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.

A dense bed of healthy adult mussels in Scotland. Copyright Sue Scott - SNH,

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.

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Growth lines visible on the freshwater pearl mussel shell.

Esk FWPM - Age and length graph - Swedish Natural History Museum

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.

Esk FWPM - Length frequency graph - Swedish Natural History Museum

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

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.

Mastering the river environment

Rosie Nelson – Masters Student

I’m Rosie and I’m two months in to my research masters at Durham University, kindly sponsored through the North York Moors National Park Authority with funding from Biffa Award. Since my second year of university, I’ve known I wanted to work with (or in) rivers, and this masters should help me get one step closer to achieving that.

I’m investigating the water quality of three hotspot tributaries of the Esk: Danby Beck, Toad Beck and Great Fryup Beck, in the hope to identify point source pollution and its cause/s. Ensuring good water quality is crucial for the health of the river and paramount for the Freshwater pearl mussels that live there. The key contaminants I will be looking at are Phosphate, Nitrogen and Ammonium. The Esk currently exceeds the thresholds for these three elements/compounds which pollute the river environment and damage freshwater systems. I hope that through my data collection and analysis I can identify point source pollution issues and help reduce the contaminants entering the Esk. Hopefully making the Freshwater pearl mussels a little bit happier!

Being based in the Authority’s Conservation Department for at least one day a week is proving to be very helpful. Not only am I extremely productive, but I’m also learning what it’s like to work in a conservation environment – something I definitely hope to be doing in the future.

At the start of May, I got to join in with the Salmon in the Classroom project alongside Simon the River Esk Project Officer and Alex the Catchment Partnership Officer. Simon taught me how to kick sample, something I really wish I’d known how to do before. You get into a safe watercourse with a fishing net, place the net downstream of you and kick the river bed. After several kicks, you empty the net into a bucket of water and hope you’ve found things, like invertebrates and potentially even fish! After several kick samples, we had collected enough living invertebrates for the children and me to identify.

Salmon in the Classroom - this is me and the children identifying what we found - check out my wicked waders! Copyright NYMNPA.

Last week I went out with Alex in Glaisdale in the Esk Catchment, and aside from us both getting stuck in the mud I had a great day (luckily I was holding a spade and could dig us out!). In the morning we visited a farm which is perfect for bank stabilisation work to lessen the amount of sedimentation. In the afternoon at a different site in the dale we planted trees and sowed grass seed to re-vegetate where a new drinking bay had been installed (to provide water for stock which are now fenced off from the river).

Well that’s just a snippet of the things I’ve been getting up to in the past couple of months, not forgetting reading as much as physically possible about anything and everything river related!

Biffa

In Extremis update

From Eloy at the Freshwater Biological Association Facility:

The Esk mussels are settling in. They are buried and stable, not moving that much, as if they had found their space in the cage.

Recently translocated mussels from the Esk now at the FBA Facility - copyright FBA

 

In Extremis

Simon Hirst – River Esk Project Officer

As mentioned before on this Blog, the River Esk in the North York Moors is the only river in Yorkshire with a Freshwater pearl mussel (Margaritifera margaritifera) population. Our population is in drastic decline – currently it is estimated there are approximately 1,000 individuals, all adults.

We’re part of a national project (funded by Biffa Award) to conserve the populations of Freshwater pearl mussel in England. Nine years ago a number of the adult mussels were collected from the Esk and moved to the Freshwater Biological Association’s Facility in the Lake District. A couple of weeks ago, early one morning, Eloy from the Association and I collected another 20 and took them across to join the others at the Facility 130 miles away.

Eloy preparing the FPM transportation unit ie a cool box - copyright Simon Hirst, NYMNPA

River Esk substrate to take to the FBA Facility - home comforts for the Esk mussels - copyright Simon Hirst, NYMNPAThe lid of the cool box had to be left open so oxygen exchange could occur during the 3 hour journey - so the box was thoroughly jammed in - copyright Simon Hirst, NYMNPA

Safely arrived at the FBA Facility - acclimatising the Esk mussels to their new home - copyright Simon Hirst, NYMNPAThe idea is the translocated adults breed and the Facility then rear the captive juvenile mussels with the ultimate idea of reintroducing the young mussels back into their native rivers. In the meantime we’re continuing to tackle the problems that have had and continue to have such a detrimental effect on the mussels. So on the Esk we’re working in partnership to improve the riparian habitat in order to increase water quality and vitally reduce the amount of suffocating sediment so that the river becomes a suitable release site and juvenile mussels have a chance of surviving. Improving the river habitat also benefits the migratory fish which are such a vital part of the mussels’ lifecycle.

We’re trying everything we can to help the Esk population and give it the best chance of survival. Mussels can live to be over 100 but if there are no juveniles, slowly but surely the Freshwater pearl mussel will become locally extinct.

Biffa

Operation Luzula

Kate Bailey – Conservation Graduate Trainee

Since starting as the Conservation Graduate Trainee last September, I have had lots of opportunities to get out and about with our hardworking National Park Volunteers undertaking practical conservation tasks across the National Park.

Last week, I joined the River Esk Volunteers for a day planting woodrush along the banks of the River Esk. Greater woodrush Luzula sylvatica is a native, perennial member of the rush family which grows in damp shady places. It thrives along river banks in the North York Moors, where it grows in tussocks providing great ground cover which helps stabilise the river bank.

A good example of Luzula sylvatica growing along the River Esk - copyright NYMNPA

However there are sites along the River Esk where the banks are void of any vegetation. When stock have access to the river, any natural regeneration gets nibbled off and the river banks are left bare and susceptible to erosion leading to sediment entering the water and choking the river habitat. Woodrush planting coupled with river side fencing to exclude stock and create a bankside buffer strip is potentially one of the solutions to this problem.

Planting woodrush as a means of stabilising the river bank has not been carried out before in the National Park. Simon, our River Esk Project Officer, identified a trial site which could benefit greatly from some conservation effort. The river was fenced off over winter, excluding stock from the damaged river banks and young trees – Hazel and Oak Luzula sylvatica being grown at Mires Beck Nursery– were planted. Last summer National Park Volunteers had helped collect woodrush seeds from other sites along the River Esk (to maintain the local provenance) which were then sent off to the Mires Beck Nursey near Hull. The Nursery primarily produces wildflowers for conservation projects whilst providing opportunities for people with learning difficulties to get involved with horticulture. Our woodrush seeds spent the last eight months being grown on and cared for by the knowledgeable staff and volunteers at Mires Beck Nursery. The plants were delivered back to the North York Moors last week, ready to be planted.

Woodrush planting task - copyright NYMNPA

It was an extremely well attended planting task for a Monday in March – and it was sunny. The River Esk Volunteers were joined by three members of staff from Mires Beck Nursery who made the journey up from Hull to deliver the 3600 woodrush plants. Hopefully the newly planted woodrush will flourish and the river banks will be covered in vegetation once more, safeguarding the River Esk habitat and all its associated species.

Planted woodrush on the banks of the River Esk - copyright NYMNPA

Woodrush planting is one element of the Esk Pearl Mussel and Salmon Recovery Project which is working to sustain Yorkshire’s last remaining population of Freshwater pearl mussels Margaritifera margaritifera. The River Esk Project has been boosted with a £300,000 grant from Biffa Award. The grant forms part of a larger £1.5 million Biffa Award project led by the Freshwater Biological Association that involves river restoration in a number of Freshwater Pearl Mussel catchments in the country, including in Cumbria and Devon, as well as Yorkshire. “This project is an exciting opportunity to save one of the most long-lived animals from extinction; the freshwater pearl mussel can live for more than 100 years and is internationally protected” – Gillian French, Biffa Award Programme Manager,

Biffa Award logo

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. More information on the award is available at www.biffa-award.org.

Carry on saving the mussels

Simon Hirst – River Esk Project Officer

Our work to safeguard Yorkshire’s last remaining population of Freshwater pearl mussels has received a £300,000 grant from Biffa Award. The River Esk in the north of the National Park is the only river in Yorkshire which still has a Freshwater pearl mussel Margaritifera margaritifera population. The population is estimated to be approximately 1,000 individuals and is in drastic decline. Pollution and sediment build up, decline in fish populations and habitat degradation are all reasons for this.

River Esk Freshwater Pearl Mussel ~40 year old - NYMNPA

The grant received is part of a larger £1.5 million Biffa Award project (2015 – 2018) led by the Freshwater Biological Association that will also see river restoration carried out in river catchments in Cumbria and Devon where freshwater pearl mussels also survive.

One of the key elements of the project will be sharing knowledge and best practice with landowners, the local community and other conservation groups to help give the mussels a more sustainable future. The project will work with farmers to reduce sediment and nutrient input into the Esk, and volunteer groups and angling clubs will be involved in monitoring work such as sampling invertebrate life throughout the river and also restoration work such as planting trees along the river bank and tackling non-native invasive species. The funding will also help sponsor a Master of Research degree at Durham University, which will look at water quality throughout the catchment.

On top of this local effort, the national project will focus on improving the reproductive success of the Freshwater pearl mussel through the Freshwater Biological Association’s captive breeding programme. In 2007, mussels from the Esk were taken to an ‘ark’ facility in the Lake District which houses and breeds populations from threatened Freshwater pearl mussel rivers in England. We’re aiming for sections of the Esk to have been restored enough by 2018 to provide suitable habitat to accommodate the return of the juvenile mussels.

This is a brilliant opportunity for people from different backgrounds to get involved in the conservation of a rare and valuable species. They may not be cute and cuddly but freshwater pearl mussels are an important indicator species; if we get conditions right for them, it will have positive knock on benefits for a range of other wildlife such as otters, Atlantic salmon, dippers and kingfishers.

BiffaBiffa 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. More information on the award is available at www.biffa-award.org.

Juvenile mussel at captive breeding facility - copyight Louise Lavictoire FBA

River Esk research work - NYMNPA

Encystement project - NYMNPA

This new project which started in March builds on the WREN funded three year Freshwater Pearl Mussel project which finished in February.  This project had similar aims to the new project – to educate and involve people, and to carry out restoration work to limit nutrient and silt input into watercourses which damages spawning gravels and juvenile mussel habitats.

WREN Project Outputs

WREN FWPM Project - river bank fencing - NYMNPAWREN FWPM Project - river bank fencing - NYMNPA WREN FWPM Project - river bank fencing - NYMNPA

 

 

WREN FWPM Project - bank stabilisation - NYMNPAWREN FWPM Project - crossing point - NYMNPAWREN FWPM Project - buffer strip - NYMNPA

 

 

 

 

WREN FWPM Project - tree planting - NYMNPAWREN FWPM Project - trough installation - NYMNPA WREN FWPM Project - tree planting - NYMNPA

 

WREN FWPM Project - river bank fencing - NYMNPAWREN FWPM Project - new cattle watering point - NYMNPA
WREN FWPM Project - gateway improvement - NYMNPA

 

 

WREN FWPM Project - Himalayn balsam control - River Esk Volunteers Task - NYMNPA

As well as nutrient and sediment free water the best habitat for Freshwater pearl mussels is a boulder stabilised substrate with pockets of coarse sand and gravel for burrowing. Water quality monitoring equipment was installed at the key potential re-introduction site on the Esk to measure a variety of water quality parameters such as dissolved oxygen, nitrogen and pH. Redox surveys were carried out to assess juvenile pearl mussel habitat quality – redox surveys measure the water quality within the river gravels (where the young mussels live). One of the Esk sites which was surveyed had redox readings which were potentially suitable for young mussels (which is really positive news), and a few other sites are very close to being suitable.

logoWREN is a not-for-profit business that helps benefit the lives of people who live close to landfill sites by awarding grants for community, biodiversity and heritage projects.

 

Potential FWPM re-introduction site on River Esk - NYMNPAThis is a long term effort. By 2018 all the work and funding over the last 10 years will hopefully come to fruition and the Freshwater pearl mussel will have a sustainable future in the River Esk.