Effectiveness of two tagging devices in the sea cucumber Holothuria (Halodeima) grisea

Abstract

A reliable and harmless mark–recapture method provides valuable information for the management of commercial sea cucumber species. Nevertheless, marking and tracking sea cucumbers is notoriously difficult and represents a serious challenge. In this study, we tested one external and one internal tag in the sea cucumber Holothuria grisea. A passive integrated transponder (PIT) tag was inserted into the coelomic cavity in one treatment, whereas a T-bar (external tag) was attached in the upper surface of the body wall in the other treatment; sea cucumbers were then followed for 17 weeks. The tagging procedure caused no evisceration in the experimental groups, nor was a significant difference in growth rate found between treatments. The retention of the PIT tag was low, with 100% lost by Week 9. Retention of T-bars was higher, with 90% still attached by the end of the Week 8, but retention decreased thereafter as T-bar absorption increased. No relationship was found between initial weight and the number of weeks PIT tags (r=–0.173, P=0.781) or T-bars (r=–0.220, P=0.652) were retained. Neither the T-bar nor the PIT tags fulfilled the requirements of high retention required for long-term studies. However, we do recommend the use of T-bars for short-term studies for H. grisea under laboratory conditions or in a habitat with low substrate complexity.