SWSFC RAY TAGGING PROGRAMME 2007 This is a tag and recovery study that has been designed to gain some insight into the location of ray nursery areas in the Bristol Channel and to find out to what extent juvenile rays move out of these areas. To achieve this we are aiming to tag substantial numbers of juvenile rays of all species. Adult rays are also being tagged when possible during the project to provide additional information on ray population dynamics in these areas, such as the movement patterns of large mature (spawning) females. Juvenile and adult rays collected from an Otter Trawl on board the UWS research vessel, the R.V. Noctiluca, are tagged externally with either a T-bar Anchor Tag or a Plastic Tipped Dart Tag, and then released. The tags are red and show a unique 5 digit identification code (e.g. T0001 or P0001) and a UWS telephone number. The species, nose to tail length, wing width, sex and condition of each individual fish are recorded by scientists on the research vessel before release. The effectiveness of the study relies heavily upon the support of local commercial fishers and anglers on both sides of the Bristol Channel who may catch tagged rays in the future. Anyone that catches a tagged ray is strongly urged to report their findings to SWSFC or Swansea University, noting:
A Ray Tagging Poster explaining what to do if a tagged ray is found and a Tag Return Form are available to download from the SWSFC website www.swsfc.org.uk to whom the details can be reported. Alternatively, phone the Swansea University number on 01792 295361 or 295359. Note to Editors: Between 2000 and 2005 the tonnage of skate and ray landed into Milford Haven ranged from 153- 258 tonnes a year (lowest in recent years), representing between 5 –9% of total landings in England and Wales by UK vessels and 3 – 5% of the entire UK declared catch of skates and rays. (Defra UK Sea Fisheries statistics) Species of skate and ray most commonly encountered in Welsh inshore waters are the Blonde Ray (Raja brachyura), the Thornback Ray (Raja clavata) the Small-eyed Ray (Raja microocellata) the Spotted Ray (Raja montagui) and more offshore the Cuckoo Ray (Leucoraja naevus). Each has specific habitat and food preferences. Typical of elasmobranch species, these fish are slow growing, late maturing and have a low fecundity (annual egg production). These characteristics mean that skates and rays are vulnerable to over exploitation by fishing, particularly the larger bodied species, such as Thornback & Blonde ray. Abundances of these larger bodied species have declined in recent years. Historically the Common Skate (Raja batis) was relatively abundant in Welsh waters but this very large fish (2m wingspan and weighing over 125kg) is now thought to be locally extinct due to over-exploitation. The IUCN Red List assessment for this species is Endangered. It is currently a UK BAP Priority Species. Skates and rays are managed as a combined species group. Some Sea Fisheries Committees, including the SWSFC, have byelaws that stipulate a Minimum Landing Size for skates and rays but this favours smaller bodied species such as R. montagui and L. naevus and doesn’t sufficiently protect the larger bodied species that mature at a larger size. There is no European MLS for skates and rays. Juvenile rays hatch from their protective egg cases at a relatively large size making them susceptible to capture in towed trawl gears set to take e.g. whiting and sole from an early age. It is believed that juvenile rays remain in certain nursery grounds for several years to maximise their survival rates. Previous studies in Carmarthen Bay, South Wales, have shown most rays found there are young i.e. in the 0-2years age groups. Skates and rays, and the areas that support important life history stages, are of conservation interest to the Countryside Council for Wales (CCW). CCW joint fund this project with SWSFC, together with the University of Wales Swansea. |
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