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Ganl. Bull. Singapore 70 (Suppl. 1) 2018 
Methodology 
Quantitative environmental and spatial survey 
A total of 36 sites were surveyed across all eight sub-catchments of the Nee Soon 
catchment (see Nguyen et al., 2018; Sun et al., 2018), together with a separate stream 
system that flowed into Lower Peirce Reservoir representing a comparable sub¬ 
catchment adjacent to Nee Soon freshwater swamp forest. For each sub-catchment, 
four sampling stations were selected at intervals from lower stream to upper stream. 
The locations were chosen based on how representative of available habitats each was 
in that sub-catchment, together with considerations of accessibility. Study sites were 
named and ordered alphabetically according to the location of the site within the sub¬ 
catchments of Nee Soon, starting from the lower to the upper reaches. 
Surveys were conducted from December 2014 to April 2016. Hydrological, 
physiochemical and habitat characteristics were recorded to analyse environmental 
factors that may determine the associated odonate community. Samplings of odonates 
were conducted between 10:30 and 13:00 h mostly during sunny weather conditions. 
For each location, sightings were recorded over 30 minutes along a 20 m transect of 
the stream and 3 m of riparian zone on either side of the stream bank. The transect was 
surveyed at a slow pace along the stream channel, counting every individual either 
perched or in flight. Species that could not be identified with certainty by sight were 
caught with an insect net and released after identification. Occasionally, unidentified 
specimens were collected for further examination. 
To further investigate the habitat characteristics of the odonate fauna, which has 
a life cycle involving an aquatic larval stage and a terrestrial adult stage, a number of 
physical and biological characteristics of the stream were quantified. Stream parameters 
were measured using measuring tape, a multiparameter and a flow meter. Hydraulic 
parameters measured included stream dimension (depth, width), proportion of pools 
and riffles, in-stream woody debris, macrophytes, leaf litter, and substrate (sand, silt, 
clay and rock). Physiochemical parameters recorded included pH, Dissolved Oxygen 
(DO), Oxidation-Reduction Potential (ORP), Total Dissolved Solids (TDS), Salinity 
(S), and Temperature (T). Riparian vegetation heterogeneity, bank form, and canopy 
cover were also assessed and recorded for all quantitative survey sites. The stream 
cross-section of each site was measured multiple times to obtain the average values. 
The surrounding habitat types, i.e. swamp, open canopy and distance to forest edges 
were also recorded (see appendix 2 for details). 
Identifications of adults were primarily based on Tang et al. (2010) and Orr 
(2005). Taxonomic classification follows Schorr & Paulson (2017). Local species 
updates and conservation status follow Ngiam & Cheong (2016). 
Odonate larvae were caught and identified to the family level. Specimens 
were caught by tray net sampling, moving upstream and disturbing the water. These 
specimens were caught together with other aquatic insect specimens and preserved in 
75% ethanol for microscopic examination. These collections were separate from and 
supplementary to those of Ho et al. (2018). 
