Poor retention of passive induced transponder (PIT) tagsfor mark-recapture studies on tropical sea cucumbers

We tested the short-term retention of passive induced transponder (PIT) tags on 20 adult sea cucumbers of both Holothuria whitmaei and Actinopyga miliaris in New Caledonia. One PIT tag was injected into the coelomic cavity of each individual. One double T-bar tag was inserted into the same hole in the body wall as a means of later identifying the individuals with PIT tags. Only eight days after release in suitable reef habitats, just one-quarter of H. whitmaei individuals retained PIT tags and no A. miliaris individuals retained them. T-bar tags caused lesions in many H. whitmaei and we concur with previous studies that these tags are unsuitable for biological studies on most tropical sea cucumber species. In view of the poor retention of PIT tags, we encourage the development of novel tags for tropical sea cucumbers that are individual, biologically benign, cheap and can be identified in the field.