Water Environment Grant (WEG): Keeping life on the bank

Christopher Watt – River Esk WEG Project Officer

Creating and expanding riparian woodland is a large component of the current WEG* funded project in the Esk Catchment, in conjunction with improving farm infrastructure. Riparian woodland is defined as trees located on the natural banks of waterbodies such as rivers, canels, ponds and lakes. The presence of riparian woodland brings an array of environmental benefits such as carbon capture, regulation of water temperature, bank stabilsation and provision of resources for wildlife. Riparian woodland is important feature of the Esk and provides benefits to conservation focus species in particular Freshwater pearl mussel (Margaritifera margaritifera), but also Atlantic salmon (Salmo salar) and Sea trout (Salmo trutta).This is why tree-planting efforts have been prioritized with project distribution located in both the upper and lower parts of the catchment.

Riparian woodland creation has focused on introducing a mix of tree species to the bankside to enhance structure and composition. Species which have a tolerance for wet conditions and partial submergence such as alder, aspen, birch and willow make a significant contribution to the mix. Other species such as alder-buckthorn, hazel, hawthorn and oak add additional variety. Planting design has incorporated adding open spaces such as rides and glades into the new small scale woodland as these are valuable habitats in their own right. All new woodland projects have an emphasis on long-term management to maintain habitat function with actions such as deadwood retention, grass-margin establishment, coppicing, pollarding and recycling tree-guards included in management plans. The vision is for these small scale woodlands to stabilize banksides, intercept agricultural run-off and reduce sedimentation entering into the Esk, leading to improvements in water-quality. Monitoring will record physical and biological change through measures fixed-point photography, vegetation monitoring and species recording.

Despite the ongoing challenges of the Covid situation and fickle weather conditions, work has been progressing on the Esk catchment with 2,095 new trees planted with much assistance from land managers, staff and volunteers. Planting efforts will continue with the aim to have all 3,000 remaining trees in the ground by March. This will also be accompanied by the planting of 1,060m of new hedgerows, wetland creation and bank stabilization works. Along with the habitat creation and enhancement works, measures to improve farm infrastructure are continuing such as concrete yard renewal, installation of sediment traps and rainwater guttering. Combined these efforts seek to work at the farm-level and tackle pollution pathways from yard/field to river and lead to the improvement of water-quality of this special river.

 All work carried out has been in line with current COVID restrictions and guidelines at the time. To keep up to date with the latest National Park situation in regards Covid-19 – see here.  

*WEG stands for Water Environment Grant which has been providing funding to improve the water environment in rural England. This has been part funded by the European Agricultural Fund for Rural Development.

 

The European Agricultural Fund for Rural Development: Europe investing in rural areas

Esk ventures

Ryan Harvey – River Esk & Coastal Streams Catchment Partnership Officer

Hi there, I’m Ryan the new Partnership Officer for the River Esk & Coastal Streams Catchment – its part of a Catchment Based Approach and my post is jointly hosted by the National Park Authority and the Yorkshire Esk Rivers Trust (YERT) . I started back in August and what a fantastic experience I’ve had so far. My role is very varied and fulfills a broad range of objectives: liaising with landowners and farmers, managing volunteers, working with partner organisations and carrying out surveys. All this effort is in the hope of benefiting the ecology of the Esk and building strong relationships and partnerships to maintain the ecology into the future.

It all started with the electro fishing season. That meant getting to know our e-fishing volunteers and arranging some refresher training for them. This was a great opportunity for me to meet the team ahead of our actual surveys and set the scene for the coming weeks. Once the work started along with volunteers I had the much appreciated help of Victoria Franklin (our Conservation Trainee) and Ami Carrick (our Ryevitalise Education & Engagement Officer). Electro fishing is a hugely important element of our data collection on the Esk. It allows us to gain a better understanding of our fish species diversity and abundance, in particular migratory species such as salmon (Salmo salar), sea trout (Salmo trutta), European eel (Anguilla anguilla) and lamprey (Lampreta planeri).

Our sites are repeated year on year and we now have a record of each species population over the last six years. This along with a whole suite of other data collecting techniques better informs our next steps and future conservation measures.

We are looking for new electro fishing volunteers for the 2020 season, so if this is something that may interest you please don’t hesitate to get in touch with our Volunteers Team. We can offer all the training you might need.

Another aspect of my role has been working alongside our Pearl Mussel Volunteers who have a long standing history in the National Park; some of its volunteers have been working with us for over 10 years. The volunteers’ work is invaluable because it’s through this group (along with contractors) that we get most of the physical works and restorations done on the river. There are usually volunteer tasks every two weeks at locations along the Esk and in surrounding riparian habitats. Tasks can vary from week to week for instance woodrush and tree planting for bank stabilization and habitat creation, riverbank fencing and repair to help water quality, as well as hedgerow and riverside grassland management to enhance biodiversity. We don’t stop for winter; this year so far we’ve tackled left over Himalayan Balsam pulling/bashing tasks on the upper Esk catchment.

Our 26 existing Riverfly Volunteers have been busy as ever in 2019, providing vital spot data on the Esk’s freshwater invertebrates. This data is crucial as many of our invertebrates are indicator species and being very sensitive they act as useful litmus for water quality and pollution. Many invertebrates are key component of freshwater and riparian food webs and many other species feed on them. Rivers need to be clean for them to thrive and in turn every other species will benefit. The data returns from 2019 have all been highly valuable for us and the national Riverfly Partnership, with most sites showing high levels of target group abundance and a few showing the highest levels in the last three years, which is encouraging news – hopefully this trend continues into 2020!

Our Adopt a Stream initiative is also a great source of data for the catchment. Another long standing citizen science project, this has volunteers who “take ownership” of given sections of the Esk, which they monitor on a month to month basis. Volunteers note down the general ecology of the site, the state of the river (flow regimes and water levels), any pollution inputs, any litter and invasive non-native species. This allows us, through the eyes of the volunteer, to recognise any apparent issues along the Esk. So if this is something you might be interested in, if you have a favourite walk or spot along the catchment you care about and like to visit frequently, then please get in touch and help us to continue to monitor the ecological health of the Esk Valley.

In addition we are hoping to start addressing some of the remaining in-river obstacles such as weirs, culverts and fords. This work could help towards the restoration of natural river processes and hydrology of the Esk and also importantly aid the passage of migratory fish species, such as salmon, trout, lamprey and eels. Structures can prevent fish species migrating up river to spawning sites and also prevent successful downstream migration of our salmon smolts which, added to the decline of salmon at sea, has further compounded population declines in the catchment in the last few decades. We found extremely low juvenile salmon numbers from our electro fishing surveys; this suggests that the installation of fish passage and fish easements could be a vital part of the continued conservation efforts along the Esk.

Lastly but most importantly there are our pearl mussels. The catalyst for all this work over the last decade and into the future is our Freshwater pearl mussel (Margaritifera margaritifera) population in the River Esk. We work with land managers as well as our volunteers and contractors to fence river corridors, plant trees/vegetation, stabilise and restore river banks in order to:

• reduce diffuse pollution because mussels require oligotrophic (low nutrient) conditions, and
• tackle erosion and sedimentation leading to suspended solids in the river because juvenile mussels require clean gravels with good oxygen circulation.

A strong salmonid population supports good healthy mussel numbers as the fish are crucial to the mussel’s life cycle – the larval form (glochidia) use the fish as hosts by attaching to the gills until large enough to detach and then self sustainably live within the river gravels. This is why we’re so keen on our river obstacle work because we want fish to spawn all the way up the catchment, creating strong, wide spread populations. Helping the fish helps the mussels and the mussels, being bivalves, help clean the river which in turn provides better conditions for our freshwater invertebrates, which then are fed on the by the fish and the cycle continues….

Everything in the river is connected and helping one species will help another, this is why all our conservation work is so important and why partnership and cooperation between our volunteers, land managers and partners is crucial for the future of the River Esk.

Traversing the Esk

Christopher Watt – River Esk Project Officer

Hi there, I’m Chris and I’ve just recently joined the National Park Authority as a River Esk Project Officer, having moved down from Scotland, and seemingly brought the weather with me! My role will involve working with farmers and landowners to implement river restoration techniques that seek to improve the water quality of the River Esk catchment.

Over the last month I have started to piece together the Esk catchment, worked with volunteers in delivering practical tasks and began undertaking fish obstacle river surveys. It has certainly been a varied introduction to the role and area.

Volunteers braved the drizzly elements back in October to repair a broken fence on the River Esk, near Castleton. Thankfully, the task allowed us to remain on dry land and avoid venturing into the river which was rather swollen after recent heavy rainfall. A bankside tree had fallen and crushed a section of the fence-line, slackening the wire and dislodging posts. The volunteers assisted with installing new posts, including a heavy duty straining post, re-attaching the wires and finally tightening them. The volunteers worked extremely hard and it was a pleasure to meet and work with them. The task was also completed in one afternoon and the sun even came out, which is a bonus!

This task was one of the many on-going works to restore and enhance the riparian habitats of the River Esk. Maintaining riverside fences assists in keeping cattle and sheep away from the bankside vegetation and so causing sediment loading through erosion. Bankside vegetation stabilises the soil and is an important habitat in its own right. The reduction of sediment loading should help improve conditions for conservation priority species such as Atlantic salmon (Salmo salar), Sea trout (Salmo trutta) and Freshwater pearl mussel (Margaritifera margaritifera) which favour clean, fast-flowing rivers and streams.

In combination to riparian habitat enhancements, we have also been undertaking fish obstacle surveys stretching from Westerdale down  to Goathland. These involve inspecting an assortment of obstructions from weirs, fords and culverts and assessing how severe they impinge on fish migration. At each obstacle the length, width and height are recorded, along with a written assessment of the level of severity the obstacle poses to migrating fish populations.  

Due to recent high rainfall, many of these obstacles have been partially or fully submerged, and although looking dramatic, have been just too dangerous to take measurements from. Electro-fishing will also accompany these surveys at a later date to inform us about fish species diversity and abundance at each obstacle. The purpose of these surveys is to update our records on obstructions across the catchment and prioritise where mitigation measures would best be targeted to benefit fish populations of the Esk. Migratory fish are a vital aspect of the biodiversity of the river.

Big Thank You’s

Kate Bailey – Catchment Partnership Officer

The BIFFA funded project ‘Restoring Freshwater Mussel Rivers in England’ came to an end in 2018. We were involved because of the River Esk in the north of the National Park. The £300,000 made available helped towards safeguarding Yorkshire’s last remaining population of Freshwater pearl mussels (Margaritifera margaritifera).

A huge amount of work was achieved in the Upper Esk catchment during the three year period of this project, working closely with the farming community to address diffuse pollution from agriculture. Pollution including sedimentation detrimentally affects water quality and therefore impacts on aquatic species like the mussels.

For most of its three years the project was led by Simon Hirst, our River Esk Project Officer. Simon worked with 38 land managers in the Upper Esk catchment delivering improvement works to help keep pollution including sedimentation out of the river and its tributaries. This has meant:

• Over 8km of riparian fencing installed
  This helps stabilise the river banks and creates buffer strips to reduce the amount of runoff from fields getting into watercourses, as well as providing rough habitat along the river corridor for insects which are so important for fish, birds and small mammals.
• 650 trees planted along the river banks of the Esk and its tributaries
  The majority of which were planted by our dedicated River Esk Volunteer Group.
  Trees help stabilise the banks and so. like with the fencing, reduce sedimentation.
• 34 alternative watering points installed
  This is to reduce poaching in fields and along the river banks, and to keep stock and their effluent out of a watercourse.
• Approximately 5.5km of riverbank re-vegetated with woodrush planting
  Another 130m of river bank was stabilised using hazel/willow whips. Re-vegetation helps stabilises the river banks
• Over 500m of guttering and downpipe installed on farm buildings
  To capture clean water before it gets onto the ground, picks up nutrients and sediment, and then runs into a watercourse.
• 1,237 m³ of concreting in farm yards.
  The new surface is profiled to collect dirty water before it can enter a nearby watercourse.

Big Thank You to Biffa for supporting the Restoring Freshwater Mussel Rivers in England project.

Big Thank You to all the local land managers who worked alongside Simon on the Esk, contributing a lot  of their own time and capital to complete these improvement works.

Big Thank You to our dedicated Mussel Volunteers who have played such a vital role in this delivery project, and all the other volunteers that helped out like the Explorer Club and the 1st Marston Moor Scout Group.

And one more Big Thank You to Simon Hirst. Last year the North York Moors National Park had to say goodbye to Simon because he moved on to a new role working on the River Holme in Huddersfield. His enthusiasm and knowledge will be greatly missed by us and the Esk’s Freshwater pearl mussels.

Born to be Wild

Dr Ceri Gibson – Pearl Mussel Projects Manager, Freshwater Biological Association

The Freshwater Biological Association has been working with the North York Moors National Park for the last 3 years on the ‘Restoring Freshwater Mussel Rivers in England’ project (funded through Biffa Award). Our role has been to rear juvenile mussels ready for reintroduction back into the River Esk at some appropriate time in the future when the habitat is restored and the water quality improved enough to support them.

Rearing juvenile freshwater pearl mussels (FPM) is a 24 hrs a day, 365 days of the year operation with our staff attending the hatchery even on Christmas Day to ensure that the mussels, and the host fish that they rely on as part of their lifecycle, are all okay.

But it’s not a bad job over here on the shores of Windermere. Whilst the wind may funnel up the lake at times, come rain, snow or sunshine, the views are wonderful and we have a great team.

The adult mussels are kept in circular tanks in our hatchery connected to tanks which contain host fish. Keeping fish and mussels in close proximity under controlled conditions improves the chances of the mussels successfully completing their lifecycle. We try to maintain the mussels in as natural an environment as possible so they are kept outside in flowing water provided from Windermere.

We constantly monitor the mussels and fish to record when glochidia (freshwater pearl mussel larvae) are released from the females and when these glochidia have grown sufficiently on the fish gills. Then we set nets to collect juveniles as they drop off their fish hosts and transfer them to trays in our juvenile rearing facility. Whilst other techniques of bank-side encystment and seeded gravel reintroductions have been used for some rivers we believe that rearing juveniles beyond their most vulnerable pedal feeding stage, when they live amongst the gravels before filtering free-flowing water, will yield better reintroduction survival rates and allows us the opportunity to learn more about these fascinating creatures.

Back in 2016, we worked with Simon Hirst (River Esk Project Officer) to translocate more adult mussels from the Esk to the hatchery. This exercise followed a recently commissioned brief from Natural England and was very carefully monitored. It proved successful and we have been collecting the captive bred juveniles in large numbers over the last two seasons. FPM larvae are carried on the gills of specific fish hosts for up to 10 months as part of lifecycle. It is interesting that in recent years the Esk glochidia grow to excystment size (350-400 microns long) and drop of the fish hosts within 2 to 3 months at the hatchery. We are therefore monitoring their survival in the rearing trays carefully.

We have been working with other river populations to prepare juveniles for reintroduction into their native rivers. The trays they are reared in are indoors where the juveniles are well protected. So we have set up flume systems to expose captive-bred juvenile mussels to diurnal and seasonal conditions which better reflect the river situation they will be reintroduced to. Once in the flume we can control flow to ‘teach’ them how to adapt to flood and drought conditions. During these experiments we record how many mussels are deeply buried, how many remain on their side on the surface of the gravels and how many are roaming about using their muscular foot. We also record whether they are siphoning water or not.

We look forward to the time that we can repeat these experiments for the Esk population but in the meantime have a look at some of our other, older juveniles filmed in their flume – click here. Or organise a group visit and come and see us at the Ark to visit the Esk juveniles and learn more about what we do.

Biffa Award is a multi-million pound fund that helps to build communities and transform lives through awarding grants to community and environmental projects across the UK, as part of the Landfill Communities Fund. 

 

Letter from Scotland

Sam Jones – previous River Esk Project Student

I still recall the morning as, fresh-faced and hopeful, I sat in the back of a bus trundling along country roads towards the North York Moors. As we turned a corner and crested a ridge I was gifted my first view of the National Park and I could feel butterflies in my stomach, this would be my first real job in conservation. This was the start of my life serving the environment as I saw it then (and still do now I suppose). That was about four years ago, things have moved on quite a bit since then.

I worked for the National Park Authority on a year in industry placement back in my third year of University assisting with the Esk Pearl Mussel Salmon Recovery Project lead by Simon Hirst aimed at conserving the remaining Freshwater pearl mussel population in the River Esk. It was a wonderful and varied experience.

At the end of my time I spent a week wading through ocherous becks in the very upper reaches of the Murk Esk. I was rather cheekily using my last few weeks working at the National Park to collect data for my upcoming final year project. I collected samples of upland invertebrates from becks through moorland and coniferous woodland to test the effects of acidification on aquatic life, and to see how the impacts of acidic moorland and plantation woodlands compare. My project has now been published although you need journal access to see the whole thing. Simon has asked me for a basic summary of my findings and conclusions – so here goes…

I used aquatic invertebrates as indicators of environmental degradation. It’s well recognised that moorlands and uplands can have acidification issues, and the North York Moors may well be one of the most extreme areas for it in the UK with its nearby zones of industry. Acid issues have been recorded in local becks in the past, including severe fish kills. However my results were a little surprising. Originally I thought that plantation woodland, being the newer and least natural habitat (compared to moorland which is also man-made habitat), and having less ability to slow down and buffer the incoming water, would have a much more degraded community. However, my results showed significantly more acid sensitive species living in the woodlands than the moorland. This was despite the fact that previous studies had recorded lower pH values (i.e. more acidic) in plantations than in moorlands. I think that the reason for this is the woodlands provide a more diverse and richer freshwater environment for the invertebrates to live in. This is a good sign as it shows that the conifer plantation woodland, that so much of our countryside is dominated by, may not have such a bad effect on aquatic life as once assumed. The aquatic communities were also generally healthier than would have been expected given the severe acidification. I think this shows that the species of invertebrates living in the uplands of the North York Moors are well adapted for highly acid conditions and that, despite the seemingly poor chemical results, life in the upland becks is thriving.

What happened next? After I graduated from the University of York I went on to work for Natural England, the Environment Agency and now I’m part of an ecological consultancy. I’ve come full circle, and recently I was lucky enough to get accepted for a PhD up in Inverness studying Freshwater pearl mussels. Apparently they needed someone with more waders and bucket experience than lab experience, and I fitted the bill.

Scotland is one the great bastions of the Freshwater pearl mussels with populations of tens of thousands in numerous rivers and multiple populations with favourable age structures and reproductive ability (unlike in the Esk sadly). As such, my PhD is to study these populations and monitor them using traditional methods. However the focus of the investigation is to allow comparison of conventional survey methods with new eDNA techniques. Environmental DNA (eDNA) is a method of monitoring species or habitats using the DNA that is freely found in the environment. All organisms living in an environment discard DNA, whether through waste, dead cells, carcasses, etc. and this can be picked up in trace amounts in water, soil, and even air. With Freshwater pearl mussels the hope is that DNA markers and techniques can be designed to allow detection of small or isolated populations of pearl mussels in rivers simply from a scoop of river water downstream of these prospective populations. There is also potential that the techniques could be used to monitor the size, health and population structure of these populations and perhaps even help identify sub species or genetically distinct populations. Whether this is possible or not, the possibility of cheaper and easier monitoring of pearl mussels fundamentally helps with conservation efforts.

I’m hoping to be able to keep Simon and the Esk Project up to date with our findings and perhaps provide some new information and techniques that may help the Esk’s own struggling mussels over time.

Anyway, that’s my little summary of things. I hope you guys found this interesting.

Thanks for reading, and keep on supporting the National Park,

Sam

30,000 words on water quality

Rosie Nelson – Masters Student

I have finally finished my research masters. All that stands between me and the real world is corrections and actually printing a 30,000 (ish) word document. So did I actually achieve anything. Well I’d like to think so, but first up I’ll tell you a bit about what I did, and how I did it.

I spent six blissful months walking three beautiful watercourse catchments in the North York Moors – Toad Beck, Danby Beck and Great Fryup Beck which are all tributaries into the River Esk. Aside from sun kissed skin and being chased by sheep, dogs and cows, I somehow managed to collect what I was after – a lot of useful data. To establish the water quality of a river a variety of sampling techniques is required. My favourite was using a probe which measures dissolved oxygen, conductivity, pH, salinity, temperature and much much more. Imagine, dangling a very expensive cable off the side of a bridge and waiting in anticipation for the numbers on the screen to settle. I loved it. Although once or twice the probe did ricochet off rocks to produce an alarming sound.

As my data collection evolved, I also started to gather water samples to take back to the laboratory for COD, BOD, DOC, anion and cation analysis. You might think I’ve just put some letters together to appear clever, but they do actually stand for things:
– COD is chemical oxygen demand (amount of oxygen required to oxidise the organic matter in the solution);
– BOD is biochemical oxygen demand (amount of dissolved oxygen being used by aerobic microorganisms when decomposing the organic matter in the solution);
– DOC is dissolved organic carbon (amount of organic matter in the solution);
– An anion is a negatively charged ion, a cation is a positively charged ion, and an ion is an electrically charged atom.

So what did I actually find out in these three catchments? Well I analysed the spatial and temporal variations of a variety of water parameters. The significance of focusing on both spatial and temporal variations within a catchment is it can easily identify areas of point source pollution at a small scale, something which isn’t done often enough.

For this post I’m focusing on dissolved oxygen and conductivity. The very important key species Freshwater Pearl Mussels require dissolved oxygen levels between 90 – 110% (Oliver, 2000). Other aquatic life like fish can survive on much lower saturations of dissolved oxygen, as low as <30%. The graph below shows how dissolved oxygen (a vital parameter for ascertaining the health of a river) changes through the year. Changes in water levels and plant growth can have serious effects on the amount of dissolved oxygen available for organic and aquatic life. During the summer months, plants will become abundant in a river, thus using up more oxygen and depleting the overall amount of dissolved oxygen available in a river. Once rainfall increases in the autumn dissolved oxygen levels should be replenished. As you can see September 2016 was a particularly poor month for dissolved oxygen, with average levels as low as 80%. Similarly, August on Toad Beck was low as well with an average of 75% saturation. But aside from in September for all three watercourses, and in August for Toad Beck, the dissolved oxygen levels remained within or above the proposed dissolved oxygen threshold.

Next up – conductivity. Conductivity is a measure of a watercourse’s ability to conduct electrical flow and is therefore related to the concentration of ions in a river. Particular aquatic species need higher or lower conductivity – the Freshwater Pearl Mussel likes a lower conductivity. There are variations between suggested thresholds for conductivity: Moorkens (2000) suggests it should be 65µs/cm, whilst Bauer (1988) suggests <70µs/cm and Oliver (2000) suggests <100µs/cm. So I chose the only logical way forward and used all three thresholds. Focusing again on the month of September 2016, I produced the map below.

This is where analysing data spatially comes into its element. First up, the circles represent sampling locations (every now and again samples were missed out say if there were a herd of cows approaching as I climbed the style into their field, needless to say my flight or fight response would always be flight as advised in the National Park Authority’s Risk Assessments). Using a traffic light system, green circles represent good conductivity levels. As you can see, September was a poor month for both dissolved oxygen and conductivity. What I found particularly interesting was the variations that could occur in a small watercourse like Danby Beck, where as tributary field drains entered the beck conductivity levels could spike or decrease dramatically; how fantastic!

So to round off I thought I’d quickly summarise my thesis’ findings. Water quality is good in the three catchments, but it’s not good enough for Freshwater Pearl Mussels, and that’s the gist of it. The work of the River Esk catchment officers at the National Park to address the issues is great, the water bodies are reaching and maintaining ‘good’ ecological status, unfortunately the Freshwater Pearl Mussels require pristine water conditions and ‘high’ ecological status. However the future direction is positive for the health and conservation of Freshwater Pearl Mussels. And I too am looking forward to the future; I shall be taking a few weeks off from being chased by animals and I can’t wait*.

 

 

 

 

* Editor’s note: Rosie didn’t get much time off – she’s gone off to pastures new and is now a Community (Water Quality) Modelling Project Officer at Thames21. We wish her all the best.

Ageing Mussels

Simon Hirst – River Esk Project Officer

As mentioned previously, the River Esk in the North York Moors is the only river in Yorkshire with a Freshwater pearl mussel population Margaritifera margaritifera. The population is estimated to be comprised of approximately 1,000 individuals and is in drastic decline, so much so that it is on the verge of extinction. The decline is due to a number of linked causes such as water pollution, choking of the river bed by sediment build-up, deterioration in fish numbers and habitat degradation.

We’re working to improve the riparian habitat and so help secure the local population of Freshwater pearl mussel in the River Esk. We recently sent a sample of mussel shells from the Esk* over to the Swedish Natural History Museum in Stockholm, in order to determine the age of the mussels in the River Esk. The maximum age of Freshwater pearl mussels in the wild has been shown to vary considerably, from a low of 35 years in Spain (warmer, lower latitude rivers) to over 200 years in arctic areas (colder and high latitude rivers). Information from the ageing study would tell us how long we have left to save the Esk population from extinction and help identify the approximate time when the River Esk mussel population went into decline.

Dr Elena Dunca from the Swedish Natural History Museum sectioned (cut though) the shells supplied and then counted the growth lines on the mussel shell using a high powered microscope.

Growth lines visible on the freshwater pearl mussel shell.

This age/length graph will allow us to age fairly accurately any mussels we find in the wild in the future just by measuring them.

A total of 10 shells were aged by Dr Dunca, and the graph below shows that the mussels sent to Sweden ranged in age from 45 to 88 years of age.  The mussels in the River Esk also showed normal growth rates.

Length frequency graph of mussels in the River Esk

The smallest live mussel we have found in the Esk up to now was 75mm (approximately 28 years of age). This means the last time the Esk mussels reproduced successfully in the wild was in the late 1980s. The largest mussel we have found in the Esk was 156mm (approximately 100 years of age), which means it was born around the time of the First World War. The vast majority of the mussels are around the 130mm-140mm size range (approximately 80 years of age). We now know for scientific certainty that the Esk has an ageing population in need of help!

The best hope for our mussels is for them to start to successfully reproduce again. We’re working with the Freshwater Biological Association (FBA) who are carrying out captive breeding work in the Lake District. We hope to re-introduce the captive bred young Esk mussels from the FBA Facility back into the Esk once the riparian habitat is restored enough to sustain them, and so ultimately stop this species from becoming extinct in the wild (of Yorkshire).

* Please note – No mussels were harmed in the making of this study! We used empty shells that were found on the banks of the Esk.

Thanks to our funders at Biffa Award, for their support to carry out this vital research work.

Biffa Award is a multi-million pound fund that helps to build communities and transform lives through awarding grants to community and environmental projects across the UK, as part of the Landfill Communities Fund.

A scientific perspective

Natural England‘s Chief Scientist visited the North York Moors last week to see the ongoing work in the River Esk catchment to help save our dwindling population of Freshwater Pearl Mussels.

You can read about why he came and what he thought here.

 

Patience and perserverance

We’ve launched a new concerted effort against two of the most threatening non-native invasive plant species in the North York Moors, bolstered by funding from Yorkshire Water over the next four years. We’re chasing down Himalayan balsam (Impatiens glandulifera) and Japanese knotweed (Fallopia japonica) in the River Esk and River Rye catchments.

As well as damaging existing ecosystems and decreasing diversity, both these species tend to overwhelm other plant species along river banks and the danger from this is that during the winter when these non-natives die back the banksides are left bare of vegetation so subject to erosion which increases the sediment getting into watercourses and smothering the water habitat.

Both plants are vigorous growers and virulent spreaders. Himalayan balsam disperses thousands of seeds per plant through exploding seed pods that can propel the seeds metres from the original plant. If the plants are next to watercourses the seeds can be carried downstream to colonise new areas. Japanese knotweed spreads through its underground rhizomes which are so effective that all remnants of the plants need to be carefully disposed of because even a small fragment of rhizome if given the chance to re-root will form a new plant.

The only way to have any real impact on the plants is to tackle them systematically starting at the top of catchments and moving downstream, and repeating the control year after year to remove any vestiges of the plants. This new funding will provide a much needed boost to efforts made over the last few years.

We’ll be surveying the current extent of the plants and then resurveying each year to monitor the effects of the control. We’re using tried and tested control methods – hand pulling the Himalayan balsam before it gets the chance to seed and propogate, and treating individual Japanese knotweed plants with directly administered glyphosate injections to carry the chemical down into the rhizomes. We’ll be using contractors and volunteers to carry out the work coordinated by National Park staff.

Controlling and hopefully eradicating non-native invasive species in an area takes a long time. Simon, our River Esk Project Officer, is a real enthusiast for non-native invasive species control because he sees the detrimental effects the plants have on the river environment and on his beloved Freshwater pearl mussels. He can see the years of attrition starting to pay off as native vegetation starts to recolonise sites where invasive species have been removed.

“The secret of success is constancy to purpose” — Benjamin Disraeli