They glide through Scotland’s deep waters largely unseen — with most people having no idea just how many species live just off our coasts. Today’s blog is written by shark and skate specialist Jane Dodd, and celebrates the launch of SIORC, a new report shining a light on the 45 shark and skate species found in Scottish waters.

SIORC — the Gaelic word for shark, pronounced ‘shirk’ — is a stunning visual guide, featuring detailed illustrations and information on all 25 shark and 20 skate species you might find in Scotland’s seas.

The artwork tells its own story too. The beautiful illustrations are the work of Dietrich Burkel, a remarkable man who left a lasting mark on Scotland’s natural history. Assistant Keeper, and later Depute Keeper of Natural History at Kelvingrove Museum, Dietrich was also a gifted artist, a keen angler, and the man credited with starting shark tagging in Scotland — a legacy that continues to this day. His friends have kindly allowed his illustrations to be used in the report, ensuring his passion for Scotland’s seas lives on.

Dietrich Burkel’s illustration of a porbeagle shark

Porbeagle sharks
Porbeagle are part of the small group of sharks known as mackerel sharks, which also includes the white shark and mako sharks. Porbeagle can reach around three metres in length and may live as long as 45 years. They are endotherms: this means they regulate their body temperature above the temperature of the water, which is extremely rare in fish. They produce live young known as pups. They have one to five pups which develop and hatch from eggs inside the mother’s body. They also employ an additional reproductive strategy known as oophagy, in which the female continually produces eggs, which are then ingested by the embryos. The strategy is common in sharks and also occurs in spiders, amphibians, and some reptiles.

From left to right, Dietrich Burkel’s illustrations of a blonde skate (120cm),
white skate (200cm) and flapper skate (200cm).  

Skate

Skate, on the other hand, lay eggs. The female can store sperm, so she can produce eggs long after mating and may produce eggs with different fathers at the same time. This was discovered when female skate in captivity continued to produce viable eggs in the absence of male skate. The egg is fertilised internally and passes through a shell gland to be encased in leathery protective covering to produce a ‘mermaid’s purse’. All skate eggs or mermaid’s purses are similar in shape but vary in size according to species. You can record your finds of skate eggs on the beach at the The Shark Trust Great Egg Case Hunt. They have a key to help you to identify any species you find.

White skate

White skate are the much rarer cousin of the flapper skate; they are similar in size but have a much pointier rostrum or nose. The rostrum also has a translucent area, so the seabed is visible through it when the skate is lying on the bottom. This is thought to help the skate camouflage itself. Over the last 100 years or more, white skate have significantly declined and are thought to be nearing local extinction in several areas, including the area from the west coast of Scotland to the north of Shetland. Fisheries records are very limited for white skate in Scotland, perhaps because they are confused with other species and the survey methods used do not catch them.

White skate are thought to produce a whopping 55 to 158 eggs per year and incubation is approximately 15 months. Temperature influences the incubation time of skate eggs and the Pacific white skate ingeniously lays its eggs near hydrothermal vents to speed up development.

Blonde skate egg case (average length 11cm (excluding horns) average width 6.5cm), white skate egg case (average length 15cm (excluding horns) average width 12.5cm), flapper skate egg case (average length 22cm (excluding horns), average width 12cm).