• Leanne Rosser

Searching for Sunameri

After 7 months of keeping my feet on dry land in my new home of Osaka, I was in desperate need of some time at sea. So I jumped at the chance to explore Osaka Bay and discover the rare little cetacean that’s been calling the bay home. Finless porpoise, or スナメリ (sunameri) in Japanese, are currently listed as an endangered species. In Japan, they inhabit multiple bays around the country including Tokyo Bay, Ise Bay (Mie prefecture), Seto Inland Sea and areas around Kyushu in the East China Sea. Research on this elusive species in Osaka bay has been carried out by Kaiyukan Osaka Aquarium since 2010 to form a better understanding of these cetaceans and their life in this busy port bay. They have been conducting ‘Sunameri Surveys’, with the help of students and volunteers, to assess population and distribution.


Osaka Bay

There are two species of Finless porpoise, the narrow-ridged and the indo-pacific. Osaka Bay is home to the 2 meter narrow-ridged, who favour the shallow water and sandy sea floor. Due to their small size and non-existent dorsal fin, catching sight of a finless porpoise can be tricky. They are relatively discreet when surfacing, unlike acrobatic oceanic dolphins, often flitting around the surface making it difficult to observe them.


Finless porpoise lecture before the survey


Finless porpoise model

So, after a lecture (in Japanese!) from a local professor and finless porpoise researcher on what to look out for we set sail. The survey boat made its way towards Kansai International Airport, an artificial island airport within the bay and a recently discovered hotspot for finless porpoise. Perhaps one of the reasons for this could be the prohibiting of fishing around the airport, creating a suitable feeding ground for the porpoise. After an hour of searching we stopped to chat with local fishermen to see if they had spotted any.


Beautiful day for a survey

The excitement started as the boat began to slow down, everyone on board perked up and headed to the sides to gaze out at the sea as the captain’s voice drifted through the speaker. That familiar buzz that comes with any cetacean sighting kicked in as my eyes darted across the water, scanning for signs. A distant splash revealed the gleaming back of a porpoise quickly surfacing, followed by two more dark grey mounds. The boat kept it’s distance as we all struggled to capture the moment and staff jotted down the size and structure of the group and any noticeable behaviours. Although photo identification would be a difficult method to use for finless porpoise research, photography is always a useful tool for spotting things the eye can’t see in real time. It’s incredible that this rare species can be seen here and whenever I tell my English students that the cute sunameri they see in aquariums can be spotted in Osaka Bay it always generates waves of surprise.


Finless porpoise in Osaka Bay

The study has so far revealed that these finless porpoise are generally observed alone unless it’s the breeding or calving season. Some larger groups of up to 10 have been spotted feeding together, usually during autumn in Osaka Bay. Investigations also indicate that there is a higher abundance of the species during the spring to early summer months, peaking in April, yet numbers fluctuate every year. During this particular survey day in June, three separate groups of finless porpoise were observed, totalling 10 individuals.


Although further data is needed to establish a more complete picture of the population, spotting calves on a yearly basis is a positive sign but also a clear indicator that this area is important and needs better protection. Just like other cetaceans, the finless porpoise faces many threats such as pollution, a decline in prey, net entanglement, boat traffic and is having to adapt to its ever changing environment. This species is currently recognized as endangered but it would be a terrible shame to let that status reach critical levels, such as happened to the fellow porpoise species, the vaquita, in Mexico. Conservation is a joint effort in which we all must do our part to help and it all starts with awareness and education. Thanks to Kaiyukan for the experience and their continued efforts to better understand this elusive species. Let’s hope their research can inspire people to protect the bay and protect the finless porpoise.

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