The Smallthorn Skate (Bathyraja minispinosa) is a medium-sized deepwater skate (to 91 cm total length) known from a widespread distribution in the North Pacific Ocean, from northern Japan through to the Sea of Okhotsk and the Bering Sea to the Gulf of Alaska, United States. It has been recorded on continental and insular shelves and slopes on sandy or gravelly substrates at depths of 106–1,420 m. Across the North Pacific Ocean, skates are bycatch of industrial trawl, longline, and trap groundfish fisheries, and in some areas, skates comprise up to 10% of the total recorded biomass. The Smallthorn Skate is a bycatch of fisheries targeting groundfish, including Pacific Cod (Gadus macrocephalus), Alaska Pollock (Gadus chalcogramma), and Greenland Halibut (Reinhardtius hippoglossoides). In the western Bering Sea and Sea of Okhotsk, catch-per-unit-effort of the species has generally been increasing since the late 1970s and on the eastern Bering Sea slope modelled biomass estimates indicate a stable abundance. There is increasing international demand for skate products in countries including China, Japan, and Korea and this increased demand has increased skate retention and interest in developing skate targeted fisheries. There are catch limits set for skates (as a group) in Russian and United States waters. Areas of high skate egg density in the United States Bering Sea and Aleutian Islands are designated Habitats of Particular Concern which allows management intervention where fishing activity is deemed harmful to the habitat. The population is estimated to be stable and it has deep water refuge outside current fishing activities. The Smallthorn Skate is therefore assessed as Least Concern.

The Smallthorn Skate is found in the North Pacific Ocean, from northern Japan through to the Sea of Okhotsk and the Bering Sea to the Gulf of Alaska, United States and Canada (Last et al. 2016).

Across the North Pacific (western Bering Sea, Sea of Okhotsk, Northwest Pacific Ocean), trends in catch-per-unit-effort (CPUE) have been variable, but generalized by increasing trends, between 1977 and 2021 (Orlov and Volvenko 2022). Skate abundance data are available for the Aleutian Islands, eastern Bering Sea (EBS) slope, and EBS shelf and are based on demersal trawl surveys conducted by the U.S. National Marine Fisheries Service. The Smallthorn Skate is reported almost exclusively on the EBS slope. Total modelled biomass estimates for the Smallthorn Skate on the EBS slope decreased slightly from a peak of 1,715 t in 2008 to 1,430 t in 2015 and have remained stable to 2023 (Ormseth 2020, Tribuzio et al. 2023). Global population trend is estimated to be stable based on abundance data and refuge in deep water outside of current fishing activities.

The Smallthorn Skate is demersal on continental and insular shelves and slopes on sandy or gravelly substrates at depths of 106–1,420 m (Last et al. 2016, Love et al. 2021). It reaches a maximum size of 91 cm total length (Ainsley et al. 2011, Tuponogov and Kodolov 2014). Males mature at 70 cm TL and females mature at 67 cm TL (Ainsley et al. 2011). Reproduction is oviparous. Estimated female age-at-maturity is 23.5 years and maximum age is 37 years and thus, generation length is 30.3 years (Ainsley et al. 2011).

The Smallthorn Skate is a bycatch of commercial trawl, longline, and trap fisheries targeting groundfish, including Pacific Cod (Gadus macrocephalus), Alaska Pollock (Gadus chalcogramma), and Greenland Halibut (Reinhardtius hippoglossoides). It may be retained for the meat of the skate wings with retention rates of up to 30% in some fisheries. Post-release mortality is unknown but was 40–45% for deepwater Bathryaja species in trawl fisheries (Laptikhovsky 2004, Enever et al. 2009, Ellis et al. 2017).

In Japan, demersal trawl fisheries operate at depths of 50–500 m and effort has decreased markedly over the last three decades and is continuing to decline with fewer fishers and vessels participating in the fishery (NFMT 2017, S. Tanaka pers. comm. 2019). In Russia, the fisheries usually operate to depths of 600–800 m (Ormseth and Matta 2011). There have been occasional experimental fisheries since 2016 that fish to 2,500 m depth (I.V. Volvenko unpub. data 2019) that may constitute a threat if expanded with the interest in developing targeted skate fisheries in the North Pacific. Skate fisheries in Russia are growing: the average annual skate catch reported to official statistics has grown nearly 3-fold, from 1,650 tonnes (t) in 2004–2008, 3,510 t in 2009–2013, and 4,860 t in 2014–2018; there is no species-specific skate catch reporting (Panchenko et al. 2020). In the eastern Bering Sea, skate egg cases, including the Smallthorn Skate, are brought to the surface by commercial demersal trawl and longline fishing vessels targeting deepwater fish including Pacific Cod and Greenland Halibut (Stevenson et al. 2019). The Smallthorn Skate is only commercially fished in the upper region of its bathymetric range and has significant refuge at depth from fisheries.

In Japan, skates are of low value and while there is some domestic consumption, skate wings are most likely exported to the Republic of Korea (H. Ishihara pers. comm. 2019). The meat may be processed into fish meat jelly which is used in some Japanese national dishes (Orlov and Volvenko 2022). In Russia, skates were previously discarded but more recently have been landed for export of wings to China, Japan, Korea, and the British Virgin Islands (Orlov and Volvenko 2022). International demand for skates by Korea is very high and has increased skate retention with Korea a major importer of skates from around the world (Hyun-Su et al. 2013). In the Bering Sea and Aleutian Islands fisheries, 27–51% (average 38%) of all skates were retained from 2011–2023, with larger individuals retained due to the higher market value, and while this may include the Smallthorn Skate, there is limited species-specific information (Tribuzio et al. 2023).

There is a Total Allowable Catch (TAC) for skates in Russian and United States waters. In Russian waters, the TAC has changed little since the 1990s and in the 2020s is 11,2000–11,3000 t (Orlov and Volvenko 2022). In the United States Bering Sea and Aleutian Islands (BSAI) regions this species is managed as a skate complex. The BSAI TAC for the complex is based on the age structured model for Alaska Skate (B. parmifera) and the combined other skate survey biomass multiplied by an assumed natural mortality rate and has varied little from 2012–2023 and in 2023 was 27,441 t (Tribuzio et al. 2023). In 2015, six areas in the BSAI region of high skate egg density were designated Habitats of Particular Concern which allows management intervention where fishing activity is deemed harmful to the habitat. The 82 square nautical miles of habitat is split into different areas at the continental shelf/slope break, and aims to protect egg cases of various skate species. Targeted fishing for skates in the Gulf of Alaska has been prohibited since 2005 (Ormseth 2021). In Japan, management measures have been implemented since the mid-1990s to control fishing effort that include Total allowable catches, seasonal closures and gear restrictions (White Paper 2019). Further research is needed on population size and trends, and life history, and catch rates should be monitored.