Genetic variability of wild populations of invasive redclaw crayfish (Cherax quadricarinatus) von Martens 1868 across Peninsular Malaysia

The redclaw crayfish had been listed as an invasive species in Malaysia following the various negative impacts displayed on both environment and economy. The species are largely culture in Malaysia for food, but unluckily escaped and expands to several waterbodies across the country. For effective control management of redclaw crayfish species, a total of 52 wild samples were collected from six locations in Peninsular Malaysia and analyzed using a 16S mitochondrial DNA to assess their genetic diversity and introduction history. Five haplotypes were detected associated with an overall low genetic diversity (Hd = 0.385, π = 0.00133). A single genetic structure was detected with a phylogenetic relationship showing two clusters related to the haplotypes from Australia and Papua New Guinea. The finding of this study provides the basic data that will aid the appropriate Malaysian authorities for both monitoring and management strategies of redclaw crayfish in Peninsular Malaysia

Prey identification of invasive peacock bass from Telabak Lake Malaysia using DNA barcoding technique

Invasive peacock bass Cichla spp. have recently invaded freshwater habitats across Malaysia. Stomach contents of 135 peacock bass captured from the Telabak Lake of East Coast of Peninsular Malaysia were analysed. The preys were examined using visual identification method and mitochondrial DNA barcoding technique to identify the partial digested and decaying preys in the stomach. The current study identified 7 prey species (6 fishes 43.0% and 1 shrimp 5.1%) belongs to 5 families in fishes’ stomach. The results revealed that peacock bass is highly predator and generalist feeder with an opportunistic feeding behaviour. It is highly important to reduce and monitor the abundance of this species for future survival of native species in the lake

Predicting Cherax quadricarinatus habitat distribution patterns through the usage of GIS and eDNA analysis in Terengganu, Malaysia

Cherax quadricarinatus (von Martens, 1868) is a highly invasive species that is resilient and highly adaptable to environmental conditions in new locations. Its presence brings along ecosystem imbalances and causes socioeconomic losses in invaded areas. Due to the destructive behaviour, it is important to conduct preliminary assessment methods and scientific studies especially on its behavioural and dispersal patterns. Thus, this study aims to determine the habitat distribution patterns of C. quadricarinatus based on the methods of GIS and environmental DNA (eDNA) analysis. The study was done at Felda Tenang, Terengganu, Malaysia. Based on the geographical features and climate conditions of the study area, we theorized that there are fewer and older C. quadricarinatus present at higher areas but more and younger C. quadricarinatus at lower areas. We found that 91.67% of the study area to be invaded, thus imploring the need for future mitigation plans to curb their dispersal into new areas. Future studies should also be done to determine the habitat distribution patterns of C. quadricarinatus in other areas

Length weight relationship and condition factor of Australian red claw crayfish (Cherax quadricarinatus) from three locations in Peninsular Malaysia

Australian redclaw crayfish, Cherax quadricarinatus, is a species of crayfish native to northern Australia and southern New Guinea but has been introduced and established feral population in many parts of the world including in Malaysia. In this present study, we examined some morphometric characteristics of C. quadricarinatus collected from three locations in Malaysia which are Tasik Ayer Keroh (Melaka), Muar (Johor) and Besut (Terengganu). The wild-caught crayfishes found in these selected locations were analyzed for sex ratio, length-weight relationships (LWRs) and condition factor (K). The sex ratio of C. quadricarinatus from Melaka, Johor and Terengganu was found to be 0.73:1 (19 females/26 males), 2.9:1 (26 females/9 males) and 0.28:1 (4 females/14 males) respectively. The LWRs for redclaw crayfish from Melaka, Johor and Terengganu were W = 0.018L3.06, W = 0.011L3.19, and W = 0.016L3.08, respectively. C. quadricarinatus from the three locations show positive allometric growth (b>3). The K values for Melaka, Johor and Terengganu were 2.07, 1.76 and 1.84 respectively. The findings show that redclaw populations from different localities in Peninsular Malaysia attained good condition and this might reflect that the species has adapted well in our environment

Detection and Management of Freshwater Invasive Alien Species through Environmental DNA Analysis and Geographic Information Systems: A Review

Freshwater invasive alien species (IAS) are non-native organisms that were intentionally or unintentionally released into local water bodies and later harmed the invaded habitat by disrupting the ecological processes. Over the last few years, environmental deoxyribonucleic acid (eDNA) analyses have been used in many studies to detect IAS, with positive results. However, with the help of geographic information systems (GIS), efforts to detect the presence of IAS can be made faster and more efficiently. In this paper, we review the background of IAS in Southeast Asia and management efforts undertaken involving the input of known habitat-specific geographical parameters into GIS mapping. Via this strategy, it is possible to identify and distinguish areas that fit IAS habitat features from those that do not. eDNA analysis can later be applied to confirm the presence of IAS in detected areas, enabling further studies and actions. The presence of IAS in certain areas can be used as an indicator to assess the environmental integrity of native waterways. This combined method is likely the first approach to be applied to the detection of freshwater IAS in local water bodies. Apart from saving energy and resources, embedding GIS and eDNA into the study of IAS not only benefits the ecosystem but also assists locals and authorities in managing and taking necessary enforcement actions to curb further spread