• Leanne Rosser

Observations: Mutsu Bay Dolphin Season 2020

It's been three months since my husband and I moved our life from the bustling city of Osaka to the tiny coastal town of Kawauchi, Aomori. After living in a museum for the first month before finding our own place, we have settled into a routine of country life. Whether it's the frankly startling town announcements warning of a bear who has just strolled in or the jingles that play three times daily through the town's loudspeakers, it feels like Osaka is a million miles away.

The job started out in the peak of the Pacific white-sided dolphin season, which is every May - June, so we tried to get out on the boat as much as the weather would allow. This turned out to be 11 times in June, however on two occasions we were unable to locate any dolphins. Nevertheless, we saw some very interesting things this season, including the largest feeding gathering I've ever witnessed of around 200 dolphins, as well as a chance minke whale encounter. Each day at sea always brings something new and exciting, you never know what you're going to see. On a number of surveys we found ourselves surrounded by hundreds of dolphins either travelling or feeding together. On one such occasion the group was so large it passed by our boat for over an hour. On another survey, another large group escorted our boat at a speed of 10kmph for 40 minutes, as some individuals delighted us with bowriding, often rolling over on their side to meet our gaze.



We witnessed the playful groups of juveniles developing their social skills right in front of our boat, displaying multiple 'triple-jumps' where three dolphins acrobatically leap in synchrony. We were joined a couple of times by a drone crew. Studying dolphins from above is a really fascinating way to decipher their behaviour and is something Mutsu Bay Dolphin Research is currently doing to better understand their feeding behaviour. The surveys also sadly revealed the continued presence of anthropogenic threats from plastic pollution to injuries caused by boats and entanglements. On one lively, sunny survey day a juvenile dolphin leaped into the air and as I managed to quickly get a shot I noticed something bright blue. The photo later revealed the individual had a piece of blue vinyl tape wrapped tightly around its pectoral fin with a fresh wound above where the tape was digging into the skin. An important reminder of why it's important to consciously think about our actions and the impact we have on the planet.

After the last of the dolphins had left the area and travelled up to Hokkaido our surveys sadly came to an end and the hard work began. Now that the fun of our boat based surveys had finished, I had to begin data analysis, organising photos and piecing together what we had found out this year. In fact, the season turned out to be so interesting that I am writing my first scientific paper, based on a chance encounter that uncovered some very interesting Pacific white-sided dolphin behaviour.

Writing a paper is a challenging and lengthy process, it not only takes time to write the text itself, but also to painstakingly go through all the photos and video footage, make tables to try and show your findings more clearly, read other relevant work and then put it all together to try and get a sense of the dolphins' behaviour. I learned a lot from this experience and continue to do so as I edit my first draft! While most days since the surveys ended have been spent at a computer working on the paper we (the very small team of myself, my husband and our boss) have also been working on building the Mutsu Bay Dolphin Research social media presence as well as spreading the word to Northern Japan through teaching, TV and radio appearances, which included me blanking on live radio and being recognised in a clinic from my TV debut.

In August I finally started what I was actually hired to do, building a photo identification catalogue. This means going through five years of photos looking for identifiable dolphins through the marks and notches on their dorsal fins and then comparing these individuals with other years to establish if these dolphins are the same individuals returning to the bay each spring. I'm excited to see what new information this work brings.


49 views0 comments

Recent Posts

See All