Nakamura River Catfish Habitat

Nakamura River Nekogigi Habitat: A Sanctuary for One of Japan's Rarest Fish

Tucked away in the northern reaches of Matsusaka City, Mie Prefecture, the Nakamura River flows quietly through a verdant valley — its clear waters hiding an extraordinary secret. Beneath the mossy boulders and smooth river stones of this unassuming waterway lives the Nekogigi (Pseudobagrus ichikawai), a tiny freshwater catfish found nowhere else on Earth. In 2011, the Nakamura River became the first location in all of Japan to have its status as a Nekogigi habitat formally designated as a National Natural Monument — a testament to the exceptional quality of this ecosystem and the passionate conservation efforts of the local community.

What Is the Nekogigi?

The Nekogigi is a small freshwater catfish belonging to the order Siluriformes and the family Bagridae. Adults typically measure just 10 to 15 centimeters in length, making them one of Japan's more diminutive native fish species. Their compact, rounded bodies are dark brown with a distinctive mottled pattern of yellowish-brown spots — markings that are especially vivid in juveniles and gradually become more subtle as the fish matures.

This species is endemic to Japan, occurring only in rivers that flow into Ise Bay and Mikawa Bay across three prefectures: Mie, Aichi, and Gifu. The Nekogigi is strictly nocturnal; during the day, it rests hidden beneath large rocks and boulders on the riverbed, emerging at night to feed on aquatic insects, small crustaceans, and other bottom-dwelling invertebrates. It shows a strong preference for meandering streams with calm pools and riffles, where the varied flow creates an abundance of sheltering spots among the stones.

The species was originally described under the name "Gigimodoki" (meaning "false Gigi"), but was later renamed Nekogigi — literally "Cat Gigi" — because the earlier name had already been assigned to a different Asian catfish species. Interestingly, while catfish are called "catfish" in English, the Nekogigi is one of only a handful of Japanese fish whose name actually references a cat.

Why Was This Habitat Designated a Natural Monument?

The Nekogigi species itself was first designated as a National Natural Monument in 1977, recognizing its rarity and the urgent need for protection. However, it took more than three decades before a specific habitat received the same level of protection.

In September 2009, a survey conducted by the Mie Prefectural Board of Education along the middle reaches of the Nakamura River revealed an extraordinarily high density of Nekogigi. The approximately one-kilometer stretch of river that was surveyed yielded more individual sightings than any other location previously studied. Crucially, the survey found that this section of the river had been largely untouched by river engineering projects, preserving the natural rock formations, pools, and riffles that the Nekogigi depends upon for shelter and breeding.

Adding to the biological significance of the site, the Nakamura River Fisheries Cooperative had been conducting voluntary anti-poaching patrols for years, reflecting a deeply rooted culture of environmental stewardship among the local residents. The combination of a thriving Nekogigi population, an exceptionally well-preserved habitat, and strong community-level conservation awareness led to the formal designation of the Nakamura River Nekogigi Habitat as a National Natural Monument on September 21, 2011.

The Nekogigi is currently classified as Endangered (Category EN / IB) on the Ministry of the Environment's Red List, as well as on the Red List of the Fisheries Agency. In 2017, Mie Prefecture further designated the Nekogigi as a Prefectural Designated Rare Wild Species, making unauthorized capture subject to criminal penalties.

The Nakamura River: A Living Ecosystem

The Nakamura River is a tributary of the Kumozu River, one of the major first-class river systems in central Mie Prefecture. Originating in the mountainous western reaches of the former Ureshino Town (now part of Matsusaka City), it flows eastward through the Ureshino district before joining the Kumozu River at Ureshino Kuroda-cho.

The middle section of the river, where the designated habitat is located, is characterized by a natural, meandering course lined with large boulders and gravel beds. The water is remarkably clear, fed by clean mountain runoff, and the surrounding riparian forest provides shade and organic matter that sustains a diverse aquatic food web. This section has been largely spared from the channelization and concrete embankments that have altered many Japanese rivers, making it a rare example of a near-pristine river environment in a settled area.

Beyond the Nekogigi, the Nakamura River supports populations of sweetfish (ayu) and amago trout, both of which are stocked annually by the local fisheries cooperative, making the river a popular destination for recreational fishing during the warmer months.

Highlights and Visitor Experience

Visiting the Nakamura River Nekogigi Habitat offers a chance to experience a side of Japan that most international tourists never see — a tranquil rural river valley where the rhythms of nature and community coexistence have been preserved for generations.

Surrounding Area and Nearby Attractions

The Ureshino district and broader Matsusaka City area offer a rich variety of experiences for visitors who wish to extend their exploration beyond the Nakamura River.

Important Notes for Visitors

The Nakamura River Nekogigi Habitat is a protected area. Visitors should observe the following guidelines to help preserve this precious ecosystem:

• Capturing, disturbing, or attempting to observe the Nekogigi by moving rocks is strictly prohibited. The species is protected by national and prefectural law, and violations may result in criminal penalties.
• Do not leave any litter or waste along the riverbanks. Carry all trash with you when you leave.
• Avoid entering the water in the designated habitat area, as disturbance to the riverbed can damage the Nekogigi's sheltering and breeding sites.
• Respect any posted signs and the instructions of local authorities or fisheries cooperative members.
• The area is best appreciated quietly and from a respectful distance, allowing the natural environment to remain undisturbed.