Twaite Shad (Alosa fallax)
Key Details
| Taxonomic Groups: | Vertebrate > bony fish (Actinopterygii) > Fish |
| 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: | Alosa fallax |
| UKSI Recommended Authority: | (Lacepède, 1803) |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | Nunn et al., 2023 |
| Notes on taxonomy/listing: | Hybridisation with Allis shad (Alosa alosa) but extent poorly understood |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | Restricted to only 4 rivers in Britain and 2 rivers in England. Population size is declining. |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | Although Red List assessed, the lack of targeted monitoring in England means we don't have strong evidence of the current extent of populations in English rivers, populations sizes or trends, spawning extent and extent/suitability of habitat. It is considered unlikely that sufficient individuals would immigrate from outside of the region to rescue the British population in the event of its extinction, given that genetics and telemetry studies suggest that straying rates are low. There is strong evidence that shad show high site fidelity and that sub-populations are genetically distinct, however there is significant evidence that other breeding populations around England do occur and this needs to be clarified with investigative monitoring, such as eDNA, recreational catches, commercial bycatch and egg sampling. Straying does occur as has been shown in Northern Europe and populations can quickly become established. |
| 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: | Yes |
| Justification: | Pollution & migration barriers are threats that not only impact shad |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 2. Biological status assessment exists |
| Recovery potential/expectation: | Low - Combination or other (detail in comments) |
| National Monitoring Resource: | Opportunistic - insufficient |
| Species Comments: | Impacted by barriers to migration, pollution & exploitation / bycatch. Although recovery potential is low because of restricted range, shad are relatively fecund so if conditions are right expansion both in distribution and populations can be rapid. The species is not routinely monitored, so small but sustaining populations might be overlooked. This also means existing pressures might be overlooked. Unrecorded mortality pressures from abstraction (juveniles and adults) and marine bycatch might be playing an equally large role to known freshwater barrier issues in suppression of the species. |
Key Actions
Key Action 1
Proposed Action: Address barriers to migration on known and potential shad rivers. While the Unlocking the Severn project has greatly facilitated shad passage on the R.Severn there are still a number of barriers on the Severn and tribs such as the Teme which may present barriers to upstream migration. Migratory passage should be facilitated through targeted interventions on all current and potential shad rivers.
Action targets: 7. Best approach adopted at appropriate scales
Action type: Pressure mitigation
Duration: 3-5 years
Scale of Implementation: ≤ 10 sites
High priority sites: River Severn
Comments:
Key Action 2
Proposed Action: Monitor the Severn Estuary twaite shad spawning runs to determine success of barrier removal and undertake surveys to identify other current and potential spawning locations.
Action targets: 3. National Monitoring Plan agreed and implemented
Action type: Targeted monitoring
Duration: >10 years
Scale of Implementation: ≤ 10 sites
High priority sites: River Severn River Wye
Comments:
Key Action 3
Proposed Action: Given the opening up of the Severn, it is possible the species range could increase, therefore there is a need to identify, restore and maintain any additional spawning grounds that could occur across their range through targeted monitoring and restoration actions. This will provide the evidence base for potential site designation.
Action targets: 5. Remedial action identified
Action type: Status survey/review
Duration: 3-5 years
Scale of Implementation: Unknown
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.