Anesthesia and surgery procedures for implanting radio transmitters into the body cavity of adult brown trout (Salmo trutta)

The aim of this study was to determine the best intraperitoneal surgical tagging technique for brown trout (Salmo trutta) by radiotransmitter. Two types of anaesthesia, using either clove oil or electricity were compared. Two types of transmitters, with external trailing antenna or internal coil antenna, and two incision zones, anterior and posterior to the pelvic girdle, were tested. Clove oil was a satisfactory anaesthetic but anaesthesia by electricity was immediate, and did not seem to cause post operational stress. It offered a better ease of intervention than chemical anaesthesia and presented no risks for fish and experimenter. It is thus perfectly suitable for the insertion of radiotracking transmitters. If no maximum field range is needed, the internal antenna transmitter is preferable to the external antenna: it is more stable inside the abdomen and its expulsion seems less frequent. However, the loss of transmitter is relatively frequent in either case and must be taken into account during any monitoring by radiotracking, for duration longer than 40 days. In addition it does not seem that the location of the incision has an influence on survival, risk of expulsion, healing and situation of tags inside the abdomen.