Japanese River Fish (Part 1) :What Types of Fish Are There? – with Fish Fauna List

Japanese seafood, such as sushi and sashimi, is famous worldwide, and many are familiar with the fish found in the sea. However, some might wonder, what kind of fish inhabit Japan’s rivers? In this article, I will discuss the types of fish found in Japanese rivers, based on a comprehensive survey and analysis of a fish species list. The focus will be on the composition of these species and their distribution across different regions.

The Japanese government conducts fixed-point surveys of wildlife along the entire stretch of 109 rivers nationwide. This project, known as “The National Survey for River and Riparian Environment.,” is carried out every five years in each river.

While the survey results are published online, unfortunately, they are not widely known to the public. I am not sure if other countries conduct similar surveys, but I believe that these results should be recognized by more people. By doing so, many will be able to share information about the current state of nature and its changes, based on scientific evidence. Therefore, I will discuss the fish species living in Japan’s rivers here, based on the latest survey conducted from 2016 to 2020.

1.Features of Fish Species by Taxonomic Group.

Due to Japan’s elongated north-south geography, there is a significant difference in the types of fish found in various regions. In the northernmost Hokkaido, 76 species have been identified, while in the southernmost Kyushu, 199 species have been confirmed, more than double the number in Hokkaido.

When looking at the distribution by taxonomic groups, a high proportion of fish from the orders Cypriniformes and Perciformes can be observed. In Japan, Cypriniformes, such as carps , minnows , and loaches, predominantly inhabit freshwater areas, especially in central areas like Kinki and Chubu regions. Within the Perciformes, gobies make up a significant portion. Gobies, which often require brackish or saltwater during their lifecycle, become more common further south. My research primarily covers from Hokkaido to the Chubu region, and it includes many species that are less familiar to me.

Notably, Hokkaido possesses a unique fish fauna, with fewer Cypriniformes and Perciformes, but a higher presence of Salmoniformes. This is due to the common species shared with regions like Russia and Alaska.

In summary, in many of Japan’s rivers, carp and goby species play a leading role. It is clear that due to the length of the country from north to south, the fish fauna differs between these regions.

2. Native Species and Introduced Species

In recent years, Japan has experienced an influx of numerous invasive species. These are particularly prevalent in regions such as Kanto, where Tokyo is located, Kinki, home to Osaka, and the Chubu region, where Nagoya is situated. Among the invasive species, those known as targets for fishing, such as Rainbow Trout (Oncorhynchus mykiss), Black Bass (Micropterus salmoides, Micropterus dolomieu dolomieu), and Bluegill (Lepomis macrochirus macrochirus), are well-known. Additionally, species like Silver Carp (Hypophthalmichthys molitrix) and North American Freshwater Catfish (Ictalurus punctatus), which were once brought in as useful fisheries species, and ornamental fish like Carassius auratus (Goldfish) and Rhodeus ocellatus ocellatus (Rose Bitterling), have also been introduced.

As mentioned in the previous section, there is a tendency for the number of native species to increase as one moves southward.

3. Distribution Features of Freshwater Fish, Migratory Fish, and Euryhaline Fish Species

When classifying the fish species in Japan based on their life cycles into ‘Freshwater’, ‘Migratory’, and ‘Euryhaline’, significant differences in distribution trends between the north and south of Japan become apparent.

(1). Freshwater
For freshwater fish, there is a tendency for a higher number of species in the central parts of Japan, including the Kinki and Chubu regions. Notably, species closely related to fish from the Korean Peninsula, such as Coreoperca kawamebari and Cobitis striata, are particularly prevalent.

(2). Euryhaline
The number of Euryhaline species clearly increases as one moves southward. Especially among brackish goby species, many are found exclusively south of the Chubu region.

(3). Migratory
While migratory fish are less numerous compared to the other two categories, there is a tendency for their numbers to increase further north. Hokkaido, for instance, is rich in migratory species such as smelts (including Wakasagi and Shishamo), sculpins, and salmonids. Conversely, the southernmost region of Kyushu also has a significant number of migratory fish, derived from species closely related to freshwater fish found in rivers of China and Vietnam, such as Coilia nasus, Salanx ariakensis, and Trachidermus fasciatus.

※Classification of Life Cycles

・ Freshwater: Species that can spend their entire life in freshwater.
・ Migratory: Species that must migrate between freshwater and saltwater during their lifetime.
・ Euryhaline: Species that primarily inhabit brackish or saltwater, but may also venture into freshwater.

However, since there are species with intermediate characteristics, such species have been categorized at the author’s discretion.

Table1　List of Freshwater Fish Species Found in Japan’s National Environmental Survey

4. Conclusion

I have written at length about many things, but I hope that if the following is conveyed to you, it will be worthwhile to write this article.

・Japan is longitudinal from north to south, and the fish fauna differs considerably from north to south.
・In most areas of Japan, the dominant fish fauna is carp and goby families.
・Hokkaido is unique compared to other regions in Japan, and salmonids are dominant in Hokkaido.
・The south is dominated by brackish and saltwater fishes using rivers as habitats.

See you soon.