Current status
This aquatic plant occurs in clear lowland waterbodies with low to medium concentrations of plant nutrients. These often have underlying shell and sand or limestone outcrops making the water rich in lime. It is seldom found in water less than 1 m in depth.
In the UK, this species is now found exclusively in Scotland, where it has been recorded from 34 lochs within 18 ten km squares since 1980 . The majority of sites are on islands off the west coast, although it is also recorded from one site in Central Region and in a cluster of lochs in Tayside. The only known site in England was in Esthwaite Water in the Lake District where, despite a survey in 1994, it has not been recorded since 1982. This plant also occurs in a number of sites in Ireland, but is absent from Northern Ireland.
Slender naiad is listed under Annexes II and IV of the EC Habitats Directive and Appendix I of the Bern Convention. It is protected under Schedule 4 of the Conservation (Natural Habitats, etc.) Regulations 1994 and Schedule 8 of the WCA 1981.
Current factors causing loss or decline
Restrictions on light penetration due to heavy weed growth and nutrient enrichment from sources such as sewage effluent and fertiliser run-off from fish farms.
Current action
SNH carried out surveys in 1994 and 1995 and increased the number of known Scottish sites from 24 to 34. The status of previously known populations was also assessed.
Three SSSIs containing this species have been proposed for SAC designation under the EC Habitats Directive.
Action plan objectives and targets
Maintain remaining populations.
If biologically feasible, restore the species to its former range, including to its known site in the Lake District by 2004
Proposed actions with lead agencies
Policy and legislation
Establish a strategy for monitoring and for maintaining the conditions which will ensure the natural distribution of this species in Scotland does not decline. (ACTION: SNH)
In light of information collected through action 5.5.2 which aim to identify water quality and general habitat conditions for slender naiad, implement necessary actions which will benefit the species at sites where it occurs.
Site safeguard and management
Where necessary within SSSIs, negotiate management agreements to prevent damaging fish management or fish farming activities and to maintain sympathetic low intensity agricultural and forestry works in the catchment of standing waters containing this species. (ACTION: FA, SNH)
Review the present programme of phosphorus stripping for treated sewage effluent entering Esthwaite Water and determine what further actions are necessary which will produce suitable conditions for re-introduction. (ACTION: NW Water)
Where necessary, negotiate appropriate management measures to prevent potentially damaging activities, such as fish management or fish farming activities, and to maintain sympathetic low intensity agricultural and forestry works in the catchment of standing waters containing this species.
Species management and protection
Collect seed from a range of Scottish sites and (if the plant is still present) also from Esthwaite Water, for preservation at RBG Kew’s seed bank. (ACTION: RBGs Edinburgh and Kew, NE, SNH).
If found to be absent but conditions are suitable, consider restoring population to former site in the Lake District by 2004. (ACTION: NE)
Advisory
Maintain a flow of information between statutory conservation agencies and agencies responsible for water quality over the location of Najas flexilis and its requirements. (ACTION: SEPA, JNCC, SNH)
Future Research and Monitoring
Survey former and potential sites to ascertain the precise distribution of this species in Britain, including the use of underwater survey techniques where necessary. (ACTION: NE, JNCC, SNH)
Promote ecological studies on population dynamics and the habitat requirements of this species to underpin management advice and assess the feasibility of restoring it to the Lake District. (ACTION: NE)
Encourage research on the distribution and ecology of this species on an international level and use the information and expertise towards its conservation in the UK. (ACTION: JNCC, SNH)
Subject to confidentiality and data ownership, pass information gathered during survey and monitoring of this species to JNCC or BRC so that it can be incorporated in national databases. (ACTION: NE, SNH)
Provide information annually to the World Conservation Monitoring Centre on the UK status of the species to contribute to maintenance of an up-to-date global Red Data List. (ACTION: JNCC)
Communications and Publicity
No action proposed.
Links with other action plans
None given.
Publication details
Originally published in: Biodiversity: The UK Steering Group Report - Volume II: Action Plans (December 1995, Tranche 1, Vol 2, p189)