Rosy bitterling
The Rosy bitterling (Rhodeus ocellatus) is a small fresh-water fish belonging to the family Cyprinidae (carp) and genus Rhodeus. Females are approximately 40-50mm long and males range from 50-80mm. Their bodies are flat with an argent-colored luster. However, males change to a reddish (sometimes purple) color during the spawning season (Mar~Sep) which functions to attract females. This reddish color is similar to the color of a red rose, which is why it is called a Rosy Bitterling.
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| Rosy bitterling |
image source: http://en.wikipedia.org/wiki/Japanese_Rosy_bitterling
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| Rosy bitterling |
image source: http://commons.wikimedia.org/wiki/User:Seotaro
Ecology and Reproductive system
Rosy bitterlings live in farm ponds (reservoirs) where freshwater mussels are abundant. Farm ponds are very important habitat for not only rosy bitterlings themselves also mussels and planktons. Freshwater mussels such as Dobugai play an important role in Rosy Bitterling reproduction.
Every female rosy bitterling has a unique pipe about the same length as its own body that is used for laying eggs on a (specific spot of mussels). Usually 2-3 eggs are laid at once and placed at the gill of the mussel. A male spawns into the gill cavity of the mussels right after a female lays eggs to ensure fertilization. Normally a female lays eggs repeatedly at 6-9 day intervals and about 10 times in a season.
Eggs grow in the mussel gill and juveniles stay inside of the mussel for approximately 15~30 days after fertilization. Eggs hatch after about 3 days when juveniles are about 2.8 mm long. The body has a unique shape resembling the bud of a matsutake mushroom. Juveniles swim out of the mussel from the margin of the excurrent siphon. At this point, juveniles are about 7.5 mm long and about the same shape as adults. Usually juveniles grow around 40–50 mm within one year at which point they become adults. R. o. kurumeus(Nippon baratanago) live for approximately 3 years and rarely exceed this lifespan.
Every female rosy bitterling has a unique pipe about the same length as its own body that is used for laying eggs on a (specific spot of mussels). Usually 2-3 eggs are laid at once and placed at the gill of the mussel. A male spawns into the gill cavity of the mussels right after a female lays eggs to ensure fertilization. Normally a female lays eggs repeatedly at 6-9 day intervals and about 10 times in a season.
Eggs grow in the mussel gill and juveniles stay inside of the mussel for approximately 15~30 days after fertilization. Eggs hatch after about 3 days when juveniles are about 2.8 mm long. The body has a unique shape resembling the bud of a matsutake mushroom. Juveniles swim out of the mussel from the margin of the excurrent siphon. At this point, juveniles are about 7.5 mm long and about the same shape as adults. Usually juveniles grow around 40–50 mm within one year at which point they become adults. R. o. kurumeus(Nippon baratanago) live for approximately 3 years and rarely exceed this lifespan.
Subspecies
Rhodeus ocellatus kurumeus which is used to be called R. o. smithi (Nippon baratanago) is a Japanese native species but Rhodeus ocellatus ocellatus (Tairiku baratanago) is found in China, Taiwan, as well as in Japan. Nippon baratanago was widely spread in the west side of Japan (Kyushu and western part of Honshū) before World War II. In 1942 Tairiku baratanago was accidentally introduced with grass (Ctenopharyngodon idellus) and silver carp (Hypophthalmichthys molitrix) from mainland China to Japan.
These two subspecies are morphologically very similar but there are several distinguishing characters such as the number of longitudinal scales, principal rays in the dorsal and anal fins, and shape of eggs. Also, R. o. ocellatus (Tairiku baratanago) has a silvery-white area anteriorly (white lines) on the ventral fin but R. o. kurumeus (Nippon baratanago) does not. In comparison the ventral fin of R. o. kurumeus (Nippon baratanago) is a dark color. Another notable difference is body size. R. o. kurumeus (Nippon baratanago) do not commonly exceed 60mm in length, whereas males of R. O. ocellatus are larger than 80mm and females of this subspecies commonly exceed 60mm (Tairiku baratanago).
These two subspecies are morphologically very similar but there are several distinguishing characters such as the number of longitudinal scales, principal rays in the dorsal and anal fins, and shape of eggs. Also, R. o. ocellatus (Tairiku baratanago) has a silvery-white area anteriorly (white lines) on the ventral fin but R. o. kurumeus (Nippon baratanago) does not. In comparison the ventral fin of R. o. kurumeus (Nippon baratanago) is a dark color. Another notable difference is body size. R. o. kurumeus (Nippon baratanago) do not commonly exceed 60mm in length, whereas males of R. O. ocellatus are larger than 80mm and females of this subspecies commonly exceed 60mm (Tairiku baratanago).
Status
Rhodeus ocellatus kurumeus (Nippon baratanago) was widely distributed in small ponds, reservoir, and creeks in Kyushu and the western part of Japan. However, since Rhodeus ocellatus ocellatus (Tairiku baratanago) was introduced, the population of Tairiku baratanago has been increasing dramatically all over Japan. By coexisting those two species in many area it tended to occur hybridization easily.
In fact hybridization and subsequent gene introgression has been observed within these subspecies in Kashima and Ogori. Because of these interbreeding events the number of R.o.kurumeus has dramatically declined all over Japan and now the population of R. o. kurumeus (Nippon baratanago) is in danger of extinction. In 1994 R. o. kurumeus (R. o. smithi, Nippon baratanago) was on the IUCN Red List as an endangered species, and now it is critically Endangered. Nippon baratanago (R. o. kurumeus) is also listed as a critically endangered species on the Japanese Red Data Book.
In fact hybridization and subsequent gene introgression has been observed within these subspecies in Kashima and Ogori. Because of these interbreeding events the number of R.o.kurumeus has dramatically declined all over Japan and now the population of R. o. kurumeus (Nippon baratanago) is in danger of extinction. In 1994 R. o. kurumeus (R. o. smithi, Nippon baratanago) was on the IUCN Red List as an endangered species, and now it is critically Endangered. Nippon baratanago (R. o. kurumeus) is also listed as a critically endangered species on the Japanese Red Data Book.
Conservation
Environmental pollution, reservoir conditions, etc. have propagated the decline of native Japanese Rosy bitterlings in various places. Also, because the numbers of black basses and bluegills increase in such places, the amount of food availability for rosy bitterling declines.
Since R. o. kurumeus (Nippon baratanago) is critically endangered, non-profit organizations and study groups were established in Japan to help protect this subspecies.
Yao study group, one of the Japanese rose bittering conservation group, started activities for protecting endangered Nippon baratanago. For example this organization (Yao city, Osaka) made the protection pond in May 1999 where 41 male and 60 female Nippon baratanago were released with prawns. Also, 45 fresh-water mussels were transplanted at the same time. They monitored and collected data regularity through 2001. In 2000 they succeeded in increasing the Nippon baratanago population to 6000 individuals and they transferred 500 individuals to another 5 ponds from the protected pond. However, in 2001 few individuals were collected. Due to the poor water quality this year compared to previous years, the study group concluded that eutrophication has a negative effect on reproduction in the Rosy bitterling. Since then, Yao study group has considered designing new purification system to conserve Japanese native rosy bitterling. They also educate children (as an environmental study) CHANGE THIS for the next generation.
Since R. o. kurumeus (Nippon baratanago) is critically endangered, non-profit organizations and study groups were established in Japan to help protect this subspecies.
Yao study group, one of the Japanese rose bittering conservation group, started activities for protecting endangered Nippon baratanago. For example this organization (Yao city, Osaka) made the protection pond in May 1999 where 41 male and 60 female Nippon baratanago were released with prawns. Also, 45 fresh-water mussels were transplanted at the same time. They monitored and collected data regularity through 2001. In 2000 they succeeded in increasing the Nippon baratanago population to 6000 individuals and they transferred 500 individuals to another 5 ponds from the protected pond. However, in 2001 few individuals were collected. Due to the poor water quality this year compared to previous years, the study group concluded that eutrophication has a negative effect on reproduction in the Rosy bitterling. Since then, Yao study group has considered designing new purification system to conserve Japanese native rosy bitterling. They also educate children (as an environmental study) CHANGE THIS for the next generation.