Technical Reports of the Ins�tute of Cetacean Research (2021)

pp. 58–63

Technical Report (not peer reviewed)

Stranding record ac�vi�es at the Ins�tute of Cetacean Research
Toshihiro Mogoe*, Mutsuo Goto, Tatsuya Isoda and Hiroyuki Oikawa
Institute of Cetacean Research, 4–5 Toyomi-cho, Chuo-ku, Tokyo 104–0055, Japan*Contact e-mail: mogoe@cetacean.jp

ABSTRACTThe Ins�tute of Cetacean Research (ICR) has been engaged in collec�ng and analyzing cetacean stranding
records along the coast of Japan for a number of years. Stranding records are reported to the ICR voluntarilyby the general public as well as staﬀ from local governments, universi�es, aquariums and museums. In thisdocument, the stranding record ac�vi�es of the ICR are described brieﬂy. A total of 4,275 individual records
involving toothed and baleen whales were made during 1996–2015. Of these, 297 related to baleen whale
species and 3,943 to toothed whale species. In 35 cases the species could not be determined due to insufﬁcient morphological informa�on or evidence from gene�c analysis. When possible, samples and data havebeen collected from stranded cetaceans and used in diﬀerent studies.

INTRODUCTION
Cetaceans can become stranded along the coast line
due to a variety of reasons. They can be stranded alive
or found dead a�er dri�ing to the shore. A mass stranding is deﬁned as two or more individuals (excludingparent-calf pairs) stranded in the same loca�on at thesame �me (Geraci and Lounsbury, 2005). This kind of
stranding is common in a few species of toothed whales
that strand in groups of 15 to 100 or more (Geraci andLounsbury, 2005). There are records of at least 19 species of toothed whales and four species of baleen whales
related to mass stranding events (Mar�n et al., 1990).
While mass stranding is generally rare in baleen whales,
one excep�on is the mass stranding of sei whales that
occurred in the Chilean Central Patagonia region in early2015 (Häussermann et al., 2017).
As a review study by Sergeant (1982) shows, there area variety of possible reasons for stranding. Cetaceans candri� to the shore as a result of natural death. In manycases, calves separate from their parents and become
stranded. In other cases, animals can be stranded due toweakness or diseases. Some of the diseases are causedby virus (Hinshaw et al., 1986; Groch et al., 2020), bacteria (Guzmán-Verri et al., 2012), or parasite infec�ons(Bowater et al., 2003). In addi�on, whales may become
lost due to the inﬂuence of wind, �de, or ocean currents
and become beached or dri� into harbors. In some cases,
whales have been stranded because of man-made causes,
such as entanglement or ship strike. The mass strandingof beaked whales has been related to mid-frequency ac58

�ve sonar (Piantadosi and Thalmann, 2004; Bernaldo deQuirós et al., 2019). Further, some mass stranding events
have been related to the geomagne�c ﬁeld.
Cetacean stranding provides biologists with a wide
range of informa�on. This includes gene�c samples foraddressing taxonomic ques�ons (Wada et al., 2003;
Yamada et al., 2019; Rosel et al., 2021), and biologicalsamples for pathological (Hinshaw et al., 1986; Bowateret al., 2003; Guzmán-Verri et al., 2012) and environmental pollutant studies (Law et al., 2012; Bowater et al.,
2003; Garcia-Cegarra et al., 2021). Also, data and samples
have been used in popula�on studies (Pel�er et al.,2012; 2013). Necropsies provide informa�on to ascertain
possible causes of death. A recent study based on stranding inves�gated microplas�cs inges�on (Burkhardt-Holmand N'Guyen, 2019). Analyses of stranding data allow theassessment of the impact of human ac�vi�es on cetaceans (e.g., ﬁshing gear entanglement, ship strikes, etc.).
In this document, the stranding record ac�vi�es of theIns�tute of Cetacean Research (ICR) are described brieﬂy.

STRANDING RECORD HELD AT THE ICR
NetworkICR has been collec�ng whale stranding records along thecoast of Japan for a number of years. Stranding events
can be reported by volunteers from the general public,
local governments, universi�es, aquariums and museums. There is an established protocol and as well as adata sheet form available for providing stranding informa�on to the ICR.

Stranding record ac�vi�es at the Ins�tute of Cetacean ResearchProtocol for data recording and species iden�ﬁca�onThe objec�ve of this protocol is to facilitate and standardize the collec�on of data and samples from stranded animals. Such samples and data can be useful in understanding the reasons for the stranding as well as being useful indiﬀerent research ac�vi�es. The data sheet in Appendix
1 is a key part of the protocol, and show the basic items
on data and samples to be collected. This form should becompleted for each stranding event. Collec�on of samples are avoided when animals are found alive or when
there are any safety concerns (Ishikawa and Ogino, 2001).
The collec�on of gene�c samples is important because
subsequent gene�c analyses allow the conﬁrma�on ofthe species iden�ty of the stranded animal. Furthermore,such gene�c samples can be added to a larger collec�onof samples at the ICR, contribu�ng to other studies a suchas taxonomy and stock structure of the species involved.

temperature (Figure 1). Other types of samples are kept
in a frozen state.

NUMBER OF STRANDING EVENTS
Between 1996 and 2015 a total of 4,275 cetacean individuals were recorded in the ICR database related to stranding events (Table 1). Most of the cases corresponded totoothed whales.

EXAMPLES OF STRANDING RECORDS
The ﬁrst example is on a large baleen whale foundstranded on 1 April 2003 at Hitachi City, on the Paciﬁccoast of Ibaraki prefecture, Japan (36°39ʹN, 140°42ʹE).
Local authori�es towed the carcass (via sea) to a sandy
shore area within the Kawajiri Harbor, where the whalewas buried. Prior to burial, however, biological research
was conducted by staﬀ of the Ibaraki Prefectural Oarai
Aquarium, Ibaraki Nature Museum, Na�onal Museum

Database
The basic informa�on of stranding events recorded in theform in Appendix 1 is stored electronically in an Excel ﬁle.
When the exact loca�on in terms of la�tude and longitude is not provided, geographic coordinates are assigned
using geocoding from the address submi�ed. Only thecases where the species iden�ty has been conﬁrmed are
added to the Excel ﬁle. The Excel ﬁle is updated annuallyand is upload to the ICR site h�ps://www.icrwhale.org/
zasho2.html (accessed 2021-09-30).
Sample storage
Samples for gene�cs analysis are kept in 99% ethanol ina sealed bo�le that is pre-labeled and stored at room

Figure 1.

Storage samples for gene�cs analysis.

Table 1
Number of stranded cetaceans recorded in the ICR database during 1996–2015.
SuborderFamilyMys�ce� (Baleen whales)

Balaenidae
Balaenopteridae
Eschrich�idae
Unknown 1)

Odontoce� (Toothed whales)

Delphinidae
Kogiidae
Phocoenidae
Physeteridae
Ziphiidae
Unknown 1)

Unknown 1)
1)

EventsIndividuals

Gene�c samples(percentage of individuals)

7
264
4227
264
422

6 (85.7)
115 (43.6)
2 (50.0)
6 (27.3)

577
143
1,763
123
259
235

1,357
156
1,777
139
265
249

86 (6.3)
24 (15.4)
161 (9.1)
27 (19.4)
75 (28.3)
15 (6.0)3535

1 (2.9)The cetacean could not be iden�ﬁed to the family level because extreme decomposi�on and/or lack of gene�c samples.
59Technical Reports of the Ins�tute of Cetacean Research (2021)

of Nature Science and ICR. The procedure followed theprotocol and the Stranding Recording Form (Appendix 1)
was used to take photographs and collect biological �ssue samples (Figure 2).
The whale was morphologically iden�ﬁed as a maleNorth Paciﬁc right whale with a body length of 12.95 m
and body weight of approximately 33,000 kg. Three yearsa�er its burial, the carcass was cleaned, and the skeleton,
together with relevant informa�on, were displayed for
educa�onal purpose at the Ibaraki Prefectural Oarai
Aquarium in January 2006.
The second example is that of a whale found stranded
on 14 May 2015 in a decomposed state in the city of Takahagi (Figure 3). Ibaraki Prefectural Oarai Aquarium inves�gated the carcass and completed the sheet in Appendix
1, which was sent to ICR together with a skin sample forgene�c analysis. The length of the whale was 4.6 m. Due

Figure 2.

Figure 3.

60

to the advanced state of decomposi�on, only subsequent
mitochondrial DNA (mtDNA) analyses were able to iden�fy the animal as a North Paciﬁc common minke whale.
Gene�c analyses on stock structure have been conducted based on gene�c samples from stranded whales.
For example, Pastene et al. (in review) used mtDNA
analyses for inves�ga�ng the stock structure of westernand eastern North Paciﬁc right whales. The westernsamples included a number of stranded whales along theJapanese coast. Results of the analyses were consistent
with the hypothesis that separate popula�ons inhabit theeastern and western North Paciﬁc Ocean respec�vely.
As shown in these cases, gene�c samples from stranded animals make valuable contribu�ons to the gene�canalyses for species iden�ﬁca�on/conﬁrma�on, and tostudies on stock structure.

Inves�ga�on of a stranded North Paciﬁc right whale.

A stranded baleen whale. Subsequent gene�c analyses iden�ﬁed the animal as a North Paciﬁc common
minke whale.

Stranding record ac�vi�es at the Ins�tute of Cetacean Research

ACKNOWLEDGEMENTS
We thank Tsutomu Tamura (ICR) for his comments pertaining to this manuscript. We also express our gra�tude
to those working on stranding records and the contributors of informa�on. Thanks also to Luis A. Pastene (ICR)
for his assistance in preparing this manuscript.

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Technical Reports of the Ins�tute of Cetacean Research (2021)

Appendix 1.

62Stranding record ac�vi�es at the Ins�tute of Cetacean Research63