have found many unknown populations and the 50% UK figure may need revising. Regardless of the exact numbers, we still have a large proportion of the world's remaining viable populations and our conservation action should reflect this. It sounds like you may soon have to travel north of Hadrian's Wall to see this species in the wild in the UK.

  5. A very interesting post. Especially the implication of siltation.

    Siltation being a result of soil erosion, one has to wonder at the commitment of our politicos regarding soil conservation. Soil underpins all terrestrial food chains so in many aspects is more important than the efforts to conserve all the Big Things, whether they are affected by habitat loss, criminal acts, or pesticides.

    They had the chance to get something significant done in 2006 under a proposed EU soils directive. This would have required Member States to tackle degradation (erosion, loss of soil organic matter, salinisation, landslides, acidification, compaction), identify and remediate contaminated land, consider soil protection and soil functions in national policy-making, and control loss of soil resources to development*.

    But instead the UK - among others - kicked this into the long grass, explaining that "The UK has taken the view that whilst we strongly support the overall objective of protecting Europe’s soils, and agree there is a need for action to deal with serious soil degradation in some parts of Europe, we already have robust domestic policies in place to protect soils. UK Ministers have called for a different approach to these issues. One which better respects the principles of subsidiarity and better regulation in order to avoid unnecessary additional administrative burdens and disproportionate costs."

    So there you have it - too costly. But they are spending squillions on other replaceable stuff, like cattle they have killed. Soil isn't replaceable within a human timeframe.

    * O**n Pat**son has banned the use of the Oxford comma by Defra, which means we should all use it whenever appropriate

    1. Thanks Filbert,
      Our Swedish colleagues have put considerable time and effort into restoring degraded pearl mussel streams and in particular the issue of siltation:

      Of course not degrading the soils and streams in the first place is a the best use of scarce resources, but we are where we are and the report linked above is pretty good at summarising best practice on restoration. Soil Conservation - one of the least discussed conservation issues of recent years and one I know very little about myself.

  6. While reading your fascinating article in British Wildlife, I couldn't help thinking how much more difficult it must be to motivate people about mussels, than about raptors for instance. I find these animals so interesting and remember your previous article in BW. Is it possible to re-establish populations where they have been lost?

  7. Thanks Phil,
    The short answer is yes. I have been involved with colleagues on a long term SNH project looking at the feasibility and practicalities of pearl mussel reintroductions. We have surveyed dozens of former Scottish pearl mussel rivers, but many have changed and are no longer apparently suitable for pearl mussels (most becoming very unstable in terms of substrate habitats). Nevertheless, some are suitable and we have translocated mussels into three former pearl mussel catchments and met with mixed success. One river seems to have become very spatey (climate change?) and whilst the adults survived moving, most appear to have washed away. The second site did much better and many of the mussels still survive well there, but we have little evidence of recent successful recruitment. Finally, our third site has been much more successful, with the adults surviving and our work on the host fish has found quite a lot of tiny juvenile mussels attached to their gills, so they are breeding successfully. We now just need the tiny juveniles to settle successfully on the river bed to become self-sustaining. The difficulty in monitoring success is that the mussels are tiny-very small for ca. 15 years, so we might not be very good at spotting them for another dozen or so years. At least we know the complex breeding cycle is working.

    We have trialled different reintroduction methods (in-situ and ex-situ), but all require suitable donor stock, which is rare itself. It is hoped that the emergency rescue work undertaken in English rivers will provide a last refuge until suitable conditions in English rivers can be restored. The on-going problem with wildlife crime from illegal pearl fishers means we have to treat reintroduction sites as confidential, which is a pity because it limits awareness raising efforts and wider public involvement to an extent.

  8. Peter
    A very interesting post on a very important topic. I quite agree that we should be as agitated about these crimes as about persecution of birds of prey.
    As the criminals in this case are looking to harvest pearls I wonder if anything can be done in relation to the market for these. Not that I buy much jewellery you understand(!) but is there such a thing as a sustainably sourced fresh water pearl and is there any scope for setting up a certification scheme along FSC/MSC lines or should we be pushing for a complete ban?

    1. Hi Jonathan,
      The market for these pearls is not simple and so the solutions aren't either. Also, before I comment further I should say I am not a jewellery or legal expert! Old pearls from freshwater pearl mussels collected before full legal protection was introduced can be legally sold by a very few licensed and registered dealers (much in the way that antique ivory can be) and the authorities work closely with these dealers to make sure no new UK freshwater pearl mussel pearls enter the market. When these legal registered stocks run out they cannot be replenished.
      It is perfectly legal for dealers to sell pearls from common, non-threatened overseas species (marine and freshwater) also and so it is possible some UK pearls get through the system hidden this way. There is a huge legitimate Asian market in cultured pearls for example. However, the UK authorities are aware of other potential loopholes and I'd rather not list them here for obvious reasons.
      Catching someone selling an illegal pearl they collected in the UK is very difficult. To my mind, the most likely time someone is going to get caught is when they are up to their waist in a river in a pair of chest waders with a viewing bucket. I can vouch that you can't run away quickly in chest waders! As with other wildlife crime, like egg collecting, the courts have the power to fine and imprison offenders and also to confiscate their tools of the trade (including the vehicle used to get to the river). Thus, I really do feel that someone being caught pearl fishing and successfully prosecuted would have the most significant deterrent value and help reduce or stop illegal pearl fishing. Pearls are difficult to find and most are of low monetary value and so is a custodial sentence and loss of your car etc worth it for the remote possibility of a few tens of pounds?


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