874 
Fishery Bulletin 95(4), 1997 
Fish were passed through a quality control device 
(QCD) to ensure tag presence. Fish in the untagged 
treatment were handled and passed through a QCD 
in the same manner as tagged fish but were not im- 
paled on a tagging needle. Tagged and untagged fish 
were placed in separate 1,300-L tanks. Control fish 
were transferred directly to a 1,300-L tank with mini- 
mal disturbance. 
The three tanks were aerated and had sand, di- 
atomaceous earth, ultra-violet light, and biological 
filters. To prevent fish from jumping out, half of each 
tank was covered with 5-mm nylon mesh net and 
the other half was covered with opaque black plas- 
tic. Water temperatures averaged 24°C (range: 17- 
30°C); salinity averaged 26 ppt (range: 22-30 ppt); 
dissolved oxygen averaged 6.4 ppm (range: 4. 0-7. 4 
ppm), and pH averaged 7.8 (range: 7. 7-7. 9). Fish 
were fed baitfish or commercially prepared fish chow 
daily. 
Fish in the tagged treatment were checked for tag 
retention at 3, 30, and 60 days after tagging. At each 
tag check, fish were anesthetized ( 100 ppm MS-222), 
checked for tag presence with a field sampling de- 
tector (Northwest Marine Technology), and mea- 
sured. Fish in the untagged treatment were simi- 
larly anesthetized and measured at 3 and 30 days 
after tagging. Dead fish were removed from the tanks 
and checked for tag presence. 
We assumed that mortality associated with tag- 
ging or handling would occur within 30 days of tag- 
ging (Szedlmayer and Howe, 1995). Therefore, after 
30 days, fish in the untagged and control groups were 
combined and then randomly divided into two groups 
that received either the tagged or untagged treat- 
ment. This created a second trial of the experiment 
to evaluate CWT retention. Fish in the second trial 
were checked for tag retention at 3 and 30 days after 
tagging. 
The entire experiment was repeated three times 
with fish from different culture facilities, resulting 
in three trials in which tag retention was evaluated 
for 30 days and three trials in which tag retention 
was evaluated for 30 and 60 days. Mean initial fish 
sizes varied among trials from 62 to 115 mm SL, and 
numbers of fish per treatment varied among trials 
from 24 to 76 (Table 1). 
Table 1 
Tag (coded wire) retention rates and fish survival rates at 3, 30, and 60 d after tagging for each treatment (tagged fish, untagged 
fish, and control fish) and fish sizes at the time of tagging. Starting no. = number of fish at the beginning of the experiment. 
Survival rates are from the start of the experiment until 3, 30, or 60 d after tagging. Standard length at the time of tagging is 
given as the mean with standard deviation in parentheses. 
Tag retention rates (%) Survival rates (%) 
Starting Standard length 
Trial 
Treatment 
no. 
(mm) 
3-day 
30-day 
60-day 
3-day 
30-day 
60-day 
1 
Tagged 
26 
92 (6.8) 
100 
100 
100 
100 
92.3 
92.3 
Untagged 
24 
95 (5.9) 
— 
— 
— 
92.3 
92.3 
— 
Control 
26 
94 (6.4) 
— 
— 
— 
100 
100 
— 
2 
Tagged 
24 
115 (9.7) 
100 
100 
— 
100 
95.8 
— 
Untagged 
24 
117 (9.6) 
— 
— 
— 
100 
100 
— 
3 
Tagged 
76 
62 (8.3) 
98.6 
92.0 
85.4 
98.7 
67.1 
63.1 
Untagged 
76 
59 (8.3) 
— 
— 
— 
100 
93.1 
— 
Control 
75 
59 (8.2) 
— 
— 
— 
100 
81.3 
— 
4 
Tagged 
62 
63 (9.2) 
100 
87.1 
— 
100 
100 
— 
Untagged 
61 
63 (9.2) 
— 
— 
— 
100 
100 
— 
5 
Tagged 
74 
74 (7.8) 
100 
95.8 
95.8 
98.6 
98.6 
98.6 
Untagged 
75 
71 (8.4) 
— 
— 
— 
98.7 
98.7 
— 
Control 
75 
75 (8.7) 
— 
— 
— 
100 
100 
— 
6 
Tagged 
74 
82 (10.1) 
100 
98.6 
— 
100 
97.3 
— 
Untagged 
75 
81 (9.4) 
— 
— 
— 
100 
100 
— 
Overall 
Tagged 

71 (14.5) 
99.8 
95.6 
93.7 
99.6 
91.9 
84.7 
Untagged 
— 
73 (16.6) 
— 
— 
— 
98.5 
97.4 
— 
Control 
— 
72 (17.3) 
— 
— 
— 
100 
93.8 
— 
