Table 5. — Experiment 5; effects of tag coating and different taggers on the mortality and shedding 

 in groups of 20 adult fish. 















Tagger 















1 





2 







3 





Total 





Tag coating 



Dead 



Shed 



Total 

 loss 



Dead Shed 



Total 

 loss 



Dead 



Total 

 Shed loss 



Dead 



Total 

 Shed loss 













-Number- - - 











Number- - - 



Percent 



Vaseline 



7 



4 



11 



8 3 



11 



4 



4 



19 



7 26 



43 



Tetracycline- 

 vaseline 



2 



1 



3 



5 1 



6 



1 



1 2 



8 



3 11 



18 



Untreated 



10 



4 



14 



4 



4 



2 



2 



16 



4 20 



33 



Total 



19 



9 



28 



17 4 



21 



7 



1 8 



43 



14 57 



32 



determine if a smaller version of the adult tag 

 would be successful. 



Experiment 7 



Objective: To determine the survival rate of 

 juvenile fish tagged with adult and juvenile tags. 



Procedure: Thirty -five fish (mean length 77 

 mm) were tagged with adult tags and 41 fish 

 of similar size were tagged with juvenile tags. 



Results: The tag loss was 100% for adult 

 tags and 59% for juvenile tags (Table 6). 



Discussion: Death caused 97% of the adult 

 tag loss, but only 7% of the juvenile tag loss. We 

 thought the high rate of juvenile tag shedding 

 (51%) resulted because construction of the gun 

 prevented the small tag from being injected far 

 enough into the body cavity. The gun was modi- 

 fied to give deeper tag penetration in the re- 

 maining experiments. Most of the mortalities 

 occurred within 3 days, as found by Bayliff and 



Table 6. — Experiment 7; effects of adult and juvenile tags 

 on the mortality and shedding in juvenile fish. 





Number of 









Type 



fish in 









tag used 



experiment 



Dead Shed 



Total 



loss 







Number 



Number 



Percent 



Adult tag 



35 



34 1 



35 



100 



Juvenile tag 



41 



3 21 



24 



59 



Control (not 



tagged) 66 



1 — 



1 



2 



Klima (1962), suggesting that tagging injuries 

 caused death. The tag shedding was 95% com- 

 plete within 2 weeks. 



Experiments 8, 9, and 10 



Objective: To compare the losses of adult 

 and juvenile tags from juvenile fish and to sub- 

 stantiate the results obtained in Experiment 7. 



Procedure: In each experiment, 50 fish (mean 

 length 77 mm) were tagged with adult tags and 

 50 with juvenile tags, and both groups were put 

 into a tank with equal numbers of control fish. 



Results: Nearly 95% of the tagged fish in each 

 experiment died, as did 12 to 50% of the control 

 fish. 



Discussion: Since many control fish died, we 

 assumed some of the mortality resulted because 

 of the poor condition of the fish. The most notice- 

 able difference, however, between the fish in 

 Experiment 7 and those in Experiments 8-10 

 was the fullness of their intestines. The fish in 

 Experiment 7 had very little food in their in- 

 testines, but those in Experiments 8-10 had 

 consumed much food and had distended intes- 

 tines. In the well-fed fish, tags probably punc- 

 tured the distended intestines, but in the starved 

 fish, tags evidently slipped past the flaccid in- 

 testines without damaging them. Fry and Roe- 

 del (1949), after finding that the guts of gorged 

 mackerel were likely to be pierced when making 

 tag incisions, allowed the fish about an hour to 

 digest the food before tagging them. We de- 

 cided to further test the effects of intestinal 

 contents on juvenile tagging mortality. 



