Purpose: The Manx shearwater flea Ceratophyllus (Emmareus) fionnus Usher, 1968 is a host-specific parasitic insect apparently restricted to the Isle of Rùm, off the west coast of Scotland. Although C. (E.) fionnus is one of only a small number of insect species endemic to the British Isles, its conservation status has never been evaluated. To enable effective management, the conservation status of the species was assessed.
Methods: The conservation status of C. (E.) fionnus was evaluated using host and distribution records in conjunction with two assessment rubrics; the IUCN Red List Categories and Criteria: Version 3.1, and a flea-specific assessment rubric developed previously.
Results: Ceratophyllus (Emmareus) fionnus was found to be threatened with extinction due to its hyperendemicity on the Isle of Rùm and was classified as vulnerable.
Conclusion: Based on the findings of the assessment, immediate conservation action to protect C. (E.) fionnus is encouraged and a recovery plan is outlined. This includes surveys and studies of the bionomics of the species in conjunction with in-situ management of the known population. The creation of insurance populations through conservation translocations is also encouraged.
Keywords: Co-threatened; Flea; Isle of Rùm; Lice; Manx shearwater; Parasite conservation.