Hydraena pygmaea
Key Details
| Taxonomic Groups: | Invertebrate > insect - beetle (Coleoptera) > Water beetle |
| 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: | Hydraena pygmaea |
| UKSI Recommended Authority: | Waterhouse, G.R., 1833 |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | Foster, 2010 |
| Notes on taxonomy/listing: | (none) |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | The riverine Hydraenas, H.minutissima, H. pulchella and H. pygmaea, all show alarming levels of decline in GB and especially in England. This is despite much wider coverage of flowing waters in recent decades. They are likely to be sensitive indicators of riparian habitat quality. |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | The specific requirements of the riparian Hydraenidae are poorly understood but collectively they seem to require complex habitats along the water-line of unpolluted streams and rivers. The features with which they are associated variously include submerged or partially exposed fibrous tree roots, small bars of grit or fine gravel, mossy rocks and the bases of exposed clay banks. Such features are more nuanced and small-scale than those traditionally described as exposed riverine sediments. These 3 species are unlikely to be collected by kick-sampling in riffles and have been recorded very rarely in the Environment Agency's biological monitoring programmes. A better understanding of the ecology and distribution of these species is a pre-requisite to effective conservation. |
| 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: | Generic river improvement measures could be detrimental to invertebrates associated with river margins such as the rarer flowing-water Hydraenidae. For example, over-stabilisation of stream banks, e.g. as a result of fencing and tree planting, could result in greater homogeneity and reduced complexity of riparian habitats. However, improvements in river water quality should benefit riverine water beetles. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 3. National Monitoring Plan agreed and implemented |
| Recovery potential/expectation: | Unknown |
| National Monitoring Resource: | Opportunistic - insufficient |
| Species Comments: | Ad hoc recording as part of GB water beetle recording scheme (Balfour-Browne Club/Aquatic Coleoptera Conservation Trust) |
Key Actions
Key Action 1
Proposed Action: Review options for monitoring this species as part of an England threatened riverine invertebrate assemblage. A broad framework is likely to be more efficient than a multitude of single-species monitoring actions. Any such framework should consider EA biological monitoring coverage, and taxa unlikely to be detected by standard kick-sampling methods.
Action targets: 3. National Monitoring Plan agreed and implemented
Action type: Status survey/review
Duration: 2 years
Scale of Implementation: Not applicable
High priority sites:
Comments:
Key Action 2
Proposed Action: Undertake a literature review of the species' ecological requirements to inform river managers and river restoration practitioners. Consider a multi-species project involving other threatened riverine water beetles (perhaps encompassing other river taxa?). This review should enable its audience to understand when standard measures might need to be re-considered and should include a series of species factsheets with distribution maps.
Action targets: 4. Autecology and pressures understood
Action type: Scientific research
Duration: 3-5 years
Scale of Implementation: National
High priority sites:
Comments:
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.