Evaluation of calcein as a marking agent for paddlefish

Although paddlefish were once endemic to the Ohio River basin of western Pennsylvania, they are currently listed as extirpated. Paddlefish stocking in Pennsylvania has been a fishery management practice since 1991. The objective of our experiment was to assess calcein as a chemical marking agent for paddlefish using two different delivery techniques, immersion and dietary additive. Paddlefish fry were reared in six-foot circular tanks at the Northeast Fishery Center, Lamar, Pennsylvania. Forty-two paddlefish were fed a modified commercial diet containing powdered calcein (8 g calcein/kg feed) for 5 consecutive days at 2% body weight. Another forty-two paddlefish were exposed to a 4 minute 1.5% NaCl bath before a 4 minute 0.5% calcein immersion. Forty-one non-treated individuals were sampled as controls. Specimens were collected on post treatment days 32, 63, 96, and 120 and frozen for subsequent evaluation.   Mark quantification was accomplished with a bench top calcein detector, digital photographic equipment, and luminosity measuring software. Results from this study may eventually provide researchers and managers with stock identification, age verification, and other important management tools.