The spread of loach in the outpatient system in Saitama
Urawa Jitsugyo Gakuen High School Kosei Miyamoto, Haruto Kanazawa, Akitaka Okuno
Background and Purpose
Misgurnus anguillicaudatus is one of the freshwater fish same asOryzias. However, as Oryzias was registered as an endangeredspecies in 1999, M. anguillicaudatus was registerd as an semiendangered species in 2018. For the reason of decreasing
number in habitats of M. anguillicaudatus there are 3 main causes.
①Deterioration of water quality. ②Modification of environmental
structure. ③Effects of foreign species. Above all, we have begun
the research focusing on ③. Foreign species are Paramisgurnus
dabryanus and 2 strains of loads of alien species. P. dabryanus is

you can tell them apart from others easily by observing angle of themustache,Peduncle and so on. On the other hand, alien loach isregarded as the same species as conventional species in terms ofclassification. However ,there is much difference in the number ofsoft bars, since the origin is extensive, it is difficult to distinct fromconventional loach only by the appearance of characteristics. Alienloaches were imported in Japan as edible fish late 1960s. Spread ofalien loaches in Japan has not grasped enough yet. On this paper, weinvestigated on spread of habitats of alien loaches and conventionalloaches is Saitama Prefecture.

genetically different from M. anguillicaudatus as shown in Fig-1 and❶

❶❷
❸
❹
❺
❻

❷
❸
❹
❺ Number of branched soft bars❻❼

Number of branched soft bars

Peduncle
Angle of the mustache
Angle of mustache

Fig-1

3 species of loaches captured in Saitama Prefecture（L：P. dabryanus C：Alien Loach R：Conventional Loach）Method of Investigation
We have conducted an investigation since June,19,2023 toOctober,1,2023 at agriclutural waterways and rivers in Saitama.
The collection was carried out by scooping laches hiding in theriverbed and the bushes of aquatic plants with a Tamo net. We set

it as an goal to capture 10 loaches in each places and we kept theirbody as specimen soaking in 70% ethanol. Also, we kept their chesttin saoking in 100% ethanol preparing for genetical analyzing in thenear future.

Results and Consideration
We summarized the results by mixing the topography and river
map of Saitama Prefecture. Conventional loaches lived widely inhilly areas and plateaus. On the other hand, the loach, which seems
to be a P. dabryanus and a foreign species lineage, were mainly

population moved through the Tone River and Arakawa River whileleaving offspring, and spread to compensate for the decrease in
the loach of native species. The flow speed from the middle to thedownstream of the Tone River and the Arakawa River is about 60
cm/s, and it is thought that it is possible to go upstream if it is alarge individual. However, the retrograde of the loach, which seems
to be a redwood and a foreign species lineage, was blocked by thechange in the flow rate when it moved from the plain to the plateau
and hills. Therefore, it is very interesting that the native loach has
been confirmed alone at many points such as the Omiya Plateau,
the Kita-Musashi Plateau, the Hiki Hills, and the Iruma Plateau. In
the future, while investigating the distribution of loaches in areas
facing outside the prefecture along the Tone River, we will measure
the flow speed of the river at the border between the pleas and theplains, investigate whether loaches can go upstream, and explore
the diffusion route of loaches in the alien species lineage. I want toexplore it.

distributed along the river flowing through the plains. Dependingon the region, the habitat of the native species lineage may not beconfirmed.The reason why several species of foreign species ofloach increased their population may be that there was competition
between species and native species by competing for their homesand food. However, all the loaches raised in the aquarium were very
gentle, and we could not confirm that they showed competition andaggression. Therefore, we proceeded with the following
considerations.The topography of Saitama Prefecture is located inthe Chichibu Mountains in the West, and there are 2000-meterclass mountains, including Mt. Sanbo at an altitude of 2,483
meters, which boasts the highest peak in the prefecture. On theother hand, the Kanto Plain spreads to the east, and it has become
a flat terrain formed by the flow of rivers such as the Tone
River and the Arakawa River since 10,000 years ago. In thisarea, especially in areas with low sea level, it was greatly
influenced by the Jomon Sea from 6500 to 6000 years ago.
In addition, at the border between the mountainous area
and the Kanto Plain, the hills spread from north to south,
making it a clear western high and east low terrain. The loafof the native species lineage at the time of the Jomon Sea
is widely distributed in the current hilly area and plateau,
and then spread to the landized plains, expanding its
distribution to a wide area except for mountainous areas. Inaddition, by the formation of paddy fields in reclamation,
the number was further increased and it became familiar tothe common people, and it was useful as an importantsource of nutrition due to its high nutritional value.
However, after the 1960s, the environment changed due tothe urbanization of the Kanto Plain, and the number of
山 地
凹 地
mobs such as native species decreased. And to make up

丘陵台地

低地

for it, we introduced P. dabryanus and exotic loach as food,but some of them invaded the natural world. The invading

Fig-２

Result of Investigation on