Validation of Oligohaline Elemental Otolith Signatures of Striped Bass by Use of In Situ Caging Experiments and Water Chemistry

The spatiotemporal variability in strontium (Sr), barium (Ba), magnesium (Mg), and manganese (Mn) elemental signatures of water and fish otoliths was assessed from July to October 2008 across river habitats of Albemarle Sound, North Carolina. We examined whether relationships in these signatures exist and the potential of otoliths to serve as innate chemical tags. Hatchery-reared age-0 striped bass Morone saxatilis were placed in cages at four different locations to test development of habitat-specific otolith signatures. Dissolved elemental water and otolith signatures exhibited spatial variability but did not vary temporally. Chemical water signatures classified habitats with 76-81% accuracy, and otolith signatures of caged fish displayed 59-63% total classification accuracy depending on the classification method used. The elements Sr, Ba, and Mn were the main habitat discriminators, as their concentrations in otoliths were significantly correlated with concentrations in the water. Otolith Mg was not related to water chemistry and did not vary among habitats. Natural physiochemical gradients, geochemical processes, and possibly anthropogenic inputs influenced the trace elemental signatures of Albemarle Sound habitats. The unique chemical signals of the sound's river habitats validate the use of otolith signatures for determining striped bass habitat utilization in this system. Use of otolith elemental signatures as natural tags provides a quantitative method to determine the proportion of juvenile striped bass recruiting to the adult spawning stock from specific habitats, thus aiding resource managers in identifying habitats that should receive priority in restoration and conservation decisions.