Goodbye cod, hello herring: why putting a different fish on your dish will help the planet

In the first of a new series, we look at why people reject so much of the bountiful catches from our seas in favour of the same few species, mostly imported - and how to change that

Perched on a quay in the Cornish port of Falmouth is Pysk fishmongers, where Giles and Sarah Gilbert started out with a dream to supply locally caught seafood to the town. Their catch comes mainly from small boats that deliver a glittering array of local fish: gleaming red mullets, iridescent mackerels, spotted dabs and bright white scallops, still snapping in their shells.

Occasionally, they will get a treasured haul of local common prawns - stripy, smaller and sweeter than the frozen, imported varieties in UK supermarkets. So, when customers come into the shop asking for prawns, Giles Gilbert presents these bouncing jack-in-a-boxes" with a flourish, hoping to tempt buyers with the fresh, live shellfish.