Recruitment sources and dispersal of an invasive fish in a large river system as revealed by otolith chemistry analysis

Abstract

The contributions of nursery habitats to recruitment of non-native common carp (Cyprinus carpio) were estimated via analysis of water and otolith 87Sr/86Sr and otolith trace element concentrations (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) over 3 years in the Lachlan River, Australia. Water samples and otoliths of postlarval carp were analyzed to characterize 87Sr/86Sr and multi-elemental signatures of nursery habitats. Considerable temporal variation occurred in both water 87Sr/86Sr and otolith multi-elemental signatures, which limited our ability to directly match water and otolith 87Sr/86Sr in nurseries of the lower catchment. However, spatial variation in multi-elemental signatures was sufficient to allow accurate classification of nurseries within years. Assignment analysis of young-of-year fish suggested that several wetland and floodplain systems made significant contributions to young-of-year recruitment in the lower catchment. These contributions were strongly influenced by river flows and water management. Nurseries contributed fewer recruits to the main channel as distance from the nursery increased. Fish from the upper catchment originated from local sources, and there was no evidence of mixing of recruits between the upper and lower catchments. We conclude that identification of recruitment “hotspots” via otolith chemical analysis can assist in developing strategies to control invasive fishes in large river networks.