Detachment and grading of the tropical sea cucumber sandfish, Holothuria scabra, juveniles from settlement substrates

Abstract

The International Centre for Living Aquatic Resources Management (ICLARM) in the Solomon Islands has a 5-year project to develop methods for mass rearing of tropical sea cucumbers for the purpose of enhancing wild stocks (ICLARM, 1995). The project is now in its third year and has produced over 150,000 juveniles up to 120 mm in length. The detachment of settled juveniles has been a technical constraint to the culture of H. scabra in Solomon Islands. The aim of the study was to examine whether the methods used for detachment of S. japonicus were appropriate for H. scabra. In particular, our objectives were to determine: (i) a concentration of potassium chloride (KCl) that detached all juvenile sea cucumbers within 60 s, (ii) how long the juveniles remained detached following exposure to KCl, (iii) if the time required for detachment and re-attachment changed as juveniles grew, and whether any such trend would influence grading, (iv) if exposure to KCl caused damage or mortality of sea cucumbers in the size range of 2 to 20 mm and, (v) if results from laboratory experiments could be applied to juveniles on settlement plates and (vi) whether freshwater could be used to detach juvenile sea cucumber instead of KCl.