Reconstructing habitat use, identifying origin and discrimination of the barramundi (wild and farmed) populations using otolith stable isotope analysis

Abstract

Barramundi or Asian seabass, Lates calcarifer (Bloch, 1790), is a euryhaline fish that is widely distributed in the Indo-West Pacific. This species is a commercially important fish which is extensively farmed in Taiwan. Currently, there is a lack of information on the origin, habitat use and migratory behavior of barramundi in Taiwanese waters. Here, δ13C and δ18O values of otolith growth time series were evaluated in barramundi (wild and farmed), and salinity was estimated from otolith δ18O values to report the habitat use and origin of wild individuals. Also, wild individuals and farmed individuals were discriminated using δ13C and δ18O values of otoliths to explore whether the individuals captured from Danshui River Estuary have aquaculture origin. The wild individuals collected from the Danshui River Estuary displayed a relatively wide range of δ13C and δ18O values however farmed samples showed a consistent change among the individuals within a group. Based on otolith δ18O values and estimated salinity, the most of wild fish samples were born in the brackish water environment. The estimated salinity experienced by the wild individuals also suggests that migration behavior varies among individuals. Moreover, some wild individuals showed a regular migration pattern but the range of salinity experienced by individuals varied greatly. By comparing the δ13C and δ18O values, it was found that significant differences existed among groups of fish and overall the correct classification accuracy was 95% using quadratic discriminant analysis. The δ13C and δ18O values of the otolith core revealed that only one sample caught in the Danshui River Estuary might have aquaculture origin. In this study, stable isotope (δ13C and δ18O) values were effectively applied to reconstruct the life history of barramundi and to distinguish individuals having a different origin. The results of this study can be used as a reference for sustainable management of this important fishery resource.