Trace elemental and stable isotopic signatures to reconstruct the large-scale environmental connectivity of fish populations

Abstract

Animal movements and connectivity across different environments constitute essential components of virtually all ecological and evolutionary processes. In the present study, we measured multiple trace-element profiles and stable isotopes to reconstruct life cycle patterns of Eleutheronema rhadinum, and patterns of connectivity among populations of E. rhadinum across 3 distinct ecoregions in the eastern China Sea. Our results indicated that E. rhadinum larvae from different regions exhibited distinct otolith core levels of trace elements and stable isotopes, serving as discriminative markers of geographical origin. We used the maximum likelihood approach and linear discriminant analysis to trace back the origins of the mixed adult fish stocks. After leaving their nursery areas, juvenile fish from colder northern regions migrated south to overwinter in the South China Sea, where they mixed with the local populations. After overwintering, the adult fish began their long journey north, with the migrating population including individuals of both East China Sea and South China Sea origins. Meanwhile, fish in the Beibu Gulf exhibited a lower degree of interaction with the South China Sea populations and minimal interaction with those in the East China Sea. Trace elements and stable isotopes revealed the spatiotemporal connectivity of E. rhadinum across the 3 different ecoregions. This study provides critical information on how marine connectivity supports temperature-mediated fish community movement patterns within coastal ecosystems.