Allis Shad (Alosa alosa)
Key Details
| Taxonomic Groups: | Vertebrate > bony fish (Actinopterygii) > Fish |
| Red List Status: | Critically Endangered (Not Relevant) [CR(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 alosa |
| UKSI Recommended Authority: | (Linnaeus, 1758) |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | Nunn et al., 2023 |
| Notes on taxonomy/listing: | Hybridisation with twaite shad Alosa fallax but extent poorly understood |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | Restricted geographical range, one location, continuing decline in area/extent and/or quality of habitat and small population size, 90-100% of mature individuals in one population. |
| 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. Unlikely that sufficient individuals would immigrate from outside of the region to rescue the British population in the event of its extinction given that allis shad are not known to have colonised other British rivers via individuals straying from the Tamar. |
| 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 etc 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: | There are populations of allis shad in northern France from which individuals may stray, albeit in low numbers. There appears to be a current recolonisation of shad (one individual examined is A.alosa) on the River Taw and tributaries so it is unlikely that the Tamar is the only population. Impacted by barriers to migration, pollution & exploitation / bycatch. |
Key Actions
Key Action 1
Proposed Action: Facilitate migratory passage past Gunnislake weir to allow access to additional spawning areas in the lower Tamar and investigate passage opportunities at other sites both within and outside of the Tamar.
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 Tamar
Comments:
Key Action 2
Proposed Action: Monitor known allis shad populations on the Tamar to understand current population trends and to assess the impact of barrier removal and river restoration at known and potential / future shad sites.
Action targets: 3. National Monitoring Plan agreed and implemented
Action type: Targeted monitoring
Duration: >10 years
Scale of Implementation: ≤ 5 sites
High priority sites: River Tamar
Comments:
Key Action 3
Proposed Action: Identification of other current and potential spawning locations, with appropriate habitat restoration and maintenance actions applied (quality and connectivity).
Action targets: 5. Remedial action identified
Action type: Status survey/review
Duration: 3-5 years
Scale of Implementation: ≤ 10 sites
High priority sites:
Comments: By 'sites' is meant rivers or river catchments
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.