Thornback ray, West of Scotland, demersal otter trawl
- Content last updated
- 29 May 2019
- Thornback ray (Raja clavata) in Sub Area 6
- European Union
- Stock Status
The status of thornback ray in ICES Sub-area 6 (West of Scotland) has been scored as high risk. This is because the state of the stock is uncertain, but abundance appears stable.
No quantitative stock assessments have been undertaken and ICES cannot advise on the stock’s exploitation status relative to maximum sustainable yield (MSY) or precautionary approach (PA) reference points because the reference points are undefined. Consequently, the risk score was calculated using the RASS scoring guidelines data-limited approach where the vulnerability score for thornback ray (72/100; FishBase, 2015) was weighted with a stable population trend.
The management of thornback ray in the West of Scotland (ICES Sub-area 6) has been scored a high risk. This is because management controls (Total Allowable Catches; TACs) are derived from limited data and are advised on a biennial basis.
The most recent data indicates that the levels of catch are higher than advised. Furthermore, there is no specific TAC for this stock, and fishing opportunities are managed under the framework of a generic TAC for all skates and rays (Rajidae) over a broader management area which includes the West of Scotland, Irish and Celtic Seas and western English Channel (Divisions 6a, 7a-c,e-k), and which does not control exploitation of individual species. Compliance can be patchy and misidentifications in skate and ray species can occur (e.g. between thornback ray and starry ray).
The bycatch risk of this fishery is scored as high risk. This is because otter trawls have the potential to take relatively high quantities of bycatch of non-target and vulnerable species (> 30% of catch weight), including demersal elasmobranchs and protected, endangered and threatened (e.g. sharks and rays) species in certain circumstances. However, the incoming EU landings obligation is intended to reduce discarding.
The habitat risk of this fishery is scored as a moderate risk. This is because, although otter trawls are considered to have a potential to cause significant habitat damage, damage to vulnerable and sensitive marine habitats is likely to be minimised given that the footprint of the fishery is within core areas, typically historically fished ground. Spatial management to reduce potential interactions with vulnerable habitats are being developed, but there remain uncertainties about the location of some sensitive seabed habitats and therefore some risk of further impact.