Many marine taxa benefit from accessing juvenile “nursery” habitats with high food availability and reduced risk of predation. However, coastal development can result in negative impacts on the accessibility and health of nursery habitats. Barramundi (Lates calcarifer) is an iconic fishery species in Northern Australia with a complex life history strategy involving opportunistic juvenile migration into and residency in freshwater, facilitated by wet season flooding.
In this study, we used high resolution otolith microchemistry profiling to reconstruct the lifetime movement history of >600 barramundi in the Dry Tropics region of Queensland, a heavily anthropogenically modified system. Barramundi is nominally considered a catadromous species; however, we found that just 33% of adult barramundi harvested in the estuarine/marine fishery displayed evidence of extended residency (≥1 year) in freshwater habitats during early life. Individuals that displayed evidence of extended juvenile freshwater residency attained significantly larger size-at-age than conspecifics that remained in estuarine and/or marine water their whole lives, corroborating previous work on the significant benefits of freshwater access for this species. Spatiotemporal patterns in juvenile freshwater residency suggest that the prevalence of catadromy in Dry Tropics barramundi may be limited by anthropogenic barriers to juvenile fish movement into suitable freshwater nursery habitats.