Fig. 1

A series of diagrams illustrating the use of the trocar and barbed sutures. The shark abdomen consists of denticles, epidermis, dermis and abdominal wall muscle (a), all of which must be penetrated to reach the peritoneal cavity. A scalpel was used to incise the skin down to the abdominal muscle (b). A large bore trocar was then used to twist through the muscle layers into the cavity (c). The obturator was then removed from the trocar and the acoustic transmitter inserted (d). The obturator was then reinserted to push the tag into the cavity (e). With the tag in place, a continuous barbed suture was used to close the skin, without the need for tying (f)—the muscle pushes back together as it was not cut