River Kent and Tributaries

Also within

Cumbria County LAKE DISTRICT National Park

Condition (Natural England)

Habitats

Fast flowing river and stream

Geology & landscape

Geological Period: Ordovician, Silurian · Rock Type: Limestone

Landscape processes: Fluvial

Birds & fish recorded

Fish

Description

Description The River Kent and its tributaries support nationally important populations of white clawed crayfish Austropotamobius pallipes. One of the headwaters also supports one of the largest populations of fresh water pearl mussel Margaritifera margaritifera in England. General Description The River Kent’s main tributaries have their catchments in the south eastern Lake District fells. On the higher ground these drain from rocks of Ordovician and Silurian age. Natural mineral enrichment provides the calcium necessary for growth of crayfish. Downstream from Kendal, the main channel of the Kent flows through a series of limestone defiles and gorges. This stretch is influenced by calcium rich limestone springs. White clawed crayfish are found throughout the river system, from the headwaters of the Rivers Kent, Gowan, Mint and Sprint downstream to the lower reaches of the main Kent channel near Sedgwick. The Kent is the only major river system in England where populations of white clawed crayfish can still be found throughout the catchment, wherever there are suitable habitats. Within the Kent catchment, crayfish are found in the lower reaches near sea level up to at least 250 metres above sea level in the headwaters of the Rivers Kent and Mint. Dubbs Beck, the headwater of the River Gowan, also has populations in two small reservoirs. The Kent system presents a variety of habitats for crayfish. This includes extensive areas with a loosely structured but stable stream bed of cobbles and stones. Crayfish are also found in the more unstable, turbulent reaches of the upper Kent and Sprint wherever there are small areas of cobbles and stones at the edge of channels. In the lower reaches and particularly through Kendal, there are extensive beds of water crowfoot Ranunculus spp and alternate flowered water milfoil Myriophyllum alterniflorum providing a further habitat and food source for crayfish. In the headwaters of the River Gowan, populations are found in streams less than a metre wide with only a few centimetres depth of water. This contrasts with the lower stretches of the main Kent channel where crayfish are found in much deeper water amongst boulders and shattered bedrock. The main channel of the River Kent has extensive reaches with undisturbed riparian habitats of woodland and tall riparian vegetation. Much of the river system is lined with tall, marginal vegetation of reed canary grass Phalaris arundinacea, hemlock water dropwort Oenanthe crocata and associated tall herbs and grasses. The submerged roots of these plants and the diversity of habitats created by the riparian vegetation, provide excellent refuges for crayfish. Apart from the quality and extent of habitats, the Kent is an excellent river for crayfish for a number of other reasons. The Kent and its tributaries have generally high water quality. With a short distance from the headwaters to the mouth of the river and heavy rainfall on the catchment fells, the river has a high degree of flushing. This maintains the river bed relatively free of silt and algal growth. This means the spaces between and under river stones and cobbles provide excellent habitat for crayfish and their invertebrate food. Finally, the Kent catchment is free from introductions of non native crayfish and there is no record of crayfish plague. Although white clawed crayfish is still present throughout most of its natural range in England, there are only three catchments where this once common freshwater crustacean can still be considered to be abundant and widespread. These are the Eden and Kent in Cumbria and the Wye on the English / Welsh border. In other catchments, populations are small and scattered or under threat from non native crayfish and crayfish plague. Apart from the impact of non native crayfish, declines in water quality, loss of natural riparian habitats and river channel modifications have all led to declines in crayfish populations. The Kent catchment remains one of the few catchments in the country where crayfish can still be found throughout the river system, in a variety of habitats and at high densities. White clawed crayfish and freshwater pearl mussels are found together in one of the upper tributaries. Freshwater pearl mussels generally prefer soft oligotrophic waters, although they are also found in hard water conditions in a few rivers in Ireland and Wales. In addition to good water quality, this headwater also provides the moderate to fast flow regime, cool temperatures and suitable areas of stable river channel, required by freshwater pearl mussels. The Kent system supports one of only two populations of pearl mussel in England which are currently known to be recruiting young mussels. Freshwater pearl mussels can live for over 100 years. Their life cycle is however complex and in part dependent upon the maintenance of a healthy salmonid population. The mussels do not mature until 15 years, when the females produce eggs. After initially remaining within the mother’s shell the larvae 0.2 millimetres attach themselves for a short period to young salmon and trout. Once dropping off, they remain buried within clean sand and gravel in the stream bed for a further five to ten years. This buried stage within the life cycle is particularly susceptible to changes in the flow regime, siltation and algal deposition. Populations of freshwater pearl mussels are aging and declining across their European range. This is attributed to pollution, alterations to river channels, changes in flow regimes, exploitation and decreasing salmonid numbers. The populations within the British Isles are now considered to be of international importance. Other Information The site interest includes the following species listed in the EU Habitats and Species Directive 92/43/ EEC, White clawed crayfish Austropotamobius pallipes freshwater pearl mussel Margaritifera margaritifera bullhead Cottus gobio floating vegetation of plain and sub mountainous rivers Annex II, V Annex II, V Annex II Annex I Austropotamobius pallipes and Margaritifera margaritifera are protected under Schedule 5 of the Wildlife and Countryside Act 1981 as amended. They are also listed on Annex III of the Bern Convention. Parts of this site lie within the Lake District National Park and the Lake District Environmentally Sensitive Area. This is a new site.

Species mentioned

Plant communities