A terrier called Bonny horrified her owners when she made a grim discovery on Caister beach this week.The 18-month-old Patterdale is noted for rooting amongst the flotsam and jetsam but even marine experts at Great Yarmouth Sea Life centre were amazed by her find of a rare sea lamprey on Wednesday.

A terrier called Bonny horrified her owners when she made a grim discovery on Caister beach this week.

The 18-month-old Patterdale is noted for rooting amongst the flotsam and jetsam but even marine experts at Great Yarmouth Sea Life centre were amazed by her find of a rare sea lamprey on Wednesday.

Bonny was enjoying a walk with Sam Johnson, 13, of Victoria Street, Caister, when he picked up the 15in pre-historic blood-sucking “vampire” fish on the shoreline.

“Sam took it home with him, but neither his dad nor a local fisherman could identify it, so they brought it here,” said Sea Life senior marine biologist Darren Gook.

“I could see it was a lamprey of some kind, and a quick check in the reference books confirmed it as a sea lamprey,” he added.

“They are pretty rare creatures these days and I've certainly never heard of one turning up off our local coast.”

Sea lampreys are parasitic beasts that attack larger fish and fasten onto them with sucker-like mouths lined with

teeth.

They scrape a hole in the skin and suck out blood and grated flesh, and

an anti-coagulant in their saliva

prevents the victim's blood from

clotting.

“They used to be a delicacy,” said Darren, “but they've largely disappeared because a lot of their migration routes from rivers and streams to ocean spawning grounds have been blocked by dams and in some cases, hydro-electric power stations.”

Darren cut open the lamprey to clean it ready to preserve in formaldehyde, and discovered that it was an egg-laden female.

“I guess this was another individual that, for whatever reason, never made it to those spawning grounds,” he said.

“Even though many would consider it to be quite a gruesome fish, I think that's actually quite sad.”