Diverse migration strategies of ariid catfishes along a salinity gradient in the Mekong River

Ariid catfishes (Ariidae family) are important migratory fish species in the Mekong River, with some species representing a major harvest component from the river. Limited biological information exists, and in particular their migration patterns are not well understood. This study examined life history strategies of three abundant ariid catfishes (Cephalocassis borneensis, Arius maculatus, and Osteogeneiosus militaris) in the Mekong River using otolith chemistry. Multiple trace elements in otolith sections were quantified using two analytical techniques: Laser Ablation – Inductively Coupled Plasma – Mass Spectrometry and X-ray fluorescence microscopy. We found that 83 % of C. borneensis samples completed their life cycle exclusively in fresh water in the Mekong River, while 17 % samples of this species were occasionally found in higher salinity (brackish) waters. The two other species (A. maculatus and O. militaris) generally occupied higher salinity (estuary and coastal) areas, but demonstrated complex migratory patterns with up to three migration strategies observed (including both residents and migrants). With such complex migration strategies, management and conservation interventions are a challenge for these fish species.