Bathyraja mariposa 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Rajiformes Arhynchobatidae

Scientific Name: Bathyraja mariposa Stevenson, Orr, Hoff & McEachran, 2004
Common Name(s):
English Butterfly Skate
Taxonomic Source(s): Eschmeyer, W.N., Fricke, R. and Van der Laan, R. (eds). 2016. Catalog of Fishes: genera, species, references. Updated 1 July 2016. Available at: (Accessed: 1 July 2016).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2016
Date Assessed: 2014-12-31
Assessor(s): Lawson, J., Machuca, B., van Hees, K. & Ebert, D.A.
Reviewer(s): Barry, S.N. & Bigman, J.S.
Facilitator/Compiler(s): Kyne, P.M., Walls, R.H.L. & Dulvy, N.K.
The Butterfly Skate (Bathyraja mariposa) is found at depths of 90-448 m, and is endemic to the western Aleutian Islands, Bering Sea, Alaska. This species is caught as bycatch in commercial bottom trawl fisheries and is not targeted. While little is known of its ecology, biomass estimates were generated for this species from 2010-2014 and it is assumed to be stable, although the existing time series is too short to effectively assess the stock. A depletion in biomass of the skate stock complex in the Aleutian Islands, which this species is included in, occurred between 1950 and 1980, but was followed by a large recruitment event in the 1980s that resulted in higher biomass in 2014. Given that this species is monitored and managed throughout its range, a formal stock assessment is conducted annually, and biomass trends thus far suggest that the population is at least stable, this species is assessed as Least Concern. However, the current National Oceanographic and Atmospheric Administration Fisheries goal of improving species-level catch accounting is critical to monitoring the sustainability of this species in bycatch.
Previously published Red List assessments:

Geographic Range [top]

Range Description:The Butterfly Skate is considered endemic to the Aleutian Islands (Ormseth 2014), and was initially recorded in Seguam Pass, Tanaga Pass, and Petrel Bank (Stevenson et al. 2004).
Countries occurrence:
United States (Aleutian Is.)
FAO Marine Fishing Areas:
Pacific – northwest; Pacific – northeast
Additional data:
Lower depth limit (metres):448
Upper depth limit (metres):90
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Survey biomass estimates from 2010-2014 are available for the Butterfly Skate in the Aleutian Islands. Biomass has increased since trends were first available in 2010; in 2010 biomass was estimated at 123 metric tonnes (t), in 2012 biomass was estimated at 307 t, and in 2014 biomass was estimated to be 409 t (Ormseth 2014). Based on these data, biomass is assumed to be stable for this species, however the existing species-specific time series is too short to effectively assess the stock (Ormseth 2014). When considered as part of the skate stock complex present in this area, the assessment showed a general depletion in skate biomass between 1950 and 1980, followed by a large recruitment event in the 1980s which resulted in higher biomass in 2014.
Current Population Trend:Stable
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:Habitat preferences of the Butterfly Skate are not known. This species is found at depths ranging from 90-448 m.

Maximum recorded size is 76 cm total length (TL; Stevenson et al. 2004, Ormseth 2014). Females are mature at 76 cm TL and males at 70.2 cm TL (Stevenson et al. 2004). Reproduction is presumably oviparous, as in other skates. No other information is available on the habitat or biology of this species.

Use and Trade [top]

Use and Trade: This species is not known to be utilized and no further information on the use or trade of this species is known.

Threats [top]

Major Threat(s): The Butterfly Skate is not targeted but is caught as bycatch in commercial bottom trawl fisheries operating in the Aleutian Islands. Additionally, this species likely has natural refuge from trawling as the Aleutian Islands are an area of very steep, rocky terrain that is mostly un-trawlable (D. Ebert, 4 November 2015, pers. comm.).

Conservation Actions [top]

Conservation Actions: This skate is managed under the Bering Sea Aleutian Islands Fisheries Management Plan as part of a skate assemblage made up of 15 species in the genera Bathyraja, Amblyraja and Raja (Ormseth 2014). The NOAA Fisheries Alaska regional office's Catch Accounting System aims to report species-specific catch for selected skate species, but most skates are only able to be identified to the genus level by fisheries observers. Current management goals in Alaska aim to improve species-level catch accounting.

In addition, in January 2015, the National Oceanographic and Atmospheric Administration (NOAA) Fisheries approved amendment 104 of the Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area, which allocates 81.7 square nautical miles as habitat for high skate egg case density as Habitats of Particular Concern (National Marine Fisheries Service 2014). This amendment will allow NOAA Fisheries to intervene when fishing in these areas is deemed harmful to the habitat.

Citation: Lawson, J., Machuca, B., van Hees, K. & Ebert, D.A. 2016. Bathyraja mariposa. The IUCN Red List of Threatened Species 2016: e.T161319A80675021. . Downloaded on 15 October 2018.
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