Seafish Responsible Sourcing Guide: Skates & Rays

Version 2 July 2009 responsible sourcing guide: skates & rays Introduction Skates and rays comprise a large group of fish, which includes the true skates (Order Rajiformes) and species such as electric ray and stingray. The main commercial species within northern European waters are the true skates, which have common names that generally distinguish the large species with long snouts (skates) from the smaller species with short snouts (rays). For the purposes of this guide, the term skate is used Thornback Ray in its generic (and commercial) sense to refer to all the true Raja clavata © Marc Dando skates, and includes those skate species that have the term ‘ray’ in their common name. Skates have a relatively high commercial importance in Europe and BUYERS’ TOP TIPS the UK. The total weight of the seven or eight most commonly landed 1. Know your source of supply 3. Comply with regulations species in UK ports in recent years and stock status Supporting those vessels that has been 2–3,000 tonnes (t) per year For management purposes, the record their landings by species will (1), with a first-sale value of about stocks of the various skate species help to improve stock management. £3million. There are more than 500 are allocated to management areas. Some Sea Fisheries Committees (7) species of skate and ray throughout To understand sustainability issues enforce a minimum landing size the world (2), including about 230 concerned with your supply, you (MLS) which should help to protect species of true skate, and total world need to know from which area a juvenile skates and rays. catches are about 250,000 t (3). species has been caught. Table 1 The purpose of this guide is to provide gives an overview of the status of 4. Use the Seafish Responsible a brief account of north European the stocks in the North East Atlantic. Sourcing Service skates that are of commercial Seafish has created a service at importance, outline the conservation 2. Have an informed buying policy www.seafish.org/b2b/rss that gives status of the main stocks marketed in Some skate species remain information on sustainability issues. the UK, and describe the measures abundant and, in many areas, There are also skate and ray being taken to manage and conserve cuckoo, spotted, smalleyed and identification sheets. This links to them. The guide also outlines some of thornback ray appear to have stable other sources of information and the the research being undertaken for catch rates. It should be possible to Responsible Fishing Scheme (BSi: improving the assessment and harvest these species sustainably. PAS 72:2006), aimed at ensuring management of skate fisheries. In contrast, the larger species such best quality and environmental as white skate and common skate, practice onboard vessels. Advice on the status of the various have disappeared from large parts stocks is based on data from scientific trawl surveys (4, 5) and on knowledge of their former range (6) and should of the ecology and life-history of the be avoided. various species. 1. Species and biology Some 25 species of skate and ray Norway and Iceland. Many species thornback ray and blonde ray grow to occur in waters around the British have distributions that extend to 110–120cm, whilst common skate and Isles (8). The most abundant species southern Spain and northwest Africa, white skate grow to more than 200cm. in inshore waters are thornback ray with several also occurring in the Skates typically mature at between (Raja clavata), blonde ray (Raja Mediterranean. The UK is at the five and 10 years of age, with the brachyura) and spotted ray (Raja southern limit of the starry ray smaller-bodied species maturing at an montagui) (4, 9). Cuckoo ray distribution in the North East Atlantic, earlier age. Male and female skates (Leucoraja naevus), shagreen ray and this species also occurs in the are easily identified, as males have a (Leucoraja fullonica) and common northwest Atlantic. pair of claspers (used in copulation) skate (Dipturus batis) are found alongside the pelvic fins. The females further offshore, with long-nosed skate Although locally-abundant skate lay fewer than 100 eggs per year, on (Dipturus oxyrinchus) and sandy ray species are targeted in some areas the sea floor, and these hatch after (Leucoraja circularis) occuring along (such as the thornback ray in the four to six months (10). the edge of the continental shelf. In Thames Estuary and blonde ray in St the central and northern North Sea, George’s Channel), most skates are The juveniles of inshore species (such starry ray (Amblyraja radiata) is the landed in mixed demersal fisheries, as thornback, spotted, blonde and most abundant skate species, along with flatfish and roundfish. smalleyed rays) occur in bays and although it is of little commercial coastal waters and move into deeper importance due to its small size. Skates are elasmobranchs, that is, water as they grow (9). Nursery Smalleyed ray (Raja microocellata) fish with a cartilaginous skeleton. grounds for offshore species are less and undulate ray (Raja undulata) are These fish are typically large bodied, well known. Adult fish move over most frequently found in the Bristol slow growing and with a late age at wider areas, though they may return Channel and English Channel maturity. They produce few young to certain areas to feed or breed respectively. compared to most bony fish, such as (11–13). Skates feed primarily on the cod, which may each shed millions of sea floor; juveniles eat small All these species occur widely in eggs every year. As a consequence, crustaceans, and the larger species European seas, though the British skates are susceptible to overfishing. eat shrimps, crabs and fish (14). Isles are at the northerly limits of blonde, spotted, smalleyed and There are differences in the growth of undulate ray distribution. Common skate species: smaller-bodied species and long-nosed skate, and shagreen such as spotted ray and cuckoo ray ray, may be found as far north as grow to about 70–80cm in length; Assessment Historically these species have been upon this information which is A general rule is that the abundance recorded in a generic 'skates and summarised for sea areas around of large skates has declined and they rays' category. However, from 2009 the British Isles in Table 1. Whilst this are relatively more vulnerable to species-specific recording is is not a full stock assessment, it does exploitation, whilst those species that compulsory and the UK fishery give an overview of the relative status mature at a smaller size have departments have been implementing of these stocks. healthier populations. This is this recording from 2008. illustrated in Table 2, which shows the There is less known about the status IUCN conservation categories in Analysing the catch-per-unit-effort of skates in southern European seas. relation to body size of the more (CPUE) of skate species, that is the The disappearance of the largest commercially important skate species. catch per hour trawling taken in skate species has been reported from scientific fishing surveys, allows the the Bay of Biscay and Mediterranean, status of particular stocks to be whilst surveys off the northern coast assessed in the various sea areas. of Spain suggest that catch rates of These surveys, however, do not some of the smaller species (such as sample all skate species effectively. In thornback and cuckoo ray) are stable. 2008 ICES provided advice based Egg cases (left to right) of blonde, thornback and spotted ray 2. Table 1 Status and Total Allowable Catches (TACs) for skates and rays e m ) t a ( d n n 9 s a 0 ) e i 0 e 4 c c 2 i ( e t v t p n d n s C e a e A y n t c a T m i i m o f e d e r i e r m e g o t g A a n a e ) h m n t e n a r i o g 5 a u a e 1 c S C A ( M A S m NORTH EAST ATLANTIC SKATE AND RAY STOCKS www.ices.dk North Sea and eastern Thornback Ray North Sea EU The distribution of thornback ray has declined in the North Sea, as English Channel 1643, has the overall catch-per-unit-effort. The stock status is classified as uncertain in the northern North Sea (ICES VIa,b) and stable or EU waters of ICES div IIa, Eastern English increasing in the southern North Sea (ICES VII d) and eastern English ICES sub area IV and VIId Channel 1044. Channel. Spotted ray Catch-per-unit-effort seems to be stable or increasing; stock classified as stable/increasing. Cuckoo ray Catch-per-unit-effort is considered to be stable; stock is described as stable. Starry ray Catch-per-unit-effort increased in the 1980s and, although it has recently declined, starry ray remains one of the most abundant rays in the North Sea; stock described as stable. Irish Sea, Bristol Channel, Thornback ray 15,748 EU One of the most commonly caught skate species in the area and western English Channel catch-per-unit-effort is generally stable; stock classified as stable/increasing. and North West Scotland (ICES VIIa-c, e-k and sub Spotted ray One of the most commonly caught ray species in the area and catch- area VI) per-unit-effort is generally stable or increasing; stock in ICES VIa VIIf,g classified as stable/increasing. Cuckoo ray Catch-per-unit-effort has declined slightly, but this remains one of the more common species in offshore areas of the Irish Sea and western English Channel.

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