629 
Mark retention and growth of 
jet-injected juvenile marine fish 
John F. Thedinga* 
Adam Moles 
Jeffrey T. Fujioka 
Auke Bay Laboratory, Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
1 1305 Glacier Highway, Juneau, Alaska 99801-8626 
*E-mail address: John.Thedinga@noaa.gov 
The type of mark or tag used for a 
particular study depends on the 
objectives of the study. Retention 
and recognition of a mark are criti- 
cal to the success and reliability of 
a study. External tags have been 
the most common fish tags used 
(McFarlane et al., 1990), but they 
may affect survival, behavior, and 
growth of fish (Andersen and Bagge, 
1963; McFarlane and Beamish, 
1990). Each tag type has limita- 
tions and capabilities, but ideally 
external tags should be easily and 
rapidly applied to many fish, be 
inexpensive, easily identified, not 
easily lost or entangled, and not be 
stressful enough to alter fish sur- 
vival, behavior, or growth. Studies 
that require such characteristics, 
therefore, are restricted in the type 
of tag that can be used and thus 
must rely on internal marks or dyes 
to identify fish. Identification of 
internal marks, however, generally 
requires that fish be killed, thus 
eliminating any possibility of re- 
peated measurements of individual 
fish. Choice of mark is further re- 
stricted when marking juveniles 
that are of small size and that ex- 
hibit rapid growth. 
Jet injection is a method of ap- 
plying external marks to fish (Hart 
and Pitcher, 1969) that is relatively 
fast and can apply a variety of col- 
ors for either batch or individual 
marking. Jet injection does not af- 
fect survival or growth of juvenile 
salmonids in the laboratory (Cane, 
1981; Herbinger et al., 1990; The- 
dinga and Johnson, 1995) but may 
contribute to increased mortality in 
field situations (Thedinga et al., 
1994). Injection by Panjet has been 
used primarily on freshwater fish 
species (Hart and Pitcher, 1969) in 
addition to salmonids (Cane, 1981; 
Pauley and Troutt, 1988; Laufle et 
al., 1990). Juvenile flatfish have 
been marked with needle-injected 
latex (Riley, 1966) as well as by 
freeze branding (Dando and Ling, 
1980), but not by jet injection. To 
our knowledge, juvenile sablefish 
have been marked only with Floy 
anchor tags (Rutecki and Meyers, 
1992). Our objectives were to evalu- 
ate retention of jet-injected marks 
and their effect on growth of four 
marine fish species, as well as their 
effect on the tissue structure of 
three marine species held in the 
laboratory. 
Methods 
We tested the retention of jet-in- 
jected marks and effects of marks 
on growth of four species of marine 
fish and histological effects on three 
species of marine flatfish. We in- 
jected two substances into juvenile 
sablefish, Anoplopoma fimbria, and 
one substance into juvenile yellow- 
fin sole, Pleuronectes asper, rock 
sole, Pleuronectes bilineatus, and 
Pacific halibut, Hippoglossus sten- 
olepis. Sablefish were captured by 
hand-jigging in St. John Baptist 
Bay near Sitka, Alaska, September 
1993 (Rutecki and Meyers, 1992). 
Sole were captured by beach sein- 
ing in Auke Bay, Alaska, May to 
July 1994, and halibut were col- 
lected by trawling in Sitkinak 
Strait and Ugak Bay near Kodiak 
Island, Alaska, August 1994. 
A total of 28 sablefish and 30 flat- 
fish were injected with a Panjet in 
1993-94. Sablefish were marked 
with alcian blue dye (65 mg/mL 
aqueous solution) and fluorescent 
orange acrylic paint (Liquitex, 50% 
aqueous solution); 10 of each flat- 
fish species were marked with 
alcian blue dye. All sablefish were 
marked on the abdomen between 
the pelvic fins (Fig. 1). Flatfish, 
however, were marked with indi- 
vidual identifying marks on the 
ventral surface at one to four loca- 
tions along the lateral margin and 
on the caudal peduncle (Fig. 2); 12 
sablefish and 10 of each flatfish spe- 
cies were left unmarked as controls. 
The Panjet was held about 25 
mm from the fish’s skin during 
marking. Sablefish were anesthe- 
tized with tricaine methanesul- 
fonate ( MS-222 ) before marking but 
flatfish were not. After marking, 
excess dye or paint was rinsed off 
with water to check mark quality. 
If a mark was good, the fish was 
put in a recovery tank; if poor, the 
fish was remarked. 
Sablefish and flatfish were held 
in different environments. After 
being marked, sablefish were held 
in 600-L flow-through tanks for 238 
days. Because of space restrictions, 
blue-marked and control fish were 
held in one tank, but each group 
was kept in separate compart- 
ments. Orange-marked fish were 
held in another tank but died pre- 
maturely in a laboratory accident 
Manuscript accepted 7 January 1997. 
Fishery Bulletin 95:629-633 (1997) 
