4035 Fisher's estuarine moth Gortyna borelii lunata
Description and ecological characteristics
Fisher’s estuarine moth Gortyna borelii lunata is a noctuid moth restricted to a small area of sea-walls and coastal grassland in north-east Essex. Within this area, there are a number of semi-isolated sub-populations. The species overwinters as eggs laid on long, coarse grass, and the larvae hatch in late spring. Young larvae feed in the stems of hog’s fennel Peucedanum officinale, later boring into the roots. The number of larvae and affected plants declines over the summer, and it is likely that no plant supports more than a single large larva. After pupation, the adult moths emerge in autumn, and are nocturnal, with a wingspan of 42–60 mm. The main threats to the species in Britain are sea-level rise and inappropriate management of its habitat. Studies of its requirements and conservation management are underway (Ringwood et al. 2004).
European status and distribution
Gortyna borelii lunata has a widespread but very localised European distribution, restricted by the limited distribution of its food plants, all within the genus Peucedanum. Recent genetic studies have suggested that the British form may be an endemic subspecies, distinct from the mainland European populations.
UK status and distribution
Fisher’s estuarine moth Gortyna borelii lunata is a rare moth with its known native distribution in the UK restricted to an area near Walton-on-the-Naze in north-east Essex. Searches of the larval food plant (itself a very local species) elsewhere have not found any other native populations, and the species is very sedentary – only a handful of moths have ever been found more than 10 metres from a food plant. The total population has been estimated at 1000–5000 adult moths (Gibson 2000). A colony in north Kent is believed to be derived from an unauthorised introduction.
The species was vulnerable to collection of specimens, but is now protected under the Wildlife and Countryside Act.
View UK distribution of this species.
Site selection rationale
Gortyna borelii lunata was added to Annex II in 2003.
Site accounts
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Hamford Water
Essex
Fisher’s estuarine moth Gortyna borelii lunata has a localised population distribution in the UK, due to its specific habitat requirements and is only found in two areas, the north Essex coast and the north Kent Coast. Hamford Water supports the majority of the Essex population and is the most important UK site for this species, supporting approximately 70% of the population. Hamford Water is a large, shallow estuarine basin comprising tidal creeks, islands, intertidal mud, sand flats and saltmarshes. Above the saltmarsh there is unimproved and improved grassland (including grazing marsh), scrub, woodland, hedges, ditches, ponds and reedbeds. The site encompasses those areas where the moth's food plant hog's fennel (Peucedanum officinale) grows and where there is an abundance of the grasses required by the species for egg laying.
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Tankerton Slopes and Swalecliffe
Kent
Fisher’s estuarine moth Gortyna borelii lunata has a localised population distribution in the UK, due to its specific habitat requirements and is only found in two areas, the north Essex coast and the north Kent Coast. Tankerton slopes and Swalecliffe supports the majority of the north Kent population of this moth which is approximately 20% of the UK population. The site's north facing slopes are composed of London Clay and support a tall herb community dominated by its food plant hog's fennel (Peucedanum officinale), together with areas of neutral grassland also required by the species for egg laying.
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Please note that the map shows sites where the presence of a feature is classed as ‘grade d’, but these sites are not listed. This is because ‘grade d’ indicates a non-significant presence.