Species-level connections between larval fish and copepods revealed through ocean observing

Despite direct trophic links between larval fish and zooplankton, the two communities are rarely analysed together in taxonomic detail. As a result, important relationships between larval fish and prey species are yet to be resolved. This study uses a seven-year ocean observing dataset to explore possible relationships between 68 larval fish species and 156 copepod species from three coastal sites off eastern Australia. Two contrasting methods of network analysis were used to identify statistical linkages between larval fish and copepod species. The abundances of seven common larval fish species were modelled using key outcomes of the network analyses, of which four larval fish species showed significant relationships with specific copepod density. Densities of copepod species were consistently better predictors of specific larval fish abundance than total zooplankton biomass. Abundant copepods, Paracalanus indicus and Euterpina acutifrons, have potential for influencing the recruitment of larval Pacific sardine (Sardinops sagax). Our statistical approach provides a context for generating ecological hypotheses about larval fishes, which are realistically based on species-specific interactions between predators and prey during this critical period.