Evaluation of sequential chemical marking of Oxytetracycline, Alizarin Red S, and Calcein in calcified structures of bloaters (Coregonus hoyi)

Thomas Kehler (USFWS, Thomas_Kehler@fws.gov), John Sweka (FWS), Steve Davis (FWS)

This project will investigate the unique chemical marking patterns produced within the otoliths, lower jaw, and ribs of bloaters after sequential immersions of Oxytetracycline (OTC), Alizarin Red S (ARS), and calcein. This project is fully aligned with the Coregonine Restoration Framework Priority number 4e: Develop and organize alternative marking strategies to measure survival of different life stages or gamete sources that are introduced. The importance of the project is pertinent because the discernment between wild and hatchery-origin fish is vital to all stocking efforts. The ability to batch mark large numbers of individuals containing a unique marking sequence provides researchers with greater ability to assess the efficacy of coregonine stocking efforts. For example, unique chemical marking patterns could be used to differentiate recaptured fish that originated from different hatcheries, were stocked in different locations, were stocked at different times of the year, or stocked at life stages. The Northeast Fishery Center has completed several pilot studies using all three of these chemical marking compounds on bloater with preliminary results indicating a unique color mark corresponding with each marking compound is achievable on multiple calcified structures. We determined the optimal period between chemical immersions and concentrations of ARS and calcein. Through continuing OTC pilot studies at our facility, we will determine the OTC concentration needed to yield discernable and reproducible OTC marks for this study. Further investigation is needed to evaluate the efficacy of the marking patterns in relationship with the life stage during chemical marking and mark integrity among calcified structures. We have been instrumental in verifying chemical marks in Coregonines released from the USFWS Allegheny National Fish Hatchery and the USGS Tunison Laboratory of Aquatic Science.