Conservation propagation of American shad: History and methods

Modern hatchery efforts for American shad (Alosa sapidissima) began with the stocking of hatchery-reared larvae in 1976. Development of methods to distinguish hatchery-reared fish from naturally-spawned fish was a high priority.  Mass-marking of hatchery larvae by 4-6h immersion in 200 to 700 mg/L tetracycline was developed in the 1980’s.  Mark detection is by epi-fluorescent microscopy on double-ground sagittal otoliths. Multiple marks are produced by immersions at 3d intervals. Multiple marks have been used to distinguish between stocking sites, cohorts, and time of release (day/night). Shad hatcheries coordinate marking schemes via the OTC Marking Task Force to avoid conflicts between agencies. Based on hatchery success, as demonstrated by OTC mark recoveries, shad hatcheries have expanded from one during 1976 to 1989 to 14 in 2010. Between 1976 and 2009, more than one billion OTC marked American shad, hickory shad and river herring have been stocked in East Coast Rivers. Ancillary benefits of OTC marking include cohort analysis and concurrent calculation of survival of stocked larvae, development of a reference collection of known age otoliths from the Lehigh River, and confirmation of homing of larvae stocked in a tributary of a larger river with a self-sustaining stock of American shad.