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



1061 



triangulation (White and Garret, 1990) by 

 using identifiable landmarks and reef fea- 

 tures. Triangulation involves the estimation 

 of the location of a transmitter by using two 

 or more directional bearings obtained from 

 a known location (White and Garrot, 1990). 

 Visual triangulation uses visible land and 

 reef features that can be identified from 

 maps or aerial photographs, in conjunction 

 with directional bearings to identify the lo- 

 cation of the transmitter 



Results 



Evaluation of fish anesthetics and 

 transmitter placement techniques 



Experiment A: force feeding Gastric re- 

 tention times of force-fed transmitters 

 ranged from 18 to 216 hours; longer re- 

 tention periods were documented for 

 larger fish (Fig. 1, r=0.621, n=21). Mean 

 retention times differed between anes- 

 thetic agents used (ANCOVA, F., ^-=4.762, 

 P=0.023). The use of MS-222 resulted in a 

 shorter retention time compared with ei- 

 ther phenoxyethanol (SNK, P=0.004) or 

 metomidate (SNK, P=0.001). Mean reten- 

 tion times did not differ with the use of 

 either phenoxyethanol or metomidate 

 (SNK, P=0.216). On average, fish anesthe- 

 tized with MS-222 retained the transmit- 

 ters for 42.0 hours (±9.7 SE), in contrast 

 with fish anesthetized with phenoxy- 

 ethanol (118.0 hours [±17.2 SE]) and 

 metomidate (147.4 hours [±23.8 SE]). 



Experiment B: external attachment and 

 surgical insertion The change in weight 

 offish over the duration of the experiment 

 differed significantly between transmitter 

 placement treatments (ANCOVA, F^g= 

 5.309, P=0.018). Fish carrying external 

 transmitters displayed a substantial re- 

 duction in weight compared with fish in 

 all control groups that gained weight, 

 whereas the internal treatment group 

 showed no change in mean weight during 

 the experiment (Fig. 2). Fish with exter- 

 nal transmitters were observed spending 

 a lot of time rubbing the attached trans- 

 mitter against the substratum. Further- 

 more, most fish started feeding within two days 

 cept for fish in the external treatment group 



Lij 



c 



(0 



O 



250 



200 



150 [ 



100  



50 '- 







-50 

 ■100 

 -150 

 •200 - 

 -250 

 -300 



EC 



ET 



Treatment 



IC 



IT 



Figure 2 



Change in mean weight (before treatment to after treatment) of P. 

 leopardus as determined in experiment B. Note: negative weight indi- 

 cates a loss in weight and vice versa. Presented are means (g ±SEl. 

 Treatments:' C = routine handling control; EC = external attachment 

 control; ET = external attachment treatment; IC = internal placement 

 control; IT = internal placement treatment, n = 20. 



, ex- those anesthetized with phenoxyethanol in the in- 



and ternal control group ( Table 1 ). 



