Application of different external tagging methods to "Octopus vulgaris" Cuvier, 1797, with special reference to T-bar anchor tags and Petersen disks

Abstract

This paper presents a study on the persistence and effects caused by a wide variety of types of tag (loops, rabbit tags, girths, flexible plastic bands, small darts, Petersen disks, T-bar anchor tags, circular plastic tags, rectangular plastic flags, jewellery pins, commercial badges, and burning with liquid nitrogen) applied to the cephalopod Octopus vulgaris Cuvier, 1797, under culture conditions. Preliminary analysis of the results obtained with the different tagging systems indicates that Petersen disks and T-bar anchor tags are the most suitable types. Both provide adequate retention after 1 month (90 % and 80 %, respectively), a maximum persistence of three months, a similar cost, and they are easily recognised externally. However, Petersen disks can produce serious injuries, and require a more laborious insertion process. Therefore, in the final analysis, the insertion of T-bar anchor tags in left arm III can be considered the most appropriate system.

Full text

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Bol. Inst. Esp. Oceanogr. 22 (1-4). 2006: 3-11 BOLETÍN. INSTITUTO ESPAÑOL DE OCEANOGRAFÍA
ISSN: 0074-0195
© Instituto Español de Oceanografía, 2006
Application of different external tagging methods
to Octopus vulgaris Cuvier, 1797, with special
reference to T-bar anchor tags and Petersen disks
L. Fuentes, J. J. Otero, C. Moxica, F. J. Sánchez and J. Iglesias
Centro Oceanográfico de Vigo, Instituto Español de Oceanografía, Apdo. 1552, E-36200 Vigo, Pontevedra, Spain.
E-mails: lidia.fuentes@vi.ieo.es; jjose.otero@vi.ieo.es; covimoxica@inicia.es; javier.sanchez@vi.ieo.es; jose.iglesias@vi.ieo.es
Received November 2003. Accepted May 2005.
ABSTRACT
This paper presents a study on the persistence and effects caused by a wide variety of types of
tag (loops, rabbit tags, girths, flexible plastic bands, small darts, Petersen disks, T-bar anchor tags,
circular plastic tags, rectangular plastic flags, jewellery pins, commercial badges, and burning
with liquid nitrogen) applied to the cephalopod Octopus vulgaris Cuvier, 1797, under culture
conditions. Preliminary analysis of the results obtained with the different tagging systems indi-
cates that Petersen disks and T-bar anchor tags are the most suitable types. Both provide adequate
retention after 1 month (90 % and 80 %, respectively), a maximum persistence of three months,
a similar cost, and they are easily recognised externally. However, Petersen disks can produce se-
rious injuries, and require a more laborious insertion process. Therefore, in the final analysis, the
insertion of T-bar anchor tags in left arm III can be considered the most appropriate system.
Keywords: Octopus vulgaris, tagging, T-bar anchor tags, Petersen disks.
RESUMEN
Aplicación de diferentes métodos de marcado externo a Octopus vulgaris Cuvier, 1797 con referencia
especial a las marcas de tipo T y a los discos de Petersen
En este trabajo se presentan datos de persistencia y efectos provocados por una gran variedad de estilos de
marcas (loops, marcas de conejos, cinchas, cintas plásticas flexibles, lancetas, discos de Petersen, marcas de
tipo T, marcas plásticas circulares, banderillas plásticas rectangulares, soportes de bisutería, pines comerciales
y quemaduras con nitrógeno líquido) aplicadas al cefalópodo Octopus vulgaris Cuvier, 1797 sometido a
condiciones de cultivo. Tras una primera revisión de los resultados obtenidos con los diferentes sistemas de
marcado se concluye que los discos de Petersen y las marcas de tipo T son los más aconsejables. Ambos mues-
tran una retención adecuada después de un mes (90 y 80 % respectivamente), una persistencia máxima de
tres meses, un coste similar y ambos son detectados externamente con facilidad. Sin embargo, los discos de
Petersen producen heridas considerables y requieren un proceso de inserción más laborioso, por lo que, final-
mente, el sistema considerado más adecuado fue la inserción de marcas de tipo T en el brazo III izquierdo.
Palabras clave: Octopus vulgaris, marcado, marcas de tipo T, discos de Petersen.

INTRODUCTION
The experiments described in this article took
place within the research project titled ‘Tagging
and release of Octopus vulgaris Cuvier, 1797, paralar-
vae and juveniles’ (CYTMAR 97-0323) and were de-
veloped at the Instituto Español de Oceanografía
(IEO) in Vigo (northwest Spain). The main goal of
this project was to determine the most efficient tag-
ging systems for O. vulgaris paralarvae and juveniles.
The first phase, on efficient internal tagging for par-
alarvae, has been described by the authors in a pre-
vious article (Fuentes, Iglesias and Moxica, 2000),
where a chemical tagging method for statoliths with
alizarin complexone was used. The present paper
focuses on experiments performed using external
tagging in octopus sub-adults, in order to deter-
mine the most efficient tagging technique.
There is considerable literature on finfish tagging
(e.g., Nielsen, 1992; Sánchez-Lamadrid, 2001), but
there are far less publications related to
cephalopods, and more specifically, to the common
octopus O. vulgaris. Especially noteworthy is the
compilation made by Nagasawa, Takayagani and
Takami (1993), presenting data published in Japan
between 1927 and 1990 on 14 cephalopod species.
Cephalopod tagging has also been indirectly ad-
dressed in other publications, such as Sakurai et al.
(1993) and Gonçalves et al. (1995), who worked with
Todarodes pacificus (Steenstrup, 1880) and Loligo
forbesi (Steenstrup, 1856) respectively. Taki (1941),
Inoue, Hamaguchi and Li (1953), Katayama and
Morita (1960) showed the difficulties inherent in
tagging O. vulgaris since, despite having used metal
plaques, heat burning, wires and different colorants
(methylene blue, neutral red, trypan blue, erythro-
sine, saffranine) on the skin or injected in the mus-
cle, they failed to obtain satisfactory results.
Domain, Jouffre and Caverivière (2000) compared
O. vulgaris growth in tanks with marked wild indi-
viduals in Senegalese waters using Petersen disks.
In this article, a detailed description is given of
the steps followed to select the most efficient tag-
ging method, as well as the most suitable body area
to tag on O. vulgaris.
MATERIALS AND METHODS
Capture and acclimatisation of juveniles
Octopus specimens weighing between 0.5 and 1
kg were caught in the Ría de Vigo between 1998
and 2001 by small local fishing boats. They were
transferred to IEO facilities in 200 l tanks with prop-
erly oxygenated seawater. Before beginning the tag-
ging experiments, the specimens were acclimatised
to captivity for one week, following the recommen-
dations on water circuit, type of tank, characteristics
of den, etc., given by Iglesias et al. (1999). The food
given consisted basically of frozen crabs Carcinus
maenas L., 1758 although sporadically the diet was
complemented with fish, mainly Micromesistius
poutassou (Risso, 1826) and mussels Mytilus sp.
Types of external tag and their placement
During the first two years (1998 and 1999) a
wide range of tags were tested: injected acrylic
paint and cold burning with liquid nitrogen, plastic
tags (loops, girths, small darts, flexible plastic
bands, badges, earrings or jewellery pins, rabbit
tags and Petersen disks) and those inserted with a
gun (T-type anchor tags or Corplus®circular and
rectangular ones). Following is a brief description
of each one (some of them are showed in figure 1).
• Loops (Hallprint®, ‘Self-locking loop tags’ se-
ries SLA). The ends of this 5" (118.5 mm) plas-
tic cord join in a mechanism which prevents
tag loss. These were manually placed in the
mantle and arm.
• Metal rabbit tags (Hauptner®). A rectangular
numbered plaque (10 mm by 5 mm) with
pointed prongs on the base which pierce the
structure to be tagged –in our case, the man-
tle– and once inside are bent into place.
• Small commercial plastic girths, length 100
mm which were fixed round the arms and in
the external end of the mantle.
• Flexible plastic bands (Hallprint®‘Polyethylene
streamer tags’, series PST), especially designed
for crustaceans (shrimps, crabs, small lobster,
etc.). The band pierces the structure to be
tagged (mantle) drawn by a needle, which is
later withdrawn. The two ends of the bands
are free whilst the middle part goes through
the structure to be tagged.
• Darts (Hallprint®, ‘Small plastic tipped dart
tags’ series PD). They have a hook-like point
and are inserted by being placed into a thin
tube with a sharp end, which is introduced in-
to the area to be tagged (arms) and then slow-
L. Fuentes et al. External tagging of Octopus vulgaris
Bol. Inst. Esp. Oceanogr. 22 (1-4). 2006: 3-11
4

is inserted into the animal’s body and the
longer bar (35 mm) bears an inscription,
which includes the tag number, address and
telephone. This tag is inserted using a tagging
gun designed by the same company.
• Circular plastic tags (Insvet Corplus®). A sys-
tem similar to Petersen disks; that is, two
plaques of approximately 20 mm diameter,
joined by an element which pierces the body
structure (mantle), but in this case, the pin is
replaced by a larger diameter element. These
tags are inserted with a specific applicator.
• Rectangular plastic tags (Corplus®), a tagging
system similar to the previous one, but with
L. Fuentes et al. External tagging of Octopus vulgaris
Bol. Inst. Esp. Oceanogr. 22 (1-4). 2006: 3-11 5
Figure 1. Different kinds of tags used in the
present study
Loops Metal rabbit tags
Flexible plastic bands Darts
Petersen disks T-bar anchor tags
Circular plastic tags Rectangular plastic tags
ly withdrawn, making sure that the point of
the dart is anchored.
• Petersen disks (Floy Tag & MGF. CO., INC.).
The 9/16" (13.3 mm) diameter disks with a cen-
tral hole are made of vinyl protected against UV;
the nickel pins measure 3" (11.1 mm). The sys-
tem consists of two disks joined by a pin which
can pierce any part of the body. The inscription
on this type of tag is on the surface of one of the
disks and their insertion, unlike the T-bar an-
chor tags is, completely manual.
• T-bar anchor tags (Hallprint®‘T-bar anchor
tags’, series TBF-2 fine) are pieces of flexible T-
shaped plastic. The short bar of the T (8 mm)

the difference that the plaques are rectangu-
lar (approx. 30 mm 10 mm). Their inser-
tion also requires an applicator from the same
firm.
• Nitrogen burns were produced by pressing the
animal’s skin with rods previously submerged
in liquid nitrogen. The numbers on the end of
the rods are then tattooed on the octopus
mantle.
• Others. Other systems were tested such as, ear-
ring bases, commercial badges on the edge of
the mantle, and even subcutaneous injection
with acrylic paint in the arms and mantle.
Most of these (loops, rabbit tags, flexible plastic
girths, darts, Petersen disks and T-bar anchor tags)
carry an inscription which makes individual track-
ing possible.
To select the most appropriate tagging place, in-
sertions were made in the mantle and the arms. An
experiment was also carried out to determine
which arm was the most suitable for use with this
type of tags, so tests were made in triplicate on left
arms I, II, III and IV.
Preliminary experiments
Throughout 1998 and 1999, numerous tests
were carried out, which made it possible to evalu-
ate the degree of retention rate in a wide range of
external tags on the species O. vulgaris. All these ex-
periments took place in 1 m3tanks in an open wa-
ter circuit using 10 specimens per test, and had a
duration of 1 month. The tags were those cited in
the previous methodology section. In each experi-
ment, calculations were made regarding degree of
retention, injuries produced, and maximum persis-
tence, so that at the end of this process, it was pos-
sible to select the most suitable tag.
Comparison between T-bar anchor tags
and Petersen disks
From the preliminary experiments, the conclu-
sion reached was that the most persistent tags were
the T-bar anchor tag and the Petersen disks.
Consequently, in 2000-2001, more exhaustive tests
were carried out, with the aim of determining the
efficiency of each one and finding out which was
the most effective placement.
Before comparing Petersen disks and T-bar an-
chor tags, another experiment had been designed
to select the most suitable arm for tagging, in
which 12 octopi were tagged, three replicates each
for the I, II, III and IV left arms with Petersen disks
in individual 100 l tanks. Right arms were not test-
ed so as not to interfere so as to not interfere with
the male reproductive function (as is known, the
third right arm, or hectocotylus, is used by males to
copulate). This experiment lasted 1 month, and
the number of injuries and lost tags were moni-
tored weekly.
To compare Petersen disks and T-bar, the follow-
ing methodology was used.
To avoid the octopi becoming hyperactive dur-
ing the tagging process, they were anaesthetised by
immersion for 5 minutes in cold seawater (4-5 ºC),
to which a few drops of ethyl alcohol had been
added.
The tests were carried out with 2 replicates for
each type of mark, both in the mantle and in left
arm III. The experiments had a duration of 1
month and were kept in 2 000 l capacity tanks with
10 specimens in each, so a total of 80 specimens
were tagged. Weekly, for the period of 1 month, a
control was carried out, recording the weight of
specimens in each experiment, the number of lost
tags and any other kind of observation related to
tag evolution (correct fixing, appearance of rele-
vant injuries, etc.). Finally the possible effect of the
marking procedure on growth was analysed in both
types of tags.
RESULTS
Preliminary experiments
Concerning the different types of marks utilised,
it was observed from the first-year results that most
of the marks were lost in the first two weeks of the
experiments, confirming the difficulty of tagging
cephalopods. A brief summary of these results ob-
tained for each system are presented in figure 2.
None of the loops lasted more than 9 days. The cir-
cular plastic tags (Insvet Corplus®) lasted between
4 and 14 days; only one of them reached 27 days.
Only one of the metal rabbit tags remained 6 days
joined to the octopus. The octopi freed themselves
from the girths very easily, and when this was not
L. Fuentes et al. External tagging of Octopus vulgaris
Bol. Inst. Esp. Oceanogr. 22 (1-4). 2006: 3-11
6

the case, they caused considerable injuries where
they had been placed. The majority of the badges
became unpinned on the same day that they were
inserted; one lasted 10 days. The jewellery bases
did not survive long, except in one specific case,
which lasted 42 days. The paint disappeared almost
immediately, leaving no trace. After a month, only
37 % liquid nitrogen burns were visible, but their
numbers were unreadable; the lack of firmness and
scant consistency of octopus muscle, coupled with
its capacity for regeneration, make tag retention
difficult.
On the other hand, the results of those experi-
ments carried out with T-bar (anchor) tags were
most satisfactory, recording a retention rate of 77%
after a month (figure 2), and a maximum persis-
tence time of 89 days (data recorded after the 1-
month experiment). In the case of the Petersen
disks, a similar retention rate (62 %) was obtained
after a month, compared with the T-bar tags, but
wounds soon appeared in the insertion area when
Petersen disks were used.
From these results, it was concluded that among
all the different types of tags used, the most suit-
able were Petersen disks and T-bar anchor tags.
The study was therefore oriented towards a more
detailed comparison between these two types.
Comparative study between Petersen
disks and T-bar anchor tags
Evaluation of the most suitable arm
From the 12 individuals marked in left arms I, II,
III and IV, only one specimen, specifically one
tagged on left arm II, lost its tag before a month
had elapsed (figure 3). As the results showed no
preference among treatments and retention per-
centages were similar, left arm III was chosen for fu-
ture experiments.
Marking effect on growth
Figure 4 shows the mean wet weight observed in
the 1-month period of growth for the individuals
marked with T-bar and Petersen disk tags. Initial
mean weights were 846.5 g for T-bar and 843.6 g for
the Petersen disk, reaching final weights of 1 157.9
g and 1 000.3 g, respectively. Growth in weight was
adjusted to the following exponential equations:
T-bar: y 865.49 e0.0384x; R20.8897
Petersen disk: y 849.35 e0.0773x; R20.9867
No significant difference in growth was found
between the two groups (

0.05), indicating that
L. Fuentes et al. External tagging of Octopus vulgaris
Bol. Inst. Esp. Oceanogr. 22 (1-4). 2006: 3-11 7
0
20
40
60
80
100
120
0 7 14 21 28
P e rsist e nce (day s)
Re te ntio n r a te ( % )
Lo o p s
Nitr o g en
T- b a r
C i rcu l ar In s v et
Re c t a ngul a r C.
Rab b it/Gir th s/Ear r i n g /
Pa i n t
Ba dg e s
Pe t e r s e n di s k
Figure 2. Retention rate (%) for each type of mark from preliminary experiments (1 month long)

DISCUSSION
In this work the great difficulty in tagging
cephalopods when compared with fish tagging has
been confirmed. Considerable differences exist be-
tween the viability of same tagging technique being
used with fish and cephalopods. O. vulgaris muscle is
less firm than that of fish, and therefore tag anchor-
ing is less safe and reliable; nor do cephalopods have
no hard structures, such as a backbone, on which to
thread the tags. At the same time, the great agility in-
herent to octopi, along with the whole range of
movements they can make with their arms, play a de-
cisive part against any tagging system, since these
characteristics enable them to remove their own tags
or those of others. All of these factors have compli-
cated considerably the choice of a suitable tag for
these animals.
The retention rate and effects on the tagged
specimen with regard to survival, injuries and
growth, along with difficulties related to applica-
tion processes and tag detection, are fundamental
L. Fuentes et al. External tagging of Octopus vulgaris
Bol. Inst. Esp. Oceanogr. 22 (1-4). 2006: 3-11
8
0
1
2
3
4
0 da y s 7 da y s 14 da y s 21 da y s 28 da y s
T i m e afte r tag g i n g (d ays)
Oc t opus wi t h di s k s
Ar m I
Ar m I I
A r m III
Ar m I V
Figure 3. Persistence (days) of the tags
placed in different arms (right arms I, II, III
and IV)
there was no negative effect of the marking proce-
dure on growth.
Persistence obtained in both types of tags
In figure 5, it can be seen that inserting the tag
in the arm was more effective than in the mantle,
both with Petersen disks and T-bar anchor tags. Of
those markers inserted in the mantle, only one of
the 10 disks reached day 28 of the experiment, and
all the T-tags were lost during the first week.
Regarding the comparison between the disks
and the T-tags using left arm III as a site, average
values of 80 % T-tags and 90% disks remained in
place for the 4 weeks of the test (figure 5). Both
marks presented a maximum persistence of more
than 3 months (data recorded after the 1-month
experiment). However, it is necessary to point out
that disks caused cuts and other injuries in the in-
sertion area after the first week of the experi-
ment.
Petersen disk:
y = 865.49 e0.0384x
R
2
= 0.8897
T-bar:
y = 849.35 e0.0773x
R
2
= 0.9867
0
200
400
600
800
1000
1200
1400
012345
Time after marking (weeks)
W e g i e w t h t g ( )
Average Disk-Arm A-B
Average T-Arm A-B
Figure 4. Growth in mean wet weight (g)
from individuals marked with Petersen
disks and T-bar anchor tags during
1 month

Petersen discs on left arm III
0
2
4
6
8
10
0 5 10 15 20 25 30
Petersen disks on mantle
0
2
4
6
8
10
0 5 10 15 20 25 30
T-bar anchor tags on left arm III
0
2
4
6
8
10
0 5 10 15 20 25 30
T-bar anchor tags on mantle
0
2
4
6
8
10
0 5 10 15 20 25 30
o n : Y i f o . n d i d i v u a s l h t i w ag t
X: time after tagging (days)
issues to consider when a tagging system is to be
chosen for enhancement programmes (Collins,
Smith and Heyward, 1994). Each of these aspects
was analysed for the tags used in this experiment.
Regarding retention rate from preliminary experi-
ments, we had to reject such systems as acrylic paint
injections, plastic girths, metal rabbit tags, com-
mercial badges, liquid nitrogen burns, and loops.
The maximum persistence for earring bases, circu-
lar plastic tags (Insvet) and rectangular flags
(Corplus®) was approximately 30 days, but only a
very low percentage of these actually lasted that
long. In addition, the last two types of tags men-
tioned caused considerable injuries. Subsequently,
only the Petersen disks and the T-bar anchor tags
passed this first screening.
Several authors have already dealt with the sub-
ject of tagging O. vulgaris. Most of these works are
by Japanese authors and almost none are recent.
Taki (1941) compared the permanence of several
types of tags and marks to identify O. vulgaris indi-
L. Fuentes et al. External tagging of Octopus vulgaris
Bol. Inst. Esp. Oceanogr. 22 (1-4). 2006: 3-11 9
viduals kept in aquariums. The tags evaluated were
pieces of sewn material, metal plaques, removal of a
sucker, and dyeing techniques using trypan blue on
the dorsal part of the mantle. He observed that the
first two systems were easily removed by the animals;
the excision of a sucker was only valid during the
two months of regeneration, and that trypan blue
produced stains which were visible up to six months
after application. Inoue, Hamaguchi and Li (1953)
maintained that burning is effective for O. vulgaris,
and attained a 90-day persistence. Regarding this
particular tagging system, Katayama and Morita
(1960) suggested that the best place for its applica-
tion is the posterior end of the mantle, because
there it is easily and does not change its shape.
However, we observed poor retention rates for cold
burning. Itami (1964) also showed that 35.7% of
the animals tagged in this way died from the effects,
but these were particularly small specimens.
Takeda et al. (1981) again used trypan blue and
detected marks a month after tagging. These same
Figure 5. Persistence obtained in a comparative study between Petersen disks and T-bar anchor tags. Replica 1: ; repli-
ca 2:

authors showed that wires used to pierce the man-
tle or the umbrella were pulled out by the octopi,
in most cases in less than 20 days. This fact is agree-
ment with the results of this paper, which clearly
stated that better retention rates were obtained
when octopi were marked in the arm rather than in
the mantle.
Studies carried out more recently by Tsuchiya,
Ikeda and Shimizu (1986) examined the effective-
ness of a wide range of tags (anchor tag, dart tag,
Petersen disks, fingerling tag, metal ring and nylon
thread) and dyes (methylene blue, neutral red, ery-
throsine and saffranine T). They showed that in
general, tags (external marks) were not effective,
some of them being removed by the arms and oth-
ers becoming loosened by the injuries caused by
the tagging process. On the other hand, the meth-
ylene blue and neutral red intramuscular injec-
tions under skin of the mantle to form 1-2 cm di-
ameter stains, were successful insofar as persistence
was concerned, and hardly affected the tagged ani-
mals. This method of individual recognition using
dyes could be viable at an experimental level, but it
does not permit individual identification of tagged
specimens when the intention is to use a tag recog-
nisable to fisherman in an enhancement pro-
gramme.
In this work, Petersen disks and T-bar anchor tag
were the only methods that passed the first screen-
ing and provided adequate retention after 1 month
(90 % and 80 %, respectively). Both had a maxi-
mum persistence of three months and a similar
cost; moreover, they are easily recognised external-
ly. Domain, Jouffre and Caverivière (2000) also
used Petersen disks in growth studies, and they ob-
tained promising persistence values (up to 177
days). It must be remembered, however, that the
disks require a laborious manual insertion process,
and that the cuts and other injuries produced can
be very serious and increase mortality.
Consequently, we recommended the use of a T-
bar anchor tag inserted in left arm III to carry out
short-term studies (1-3 months) on the biology and
distribution of O. vulgaris juveniles in their natural
environment.
ACKNOWLEDGEMENTS
This work has been carried out with a grant from
the Inter-ministerial Commission for Science and
Technology and the Instituto Español de
Oceanografía, as part of the CYTMAR 97-0323 pro-
ject.
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