DNA barcoding unveils skate (Chondrichthyes: Rajidae) species diversity in ‘ray’ products sold across Ireland and the UK

Griffiths, AM; Miller, DD; Egan, A; Fox, J; Greenfield, A; Mariani, S

Abstract

Skates are widely consumed across the globe, but many large species are subject to
considerable concern regarding their conservation and management. Within Europe
such issues have recently driven policy changes so that, for the first time, reports of
skate landings now have to be made under species-specific names. Total allowable
catches have also been established for many groups, which have been set to zero for
a number of the most vulnerable species (e.g., Dipturus batis, Raja undulata and
Rostoraja alba. Whilst accurate species identification has become an important issue
for landings, the sale of skates is still usually made under a blanket term of “skate”
or “ray”. The matter of identifying species of skate is further complicated by their
morphologically conservative nature and the fact that they are commercially valued
for their wings. Thus, before sale their bodies are usually discarded (i.e., “winged”)
and often skinned, making morphological identification impossible. For the first
time, DNA barcoding (of the mitochondrial COI gene) was applied to samples of
skate wings from retail outlets across the British Isles, providing insight into which
species are sold for consumption. A total of 98 wing samples were analysed, revealing
that six species were sold; blonde ray (Raja brachyura), spotted ray (Raja montagui),
thornback ray (Raja clavata), cuckoo ray (Leucoraja naevus) small-eyed ray (Raja
microocellata) and shagreen ray (Leucoraja fullonica). Statistical testing demonstrated
that there were significant differences in the species sold in the distinct retail groups
which suggests complex drivers behind the patterns of sale in skates. The results also
indicate that endangered species are not commonly being passed on to consumers.
In addition, the practice of selling skate wings under ambiguous labels is highlighted
as it makes it extremely difficult for consumers to exercise a right to avoid species
of conservation concern. Interestingly, a single retailer chain labelled their wings as
originating from three smaller-growing species (generally to be considered of lower
conservation concern); of the six samples analysed from this company a third were
mislabelled and originated from the thornback ray (a larger species that is currently
undergoing population declines).

Citation

Griffiths, A., Miller, D., Egan, A., Fox, J., Greenfield, A., & Mariani, S. DNA barcoding unveils skate (Chondrichthyes: Rajidae) species diversity in ‘ray’ products sold across Ireland and the UK. PeerJ, 1, e129. https://doi.org/10.7717/peerj.129

• Journal Article Type: Article
• Deposit Date: Sep 20, 2013
• Publicly Available Date: Sep 20, 2013
• Journal: PeerJ
• Publisher: PeerJ
• Peer Reviewed: Peer Reviewed
• Volume: 1
• Pages: e129
• DOI: https://doi.org/10.7717/peerj.129
• Publisher URL: http://dx.doi.org/10.7717/peerj.129
• Related Public URLs: https://peerj.com/