What part of the fish provides trotters?

Trotters from a shop that sells Just Fish has me puzzled ...

[Belinda Nichols]

ha ha ha Classic!

[Marinade Spatula]

or chicken for that matter ! Fun Shot Eleanor.

[Missdeb]

What the?? That's hilarious!

[Cathy (aka Possum Mum)]

Mexican walking fish??

[Graham Harcombe]

Must be hog-fish.

Great fun shot.:-D

[Constance Brinkley]

Must be those feet cleaning fish! These are great signs. Nice catch.

[Karyn Romeis]

Coelacanth!

[Henriette Sparkes]

Ha ha wonderful sign!

[Coreycam]

Like the sign alot.