|Scientific Name:||Zostera caulescens|
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Assessor/s:||Short, F.T. & Waycott, M.|
|Reviewer/s:||Livingstone, S., Harwell, H. & Carpenter, K.E.|
Zostera caulescens is found in North Korea and Japan, and possibly China. It has a very restricted range and the population is thought to be declining due to reduced water quality. This species is particularly sensitive to pollution. Habitat loss from coastal development and dredging is also a major threat. It prefers deeper waters due to its tall growth. The species almost reaches the threshold for Vulnerable as it has an extent of occurrence of near to 20,000 km², and is known from around 10 locations with a continuing decline in population and quality of habitat. This species is listed as Near Threatened. Further research is recommended for this species, as it may fall into a threatened category if more detailed information were available.
|Range Description:||Zostera caulescens has a very limited distribution. It occurs in the northeast Pacific in northern China, South Korea and in central Japan (it may also be in North Korea). It has an extent of occurrence of near to 20,000 km², and is known from around 10 locations.|
Native:China; Japan; Korea, Republic of
|FAO Marine Fishing Areas:||
Pacific – northwest
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The population of Zostera caulescens is thought to be declining due to coastal pollution.|
|Habitat and Ecology:||
Zostera caulescens is found in both sheltered and semi-exposed bays on sandy or muddy bottoms in depths of 6-12 m along temperate sea coasts of northeastern Asia (Miki 1932, den Hartog 1970). It prefers deeper waters due to its tall growth. It is also found in Japan, in deeper habitats than Zostera marina, between 3-16 m (Aioi et al. 1998).
Zostera caulescens is believed to be the world's longest seagrass and was collected in lengths of up to seven m, with a typical length of 4.8 m in a bay of northeastern Japan. The flowering shoots are produced on a proliferation of vegetative leaves at the top of a stem. Flowering shoots take one year to mature and develop spadices, over-wintering in the bed.
Zostera caulescens is sensitive to pollution and reduced water quality is a particular threat. Habitat loss is also a major threat to this species, as is dredging.
Within its range in Japan there is industrial development in coastal regions, land reclamation, water pollution and disturbance of habitats by fish trawling. In South Korea there is a large amount of coastal eutrophication and some land reclamation.
The distribution of Zostera caulescens falls into protected areas in South Korea ( Environmental Conservation Areas or Special Coastal Management Areas). This species is also protected by 'The Marine Ecosystem Conservation and Management Act' in Korea.
Zostera caulescens is listed as Vulnerable (vulnerable stage) in the Red Data Book of threatened Japanese plant species (2000).
Further research on population and general biology of this species is recommended.
|Citation:||Short, F.T. & Waycott, M. 2010. Zostera caulescens. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 20 April 2014.|
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