Dietary Calcein Marking of Shovelnose Sturgeon and the Effect of Sunlight on Mark Retention

Abstract

Calcein, a fluorochrome dye, is a potential fish-marking agent that has not been evaluated in sturgeon. Shovelnose sturgeon Scaphirhynchus platorynchus (average weight, 9.7 g) were fed calcein, immersed in a calcein bath, or left unmarked to determine calcein mark intensity. In the first study, six treatments were evaluated in a two-by-three factorial arrangement. Feed was formulated with 2.0 g of SE-MARK/kg either as powder or in an encapsulated form. Sturgeon were fed the test diets for 5, 10, or 15 d. They readily ate feed containing powdered or encapsulated calcein. Sturgeon fed powdered calcein had more brilliant marks than those fed encapsulated calcein (8.27 versus 4.66 lm; P < 0.03) 6 months postexposure. Fish fed calcein for 15 d (11.26 lm) were more brilliant (P < 0.002) than fish fed for either 5 d (3.02 lm) or 10 d (5.11 lm). Post hoc comparison of the three treatment groups showed that sturgeon fed powdered calcein for 15 d (14.06 lm) were brighter (P < 0.01) than fish fed encapsulated calcein (8.46 lm) or fish immersed in calcein (9.68 lm). In the second study, previously marked sturgeon were exposed to sunlight for 14 months to determine their retention of calcein marks. Dorsal marks were no longer visible on fish exposed to 100% sunlight after 8 weeks. Most but not all fish exposed to 20% sunlight had no discernable dorsal marks after 8 weeks, but ventral marks at the pectoral fin girdle were present on all fish in the 0% and 20% sunlight exposure treatments. Feeding calcein for 15 d appears to have excellent potential for practical application, such as distinguishing hatchery-reared from wild fish. Ventral calcein marks remained visible after 14 months of exposure to 20% sunlight when sturgeon were reared in clear water.

Received April 2, 2010; accepted September 22, 2010

ACKNOWLEDGMENTS

We would like to thank a number of people for their support in conducting these studies: Frederic Barrows, Linda Beck, John Borkowski, James Bowker, Molly Bowman, and the Aquatic Animal Drug Approval Partnership. We would also like to thank Daniel Carty, Miranda Dotson, Dave Erdahl, John W. Fletcher, William C. Fraser, Jason Frost, Jason Ilgen, Kevin Kappenman, Tom Kehler, Wesley Orr, Ron and LeAnn Secor, Matthew Toner, and Aquatic Life Sciences, Inc., for technical assistance and donation of SE-MARK calcein and the Bozeman Fish Technology Center for their staff and facility support. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. government.