Something fishy with Simon Rhodes from Lobsterpot Fishmongers, Wood Street Food Hall

THIS week, one of the local restaurateurs came in and enquired about frozen prawns, the small type that are used in prawn cocktails. You’d think this was a simple request but no, after a lot of discussion regarding price and size it was discovered that these small north Atlantic prawns are not quite what they seem.

They are graded, sized and frozen with a glaze to make them look bigger. In fact we discovered that in a 2kg bag of prawns the net weight varied by up to 600g. In other words, in one bag of 2kg prawns the net weight (the weight of the defrosted prawns) was 1.8kg, and in another similar, cheaper, bag the net weight was 1.2kg.

How was this? Because in the one bag, which was cheaper, the prawns had been frozen and given an extra ‘glaze’ (sprayed with water), then refrozen again to make them look bigger.

Also the amount of prawns in the cheaper bag varied from the more expensive variety. This is known as the prawn count, the amount of prawns in a pound. North Atlantic prawns may have a count of 200-300 to the pound.

I get a lot of customers who ask what the difference between a shrimp and a prawn is, as the terms shrimp and prawn are widely used in the UK industry to describe the same species and this can lead to some confusion.

Species of Crangon and Pandalus, which constitute the bulk of the British commercial landings, are called shrimp, whereas species of Palaemon, which are captured only in small quantities, are called prawn.

The terms prawn and shrimp are often used in the fish trade to distinguish large specimens from small ones, although there are no guidelines for this.

Here in the UK the term prawn is more widely used than in the US, where the term shrimp is commonly used for smaller prawns. They have to be really small for us to call them shrimp, such as brown shrimps.

Phew! All this complicated information about the simple frozen prawn may have made me more knowledgeable on the subject... but it has caused my eyes to glaze over!