For much of the history of Ascension Island, comparatively little was known about the marine environment around the island. In recent years the Ascension Island Conservation Department has been pivotal in studying the biodiversity and cycles of this key ecosystem.
To get people acquainted with the biodiversity of this territory Ascension Island Post issued four special stamps depicting marine species. StampNews.com invites our readers to appreciate the original design of these bright philatelic items.
Located approximately 1600 km from the coast of West Africa and more than 2000km from South America, Ascension Island is one of the remotest land bodies in the world. This isolation, combined with the Ascension’s comparative geological youth has contributed to a relatively depauperate shallow marine fauna, with just 173 inshore fish species recorded. The total number of fish species at Ascension is low when compared with other tropical islands in the Atlantic, for example 330 coastal fish species can be found at the Canary Islands.
Being so far away from the main continental landmasses, colonisation of Ascension Island by fish species relied on them swimming or being brought by currents across large distances. Obviously, fish species that are able to cross the oceanic expanses of the Atlantic are more likely to settle at mid-Atlantic islands, including Ascension. The origins of the fish communities at Ascension can be found in both the eastern and western Atlantic.
However, a higher proportion of Ascension fish species can be traced back to a South American origin than an African one. While there is low fish species richness there is a relatively high level of endemism (that is, fish species found nowhere else in the world), with 11 species known only from Ascension, and a further 16 restricted only to the South Atlantic islands of Ascension and St Helena.
The endemic fish species of Ascension Island are found in a variety of habitat types, in rocky areas the Ascension hawkfish (Amblycirrhitus earnshawi) and Ascension wrasse (Thalassoma ascensionis) forage for small invertebrate prey while yellowtail damsels (Stegastes lubbocki) tend to their algae “gardens”, fiercely defending them from rivals. Over the sand the marmalade razorfish (Xyrichtys blanchardi) may be seen, hanging almost motionless until they perceive a threat whereupon they dive head-first into the sand for protection. Heading into slightly deeper water another key habitat is found, round balls of hard pink algae known as maerl or rhodoliths.
In some areas these rhodoliths are found in mounds and piles, becoming home to one of Ascension’s most beautiful endemics – the resplendent angelfish (Centropyge resplendens). This diminutive fish (only a few centimetres long) is coloured a vivid purple-blue with a golden stripe running along its back and has historically been highly valued in the aquarium trade, until it was protected by Ascension law in 2013.
Endemics can easily become endangered or extinct if their restricted habitat changes, especially due to human actions, including fishing, collection, pollution or the introduction of non-native species. Concerns have been raised over the threats of human activities to the endemic fish species of Ascension Island, leading to them now being protected by law by the 2013 Ascension Island Wildlife Protection Ordinance. The Ascension Island Government Conservation Department continues to investigate and study the marine environment in order to protect not only the endemic fish species, but all aspects of this unique ecosystem.