Common Skate Profile
Nothing is ever simple in taxonomy, especially in the ocean. The rate of destruction of our marine ecosystems far outstrips our rate of knowledge and gathering of understanding of what’s actually in there.
And so it is, the common skate is now considered a common skate complex, reflecting the tangled net we’re finding ourselves in when it comes to the conservation of some of the most critically endangered and lesser-known animals hiding right under our noses.
Common Skate Facts Overview
| Habitat: | Coastal, cool waters, sandy and muddy bottoms |
| Location: | Atlantic Ocean, North Sea and Mediterranean |
| Lifespan: | Possibly up to 30-100 years |
| Size: | 2.85 m (9 ft 4 in) across |
| Weight: | Up to 94 kg (207 lb) |
| Colour: | Brownish-green with lighter spots on top, dark grey underneath |
| Diet: | Other rays, bristle worms, sand eels, crabs and flatfish |
| Predators: | Sharks, seals, humans |
| Top Speed: | Medium, agile |
| No. of Species: | 1 |
| Conservation Status: | Critically Endangered (IUCN) |
The Common skates are some of the largest skates in the world. They’re members of the Rajidae family, and one of the 150 known skate genera. It’s also one of the most endangered animals in the ocean.
Once widespread, they have been overharvested both on purpose and as bycatch to the point where they are functionally or totally extinct throughout most of their range and hanging on by a thread in their strongholds.
But their story is complicated by a lack of research and understanding into what exactly a common skate is, and new research may help conservationists in their attempts to protect the species.
Interesting Common Skate Facts
1. They’re Rajids
Skates are members of the Rajiform order, which is also home to the softnose skates, sawfishes and pygmy skates. These are all very flat animals, with slender snouts that set them apart from the stingrays and other similar flat fish.
Common skates are members of a large genus of skates native to the Pacific, Atlantic, and Indian Oceans, and this Northerly species, or species complex, as we’ll discuss shortly, is probably the largest of them all.
These are cartilaginous fishes, in the same sort of ballpark as sharks, so they have similarly rough skin and a flexy skeleton that doesn’t fossilise well. This adds up to a bit of a limited record in terms of prehistoric clues but even the living examples are not very well understood.
2. They’re electric
Many skates like this have an electric organ. This is an organ that’s unusual in the cartilaginous fishes, and its application isn’t fully understood.
It doesn’t appear to be strong enough to use as a defence mechanism and instead seems to be used in an ongoing manner, though too irregularly to be used for echolocation.
It’s, therefore, possible that it’s a form of communication, which adds to the plethora of communicative tools we find in nature and opens up truly exciting questions about what these animals might have to talk about. 1
3. They’re enormous
One thing’s pretty obvious though, these are big skates. Common skates grow to around 3 m long, and are some of, if not the biggest skates in the world, let alone in Europe.
They can weigh almost 100 kg, and grow slowly, living on the sea bed. They’re found as far down as about 600 metres, but prefer shallower zones, using powerful crushing bony plates in their mouth to feed on crustaceans and other crunchy snacks.
Despite their size, they’re nimble enough to catch free-swimming animals like fish, too.
You’d think an animal this enormous and close to shore would be well understood by now, but it has only been recently that researchers discovered what was once thought to be the Common Skate is actually two distinct species.
4. There should be two of them
Around 2010, new genetic insights into the species showed that the common skate, previously thought to be a single species, needed to be split into two species: the Blue skate, would keep the name, Dipturus batis, (or, alternatively, be renamed D. flossada) and the Flapper skate, which includes the largest of the skates, and would take the name D. intermedius.
What’s frustrating is that this was the arrangement already until around the turn of the 20th Century, with both species being recognised until they wrongly were collapsed from D. flossada and D. intermedius into ‘D. batis in the ‘20s.
So, the new research validates the old way and exhaustingly demands a return to that convention, but in the meantime, a significant amount of damage has been done as a consequence of this mistake. 2
5. They’re complex
The situation with the common skate isn’t fully settled, but it looks like they will be considered a Species Complex for now, which is basically a group of distinctly identical-looking animals that are closely related but probably not the same species. If this sounds confusing, it’s because it is.
Taxonomy and systematics are frustrating, and always changing, but that’s (usually) not really the fault of the people involved – it’s just really hard and somewhat arbitrary to draw reliable lines along a spectrum.
But there’s a good reason for trying, and the saga with the common skate is a perfect example of why.
Before this new discovery, the common skate was one of the most endangered species in the UK.
This put it on the prohibited list in the EU, which is good news, but it also meant that the flapper skates being killed were being misidentified as common skates, which shrouded the true population figures and gave the illusion that there were more individuals in both species.
We now know that they are both incredibly at risk of extinction, and the flapper skate is even worse off. Without correcting this mistake, it’s possible the flapper would already be extinct by now. 3
6. They’re slow-growing
These fish are so vulnerable for a number of reasons.
First of all, they’re prized for being huge and tasty, which puts them at risk of direct attack, but secondly, they’re ground-dwelling and huge, which makes them vulnerable as bycatch from trawling nets.
This wouldn’t be such an issue if they didn’t take so long to grow and to breed. Common skates don’t reach sexual maturity until they’re about 11 years old, and even then they breed at a rate of about 40 eggs every second year.
This means that every skate taken requires a huge amount of time and stability in its habitat for its kin to reproduce successfully and replace it.
It’s estimated that a mortality rate of only 38% per year is enough to guarantee the extinction of these animals. 4
7. The fishing industry is one of the biggest threats to global biodiversity
A lot of people forget or are entirely unaware of the destructive force of the industrial fishing industry.
Terrestrial threats like the deforestation of the Amazon are impossible to ignore, but the ocean is far away and so vast, that it’s hard to imagine humans could truly impact it.
But the number of overfished stocks has tripled in the last fifty years, and in response to a reduction of fish in the oceans, companies are sending out more boats.
More boats mean more nets, and more nets mean more bycatch, so despite being on the forbidden list, animals like skates are no less in danger.
While sanctuaries do nothing to protect migratory species, the common skate is a very local species complex that likes to stay put, so protected areas would do a lot for them. 5
Common Skate Fact-File Summary
Scientific Classification
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Order: | Rajiformes |
| Family: | Rajidae |
| Genus: | Dipturus |
| Species: | D.batis or D.flossada |
Fact Sources & References
- DAVID M. KOESTER (2003), “Anatomy and Motor Pathways of the Electric Organ of Skates”, Anatomy Department, University of New England, Biddeford, Maine.
- “Flapper Skate”, IUCN Red List.
- “Common Skate”, Shark Trust.
- “Common Blue Skate”, IUCN Red List.
- Victoria J. Wearmouth (2009), “Movement and behaviour patterns of the critically endangered common skate Dipturus batis revealed by electronic tagging”, Science Direct.