Fen Raft Spider (Dolomedes plantarius)
Key Details
| Taxonomic Groups: | Invertebrate > spider (Araneae) > Spider |
| Red List Status: | Vulnerable (Not Relevant) [VU(nr)] |
| D5 Status: | Included in the baseline Red List Index for England (Wilkins, Wilson & Brown, 2022) |
| Section 41 Status: | (not listed) |
| Taxa Included Synonym: | (none) |
| UKSI Recommended Name: | Dolomedes plantarius |
| UKSI Recommended Authority: | (Clerck, 1757) |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | Harvey et al., 2017 |
| Notes on taxonomy/listing: | (none) |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | VU, criteria: D2: may lose threat status at next review. Two remnant populations in England, one in Wales. Four, English, translocated populations are not conservation dependent. |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | Highly fragmented, often very small natural remnant populations, with very limited dispersal ability. Species recovery programme to date shows strong response to targeted measures to overcome both. |
| Question 3: | At a landscape scale, would the species benefit from untargeted habitat management to increase habitat mosaics, structural diversity, or particular successional stages? |
| Response: | No |
| Justification: | This species would not benefit from untargeted management |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 8. Species recovering |
| Recovery potential/expectation: | Medium-high |
| National Monitoring Resource: | Combination - insufficient |
| Species Comments: | Shows strong response to targeted measures to overcome low dispersibility and isolation; well developed, long term recovery programme includes successful translocations. Medium-high recovery potential may be limited by climate change (droughts and sea level rise) and extent of restoration of appropriate lowland wetland habitats. Monitoring 'structured sufficient' in E. Anglia but not in E. Sussex |
Key Actions
Key Action 1
Proposed Action: Expand translocation programme beyond Broadland to reduce risk from sea level rise/salinisation, mitigate against climate change and meet recovery target of (min.) 12 self-sustaining populations.
Action targets: 7. Best approach adopted at appropriate scales
Action type: (Re-)introduction
Duration: 6-10 years
Scale of Implementation: ≤ 5 sites
High priority sites: Restored E Anglian Fen basin fens
Comments: Demonstrated potential for expansion of translocated populations means that new populations expected to fill suitable extensive habitat areas without further introductions there. Current scoping study will estimate delivery action costs.
Key Action 2
Proposed Action: Develop eDNA monitoring tools for tracking changing distributions, including of translocated populations.
Action targets: 8. Species recovering
Action type: Scientific research
Duration: 3-5 years
Scale of Implementation: ≤ 10 sites
High priority sites:
Comments: NERC PhD application with additional funding in place (BA/Natur am Byth) for next three years to develop techniques. Roll out will transform monitoring capability, though with unknown cost, in 3 years+ time. Likely to be transferable to other hard-to-monitor spider species.
Key Action 3
Proposed Action: Seek opportunities in the vicinity of all populations to aid spread by improving connectivity and extent of suitable wetland habitat.
Action targets: 8. Species recovering
Action type: Landscape/catchment/marine management
Duration: >10 years
Scale of Implementation: ≤ 10 sites
High priority sites: Upper and Lower Waveney Valley, Yare and Thurne Valleys, Pevensey Levels - core fen sites within the E. Anglian Fen basis also likely to be involved over next 5-10 years.
Comments: Delivery within landscape recovery programme/s
Acknowledgment:
Data used on this website are adapted from Threatened species recovery actions 2025 baseline (JP065): Technical report and spreadsheet user guide (Natural England, 2025). Available here.