Estimating anadromous river herring natal stream homing rates using otolith microchemistry

River herring, two closely related anadromous alosine species found along the east coast of North America, are an ecologically significant forage fish.  Populations of both alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) have declined across their range in the past 30 years.  Fisheries managers have employed a variety of techniques to increase spawning opportunities and reduce adult mortality including trap and transport seeding of previously extirpated streams newly opened by fish passage.  During spawning runs in 2008 and 2009 we collected returning adult river herring from 10 sites across the state of Connecticut.  Juvenile fish were also collected prior to emigration. We removed sagittal otoliths from these fish and prepared transverse cross sections of the otoliths for Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) analysis. LA-ICPMS-derived trace element data were isolated from the otolith core (interior to the first saltwater signatures) for adults and compared with juvenile data, and water samples to statistically determine if returning fish were spawned at the site where they were collected. Discriminant function analysis was used to provide estimates of homing and straying rates of river herring. This basic ecological information will be useful for informing management and prioritizing conservation actions in the region.