Skate, Longnosed

Dipturus oxyrinchus

Method of production — Caught at sea
Capture method — Demersal otter trawl
Capture area — North East Atlantic (FAO 27)
Stock area — All Areas
Stock detail — 1 to 10
Picture of Skate, Longnosed

Sustainability rating five info

Sustainability overview

The stock status of longnosed skate is unknown, though their populations are thought to have reduced by 30% over the past 30 years.

The landing obligation will be fully in place in 2019, which requires that all species with catch limits should be retained. However, skate and rays are exempt from the landing obligation due to their assumed high discard survival rates. There is no specific management plan for skates and rays in these waters. They are managed under a total allowable catch (TAC) for many skates and rays but greater protection is needed. Further management of the species is advised e.g. through fishery closures to allow them to reproduce.

Demersal otter trawling is also associated with discarding of unwanted fish and sometimes catch Endangered, Threatened and Protected species, but capture rates can be reduced with appropriate gear modifications.

Biology

Longnosed skates belong to the Rajidae family which includes skates and rays. The longnosed skate is a large offshore species growing to a maximum total length of 150cm and weight of 73kg. Length at maturity is above 90cm for females and 70-80cm for males.

Stock information

Criterion score: 1 info

Stock Area

All Areas

Stock information

The Longnosed Skate is an offshore species uncommon in UK waters. Their populations are thought to have reduced by 30% over the past 30 years. It is thought that in the eastern Mediterranean, the species is moderately abundant but is now absent in the western Mediterranean. Research surveys suggest that it has disappeared from the Irish Sea where it was once targeted commercially. In the North Sea, Skagerrak, Kattegat, and eastern English Channel, little information is available on their landings. Therefore, Longnose Skate are assessed as part of a group of skate and ray species. Their catches have to be recorded at species level; fishers often record them as generic skate landings. There is concern for both biomass and fishing mortality.

Management

Criterion score: 0.75 info

There is no direct management plan for skates and rays in these waters. They are usually caught as bycatch in otter and beam trawl fisheries, which target finfish (including flatfish and gadoids).

Skates and rays are managed under five regional quotas (called TACs) which are applied to a group of species, rather than individual skate and ray species. This has been deemed as an unsuitable method for protecting individual species, but species-specific quotas may increase discarding.

The European Commission have considered that skates and rays caught in the North Sea (including in ICES divisions 2a and 3a, and ICES subarea) and Northwest waters (ICES subareas 6 and 7) with all fishing gears, should be exempt from the landing obligation, based on their assumed high survivability rates. However, Member States harvesting the stocks, should supply data to STECF to review the effectiveness of the exception and, by the 31 May each year produce a roadmap to increase survivability, fill in the data gaps identified by STECF and produce annual reports on the progress on survivability programmes. Any skates and rays that are discarded are required to be released immediately and below the sea surface (European Commission 2018a) (European Commission 2018b). In the Northwest waters (ICES subareas 6 and 7), any vessels fishing using bottom trawls or seines, with catches comprising more than 10% of haddock, cod and skates and rays combined, are required to use, either a) a 120 mm cod-end, or b) an eliminator trawl with 600 mm large mesh panels and a 100 mm cod-end. For vessels fishing using bottom trawls or seines with catches comprising less than 10% of haddock, cod and skates and rays combined, vessels are required to use a cod-end mesh size of 100 mm with a 100 mm squared mesh panel, except for vessels with catches comprising over 30% of Norway lobster (European Commission 2018b).

Other management methods are currently being considered at an EU level, fishing gear modifications, education, conservation measures (such as closed seasons during spawning times). Some protected areas have been designated in these waters but offshore areas are not sufficiently managed. There are no official minimum landing sizes except for some IFCAs, which, mandate a minimum landing size (40-45 cm disc width) in inshore waters in England and Wales.

Monitoring
ICES conduct assessments for most skate and ray species on a biennial basis. There are a lack of reference points for the stock, which prevents the development of management plans (Mangi et al. 2018). Data-limited approaches have been used (using some survey and landings data) but there are important information gaps. Projects including the Fisheries Science Partnership, Sustainable Management of rays and Skates (SUMARiS), National Evaluation of Populations of Threatened and Uncertain Elasmobranch Stocks (NEPTUNE) have been collecting data to close these data gaps.

Enforcement
Surveillance legislation is underpinned by EU Law, which require that all vessels above 12m in length use vessel monitoring systems (VMS), and mandate at-sea and aerial surveillance and inspections of vessels, logbooks and sales documents. There is direct management of fishing effort for vessels since 2003, which allocates effort in kW-days to vessels of >15 m. However, the inshore (smaller) fleets are generally not managed by effort to the same extent.

Capture Information

Criterion score: 0.75 info

Longnose Skate are caught in a mixture of fishing gears, but mainly in otter trawls. They are also targeted by sea anglers.

Bycatch
There is a lack of information available on other bycatch species but may include crabs, urchins, mixed finfish and elasmobranchs and occasional interactions with Endangered, Threatened and Protected (ETP) species. Invertebrates such as crabs and urchins are vulnerable to damage.

Discards


Discards
The landing obligation will be fully implemented into our seas from 2019. Skates and rays will be exempt from the landing obligation, due to their higher likelihood of survival when discarded. Member states will be required to report on skate and ray catches and discards, and any improvements in selectivity programmes. it’s difficult to avoid catching skates and rays in nets and because of their peculiar shape and size; it’s also difficult for them to escape the net once captured. Therefore, selectivity programmes are in place reduce skate and rays catches and their survival rates. Discard rates of skates and rays vary dramatically (30 - 70%), depending on the marketability and management measures in place. For example, nearly all skates below 30 cm LT are discarded by English vessels (Silva et al., 2012). Bycatch can include juvenile skate as they can hatch from their egg cases at sizes of 10-20 cm LT and therefore, may be able to escape through the nets (Ellis et al. 2018). Their survival rates upon discarding is extremely variable, depending on the fishing and handling methods used to capture them. Elasmobranchs have the potential for relatively high survival rates because they do not have swim bladders (and thereby are not as impacted by pressure changes), they can have thick and abrasive skins and thorns (which protect them) and some have spiracles and a buccal-pump respiratory which excrete a mucus, which allows the skate or ray to ventilate and acquire oxygen when out of the water (Ellis et al. 2018). Inshore and coastal fisheries using trawls, longlines, gillnets and tangle nets generally show low at-vessel mortality. Tag-recapture studies suggest show that thornback rays were found to be in a significantly better condition when caught using longlines and tangle nets, compared to when they were captured using otter trawl or drift trammel net. When captured with tangle nets, skate condition was significantly better during shorter (17-28 hours) soak times, compared with (42-48 h soak time)(Ellis et al. 2018).

There are a lack of studies available on long-term skate and ray survival when they are released into the wild (Ellis et al. 2018).

Since they prefer soft substrate such as sand and soft mud but, can be found on loose rock and gravel beds.

Alternatives

Based on method of production, fish type, and consumer rating: only fish rated 2 and below are included as an alternative in the list below. Click on a name to show the sustainable options available.

Dab
Halibut, Atlantic (Farmed)
Halibut, Pacific
Megrim
Plaice
Sole, Dover sole, Common sole
Sole, Lemon
Turbot (Caught at sea)
Turbot (Farmed)

References

Ellis, J., Abella, A., Serena, F., Stehmann, M.F.W. & Walls, R. 2015. Dipturus oxyrinchus. The IUCN Red List of Threatened Species 2015: e.T63100A48908629. http://dx.doi.org/10.2305/IUCN.UK.2015-1.RLTS.T63100A48908629.en.

ICES. 2017. Other rays and skates (Rajidae) in Subarea 4 and in divisions 3.a and 7.d (North Sea, Skagerrak, Kattegat, and eastern English Channel).Published 6 October 2017 raj.27.3a47d DOI: 10.17895/ices.pub.3169. Available at: http://ices.dk/sites/pub/Publication%20Reports/Advice/2017/2017/raj.27.3a47d.pdf

Shark Trust; 2010a. An Illustrated Compendium of Sharks, Skates, Rays and Chimaera.: Long-nosed Skate. Available at: https://www.sharktrust.org/shared/downloads/id_guides/longnosed_skate_id_guide.pdf

Ellis, J. R., Burt, G.J., Grilli, G., McCully Phillips, S.R., Catchpole, T.L., Maxwell, D.L. 2018. At-vessel mortality of skates (Rajidae) taken in coastal fisheries and evidence of longer-term survival. Journal of Fish Biology. 92, 1702-1719. doi:10.1111/jfb.13597

Ellis, J. R., Burt, G.J., Grilli, G., McCully Phillips, S.R., Catchpole, T.L., Maxwell, D.L. 2018. At-vessel mortality of skates (Rajidae) taken in coastal fisheries and evidence of longer-term survival. Journal of Fish Biology. 92, 1702-1719. doi:10.1111/jfb.13597

Mangi, S., Kupschus, S., Mackinson, S., Rodmell, D., Lee, A., Bourke, E., Rossiter, T., Masters, J., Hetherington, S., Catchpole, T. and Righton, D. 2018. Progress in designing and delivering effective fishing industry science data collection in the UK. Fish 00:1-21. https://doi.org/10.1111/faf.12279