The qPCR results of Asian arowana eDNA detection in Muda Lake, Kedah, Malaysia

We present a qPCR-based eDNA method to detect the presence of the
endangered Asian arowana (Teleostei: Osteoglossidae: Scleropages formosus)
in Muda Lake, where resides one of its last wild populations on the west
side of Peninsular Malaysia. Flanked by a pair of newly developed
species-specific primer, a 163-base pair fragment of the cytochrome
oxidase subunit I (COI) gene was selected as the eDNA marker. We applied
our eDNA method at five sampling sites throughout Muda Lake and at five
different periods. The study observed a marked seasonal variation in
detection rates, with significantly higher rates during the wet months of
August, January, and December compared to the dry season spanning May and
June. The Asian arowana is known to breed during the rainy season and we
therefore hypothesize its reproductive biology influences the
concentration of eDNA in the lake. Our results also highlight the possible
impact of abiotic factors in tropical freshwater ecosystems (such as
high-water temperature) on eDNA persistence. In conclusion, future
applications of qPCR-based eDNA methods in tropical environments would
benefit from locally evaluating the effects of both biotic and abiotic
factors on species detection.