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Sargassum setifolium

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Taxonomy [top]

Kingdom Phylum Class Order Family
PROTISTA OCHROPHYTA PHAEOPHYCEAE FUCALES SARGASSACEAE

Scientific Name: Sargassum setifolium
Species Authority: (Grunow) Setchell
Common Name(s):
English String Sargassum
Synonym(s):
Sargassum galapagense Grunow variety setifolia Grunow
Taxonomic Notes: Taylor (1945) doubted the validity of this species because it is difficult to distinguish from S. galapagense. He favored varietal status – Sargassum galapagense var. setifolia).

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(i,ii,iii)+2ab(i,ii,iii) ver 3.1
Year Published: 2007
Date Assessed: 2007-03-01
Assessor(s): Miller, K.A., Garske, L. & Edgar, G.
Reviewer(s): Stuart, S.N. & Carpenter, K.E. (Global Marine Species Assessment Coordinating Team)
Justification:
Little reliable information on population trends is available for this species, and some problems exist with taxonomic identification. Regardless, populations of this species have clearly declined in recent decades since the alga was formerly abundant and recent collections have yielded only a single specimen. Because of some identification uncertainty, this species could be assessed as Data Deficient. However, because the locations that it was previously found in the central archipelago are no longer suitable Sargassum habitat as a consequence of herbivore overgrazing, the historical area of occupancy clearly has contracted dramatically. This represents a contraction of available habitat from about 20,000 km2 to one small area that is difficult to define because only drift material is known, but is estimated to be substantially less than 500 km2 AOO and less than 5,000 km2 EOO. Therefore this species is assessed as Endangered.

Geographic Range [top]

Range Description: Sargassum setifolium is an endemic species from the Galápagos Islands. Prior to 1983, reported from: Fernandina: Punta Espinosa (1972 UC, K.A. Miller, pers. comm; Wellington 1975). Isabela: Caleta Black (Taylor 1945) and Caleta Tagus (Taylor 1945; also many 1966 UC specimens from 0.5 mile NW of Caleta Tagus and 1 mile N of Caleta Tagus; K.A. Miller, pers. comm.). Floreana: Champion (Wellington 1975), Black Beach Anchorage (1972 UC, K.A. Miller, pers. comm). San Cristóbal: (Albatros Espedition); Wreck Bay (1972 UC, K.A. Miller, pers. comm). Santiago: Bartolome (Taylor 1945). Santa Cruz. After 1983, reported from: Santa Cruz: Tortuga Bay (1995 CDS). Isabela: Las Marielas (CDRS record 2001).
Countries:
Native:
Ecuador (Galápagos)
FAO Marine Fishing Areas:
Native:
Pacific – southeast
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: There is little information on population trends for S. setifolium, although Wellington (1975) reported it as one of the most prevalent brown algae at Punta Espinosa (along with S. albemarlense). At present, populations are almost exclusively restricted to the western archipelago. Recent surveys (2000 to 2004) have failed to find populations of S. setifolium from San Cristóbal, Bartolome, and Santa Cruz. This represents a contraction of available habitat from about 20,000 km² to one small area; estimated to be substantially less than 500 km² in area of occupancy, and less than 5,000 km² in extent of occurrence. Population trend: unknown over the past decade; declining over the past three decades.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: S. setifolium has been reported from the low intertidal to 7.2 m depth.
Systems: Marine

Threats [top]

Major Threat(s): Presumably El Niño and climate change. Ecosystem interactions involving these two factors appear to have caused widespread decline in algal populations because of an increase in density of grazing sea urchins and other herbivores, following overexploitation of predators along with ENSO disturbances.

Conservation Actions [top]

Conservation Actions: S. setifolium is present within the Galápagos Marine Reserve (IUCN category VI); Galápagos Archipelago Particularly Sensitive Sea Area (PSSA); Galápagos Island World Heritage Site (UNESCO N (i)(ii)(iii)(iv)), and Galápagos Island Man and Biosphere Reserve (UNESCO).

Citation: Miller, K.A., Garske, L. & Edgar, G. 2007. Sargassum setifolium. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 24 July 2014.
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