PRELIMINARY EXPERIMENTS FOR
DOLPHIN MARKINGMASAHARU NISHIWAKI*MASAYUKI NAKAJIMA** AND TERVO TOBAYAMA***INTRODUCTION

For the purpose of getting biological data on the stock oflarge whales, whale marking
has been done for past 30 years. However, nothing has been done on the small
toothed whales. There has been no demand for scientific investigations on thesewhales because they have little industrial value.
In Europe, these whales, mainly the common porpoise (Phocaena phocoena), hadbeen caught and utilized in the past. The oil had been used for lamplight, andthe oil and the meat had been used for human consumption. Now only in theBlack Sea area, they are still caught and utilized. In the other European countries,
none of the small toothed whales are harvested.
In Japan, exceptionally large numbers of small toothed whales are taken annually. Over 20,000, primarily the blue white dolphin and the Dall's and True'sporpoise, are harvested each year for human consumption.
The actual migration routes of these small whales are poorly known. It isknown that the during October through December groups of the blue white dolphin(Stenella caeruleo-alba) migrate from the north east coast of Japan to the east coast of
the Izu Peninsula where thousands are caught by means of the driving method.
During May through July, thousand of this species are also taken on the west coastof the Izu Peninsula.
Heedless of the scientists' warnings that the stocks of this species may soon bedepleted, the fishermen year after year continue to capture all ages of these dolphins
including the very young. If the stock of these to be maintained, problems concerning their biology must be investigated. It is of primary importance to determine
where these animals go and by what routes, once they leave the Izu shores. Occasionally this species is caught or stranded on the west coast of the United States.
It is unknown if these are close relatives of those from the Japanese side.
Briefly, a marking program is essential to determine migration routes and toestimate the size of the stock from which the harvest is being made.
Dall's porpoise (Phocaenoides dalli) occurs on both the coasts of Japan andWestern United States. True's porpoise (Phocaenoides truei) seems to occur only inlimited waters of the Japanese side. The migration routes of both these forms arecompletely unknown and therefore should be studied.
In order to investigate the above problems, it is necessary to accumulate biological data based on the results of marking. Before doing the actual marking, the* Ocean Research Institute, University of Tokyo* * Enoshima Marineland** * I to Aquarium
Contribution No. 72, from The Ocean Research Institute, University of Tokyo.
101

102M.i¥"ISHIWAKI,M. NAKAJI
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METHODOFEXPERIMENT
Thenecessit
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958.diedon5Jan.1960).

PRELIMINARY EXPERIMENTS FOR DOLPHIN MARKING

103

the Risso's dolphins (Grampus griseus) and the Pacific bottle-nosed dolphins (Tursiopsgilli) have been marked for identification prior to exhibition at the Marineland.
The marks were made of copper wire 0.5 mm in diameter and covered with a vinyl
tube 1 mm in diameter. Tubes of several different colors were used. An individual
would be marked with one or two tubes. Also the tubes were tied by various methods by which means the animals were disCTiminated.
The species and numbers of these dolphins are as follows :1. In the 65 dolphins consisting of above four species, the lines were tiedaround the base of their tail flukes. (Fig. 1 right)
2. With 13 bottle-nosed dolphins a tiny incision was made with an awl in
the edge of the dorsal fin and the lines were tied through it. (Fig. 1 left)
When the lines were tied around the tail, nearly all of them were dropped
within a month or two. Exceptional cases were the 2 Pacific white sided dolphins
which retained lines for 7 months and the one Pacific bottle-nosed dolphin whichretained one for almost one year.
In the other cases, lines were tied through an incision in the dorsal fin. Theselines lasted longer ; dolphins retained them for 3 or 4 months. The longest period
was when a bottle-nosed dolphin retained the mark for one year and eight months.
Consideration of the causes of mark failures suggests that the copper line with
its vinyl covering was too thin to be long maintained by such delicate skinned animals without doing considerable injury. The skin suffered more serious injury
than did the dorsal fin. Abrasions of the skin were usually evident within a monthafter marking. When a mark is placed in the dorsal fin a little bleeding occurs
when the incision is made. A scar results at this site. The strong up and down
swimming movements of the tail flukes usually cause any lines placed on the tailto saw or cut into that member resulting in injury to that animal.

Tuna tagging method
This method is to use the same type tag as is used for tuna marking. This isa desirable type in that a number, the place to be returned etc. can be placed on
the nylon tube as shown in Fig. 2. On one end of the tube is a nylon hook which
is used to attach the tube to the animal. These tubes were 23.5 cm long and 3 mmin diameter. The hooks were inserted into the muscle of the animal by the use of a
sharp needlelike stainless steel tube as commonly used in tuna tagging. The objectof this experiment was to determine the most suitable portions of the body in whichto place this type mark.
This type mark was placed on the dolphins used in this experiment immediately
prior to their release in the Ito Aquarium. The dolphins were divided by species.
Six rough toothed dolphins (Steno bredanensis) and four bottle nosed dolphins wereplaced in separate tanks which were each 15 m by 5 m long and 1.5 m deep.
The results of the marking are shown in Table 1.
Above experiment was done over a rather short period ; therefore the results
are not conclusive but the following facts were presumed. That is, if the marks
were placed into the front portions of the body, they were soon losted. Marks

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PRELIMINARY EXPERIMENTS FORDOLPHIN MARKJNG

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106

釦f. :¥ISHIWAKI, M.NAKAJIM
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PRELIMINARY EXPERIMENTS FOR DOLPHIN MARKING

107

are as follows; Metal bands such as used in the tagging of fur seals are a possibility.
Finding a suitable location for the placement of such a tag will require jnvestigation.
Branding both by heat or extreme cold may also provide a means by which thesmaller cetaceans and other marine mammals might be marked.
ACKNOWLEDGEMENT

Acknowledgment is made of the partial financial support of this investigation througha grant from the Japan Society for the Promotion of Science as part of the JapanU .S. Cooperative Science Program.
The authors are indebted to Mr. David W. Waller of the U.S. Fish and·wildlife Service, Fishery-Oceanography Center, Tuna Resources Laboratory, La
Jolla, California, for his kind cooperation to use the tuna tags, and thanks arealso due to the management stuffs of the Enoshima Marineland and the Ito
Aquarium for their effective cooperation.