873 
Short-term retention of coded wire 
and internal anchor tags in 
juvenile common snook, 
Centropomus undecimalis 
Julie E. Wallin 
John M. Ransier 
Sondra Fox 
Robert H. McMichael Jr. 
Florida Marine Research Institute, Florida Department of Environmental Protection 
100 Eighth Avenue SE, St. Petersburg, Florida 33701-5095 
E-mail address (forJ. E Wallin): Wallin_J@sellers. dep.state.fi. us 
Common snook, Centropomus un- 
decimalis, are popular gamefish in 
southern Florida (Bruger and 
Haddad, 1986) and throughout 
their range in the southeastern 
United States and Central America. 
Snook populations in Florida de- 
clined during the 1970’s and 1980’s 
despite increasingly strict limits on 
the fishery (Taylor 1 ). In an effort to 
enhance snook populations, the 
Florida Department of Environ- 
mental Protection has considered 
developing a stocking program to 
supplement depleted wild snook 
stocks. To evaluate a stocking pro- 
gram’s success or impact on native 
populations, hatchery-released fish 
must be marked to distinguish 
them from wild fish. Mark reten- 
tion rates must be known to cor- 
rectly interpret catch records and 
to make inferences about the stock- 
ing program or the wild population 
(Wallin and Van Den Avyle, 1994). 
Coded wire tags (CWT’s) are com- 
mon in fish stocking programs be- 
cause they can be applied quickly 
and economically to small, juvenile 
fish (<100 mm standard length, 
SL). Although retention rates of 
CWT’s vary considerably among 
different species because of mor- 
phological differences (Heidinger 
and Cook, 1988; Szedlmayer and 
Howe, 1995), retention rates are 
generally very good (>95%) if ap- 
propriate tagging tissues are iden- 
tified and used (Dunning et al., 
1990; Pitman and Isaac, 1995). 
A disadvantage with using CWT’s 
is that they cannot be detected by 
recreational or commercial fisher- 
men; therefore, recovery of CWT 
data must be obtained indepen- 
dently. Internal anchor-external 
streamer tags with imprinted infor- 
mation allow recapture information 
to be obtained from recreational or 
commercial fisheries. However, 
these tags are generally restricted 
for use on fish >110 mm SL. As with 
CWT’s, retention rates of these tags 
may vary because of morphological 
differences (Vogelbein and Over- 
street, 1987; Waldman et al. 1990). 
In this study, we evaluated reten- 
tion of CWT’s and two types of in- 
ternal anchor-external streamer 
tags in age-0 common snook. The 
fish sizes in this study were simi- 
lar to sizes that would be produced 
in a large-scale stocking program. 
We also evaluated the effects of tag- 
ging on growth and mortality. Re- 
tention of coded wire tags inserted 
in the cheek musculature was 
evaluated in common snook 60-115 
mm SL for approximately 60 days 
after tagging. Retention of internal 
anchor-external streamer tags with 
disk- or T-style anchors was evalu- 
ated in snook 110-180 mm SL for 
30 days after tagging. The major 
differences between the two types 
of internal anchor tags were the 
shape of the anchor and the size of 
incision needed to apply the tags, 
either of which could affect reten- 
tion or mortality. This study pro- 
vides baseline information on tag 
retention rates in common snook 
that can be used to interpret catch 
records correctly and to evaluate 
common snook stocking programs. 
Methods 
Coded wire tag retention 
We evaluated retention of CWT’s 
and the effects of tagging on growth 
and mortality in 60-115 mm SL 
common snook. Equal numbers of 
fish were randomly assigned to one 
of three treatment groups: 1) 
tagged fish, 2) untagged fish that 
were handled in the same manner 
as tagged fish but were not tagged, 
and 3) control fish that were not 
tagged or handled. The cheek 
muscle was chosen for tag implan- 
tation because of the high CWT re- 
tention rates for this location in red 
drum and striped bass. 
Tagged and untagged snook were 
anesthetized (100 ppm MS-222) 
just prior to treatment. One person 
applied all tags. Tags (1-mm-long, 
0.25-mm-diameter) were injected 
vertically, 2 mm deep into the left 
adductor mandibularis muscle, pos- 
terior to the eye with a Northwest 
Marine Technology (Shaw Island, 
WA) Mark IV tagging machine. 
1 Taylor, R. 1997. Florida Marine Res. 
Inst., Florida Dep. of Environmental Pro- 
tection, 100 Eighth Ave. SE, St. Peters- 
burg, FL 33701-5095. Personal commun. 
Manuscript accepted 21 March 1997. 
Fishery Bulletin 95:873-878 (1997). 
