Marking the Shells of Pediveliger Eastern Oysters Crassostrea Virginica, with a Calcein Fluorochrome Dye

The continued development of effective mark and recapture tools for marine invertebrates is required to better understand fundamental planktonic processes such as larval transport and mortality. Mass chemical marking methods provide researchers with the ability to mark large quantities of individuals at one time with reduced handling stress and costs. Although 3-day-old larvae of <em>Crassostrea virginica</em> (eastern oyster) have been marked with calcein (a fluorochrome dye) and recaptured, pediveligers have not been marked nor has mark retention through metamorphosis been verified. To track mark retention through metamorphosis, 12,000 pediveligers were marked for 24 and 48 h in calcein of 25 and 50 mg L −1 concentrations, and mark retention was tracked every 7 days for 4 wk. Results indicated that calcein did not affect initial settlement rates, that the distinct
bands on larval shells were visible after metamorphosis, that individuals marked as larvae were positively identified up to 4 wk post settlement without sacrificing individuals, and that lower calcein concentrations than previously documented were effective. This study demonstrates that calcein is a reliable method for marking <em>C. virginica</em> pediveligers and suggests that relatively low concentrations of calcein can produce marks and could reduce costs and potential harmful effects.