Fluorochrome Marking of Out-planted Green Sea Urchins, Strongylocentrotus droebachiensis, for Sea Ranching and Restocking Programs in the Gulf of Maine, USA

Marking calcified structures with fluorochromes is done in a variety of vertebrate and invertebrate species to tag individuals for growth, population, and ecological studies. Here, we describe the use of the fluorochrome tetracycline to identify hatchery reared green sea urchins released on-bottom onto two aquaculture leases known as Job and Sloop, located in *the Gulf of Maine, USA. This was done to examine the viability of sea ranching and stock enhancement by looking at recovery rates and growth of reseeded juveniles over the course of two years. 21,000 hatchery reared green sea urchin juveniles were marked with the fluorochrome tetracycline when they were at 10-20 mm test diameter, and released onto 400 m[sup 2] study areas located at each lease. Because the marked jaw structures were internally located, it was not possible to identify marked sea urchins in the field, and the animals had to besacrificed for laboratory analysis. This would enhance the ability of resource managers to evaluate restocking programs in the Gulf of Maine, as well as to assign provenance or ownership of sea ranched urchins.