Variation in lifetime movements of an Ariidae species in an eastern Australian river revealed by otolith microchemistry

Ariids, or sea catfishes, inhabit marine, estuarine, and occasionally freshwater habitats circumtropically. They are most often locally abundant and are important in artisanal and commercial fisheries, particularly in developing countries. Detailed information on the ecology and habitat preferences of many of the genera within the family is lacking. We analysed the otolith of 57 blue catfish, Neoarius graeffei, collected from the lower reaches of the Clarence River, NSW, Australia with the aim of better understanding the species movement ecology, including its ability to respond to environmental change. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) was used to quantify Sr:Ca, Ba:Ca and ⁸⁷Sr:⁸⁶Sr ratios in otoliths and infer lifetime movement patterns. Otolith microchemistry revealed inter-individual variation in the movement patterns of N. graeffei. A strong affinity for estuarine waters was evident among most individuals, with movement into upstream freshwater habitats for extended periods discernible in some individuals. Variation in movement patterns was identified by changes in Ba:Ca, Sr:Ca and ⁸⁷Sr:⁸⁶Sr otolith profiles, although Sr:Ca lacked clear patterns. Furthermore, both Ba:Ca and ⁸⁷Sr:⁸⁶Sr otolith transects revealed estuarine residence by juveniles, as well as multiple movements among chemically distinct areas throughout the lifetime of some individuals. Otolith microchemistry enabled elucidation of long-term movement patterns of N. graeffei in our study. Uncovering the variable movement patterns of a single species identifies the potential adaptable nature of other species within the Ariidae family and indicates N. graeffei is resilient to environmental changes and anthropogenic impacts.