Do Morphological Traits Predict Ecological Guilds of the Mekong Fish Fauna?

Southeast Asian riverine fishes are classified into three guilds (‘black’, ‘white’ and ‘grey’ species) based on their reproductive and migration strategies. In this study, we aimed to investigate whether fish morphology could be used to predict the Mekong fish guilds. Nine dimensionless ratios of fish morphological traits were used to describe the locomotion and food acquisition strategies of 121 fish species. The links between morphological traits and fish guilds were assessed using a principal component analysis (PCA) and a variance partitioning analysis, which revealed a strong morphological overlap between the guilds. Despite the high contribution of intra-guild variability to overall morphological variability (~90%), black and white fish significantly differed in terms of locomotion-related traits. Mekong fish guilds were satisfactorily predicted by using a random forest (RF) model, which produced a percentage of successful classification of ca 50% for each of the three guilds. Caudal propulsion efficiency, pectoral fin vertical position and body elongation were the most significant traits in the RF predictive model. Although the present study provides initial insight into the links between Mekong fish morphology and ecological guilds, further research is needed in order to clarify the relationship between species morphology, migratory status and responses to environmental variation.