Calcein Marking: A Non-Lethal Batch Marking Option for Stocking Evaluation

Chemical marking provides a mechanism for identifying hatchery fish in stocking programs.  Calcein has advantages over other chemicals.  We examined salinities for the osmotic induction of White Crappie and Black Crappie.  Experiments consisted of a 3.5-min immersion of five fish in 1 L of solution at salinities ranging from <1 to 50 ppt. Immediate and 24-h mortalities were 0% and 0—13%, respectively for Black Crappie.  Similarly, immediate and 24-h mortalities were 0% and 0—27%, respectively for White Crappie.  We examined dunking density (kg of fish/L) to maximize efficiency during the marking process. Fish were confined at densities ranging from 0.016-0.250 kg/L in 1L of water for 7 min. Immediate and 24-h mortalities were  0% and 0—3%, respectively for Black Crappie and 4—23% and 8—23%, respectively for White Crappie.  Ninety-six thousand Black Crappie and eighty-six thousand White Crappie were calcein marked during fall 2015 at 40 ppt and 0.25 kg/L.  The process took between 7 and 10 h to mark each species.  Twenty four hour survival of Calcein-marked Black Crappie and White Crappie was 99.5% and 99.6%, respectively.  Our calcein marking process is scalable and could be used by natural resource agencies.