''Rhodeus smithii'', sometimes known as the Japanese rosy bitterling, Japanese bitterling, or Nippon baratanago is a

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...

freshwater

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...

belonging to the

Acheilognathinae The bitterling-like cyprinids form the cyprinid subfamily Acheilognathinae. This subfamily contains four genera, although the Khanka spiny bitterling is often placed in ''Acheilognathus'', and at least 71 described species to date. Over half of t ...

subfamily of the family Cyprinidae. It originates in stagnant waters in inland rivers in Japan. It was originally described as ''Achilognathus smithii'' by

Charles Tate Regan Charles Tate Regan FRS (1 February 1878 – 12 January 1943) was a British ichthyologist, working mainly around the beginning of the 20th century. He did extensive work on fish classification schemes. Born in Sherborne, Dorset, he was educat ...

in 1908, and is also referred to as ''Rhodeus ocellatus smithii'' in scientific literature. Named in honor of British traveler, sportsman and naturalist

Richard Gordon Smith Richard Gordon Smith (1858 – 6 November 1918) was a Great Britain, British traveler, sportsman, and naturalist who traveled extensively in the late 19th century and lived in Japan for a number of years. image:Smith-Monoyuki-White sake.jpg, Illust ...

(1858-1918), who collected specimens in Japan for the

British Museum The British Museum is a public museum dedicated to human history, art and culture located in the Bloomsbury area of London. Its permanent collection of eight million works is among the largest and most comprehensive in existence. It docum ...

(Natural History). It is listed as critically endangered in the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biol ...

. The fish reaches a length up to , and is native to freshwater habitats with a pH of 6.8 to 7.8, a

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...

of 20 DH, and a temperature of . When spawning, the females deposit their eggs inside bivalves, where they hatch and the young remain until they can swim. It lives about three years and rarely exceeds this lifespan. It was widespread in the west side of Japan (Kyushu and western part of Honshū) before World War II. In 1942, the

rosy bitterling The rosy bitterling or Tairiku baratanago (''Rhodeus ocellatus'') is a small freshwater fish belonging to the family Cyprinidae (carp), native to East Asia from the Amur River basin to the Pearl River basin. Females are about long and males ar ...

was accidentally introduced with grass ('' Ctenopharyngodon idellus'') and silver carp (''

Hypophthalmichthys molitrix The silver carp (''Hypophthalmichthys molitrix'') is a species of freshwater cyprinid fish, a variety of Asian carp native to China and eastern Siberia, from the Amur River drainage in the north to the Xi Jiang River drainage in the south. Alt ...

'') from mainland China.Kawamura, K., Nagata, Y., Ohtaka, H., Kanoh, Y., and Kitamura, J. 2001. Genetic diversity in the Japanese rosy bitterling, ''Rhodeus ocellatus kurumeus'' (Cyprinidae). Ichthyol Res 48: 369-378 The two species are morphologically very similar, but several distinguishing characters are seen, such as the number of longitudinal scales, principal rays in the dorsal and anal fins, and shape of eggs. Also, rosy bitterling has a silvery-white area anteriorly (white lines) on the ventral fin, but ''R. smithii'' does not. In comparison, the ventral fin of ''R. smothii'' is a dark color. Another notable difference is body size. ''R. smithii'' does not commonly exceed 60 mm in length, whereas rosy bitterling males are larger than 80 mm and females of the species commonly exceed 60 mm.

Status

''R. smithii'' was widely distributed in small ponds, reservoirs, and creeks in Kyushu and the western part of Japan. However, since the rosy bitterling was introduced, their population has been increasing dramatically all over Japan. These two species coexist in many areas, and hybridization tends to occur easily. Hybridization and subsequent gene introgression has been observed within these species in Kashima and Ogori. Because of these interbreeding events, the number of ''R. smithii'' has dramatically declined all over Japan and now is in danger of extinction. In 1994, ''R. smithii'' was on the

as an endangered species, and now it is critically endangered. ''R. smithii'' is also listed as a critically endangered species in the Japanese Red Data Book.

Conservation

Environmental pollution, reservoir conditions, etc. have propagated the decline of native ''R. smithii'' in various places. Since ''R. smithii'' is critically endangered, nonprofit organizations and study groups were established in Japan to help protect this subspecies. Yao study group, one of the ''R. smithii'' conservation groups, started activities for protecting them. For example, this organization (Yao City, Osaka) made the protection pond in May 1999 where 41 male and 60 female fish were released with prawns. Also, 45 freshwater mussels were transplanted at the same time. They monitored and collected data regularly through 2001. In 2000, they succeeded in increasing the population to 6000 individuals and they transferred 500 individuals to another five ponds from the protected pond. However, in 2001, few individuals were collected. Due to the poor water quality that year compared to previous years, the study group concluded eutrophication has a negative effect on reproduction. Since then, Yao study group has considered designing new purification systems to conserve them. They also educate children (as an environmental study) for the next generation.Kanoh, Y., Yoshinaka, T., Takemoto, Y., Iwasaki, and Y., Nishino, T. (Yao study group of Japanese rose bitterling) 2002. Conservation of Japanese rose bitterling ''Rhodeus ocellatus kurumeus''. (in Japanese) 第11期プロ・ナトゥーラ・ファンド助成成果報告書

References

{{Taxonbar, from=Q3767281 Taxa named by Charles Tate Regan Fish described in 1908 smithii Taxobox binomials not recognized by IUCN