those in the other for 1 week prior to tagging. 

 From each group 70 fish were tagged with 

 adult tags and 70 were tagged with juvenile 

 tags as in Experiments 7-13. Another 70 fish 

 from each group were tagged by pushing the 

 tag through the body wall at a 45° angle, in- 

 stead of a 30° angle as in previous experiments, 

 and then rotating it to a 10° angle before in- 

 jecting it into the body cavity. 



Results: The new method of insertion had 

 only slightly less juvenile tag-shedding loss 

 than the old method (Table 9). The effect of 

 intestinal contents on tagging mortality was 

 inconclusive. 



Discussion: The fish reduced their food intake 

 as the water temperature declined during Octo- 

 ber. The intestines in both groups were flaccid 

 and not distended. Since no effect of overfeeding 

 on tagging mortality could be assessed, the 

 data were combined (Table 9). Tag shedding, 

 tagging mortality, and incision healing took 

 place over a much longer period of time in this 

 experiment than in previous summer experi- 

 ments and were evidently prolonged because of 

 the lower water temperature. 



Experiment 15 



Objective: To determine if applying tags 

 either higher in the body cavity than in previ- 

 ous experiments or posteriorly reduces tag loss, 

 especially shedding, of juvenile tags from juve- 

 nile fish. 



Procedures: Five groups of about 40 fish 

 each (mean length 101 mm) were tagged with 

 juvenile tags. In one group the tag was inserted 



anteriorly at an angle of 30° (as in experiments 

 7-13). In the second it was inserted at an angle 

 of 45° and rotated to 10° before being injected 

 (as in Experiment 14). In the third and fourth 

 groups the tag also was inserted anteriorly, 

 but the point of insertion was high on the body 

 wall above the origin of the right pelvic fin, to 

 position the tag above the stomach. In Group 3 

 the tag was inserted and injected at a 30° angle; 

 in Group 4 it was inserted at 45° and injected 

 at 10°. In Group 5 the tag was inserted at the 

 origin of the left pectoral fin and injected poste- 

 riorly into the body cavity. Five other groups 

 were tagged by identical methods with adult 

 tags. 



Results: Total loss of juvenile tags applied 

 posteriorly from the origin of the pectoral fin 

 was less than for all other methods (Table 10). 

 With adult tags, the two-angle, low method 

 caused the lowest loss. Juvenile tags applied 

 by the two-angle methods again caused lower 

 tag-shedding rates than those injected at one 

 angle. 



Discussion: Juvenile tag-shedding and mor- 

 tality rates were reduced to about 5% each 

 when the tags were inserted by the pectoral 

 method (Fig. 4). The tags did not penetrate the 

 viscera, but slid between them and the body 

 wall, whereas tags applied by anterior methods 

 penetrated the viscera. The total loss of tags 

 applied posteriorly from the origin of the pec- 

 toral fin, therefore, should not be affected by 

 the fullness of the intestines. Bayliff and Klima 

 (1962) said tags should not penetrate the vis- 

 cera, and they tried to place the tags next to 

 the body wall. Evidently the one-angle, low 



Table 9. — Experiment 14; effects of adult and juvenile tags Inserted into 

 juvenile fish at one angle (30°) and two angles (45° and 10°) on the 

 mortality and shedding in groups of 70 juvenile fish. 



Type tag 





Method 



Dead 



Shed 



Total 



loS6 











Number 



Number 



Percent 



Juvenile 



1 



angle 



4 



36 



40 



57 





2 



angles 



5 



28 



33 



47 



Adult 



1 



angle 



35 



3 



38 



54 





2 



angles 



33 



3 



36 



51 



Control 



(not 



tagged) 







- 











