|Scientific Name:||Parabotia curtus|
|Species Authority:||(Temminck & Schlegel, 1846)|
Cobitis curta Temminck & Schlegel, 1846
Hymenophysa curta (Temminck & Schlegel, 1846)
Leptobotia curta (Temminck & Schlegel, 1846)
Parabotia curta (Temminck & Schlegel, 1846) [orth. error]
|Taxonomic Source(s):||Eschmeyer, W.N. and Fricke, R. (eds). 2015. Catalog of Fishes: genera, species, references. Updated 1 October 2015. Available at: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. (Accessed: 1 October 2015).|
|Taxonomic Notes:||Parabotia curtus was originally described as Cobitis curta by Temminck & Schlegel (1846). After changes in the generic position, the species is included in Parabotia in the latest references. Because the gender of Parabotia is determined as masculine (see Kottelat 2012), Parabotia curtus (not curta) is currently used. Parabotia curtus is undoubtedly endemic to Japan, although an uncertain record of this species exists from southern China (see Watanabe et al. 2009). The species is included in the subfamily Botiinae of the family Cobitidae. Some recent references use the family name of Botiidae, based on the morphology and molecular phylogeny (e.g., Nalbant 2002, Šlechtová et al. 2006, Watanabe et al. 2009).|
|Red List Category & Criteria:||Critically Endangered A3ce ver 3.1|
|Assessor(s):||Watanabe, K., Abe, T., Iwata, A., Shimizu, T. & Hosoya, K.|
|Reviewer(s):||Smith, K., Harrison, I.J. & Freyhof, J.|
The species only survives in three very small and isolated locations which are facing severe on-going and future threats. The total area of the extent of occurrence (EOO) in the two geographically separated regions (Kinki and Sanyo) is 420 km2, and the area of occupancy is 12 km2. However the sum of the actual area of occupied habitat is only 0.9 km2. Both EOO and AOO are continuously declining. Due to the significant levels of human intervention required to support the species, it is on the cusp of being considered Extinct in the Wild, however, for this assessment we are considering the population still to be wild. The species is assessed as Critically Endangered (A3) as it is highly likely that the total population will decline by more than 80% in the next 10 years due to a combination of pressures which are summarised below.
1. All three remaining subpopulations (Kameoka, Okayama-1, Okayama-2; geographically isolated from each other) are severely threatened and maintained by conservation efforts at the present. If the conservation activities (e.g., maintaining spawning/nursery grounds, alleviating migration inhibition, etc.) ceased, all the subpopulations would seriously decline or go extinct within a few generations.
2. Although conditions needed for reproduction are produced by the operation of a movable weir for irrigation in all three sites, the necessity for such operation is decreasing due to other irrigation methods being made available (e.g., pumping water using electricity) and the abandonment of cultivation.
3. There have been years in which no yearlings were recruited at least in the Kameoka and Okayama-1 subpopulations; and the subpopulations could crash if this was to occur in two or more successive years.
4. Predation by the introduced Largemouth Bass (Micropterus salmoides) and the native Great Cormorant (Phalacrocorax carbo) is a serious problem for the Kameoka and Okayama-2 subpopulations.
5. In Kameoka, the construction of a park with a football stadium will begin in 2016 with completion scheduled for 2018. This will lead to the destruction of the major nursery grounds for the species.
6. The spawning conditions for the Okayama-1 subpopulation are currently maintained through intensive volunteer activity; this will be difficult to maintain indefinitely.
7. A road construction plan, increasing abandonment of paddy cultivation and increasing predation pressure threaten the Okayama-2 subpopulation.
|Previously published Red List assessments:|
|Range Description:||The species has a small geographical range in western Japan. Historically it occurred only in two geographically distant (>100 km apart) regions; the Lake Biwa and Yodo River basin (in the Kinki Region), and in several rivers including the Yoshii, Asahi, Takahashi, and Ashida rivers in the (Sanyo Region).|
In the last decade, reproduction of the species is confirmed only at three small sites; one at Kameoka City, Kyoto Prefecture, in the Kinki Region (referred to as Kameoka, hereafter), and two at Okayama City, Okayama Prefecture, in the Sanyo Region (Okayama-1 and -2). The subpopulations in the three sites are geographically isolated from each other. The spawning and nursery grounds are only a few hundred meters of a stream and small irrigation channels located within a ~0.15 km2 rice field at Kameoka; and a 0.002 km2 (0.2 ha) conservation field at an abandoned paddy field in Okayama-1; and a 0.005 km2 (0.5ha) around a channel and rice field in Okayama-2. Because the species shows a small-scale migration between spawning ground and winter habitat, adult fish are sporadically found near the spawning sites.
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The major population decline of the species occurred over 30 years ago, but habitat loss has continued until recently. The species currently reproduces only at three small areas in Kameoka (the Yodo River system), Okayama-1 (the Asahi River system), and Okayama-2 (the Yoshii River system). These three habitats have been maintained by intensive conservation efforts in the past one to three decades with cooperation among local people, NPOs, researchers, and governments. |
Population estimation has been conducted for the Kameoka subpopulation every autumn in the past ten years, and is between 80–730 (average 440) adult fish (Watanabe et al. 2014). The Kameoka subpopulation is the largest of the three extant subpopulations, inferred based on genetically effective population size (Ne) (Watanabe et al. unpublished data). The recruitment varies drastically among years (from 0 to more than 2,000 yearlings in autumn), making the population unstable.
In the Okayama-1 subpopulation, the number of mature fish migrated to spawning site was about 50 to 160 (average 100) between 2010-2015 (Abe et al., unpublished data). The recruitment of Okayama-1 subpopulation was estimated to be about 210 individuals in 2015. The size of the Okayama-2 subpopulation has not been precisely evaluated but is roughly estimated at about 250 mature individuals on average based on the observation of upstream migrating fish. Effective population size is estimated to be about 30 to 500 by the genetic analysis in the Okayama-2 subpopulation (Watanabe et al. unpublished data). The recruitment in the Okayama-1 and 2 changes drastically among years as in the case of the Kameoka subpopulation.
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||The species reproduced in flood plains or temporary waters around rivers and lakes. Because such natural environments have almost disappeared in western Japan, the species currently utilizes similar environments artificially produced by rice-paddy cultivation. The adult fish gather into a spawning site when the water level rises by heavy rain in the early rainy season (June). Submergence of land is the key to spawning (Iwata 2006; Abe et al. 2007a,b). Currently, this is artificially caused by raising a movable weir up at starting irrigation. The fish produce demersal adhesive eggs (Abe and Sakamoto 2011). The eggs hatch within 25 hours after spawning, and rapidly grow up using high productivity (e.g. Daphnia) in flood plains. After the irrigation period (late September), when the water level is lowered, the fish migrate to permanent waters (main channels or streams) and winter in shelters such as crevices in riverbeds and banks. The majority of fish mature at two years old, and the generation length is roughly 2.5–3 years.|
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Generation Length (years):||2.5-3|
|Movement patterns:||Full Migrant|
|Use and Trade:||Collection, trade, and possession of the species are prohibited by several Japanese laws, e.g., the Law for the Protection of Cultural Properties as a natural monument, the Law for the Conservation of Endangered Species of Wild Fauna and Flora, and other local laws. However, illegal collection and trade are sometimes revealed even in recent years. The amount of such illegal trade is unknown, but the effect of poaching seems not very large.|
Historic: After natural flood plains (spawning areas) disappeared, the species utilized the environments around rice paddies. However, paddy fields have largely been converted into housing or industrial areas. In addition agricultural field improvement projects since the 1960s, has led to a loss of environments used for spawning, early development and migration, and chemical insecticide and herbicide seriously affected the ecosystems around paddy fields. In most areas, the agricultural schedule was moved ahead along with the change in rice varieties cultivated, and became conflict with the species phenology. As a result, only three spawning areas currently remain for the species' reproduction.
Current: Conditions of reproduction are produced by human agricultural activity, e.g., operation of a movable weir for irrigation, in all three remaining sites. The necessity of such operation is decreasing due to other irrigation methods available (e.g., pumping water using electricity) and the abandonment of cultivation. Also, the weirs work as migration inhibitors after they are raised up. Surrounding paddy fields have continued to be converted to housing or commercial areas. This reduces the potential habitat, and possibly causes light and noise pollution. Predation by the introduced Largemouth Bass (Micropterus salmoides) and the Great Cormorant (Phalacrocorax carbo) is a serious problem for the Kameoka and Okayama-2 subpopulations.
Future: There is a plan to construct a city park with a football stadium by local governments (Kameoka City and Kyoto Prefecture) adjacent to the spawning and nursery ground of the species in Kameoka (the largest subpopulation). A conservation area will be created, but there is great uncertainty whether it can contribute to the conservation of this species, due to insufficient scientific evidence. The spawning conditions for the Okayama-1 and -2 subpopulations are currently maintained by intensive volunteers’ activities, which will be difficult to continue indefinitely. A road construction plan, increasing abandonment of paddy cultivation and increasing predation pressure threaten the Okayama-2 population.
Collection, trade, and possession of the species is regulated by several laws, e.g., the Law for the Protection of Cultural Properties as a natural monument, the Law for the Conservation of Endangered Species of Wild Fauna and Flora, and other local laws.
All three subpopulations have been maintained by conservation activities. If conservation activities ceased, all the subpopulations would seriously decline or go extinct within a few generations. Conserving and improvement of the spawning and nursery ground habitats have been conducted at all three sites with cooperation among local people, NPOs, researchers, and local and national governments. For example, raising a movable weir is essential to introduce the spawning conditions, but simultaneously works as a migration barrier. So, the adult fish below the weir are brought upstream of the weir by hand. Cultivation of paddy fields is compatible with the life history of the species, however, rapid water level control can pose a threat through the drying up of habitats (in such cases people move the fish to safe areas by hand).
Despite the current problems, the most important and reliable conservation strategy is to maintain the environments of the present habitats against development pressure. For the Kameoka subpopulation, a city park plan with a football stadium (to be completed in spring 2018) is expected to pose severe environmental changes to the spawning and nursery ground of the species. Based on precautionary principles many academic and conservation societies have called for the proposed plan to be withdrawn.
All three remaining habitats are too small to maintain stable viable populations. Creation of new habitats around the extant places is strongly recommended. Ex situ conservation plans with captive breeding have started for all three populations for future reintroduction or reinforcement. Effective control of predators, especially Largemouth Bass, is also an immediately priority.
|Citation:||Watanabe, K., Abe, T., Iwata, A., Shimizu, T. & Hosoya, K. 2015. Parabotia curtus. The IUCN Red List of Threatened Species 2015: e.T11661A83606443.Downloaded on 22 August 2017.|
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