The freshwater decapod crustaceans of Bukit Timah Nature Reserve, Singapore

Abstract

Freshwater decapod crustaceans serve important ecological functions in tropical stream ecosystems. Stream surveys for decapod crustacean fauna were conducted between February 2015 and April 2016 at nine sites in Bukit Timah Nature Reserve (BTNR). A total of eight species (four freshwater crab, three freshwater shrimp and one crayfish species) out of the nine species known from BTNR were recorded. In general, the species were recorded from sites matching environmental conditions previously known or reported for each species, with some crab species showing minor overlap in their spatial distributions. This highlights the importance of broad-based conservation efforts focusing on the entire stream network in BTNR rather than on specific/selected streams as the various species each appear to have largely unique habitat requirements. The updated information on freshwater decapod crustaceans in BTNR can be used to inform the formulation of conservation and management measures including the establishment of monitoring programs for the protection of our native and threatened aquatic fauna in BTNR.

Physicochemical characteristics of streams in Bukit Timah Nature Reserve, Singapore

“…The Singapore freshwater crab Johora singaporensis Ng, 1986, is listed on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species as critically endangered and regarded as one of the top 100 threatened species in the world (Ng et al, 2015a). It was thought that this crab could already be extinct in the reserve (Tan et al, 2010); its extinction in Jungle Fall stream has since been confirmed but its presence in other BTNR streams has been documented (Khoo et al, 2019). The suspected reasons for its decline include the acidification of water along with the loss of forest cover, aquatic pollution and the lowering of the water table (Tan et al, 2010;Esser et al, 2008).…”

“…These factors play out through the expected interactions between soil, groundwater and rainfall. In turn, the physicochemical characteristics of the individual streams may be linked in part to the freshwater decapod crustaceans (Khoo et al, 2019), dragonflies and damselflies (Cai et al, 2019), and fishes (Li et al, 2019) that occur within each of them.…”

Synthesis of results from the Comprehensive Biodiversity Survey of Bukit Timah Nature Reserve, Singapore, with recommendations for management

“…Stream acidification is one of the conservation concerns, as are total water flow, the amount of residual water remaining during very dry weather, and bank erosion. Concerns over freshwater crustaceans (Khoo et al, 2019) are very similar to those applying to dragonflies (Cai et al, 2019) and fishes (Li et al, 2019).…”

“…Out of the eight native freshwater decapod crustaceans known from BTNR, four freshwater crabs, three freshwater prawns and one crayfish species were recorded during the 2014-2018 survey (Khoo et al, 2019). An introduced species, the prawn Macrobrachium lanchesteri was newly recorded at one site on the periphery of the reserve.…”

“…Stream enhancement initiatives should mirror those for the terrestrial habitat, for the survival of freshwater fish, decapods, dragonflies and other aquatic plant and animal species (Cai, 2019;Cai et al, 2019;Khoo et al, 2019;Li et al, 2019;Nguyen & Cai, 2019).…”