The Tyne freshwater pearl mussel project

The Tyne Pearl Mussel Project (ref: RENE43004) is a collaboration between the Yorkshire & North East region of the Environment Agency, the Freshwater Biological Association (FBA), Northumbrian Water and the Tyne Rivers Trust. It commenced in October 2010 and runs until December 2012 with an overall strategic objective "To identify and undertake conservation actions to ensure the long term survival of the freshwater pearl mussel in the North Tyne catchment." There are four specific objectives defined:

  1. PROTECT remaining key populations of the freshwater pearl mussel in the North Tyne catchment and maintain the potential for in-situ breeding capacity.
  2. RESTORE - create the conditions that support the restoration of natural recruitment in existing, relic populations and the conditions for re-introduction of the species into suitable recipient habitats.
  3. REINTRODUCE the freshwater pearl mussel into suitable areas.
  4. SECURE - put in place the mechanisms to deliver the conditions, (e.g. modify flow regulation regime) infrastructure and support mechanisms (e.g. monitoring strategies) necessary to secure the long term conservation of the species in this habitat.

With these objectives in mind, there will be two main deliverables from this project:

  1. To identify the factors responsible for the decline of the Freshwater pearl mussel in the North Tyne catchment
  2. To design a robust, evidence-based restoration plan for the species in the North Tyne catchment

Study area

View of the river North Tyne

 
View of the river Rede

Located in Northumberland, North-East England, the North Tyne catchment is 1118 Km2 (437 square miles) in area and characterised by Lower Carboniferous sandstones and limestones of the Scremerstone group. The North Tyne originates in the Peel and Deadwater Fells (NY 626972) and is 66 km long, reaching its confluence with the River South Tyne at Watersmeet near Hexham. The confluence of the North Tyne with its main tributary, the River Rede, occurs at Redesmouth, 40 km downstream of Kielder Reservoir. The Rede originates in the Cheviot Hills (NT 905205), where the geology is characterised by Cemenstone, before the river flows through Lower and Middle Limestone. The Rede flows over carboniferous sandstones and shales covered by clay and peat for 58 km until it reaches the North Tyne at Redesmouth. The Rede headwaters have been regulated by Catcleugh Reservoir since 1905: this was originally built for water storage and affects river flow only minimally. The North Tyne flow regime has been fully regulated since 1981 after the building of Kielder Reservoir in its upper reaches.

Land use

The North Tyne catchment is a relatively isolated area with large industrial centres situated further downstream on the main River Tyne near Newcastle-upon-Tyne. Much of the North Tyne catchment is located within the Northumberland National Park. Coal mining and iron ore extraction and production took place during the industrial revolution; however this was relatively small-scale compared to the activities on the South Tyne and the Tyne estuary.

More recently, agriculture (both arable and livestock rearing) has been the dominant land use in the North Tyne catchment. This has had important implications for all aquatic organisms as increased sediment run-off and river poaching by livestock has increased the input of fine, organic particles and nutrients into the river. Detrimental effects from this include eutrophication and settlement of fine particles in river gravels thus reducing available oxygen in gravel interstices. The two main types of land use for the catchment are grassland and forestry/woodland. On the Rede, 82 % of the catchment land use is grassland and 17% is forestry/woodland. On the North Tyne, the proportion of forestry/woodland is higher, representing 37 % of the total land use; grassland represents 57%. On both rivers approximately 2% of the land use is water-related. Most of the land is privately owned (64% for the Rede and 67 % for the North Tyne). The Forestry Commission has 30% ownership on the North Tyne and 15% on the Rede. Additionally 20% of the land ownership is by the Ministry of Defence (e.g. the military camp at Otterburn) within the Rede sub-catchment.

Numerous discharge consents have been issued by the Environment Agency in the North Tyne catchment. Most discharge consents fall into two categories: secondary treated sewage to river (S2R) and septic tanks with a discharge to the river (STR). Depending upon the volume and nutrient content of the discharge, negative impacts can be observed in the ecosystem: secondary treated sewage can lead to an increase in nitrogen and phosphorus in the catchment and thus an increase in algal growth potential.

One significant change in land use within the catchment has been the development of Kielder Forest from the 1930s. The period of maximum growth of the forest occurred from the 1940s to the 1960s. Kielder Forest is the largest working forest in England and covers 600 Km2. This change in land use has altered considerably the sediment regime for the catchment. Clear felling operations result in increased runoff, soil loss and sediment input into streams. The initial plantation of trees involved the use of rock phosphate, which is likely to have contributed to phosphorus input in streams. At present 40 % of the North Tyne catchment is forested with fast-growing non-native species for the purpose of forestry exploitation. Around Kielder Reservoir, this percentage goes up to 70% of the immediate drainage basin.

Kielder Reservoir is the largest man-made lake in Europe (10 km2) and was constructed between 1976 and 1981. With a capacity of 200 million m3, the reservoir impounds the River North Tyne and regulates the river, reducing the occurrence of extreme flooding and drought events. It was originally built to meet the anticipated increased demand for expanding industry in the region but this expansion never materialised. Kielder Dam has two hydro-electric generators which supply electricity to the national grid and the Kielder Water and Forest Park also generates income from tourism.

The freshwater pearl mussel in the North Tyne

The population size of pearl mussels on the North Tyne and Rede is estimated at 47,000 according to the last survey carried out by E3 Ecology Ltd in 2006, although actual numbers found during the 2006 survey on the North Tyne and Rede were much lower. Full surveys of the rivers were carried out in 1997 and 2006 which showed that mussels are present from the middle reaches of the Rede to its confluence with the North Tyne and from there down the North Tyne to its confluence with the South Tyne.

The North Tyne catchment population is the second largest pearl mussel population in England after the River Ehen in Cumbria. There is no site within the catchment designated as a European or nationally important wildlife site and thus the mussels are not provided with the same level of legal protection.

Anecdotal evidence suggests that in the 1950's mussels could be found near the source of the Rede and they were plentiful in the North Tyne upstream of the NorthTyne/Rede confluence.  The current age structure is heavily biased towards older mussels with a mean age of 50 to 80 years old. There are very few mussels younger than 30 years and no evidence of recruitment from the last 10 years; no juvenile mussels (<20mm) were found in the 2006 survey. This indicates that the factors responsible for the decline of the population in the catchment started at least 30 years ago. Electrofishing surveys carried out by the Environment Agency between 2006 and 2008 and additional surveys carried out in spring 2011 found no glochidial encystment on wild salmonids. Actions to restore natural recruitment are urgently required. 

In 2008, 50 individuals from near Bellingham on the North Tyne were removed to the FBA hatchery for captive breeding purposes and successful encystment and juvenile collection has occurred each year on brown trout (Salmo trutta) but not on Atlantic salmon (Salmo salar). In 2010, glochidal encystment was observed on 0+ sea trout at the Kielder Hatchery.

Data analysis

North Tyne adult freshwater pearl mussel with filamentous algal growth as a result of water enrichment

Marie-Pierre Gosselin and Roger Sweeting (FBA) recording physical habitat parameters on the river Rede

Water quality monitoring (monthly samples) has been carried out by the Environment Agency since 1976 on the North Tyne and 1990 on the Rede. In this project the data collected have been analysed comprehensively for the first time. Particular attention was paid to the parameters most relevant to to freshwater pearl mussel ecology: dissolved oxygen, pH, turbidity, suspended solids, nitrate, phosphate and Biochemical Oxygen Demand.

Results show that on both the North Tyne and Rede, levels of turbidity, suspended solids, nitrate, phosphate and Biochemical Oxygen Demand are much higher than the range tolerated by freshwater pearl mussels. Reasons for these values being so high are bank and soil erosion due to agricultural practices (e.g. livestock poaching) and forestry activities and increased runoff due to land drainage.

The large scale salmonid stocking programme in place in the North Tyne catchment since 1982 also presents some cause for concern. Most of the fish released in the catchment are Atlantic salmon (up to 200,000 per year) with brown trout being released in much smaller numbers. Following the findings from trials at the FBA hatchery it was found that brown trout is the favoured fish host for M. margaritifera. The situation in the North Tyne catchment, together with anecdotal evidence from trout fishermen who say trout catches have been declining over the years, reveals that low host fish density may also contribute to the lack of recruitment from freshwater pearl mussels.

Physical Habitat Characterization

During the 2011 fieldwork season, transect surveys of depth, velocity, substrate and instream vegetation were carried out at various locations on the Rede and the North Tyne in order to establish the physical characteristics of sites with and without pearl mussels. The collected data are currently being analysed.

Engaging with stakeholders

The next stage of the project is to promote good ecological practice with local stakeholders. To this end a series of workshops is planned in the first half of 2012 to inform stakeholders and obtain their views with respect to the proposed restoration strategy.

Wednesday 25th January 2012- "People and pearl mussels of the River Rede"

Agenda

Presentation Paul Atkinson (TRT) (pdf)

Presentation Marie-Pierre Gosselin (pdf)

Presentation Roger Sweeting (pdf)

For more information please contact Dr Marie-Pierre Gosselin (MGosselin@fba.org.uk)

 

(Last updated 3rd February 2012)