NOTE Zeller: Ultrasonic telemetry: its application to coral reef fisheries research 



1059 



ter, UK). The incision was placed parallel to the 

 midventral line on the left hand side of the fish, 2 

 cm anterior to the anus and 1-2 cm lateral of the 

 midventral line. Three to four rows of scales were 

 removed from the area of planned incision, and the 

 area was cleaned with Tamodine^^'. A 2-3 cm ante- 

 rior-posterior incision was made into the body cav- 

 ity. Disinfected transmitters were coated in antisep- 

 tic cream prior to careful insertion into the body cav- 

 ity. The incision was closed with 6-8 surgical staples 

 (Ethicon Proximate UV^') as suggested by Mortensen 

 (1990), the area was cleaned with Tamodine^"', and 

 the fish given an intraperitoneal injection of antibi- 

 otic (tetracycline 50 mg/kg offish, McFarlane and 

 Beamish, 1990), before being returned to the 

 aquarium tanks. 



Aquarium experiments Owing to limited aquarium 

 space, it was not possible to evaluate all combina- 

 tions of anesthetics and placement methods simul- 

 taneously. Hence two separate experiments were con- 

 ducted. Experiment A examined the least intrusive 

 transmitter placement technique (force feeding) with 

 all three anesthetics. In experiment B the two intru- 

 sive techniques (external attachment and insertion 

 into the body cavity) were tested in conjunction with 

 the two most suitable anesthetics. 



Experiment A: force feeding All three anesthetics 

 were tested with force feeding to assess differences 

 in retention times of transmitters due to the anes- 

 thetic agent. It was hypothesized that use of the hyp- 

 notic agent Hypnodil"' (metomidate) would result in 

 the longest retention times owing to the low stress 

 levels caused by this compound (Thomas and 

 Robertson, 1991). Plectropomus leopardus regurgi- 

 tate stomach contents easily, particularly when ex- 

 posed to stressful conditions. ^ 



Twenty-one specimens of P. leopardus (size range: 

 39.0 cm-52.5 cm FL) were assigned randomly to the 

 three anesthetic treatments in -7). Individual fish 

 were anesthetized, tagged with T-bar anchor tags for 

 identification, their fork length was measured, indi- 

 vidually numbered transmitters were inserted into 

 the stomach, and fish returned to the aquaria for 

 recovery. Fish were fed daily. Aquaria were exam- 

 ined for regurgitated transmitters every two hours 

 during daytime and once during the night. The start 

 of each inspection was taken as the maximum reten- 

 tion period for any recovered units. 



^ Davies, C. 1992. Cooperative Research Centre for Reef Re- 

 search, James Cook University of North Queensland, Towns- 

 ville. 4811, Austraha. Personal commun. 



Experiment B: external attachment and surgical 

 insertion The suppression of a stress response due 

 to the use of metomidate (HypnodiF^') makes this a 

 valuable drug for the routine handling of fishes (Tho- 

 mas and Robertson, 1991). However, slightly elevated 

 levels of the stress hormone corticosteroid are con- 

 sidered beneficial for resistance to trauma, thus 

 making metomidate less suitable in situations involv- 

 ing stress, such as surgical procedures (Thomas and 

 Robertson, 1991). Given the nature of the intrusive 

 manipulations performed in experiment B, the use 

 of HypnodiF^' was discontinued. 



Experiment B compared two anesthetic agents 

 (phenoxyethanol and MS-222) and two transmitter 

 placement methods (external attachment and surgi- 

 cal insertion) in a full factorial design. The trans- 

 mitter placement factor consisted of five treatment 

 levels: external and internal placement treatments, 

 external and internal placement controls, and a rou- 

 tine handling control. All fish received the same pre- 

 liminary handling: fish were anesthetized, weighed 

 (to the nearest 50 g), measured (fork length), and 

 tagged externally. Routine-handling control fish were 

 returned to the aquaria. The external attachment 

 treatment consisted of attaching transmitters sensu 

 Holland et al. (1996), and injecting an antibiotic in- 

 traperitoneally (tetracycline 50 mg/kg offish, McFar- 

 lane and Beamish, 1990), before fish were returned 

 to the aquarium. The procedure lasted 5-8 minutes. 

 External-attachment control fish underwent the 

 same procedure, but a transmitter was not attached 

 after puncturing the musculature, and the fish were 

 returned to the aquaria after eight minutes. The in- 

 ternal placement treatment consisted of surgical in- 

 sertion of the transmitters into the body cavity as 

 described above. The procedure took 15-20 minutes. 

 Internal placement control fish were treated identi- 

 cally, but no transmitter was placed in the body cav- 

 ity prior to closure of incisions. Fish were returned 

 to the aquaria after 20 minutes. 



Twenty P. leopardus were used (size range: 34.0- 

 50.7 cm FL), resulting in two random replicates per 

 treatment combination. Fish were fed daily, and each 

 individual was examined visually without handling, 

 to record general condition, behavior, feeding and 

 wound status. The experiment was terminated after 

 24 days because gas-bubble-trauma (Weitkamp and 

 Katz, 1980) affected the behavior (lethargy and ces- 

 sation of feeding) offish from all experimental groups. 

 Upon termination, wounds were examined and clas- 

 sified as aggravated (ripped, or inflamed [secondary 

 infection] ), partially healed (40-50% wound closure), 

 or healed (possibly minor inflammation). Subse- 

 quently, transmitters were removed and fish were 

 weighed. 



