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Common Skates Complex (Flapper and Common Blue)
Identified as two separate species in 2010 (NatureScot, 2023), these skates are listed as priority features by the Scottish Government (Scottish Government, 2011). While the complex was once very common (specifcially the blue skate species), both species are now critically endangered worldwide (IUCN, 2024 a & b) due to historical targeted fishing, and the continued risk of bycatch (Shark Trust, 2020 a & b). Since 2009, it has been illegal to fish for either species, but their benthic nature means bycatch still causes significant damage to population numbers (OSPAR, 2021).
The two species used to be abundant throughout Scottish waters, however overexploitation reduced their levels to that of today (Scottish Government, 2011). While in certain regions a slight increase in abundance has been observed, overall information is so limited that the real population status is unknown (OSPAR, 2021).
Flapper Skate (Dipturus intermedius) (Fig. 2)
The larger of the two species, growing up to 230cm (Shark Trust, 2020a), this puts Flapper Skates at higher risk of bycatch compared to Blue Skates (OSPAR, 2021). Their reproductive cycle is long, taking 10 years to reach sexual maturity, and eggs taking a year to develop once laid (NatureScot, 2023). Of the two species, Flapper Skates historically had a more north easterly range than the Blue Skate (Fig. 1)
Blue Skate (Dipturus batis) (Fig. 4)
Growing up to a maximum length of 150cm, Blue Skates are the smaller of the two species (Shark Trust, 2020b). They demonstrate a slightly different range to the Flapper Skates (Fig. 1 & 3), reaching north around Iceland (IUCN, 2024b). Overfishing throughout the 20th century has left them in their critically endangered state of today (IUCN, 2024b).
Various monitoring studies of skates are ongoing, including tagging operations, the Skatespotter database, and the Shark Trust Great Egg Case Hunt (NatureScot, 2023).
Figure 1: (IUCN, 2024a) Map of Flapper Skate range
Figure 2: (Lauren Smith) Flapper Skate at Macduff
Figure 3: (IUCN, 2024b) Map of Common Blue Skate range
Figure 4: (SFPA, 2022) Young common blue skate
None
IUCN (2024b) Common Blue Skate
OSPAR (2021) Status Assessment 2021 – Common Skate
NatureScot (2023) Flapper Skate
Scottish Environment LINK (2022) Nature Champions: Flapper Skate
Scottish Government (2011) Scotland’s Marine Atlas: Information for The National Marine Plan
SFPA (2022) in McBride: Marine Scotland on studying the critically endangered blue skate
Shark Trust (2020a) Flapper Skate: Dipturus intermedius
Shark Trust (2020b) Blue Skate: Dipturus batis
12/08/2024 by Cathryn Lovie
20/08/2024 by Ian Hay
26/08/2024 by Dr Lauren Smith
12/03/2025 by Charlotte Tomlinson
Live. Next update due 22/11/25
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