Photos © Julian Evans - Live individuals of the Maltese Top-shell (left) and shell of an adult specimen showing the distinctive colour pattern (right).
The Maltese Top-shell (scientific name: Steromphala nivosa but previously known as Gibbula nivosa), is a small, attractively coloured, marine snail that is endemic to the Maltese Islands, that is, it occurs in Maltese waters and nowhere else in the world. This is a unique situation: while species that only occur in a tiny geographic area are fairly common on land, this is almost unheard of in the marine environment. Recognizing the scientific importance of this species, the editors of “Imperiled: The Encyclopedia of Conservation” invited local experts Dr Julian Evans, Prof. Joseph A. Borg and Prof. Patrick J. Schembri to include an article that describes the biology, plight, and conservation management of the Maltese Top-shell. This book, which is aimed at an international audience, provides a global synthesis of the world’s threatened species and ecosystems.
The Maltese Top-shell, being both very rare and critically endangered, certainly merits its place within this compendium of Earth’s imperilled species and ecosystems. Although this species is protected by both local and EU legislation, as well as by international conventions, around 20 years ago there was speculation that it may have become extinct, since there were no findings of live individuals for over 25 years in spite of intensive searches carried out at sites where it used to occur. Thankfully, in 2006 Dr Evans rediscovered live Maltese Top-shell individuals and, together with his colleagues at the University of Malta’s Department of Biology, he has been studying the biology of this species in order to better understand where and how it lives, and therefore which management measures will be effective to safeguard it.
In this encyclopaedia article, the Maltese researchers have summarised what we now know about the distribution, abundance, population dynamics, habitats, ecological interactions and behaviour of the Maltese Top-shell. Based on this information, the main threats and pressures faced by this species were identified as those relating to habitat alteration or destruction, including pollution (both chemical pollution and nocturnal illumination) and activities such as coastal development that cause physical disturbance of the seabed where its habitat occurs. A series of conservation actions, particularly ones to control development and pollution that may affect the species’ habitat, were hence identified. The best way to implement such actions is by designating marine protected areas, and managing them effectively with proper enforcement.
While the present situation is an improvement over fearing that the Maltese Top-shell could be extinct, the survival of this species is by no means guaranteed. The main population of this highly endangered species is located within a busy harbour, which presents the authorities with a difficult problem of how to balance conservation and socio-economic considerations. The future of this unique part of Malta’s natural heritage remains uncertain, especially since the harbour where most of the Maltese Top-shell individuals reside has not yet been offered protection, and is instead characterised by intense marine activity and ongoing coastal development by private and public entities, potentially imperilling the Maltese Top-shell.
