Sharks and Skates of Scotland Report: Richardson’s skate (Bathyraja richardsoni)

An extract from the Sharks and Skates of Scotland Report.

Richardson’s skate - Bathyraja richardsoni (Garrick, 1961)

Population status

Scotland and Northeast Atlantic: Unknown (Neat et al., 2015; Stehmann and Farrell, 2015).

Global: Unknown (Kulka et al., 2015).

Note: Species not encountered regularly enough in surveys to model temporal trends. 

Conservation listings

• IUCN Red List Europe: Least Concern (assessment 22 October 2014)
• IUCN Red List Global: Least Concern (assessment 20 February 2015)
• CITES: Not listed
• CMS: Not listed
• OSPAR: Not listed
• Included in the NEAFC measures prohibiting directed fishing for deep-sea rays 

Range and distribution 

This skate species has been recorded in deep water across much of the North Atlantic and is suspected to be more widespread than current records indicate (Stehmann and Farrell, 2015). In the Northeast Atlantic, it occurs from the northern Bay of Biscay, Rockall Trough, west of Scotland and Ireland, and the Mid-Atlantic Ridge (Ebert and Stehmann, 2013), as well as off the Azores and in the Mid-Atlantic Ridge area (Orlov et al., 2006). It is also documented in the Southern hemisphere in waters off Tasmania and New Zealand (Last and Stevens, 2009; Garrick, 1961; Kulka et al., 2015).  

Habitat 

Richardson’s skate are a rarely encountered deep-water skate species, which have been found on continental slopes, submarine rises and deep-water plains at depths of 1219−2992 m (Ebert and Stehmann, 2013; Stehmann and Farrell, 2015). In deep-water surveys of the Rockall Trough, west of Scotland, Richardson’s skate were recorded in low numbers at depths of 1500 – 2030 m (Neat et al., 2015).  

Biology and Ecology

This is a relatively large skate species, capable of reaching a maximum body size of ~174 cm (TL) and is 18.2 – 24.5 cm (TL) at birth (Tempelman, 1973). The species is oviparous (egg-laying) with egg capsules measuring between 20 - 21 cm in length and 11-12 cm in width, excluding horns (Stehmann and Merrett, 2001; Ebert and Dando 2021). In deep-water surveys west of Scotland most individuals captured were large males, with only one small juvenile female recorded. More recent ROV surveys of the Hebrides Terrace Seamount in the Rockall Trough found that Richardson’s skate deposit their egg capsules in sites with the following environmental characteristics: well-oxygenated waters between 4.20 and 4.55^oC; salinity 34.95–35.06; at depths of 1489–1580 m, and on a coarse to fine-grained sandy seabed on the seamount’s eastern flank (Henry et al., 2016). In the waters off Tasmania, Richardson’s skate egg nurseries have been observed on seamount coral reefs at depths of 950 -1350 m at temperatures of 3.94 ^oC (Maguire et al., 2023). Richardson’s skate mainly prey on bony fish and crustaceans (Tempelman, 1973; Gordon and Duncan, 1989). Little else is known about their biology and ecology (Neat et al., 2015).  

Human interactions 

Incidental catch in deepwater fisheries is the predominant potential threat to Richardson's Skate in the North Atlantic (Kulka et al., 2015); however, due to the great depths at which it lives (mainly >1500 m), it has limited interaction with fisheries and is rarely caught. Since the introduction of general measures to protect deep-water elasmobranchs (ban of static net fisheries below 600 m and trawls below 800 m; ICES 2024), the species is likely to be afforded some protection due to the depths at which it occurs.