The efficacy of calcein as a tagging agent for the long-spined sea urchin, Diadema antillarum.

The sea urchin Diadema antillarum is a restoration target due to its function as a keystone reef herbivore. However, restocking efforts are hindered by a lack of long-term tagging methods. We tested the effectiveness of calcein marking for urchin releases. Cultured individuals were tagged using a 150 mg/L calcein bath and monitored for 11 weeks. Dye markings remained fully visible in all individuals for two weeks but began to fade within three weeks. Only individuals with white spines maintained markings beyond five weeks. Unlike with other urchin species, calcein only seems suitable for short-term external tagging of D. antillarum .