Determining the Natal Origin of North Carolina's Central Southern Management Area Striped Bass Stock Through the Use of Otolith Chemistry

Striped bass (Morone saxatilis) is one of the most important recreational fisheries in the state of North Carolina. The NC Wildlife Resource Commission has an extensive stocking program for striped bass in the Neuse and Tar River systems (Central Southern Management Area). Both systems have spawning populations, but very few juvenile fish have been collected in these systems to show evidence for successful spawning and juvenile recruitment. In order to assess the success of juvenile recruitment from natural spawning in these watersheds it is necessary to determine the proportion of stocked to naturally spawned fish. Otolith microchemistry provides a reliable method for distinguishing the stocked fish from the naturally spawned. Natural striped bass within the Central Southern Management Area are thought to be resident fish and would therefore have a relatively stable elemental signature over the first year of life. Stocked fish are moved between three very different water sources during there first year of life and therefore exhibit a very unique elemental signature. Otolith microchemistry was used to examine the first year of life and determine the natal origin of fish residing within the CSMA watersheds. 251 fish were collected throughout the year from a wide variety of locations within the Tar and Neuse watersheds, as well as the hatchery that produces the stocked fish. Otoliths were removed and the cores and cross sections analyzed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). The microchemistry from the otolith’s core to the first annulus was analyzed to determine if it reflects the chemical signatures assigned to natural or stocked origin.