A method was developed to attach underwater acoustic transmitters on the knobby sea star Protoreaster nodosus. Cylindrical transmitters, each measuring 36 mm length × 13 mm diameter in size and 11 g in weight, were used in this study. Each transmitter was placed in a neoprene holder that was attached externally to the middle of one arm of P. nodosus with a nylon monofilament fishing line. Attachment was achieved by threading the monofilament line through two small perforations aborally along its mid-ridge and adorally through the ambulacral groove. Some 36 individuals were successfully tagged over a three-year period between 2007 and 2010 on an intertidal reef in Singapore using this technique. Tagging did not appear to affect survival, feeding or movement of sea stars during the period of attachment, which averaged 60 days. This method may work equally well with other types of tags, such as depth recorders and accelerometers.
