Have you ever wondered how researchers collect aquatic insects from rivers? I certainly did, not long ago, I had zero experience catching insects, and it was my first time doing insect fieldwork in Japan. Now, after visiting several rivers across different prefectures, I want to share what it’s really like out there: the techniques, the landscapes, the seasons, the people, and the little moments that make this work unforgettable.

How Do We Collect Aquatic Insects?

My journey started in the Hiji River in Ehime Prefecture, my very first aquatic insect sampling site. From there, I moved on to the Shigenobu River in Matsuyama, and later the Kibune, Takano, and Kamo Rivers in Kyoto, and finally the Tenryu River in Shizuoka. Each river had its own charm, but the sampling process was surprisingly similar.

In Hiji River alone, we sampled 60 sites, with triplicates per site. Yes, 60 sites × 3. It was massive!

We used kick nets: you place the net downstream and then start kicking the substrate, sand, gravel, pebbles, so that the insects get swept into the net. After five minutes of kicking (which is way more tiring than it sounds), we remove the larger debris while making sure we don’t accidentally toss the insects away. For big rocks, we use fine brushes to scrub off tiny larvae clinging tightly to the surface.

Once the sediments are filtered out, we check a white tray where the insects wiggle, kick, and crawl around. We pick them out one by one and place them into 100% ethanol. Before this, I honestly thought I would never be able to identify anything, everything in the water just looked like sand and leaves to me. But when they’re all moving in a white tray? You can’t miss them.

Of course, things do get challenging when there are many tiny insects all mixed together, but that’s part of the fun (and frustration).

What’s Common in All These Rivers?

If you’ve ever heard that Japan is clean, that includes its rivers. Many upstream sites have crystal-clear, cold, refreshing water. Coming from a tropical country, I’m always amazed by how pristine the headwaters are. Sometimes I just want to jump in and swim… but of course, duty calls (HAHAHA).

Sampling across seasons also gave me some unforgettable experiences. My favorite is spring! Some rivers are lined with blooming Sakura, and the scenery feels like something out of a painting. During summer, the heat’s scorching but the rivers stay cold and clean, making the work refreshing. Meanwhile, in autumn, the water gets colder, but the fiery red and golden leaves create an incredible backdrop.

I still think about how lucky I am to see these villages tucked high in the mountains, with rivers flowing right through them.

The People I Worked with are Amazing!

Fieldwork is not just about science, it’s also about the people who guide, help, and teach you. I’ve had the chance to work with researchers from Tohoku University, Stockholm University, Kyoto University, and Osaka Metropolitan University, aside from my own lab.

They’ve taught me about aquatic ecology, river habitat fragmentation, succession processes, and so much more. For privacy, I won’t mention their names, but they’ve been incredibly generous with their time and knowledge. Sampling with them has made me appreciate not just the science, but also the collaboration behind it.

My final Thoughts?

Every river, every insect, every conversation in the field has shaped how I see evolutionary biology. I hope to turn these experiences, skills, and excitement into research that contribute meaningfully to our understanding of how organisms adapt and evolve.

And finally, I’m deeply grateful not just to the people, but to the aquatic insects themselves. They may be tiny, but they play a huge role in answering big scientific questions.

I’ll do my best to honor them through good science!