Taxonomy
Najas flexilis | Slender Naiad
Distribution
Status
Conservation status
| HABITATS DIRECTIVE ARTICLE 17 REPORTING |
| Range | Favourable |
| Population | Inadequate |
| Habitat | Inadequate |
| Future Prospects | Inadequate |
| Overal Assessment of Conservation Status | Inadequate |
| Overal trend in Conservation Status | Stable |
Source: NPWS 2013.
| IUCN Conservation Status |
| Ireland (1)* | Endangered |
| Europe (2) | Vulnerable [B2ab(iv)] |
| Global (3) | Not evaluated |
Source(1): Curtis, T.G.F and McGough H.N. 1988; (2) Lansdown, R.V. 2013; (3) The IUCN Red List of Threatened Species. Version 2014.2
* This Red List is acknowledged as needing to be updated.The Red List category shown is updated from that appearing in the original 1988 document, due to changes in the Red List categories.
Legal status
Protected by the following legal instruments:
- Habitats Directive [92/42/EEC] Annex II, Annex IV
- Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) Appendix I
- Wildlife Act (1976)
- Flora Protection Order 1999
- Wildlife (Amendment) Act (2000).
Native status
Native.
Species Biology
Identification
An aquatic species, usually permanently submerged in freshwater deeper than 1 meter but shallower than 5 meters. It is a delicate, much branched, hairless annual to 30cms. Leaves are unstalked, opposite or whorled with a sheathing base, to 25mm long, narrow, linear. Leaves are sparsely toothed or not at all. Male and female flowers are separate on the same plant. No sepals or petals. Flowers are in leaf axils, the male protected by a bract or spathe until pollination. Male flowers have one unstalked anther. Female flowers have one carpel. The fruit is an unstalked drupe.
No vegetative reproduction.
Flowers in August.
Sources: Parnell J., Curtis, T., 2012; Stace C., 1997; Wingfield et al, 2004.
Habitat
Lit areas of clear, lowland, freshwater lakes of circum-neutral pH. Usually in water deeper than 1 meter, shallower than 5 meters on substrate from mud to fine sand. Najas flexilis appears to have quite specific requirements with regard to pH, alkalinity, calcium and phosphate, as well as turbidity and depth.
It occurs in clear freshwater lakes, most often in mesotrophic lakes, but will occur in some oligotrophic lakes.
- Acid oligotrophic lakes (FL2)
- Mesotrophic lakes (FL4).
Sources: Wingfield et al 2004; NPWS 2013; Fossitt, J.A. 2001.
Threats faced
| THREAT | ARTICLE 17 CODE | RANKING |
| Water abstractions from groundwater | J02.07 | HIGH |
| Diffuse pollution to surface waters due to agricultural and forestry activities | H01.05 | HIGH |
| Diffuse pollution to surface waters due to household sewage and waste waters | H01.08 | HIGH |
| Diffuse pollution to surface waters due to other sources not listed | H01.09 | HIGH |
| Pollution to surface waters by industrial plants | H01.01 | MEDIUM |
| Changes in abiotic conditions | M01 | MEDIUM |
| Invasive non-native species | I01 | LOW |
| Other point source pollution to surface water | H01.03 | LOW |
| Human induced changes to hydraulic conditions | J02 | LOW |
| Silting up | K01.02 | LOW |
| Drying out | K01.03 | LOW |
| Species composition change (succession) | K02.01 | LOW |
| Accumulation of organic material | K02.02 | LOW |
Source: NPWS 2013.
The Threats identified in the Article 17 reporting document accord well with those threats identified at a European Level for the species in the IUCN Red List account 2013. The IUCN threat list, at a European level, also includes reports from Latvia that professional fishing is a threat in that country.
Source: Lansdown, R.V. 2013
Conservation actions
In the Article 17 Habitats Directive reporting for the period 2007-2012 Conservation Measures implemented or being implemented during the period were;
- Continued legal protection of the species and its habitats inside and outside of Natura 2000 sites.
- Restoring / improving water quality'
inside and outside of
Natura 2000 sites.
Distribution
World distribution(GBIF)
North America, Europe, Asia. Most frequent in North America. Within Europe, most frequent in Britain and Ireland. (Wingfield et al 2004).
Accuracy of world distribution shown in the Global Biodiversity Information Facility (GBIF) map below will be constrained by, amongst other factors, data held but not shared by countries and organizations not participating in the GBIF.
Irish distribution
Western, mainly Donegal, Mayo, Galway, Kerry.
Temporal change
Records submitted to Data Centre in 2024
The following map is interactive. If you would prefer to view it full screen then click here.
How can you help
The National Biodiversity Data Centre is trying to improve our knowledge on the distribution of the Slender Naiad (Najas flexilis) in Ireland. Should you observe the species, please submit sighting to add to the database. Detailed observations will assist us gaining a better insight into where the species is most abundant in Ireland and we might also be able to detect regional variations. Please submit any sightings and photographs at:
http://records.biodiversityireland.ie/
All
records submitted on line can be viewed on Google Maps – once checked
and validated these will be added to the database and
made available for conservation and research.
Further information
For further information contact Dr. Liam Lysaght llysaght@biodiversityireland.ie
References
Publications
Curtis, T.G.F and McGough H.N., 1988. The Irish Red Date List 1 Vascular Plants. Wildlife Service, Dublin.Published by The Stationery Office.
Fossitt, J.A., 2001. A Guide to Habitats in Ireland. The Heritage Council.
Lansdown, R.V. 2013. Najas flexilis. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 26 September 2014.
NPWS, 2007. The Status of EU Protected Habiats and Species Vol 2.
NPWS, 2013. The Status of EU Protected Habitats and Species in Ireland. Species Assessments Volume 3. Version 1.0. Unpublished Report, National Parks & Wildlife Services. Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland.
Parnell J., Curtis T., 2012. Webb's An Irish Flora. Cork University Press.
Stace, C., 1997.New Flora of the British Isles, Second Edition. Cambridge University Press.
Wingfield, R.A., Murphy, K.J., Hollingsworth, P. and Gaywood, M.J., 2004.The Ecology of Najas flexilis. Scottish Natural Heritage Commissioned Report No. 017 (ROAME No.F98PA02)