Recent stormy weather has been blamed on masses of starfish washing up.
And dog walkers are being warned to be wary as the sea creatures are toxic to animals.
NorthWalesLive reported the starfish washing up at Porth Eirias in Colwyn Bay and in Llanddulas.
One member of the public said: "There were hundreds of Starfish washed up on the beach, I took a few pictures of what I can only describe as a 'starfish apocalypse'.
"Starfish may be of concern as they can be toxic to dogs and there are many dogwalkers in Colwyn Bay that may need to be made aware."
The walker said he has seen a few hundred, and maybe up to 500 or more, of the Starfish washed up at the Old Colwyn end of the beach just before Rainbow Bridge.
Many were quite large at up to 6-8 inches across, there were some further down to Eirias Park End but not as many.
“It did seem like Starfish Armageddon but I think most were still alive. They move very slow so it's hard to tell with Starfish.
"Some had lost limbs but Starfish have the ability to grow them back. I think they may be identified as the ‘Spiny skinned echinoderm common starfish'. "
A spokesman at Anglesey Sea Zoo said the recent bad weather may be responsible for the phenomenon.
She said: "Starfish live on rocky reefs. Really strong currents and choppy waters will dislodge them and the tide will carry them in."
This is because some contain paralytic shellfish poison (PSP) - a naturally occurring marine biotoxin.
