Conservation recommendations for Nee Soon 
205 
in the nature reserves. Enhancing riparian vegetation along the banks of streams and 
retaining woody debris in the streams helps to preserve the natural habitat of the native 
species, providing an advantage over invasive alien species which generally prefer 
disturbed habitats. Construction of artificial barriers can also prevent the infiltration of 
alien species into the core area of Nee Soon freshwater swamp forest. Prodasineura 
humeralis is believed to have been introduced into Singapore within the last decade. 
Observations from the present study show that the species is abundant in the outskirts 
and stream stretches that are associated with an open canopy. The species is commonly 
associated with fast flowing water, but hardly found in shaded forest streams with high 
canopy cover. Achatina fulica is an invasive species originating from Africa and is 
commonly known as the Giant African Snail. In Nee Soon freshwater swamp forest 
shell heights of 7.5 cm or more have been observed. It is commonly found in parks and 
degraded forest but rarely in undisturbed forest. Unfortunately, several specimens were 
recorded deep in the forest indicating that this species may have already established a 
population within Nee Soon. Lamellaxis gracilis is an introduced species found in the 
outskirts of Nee Soon freshwater swamp forest. It is likely to have spread from nearby 
plant nurseries and gardens. Bradybaena similaris is commonly found throughout the 
moist tropics in urban areas such as gardens and plant nurseries. It is an agricultural 
pest and is most likely to have been introduced due to the horticultural and agricultural 
trade. It was observed in high numbers near the outskirts of Nee Soon but none was 
recorded within the freshwater swamp forest (Lim et al., 2018). The potential impact 
upon other native damselfly and snail species needs to be closely monitored. 
Update on conservation status 
Out of the 15 species of nationally threatened freshwater fish listed in the Singapore 
Red Data Book (Lim et al., 2008), 13 species have been recorded from Nee Soon 
freshwater swamp forest in the current survey. Although Trigonostigma heteromorpha 
has been listed as “Endangered” in the Singapore Red Data Book, it was found at 
all but one of the sites surveyed in Nee Soon freshwater swamp forest and in a high 
abundance of an average 17 individuals per site per sampling occasion, with the 
highest being 168 in a single sampling event. Similarly, Nemacheilns selangoricus, 
which was previously listed as “Critically Endangered”, had relatively high mean 
population abundance and presence at 10 out of 12 sites. Although current results 
revealed numerical dominance of these species in Nee Soon freshwater swamp forest, 
it remains true that within Singapore they are confined to the Central Catchment 
Nature Reserve and (in the case of Nemacheilus selangoricus ) have stringent habitat 
requirements. Using IUCN Red Data Book criteria adapted to national level (Davison, 
2008), no change in their current conservation status is justified. More in-depth 
studies have to be conducted to understand their detailed distribution in the nature 
reserves. For the remaining 11 species, Boraras maculatus, Desmopuntius hexazona, 
Pangio muraeniformis, Pseudomystus leiacanthus, Silurichthys hasseltii, Parakysis 
longirostris, Clarias nieuhofii, Macrognathus maculatus, Luciocephalus pulcher, 
Channa gachua and C. melasoma, the results are consistent with their current national 
status (Li et al., 2016). No new records of shrimp species were found in this study but 
