Evaluation of implantation procedures for PIT tagging juvenile Nile tilapia

We evaluated three alternative procedures for tagging juvenile Nile tilapia Oreochromis niloticus (1,9-13,7 g) with passive integrated transponder (PIT) tags : injection with hypodermic syringe injectors (N=40) and abdominal surgery with or without suturing (N = 55 and 40, respectively). The survival of Nile tilapia tagged with injectors was low ( 10 -50 % at 10 d) and proportional to fish size because of the difficulty of controlling the penetration of the syringe into the intraperitoneal cavity following the piercing of the body wall. Surgically implanted fish had much higher survival rates (78 - 100 % at 10 d). Suturing reduced the risks of tag expulsion and protrusion of the viscera through the open incision within the first 3 d following surgery (10 % risk on the nonsuturated fish).Over the first 3 d after tagging tagged fish showed depressed growth rates (to a greater extend in smaller fish and proportionally greater in sutured fish) but showed normal growth later on.These results demonstrate that surgery is suitable for PIT-tagging small juvenile Nile tilapia, which offers opportunities for studies of individual performance.